Apparatus, system and method for selectively engaging downhole tools for wellbore operations

Abstract

A device for wellbore operations is configured to self-determine its downhole position in the wellbore in real time and to self-activate when it reaches a preselected target position. The device determines its downhole position based on a magnetic field signal and / or magnetic flux signal provided by its own three-axis magnetometer. The device optionally includes one or more magnets. The magnetometer detects changes in the magnetic field and / or magnetic flux caused by the device approaching or passing through multiple features in the wellbore. The device can self-activate to deploy a coupling mechanism to engage a downhole target tool from a target position. The coupling mechanism includes a seal supported by two expandable support rings, each support ring having a corresponding elliptical surface for engaging with the elliptical surface of the other support ring.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 62 / 968,074, filed January 30, 2020, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to devices, systems and methods for performing downhole operations, and more particularly to devices configured to determine their downhole position in a wellbore and self-activate based on the determination to perform downhole operations, as well as related systems and methods. Background Art

[0004] Recently, wellbore treatment equipment has been developed that includes a wellbore treatment string for staged well treatment. The wellbore treatment string can be used to form multiple isolation zones within a well and includes a system of openable ports that allow selective access to each such isolation zone. The treatment string includes a tubular string carrying multiple external annular packers that can be set in a borehole to form an isolation zone therebetween, in the annulus between the string and the wellbore wall, whether cased or open-hole. Openable ports through the string wall are located between the packers and provide communication between the string's inner bore and the isolation zone. These ports are selectively openable and include a sleeve located thereon, which has a sealable seat formed in the sleeve's inner diameter. By firing a plug, such as a ball, dart, etc., the plug can seal against the seat of the port sleeve, and the pressure behind the plug can be increased to drive the sleeve through the string, thereby opening the port and accessing the isolation zone. The seat in each sleeve can be formed to accept a plug of a selected diameter, but allow plugs of smaller diameters to pass through. In this way, a port can be selectively opened by firing a plug of a specific size that is selected to seal the seat of that port.

[0005] Unfortunately, however, such wellbore handling systems are often limited in the number of zones that can be accessed. In particular, limitations on the internal diameter of the wellbore tubing (often due to the internal diameter of the well itself) limit the number of different sized submounts that can be installed in any one string of tubing. For example, if the well diameter dictates that the largest casing submount in the well can only accept 3 3 If a 1 / 4" plug is used, the well treatment string will typically be limited to approximately 11 sleeves, and thus treatment can only be completed in 11 stages. Therefore, a wellbore treatment system is desired that allows the use of the same size sleeve base throughout the string, so that the wellbore treatment system can have more stages. Furthermore, if the sleeve bases in the string are identical to each other, the sleeve bases do not have to be installed in any particular order.

[0006] In some cases, plugs are configured to seal the wellbore during completion operations, such as hydraulic fracturing through an open port in a zone. Rubber and other elastomeric materials are commonly used as seals in settable plugs. A common problem in this area is the undesirable deformation of the seal during setting, and subsequent deformation, both of which are caused by extrusion of the sealing material. Under axial compression, extrusion may occur through any gaps in or around the compression ring of the compression setting mechanism in conventional sealing rings. This extrusion may cause the seal to deform, break, or erode, thereby compromising the integrity of the seal, which may result in undesirable leakage.

[0007] Therefore, the present disclosure is intended to solve the above-mentioned problems. Summary of the Invention

[0008] According to a broad aspect of the present disclosure, a method is provided, comprising: deploying a device into a channel of a tubular string; measuring an x-axis magnetic field on an x-axis, a y-axis magnetic field on a y-axis, and a z-axis magnetic field on a z-axis by a magnetometer in the device, wherein the z-axis is parallel to a direction of travel of the device, and the x-axis and y-axis are orthogonal to the z-axis and to each other; generating one or more of: an x-axis signal based on the x-axis magnetic field, a y-axis signal based on the y-axis magnetic field, and a z-axis signal based on the z-axis magnetic field; and monitoring one or more of the x-axis, y-axis, and z-axis signals to detect changes; and analyzing the changes to detect at least one feature in the tubular string, wherein the change is caused by one of: movement of a first magnet in the device relative to a second magnet in the device; the device approaching the at least one feature, each of the at least one feature being a magnetic feature; and the at least one feature approaching a third magnet in the device.

[0009] In some embodiments, the change is caused by movement of the first magnet relative to the second magnet, and the change includes a change in the z-axis signal, and analyzing includes determining whether the change in the z-axis signal is greater than or equal to a predetermined threshold amplitude.

[0010] In some embodiments, analyzing includes, upon determining that the change in the z-axis signal is greater than or equal to the predetermined threshold amplitude, determining whether the y-axis signal is within a baseline window during the change in the z-axis signal.

[0011] In some embodiments, analyzing includes, upon determining that the change in the z-axis signal is greater than or equal to the predetermined threshold amplitude, determining whether the y-axis signal is within a baseline window during a maximum change in the z-axis signal.

[0012] In some embodiments, analyzing includes, upon determining that the y-axis signal is within the baseline window, determining whether a time that the y-axis signal is within the baseline window exceeds a threshold time span.

[0013] In some embodiments, the method includes adjusting a baseline of the y-axis signal based at least in part on the x-axis signal.

[0014] In some embodiments, the first magnet and the second magnet are rare earth magnets.

[0015] In some embodiments, the first magnet is embedded in a first retractable protrusion of the device, the second magnet is embedded in a second retractable protrusion of the device, the first retractable protrusion and the second retractable protrusion are positioned at approximately the same axial position on the outer surface of the device, and the at least one feature includes a narrowing portion.

[0016] In some embodiments, the first and second retractable protrusions are azimuthally spaced approximately 180° apart, and the y-axis is parallel to a retraction direction of the first and second retractable protrusions.

[0017] In some embodiments, the change is caused by proximity of the device to the at least one feature, and wherein monitoring comprises calculating the ambient magnetic field M using the following formula:

[0018]

[0019] Wherein, x is the amplitude of the x-axis signal, y is the amplitude of the y-axis signal, and c and d are adjustment constants of the x-axis signal and the y-axis signal, respectively, and the change includes a change in the ambient magnetic field.

[0020] In some embodiments, analyzing includes determining whether the variation falls within a parameter distribution curve for one of the at least one characteristic.

[0021] In some embodiments, the parameter distribution curve includes a minimum magnetic field threshold, and determining whether the change falls within the parameter distribution curve includes determining whether the ambient magnetic field is greater than or equal to the minimum magnetic field threshold.

[0022] In some embodiments, the parameter distribution curve includes a maximum magnetic field threshold, and determining whether the change falls within the parameter distribution curve includes: starting a timer when it is determined that the ambient magnetic field is greater than or equal to the minimum magnetic field threshold; monitoring the ambient magnetic field after starting the timer to determine whether the ambient magnetic field is less than the minimum magnetic field threshold or greater than the maximum magnetic field threshold; and deactivating the timer after determining that the ambient magnetic field is less than the minimum magnetic field threshold or greater than the maximum magnetic field threshold to provide the time elapsed between starting the timer and deactivating the timer.

[0023] In some embodiments, the parameter distribution curve includes a minimum time span and a maximum time span, and determining whether the change falls within the parameter distribution curve includes determining whether the elapsed time is between the minimum time span and the maximum time span.

[0024] In some embodiments, the change is caused by the at least one feature being in proximity to the third magnet, and monitoring comprises calculating the magnetic field M of the third magnet using:

[0025]

[0026] Wherein, x is the amplitude of the x-axis signal, y is the amplitude of the y-axis signal, z is the amplitude of the z-axis signal, and p, q, and r are adjustment constants of the x-axis signal, y-axis signal, and z-axis signal, respectively, and the change includes the magnetic field change of the third magnet.

[0027] In some embodiments, analyzing includes determining whether the variation falls within a parameter distribution curve for one of the at least one characteristic.

[0028] In some embodiments, the parameter distribution curve includes a minimum magnetic field threshold, and determining whether the change falls within the parameter distribution curve includes determining whether the magnetic field of the third magnet is greater than or equal to the minimum magnetic field threshold.

[0029] In some embodiments, the parameter distribution curve includes a maximum magnetic field threshold, and determining whether the change falls within the parameter distribution curve includes: starting a timer when it is determined that the magnetic field of the third magnet is greater than or equal to the minimum magnetic field threshold; monitoring the magnetic field of the third magnet after starting the timer to determine whether the magnetic field of the third magnet is less than the minimum magnetic field threshold or greater than the maximum magnetic field threshold; and deactivating the timer after determining that the magnetic field of the third magnet is less than the minimum magnetic field threshold or greater than the maximum magnetic field threshold to provide the time that elapsed between the activation of the timer and the deactivation of the timer.

[0030] In some embodiments, the parameter distribution curve includes a minimum time span and a maximum time span, and determining whether the change falls within the parameter distribution curve includes determining whether the elapsed time is between the minimum time span and the maximum time span.

[0031] In some embodiments, each of the at least one feature is a magnetic feature or a thicker feature.

[0032] In some embodiments, each of the at least one feature is a magnetic feature, and wherein a first feature of the at least one feature has a first parameter distribution curve and a second feature of the at least one feature has a second parameter distribution curve, the first parameter distribution curve being different from the second parameter distribution curve.

[0033] In some embodiments, the method includes, upon detecting one of the at least one feature, one or both of: incrementing a counter; and determining a position of the device in the tubing string.

[0034] In some embodiments, the method includes: setting a target position before deploying the device; after incrementing the counter and / or determining the position, comparing the counter or the position with the target position to determine whether the counter or the position has reached the target position; and activating the device when it is determined that the counter or the position has reached the target position.

[0035] In some embodiments, activating the device comprises actuating an engagement mechanism of the device.

[0036] In some embodiments, the method includes determining the distance traveled based at least in part on an acceleration of the device measured by an accelerometer in the device.

[0037] In some embodiments, the distance is determined based at least in part on a rotation of the device measured by a gyroscope in the device.

[0038] According to another broad aspect of the present disclosure, a downhole tool is provided, comprising: a first support ring having: a first face at a first end; a first elliptical face at a second end, the first face and the first elliptical face having a first gap extending therebetween; and a second support ring having: a second face at the first end; a second elliptical face at the second end, the second elliptical face being adjacent to the first elliptical face and configured to matingly abut the first elliptical face, the second face and the second elliptical face having a second gap extending therebetween, the first support ring and the second support ring being expandable from an initial position to an expanded position, wherein the first gap and the second gap are widened in the expanded position compared to the initial position.

[0039] In some embodiments, the first support ring includes: a first short side, the first short side having a first short side length; and a first long side, the first long side having a first long side length, the first long side length being greater than the first short side length, and the first face and the first elliptical face each extend from the first short side to the first long side; and the second support ring includes: a second short side, the second short side having a second short side length; and a second long side, the second long side having a second long side length, the second long side length being greater than the second short side length, and the second face and the second elliptical face each extend from the second short side to the second long side.

[0040] In some embodiments, the length of the second long side is equal to or greater than the length of the first long side.

[0041] In some embodiments, the length of the second short side is equal to or greater than the length of the first short side.

[0042] In some embodiments, the second long side is shorter than the first long side.

[0043] In some embodiments, the second short side length is shorter than the first short side length.

[0044] In some embodiments, the first gap is located at or near the first short side.

[0045] In some embodiments, the second gap is located at or near the second short side.

[0046] In some embodiments, the second short side is adjacent to the first long side; and the second long side is adjacent to the first short side.

[0047] In some embodiments, the first gap is azimuthally offset from the second gap.

[0048] In some embodiments, one or both of the first and second faces are circular.

[0049] In some embodiments, the first elliptical surface is tilted relative to the first surface by an angle in a range of about 1° to about 30°.

[0050] In some embodiments, one or more of the following exists: the first short side length is approximately 10% to approximately 30% of the first long side length; the first short side length is approximately 18% to approximately 38% of the second short side length; and the first short side length is approximately 3% to approximately 23% of the second long side length.

[0051] In some embodiments, one or more of the following exists: the second short side length is approximately 10% to approximately 30% of the second long side length; the second short side length is approximately 18% to approximately 38% of the first short side length; and the second short side length is approximately 3% to approximately 23% of the first long side length.

[0052] In some embodiments, in the expanded position, at least a portion of the first support ring is radially offset from the second support ring.

[0053] In some embodiments, in the expanded position, the first gap has a smaller volume than the second gap.

[0054] In some embodiments, the downhole tool comprises a cone and an annular seal, and wherein the first support ring, the second support ring, and the seal are supported on an outer surface of the cone, the seal being adjacent to the first face.

[0055] In some embodiments, the downhole tool includes: an inactive position, in which the annular seal and the first and second support rings are in a first axial position of the cone, and the first ring and the second ring are in the initial position; and an active position, in which the annular seal and the first and second support rings are in a second axial position of the cone, and the first and second support rings are in an expanded position, wherein the outer diameter of the second axial position is greater than the outer diameter of the first axial position, and the outer diameter of the annular seal in the active position is greater than that in the inactive position.

[0056] In some embodiments, the first short side has a length of about 6% to about 26% of an axial length of the annular seal.

[0057] In some embodiments, the second long side length is about 109% to about 129% of the axial length of the annular seal.

[0058] In some embodiments, the first support ring and the second support ring each have a respective frustoconical inner surface for matingly abutting the outer surface of the cone.

[0059] In some embodiments, one or both of the first support ring and the second support ring include a dissolvable material. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The present invention will now be described by way of exemplary embodiments with reference to the accompanying simplified, diagrammatic, and not to scale drawings. Any dimensions provided in the drawings are provided for illustrative purposes only and do not limit the invention as defined by the claims. In the drawings:

[0061] Figure 1A is a schematic diagram of a multi-stage well according to one embodiment of the present disclosure.

[0062] Figure 1B is a schematic diagram of a multi-stage well according to another embodiment of the present disclosure, wherein the well includes one or more constrictions.

[0063] Figure 1C is a schematic diagram of a multi-stage well according to yet another embodiment of the present disclosure, wherein the well includes one or more magnetic features.

[0064] Figure 1D is a schematic diagram of a multi-stage well according to yet another embodiment of the present disclosure, wherein the well includes one or more thicker features.

[0065] Figure 2A is a schematic axial cross-sectional view of a dart according to an embodiment of the present disclosure.

[0066] Figure 2B is a schematic axial cross-sectional view of a dart according to another embodiment of the present disclosure, wherein the dart includes a protrusion.

[0067] Figure 2C is a schematic axial cross-sectional view of a dart having a magnet embedded therein according to yet another embodiment of the present disclosure. Figures 2A to 2C In this article, it can be collectively referred to as Figure 2.

[0068] Figure 3A is a schematic axial cross-sectional view of a dart according to one embodiment of the present disclosure, illustrating the magnets in the dart and their corresponding magnetic fields. Figure 3A Some parts of the dart.

[0069] Figure 3B and Figure 3C They are Figure 3A The schematic axial cross-sectional view and the schematic side cross-sectional view of the dart are shown, showing the effect of the magnet on the dart when the magnet is in contact with the dart. Figure 3A The magnetic field of the magnet in the dart is determined by the different positions of the magnet in the dart. Figure 3A 、 Figure 3B and Figure 3C This may be collectively referred to as FIG3 in this article.

[0070] Figure 4 is an exemplary graphical representation of x-axis, y-axis, and z-axis components of magnetic flux as a function of time as measured by a magnetometer of a dart as it travels through a channel according to one embodiment of the present disclosure.

[0071] Figure 5A is a schematic axial cross-sectional view of a dart shown in an inactivated position according to one embodiment of the present disclosure.

[0072] Figure 5B yes Figure 5AA magnified view of area "A" showing the intact burst barrier.

[0073] Figure 6A According to one embodiment of the present disclosure, Figure 5A Schematic axial cross-sectional view of a dart shown in an activated position.

[0074] Figure 6B yes Figure 6A A magnified view of area "B" showing a ruptured burst disk.

[0075] Figure 7A 、 Figure 7B and Figure 7C are side cross-sectional, side plan, and perspective views, respectively, of an engagement mechanism and cone of a dart shown in an inactivated position, according to one embodiment of the present invention. 7A to 7C In this article, it can be collectively referred to as Figure 7.

[0076] Figure 8A 、 Figure 8B and Figure 8C 7 , respectively, a side view, a side exploded view, and a perspective view of the engagement mechanism without showing the cone. Figures 8A to 8C In this article, it can be collectively referred to as Figure 8.

[0077] Figure 9A 、 Figure 9B and Figure 9C 7 are side cross-sectional, side plan, and perspective views, respectively, of the engagement mechanism and cone of FIG. 7 shown in an activated position, according to one embodiment of the present invention. Figures 9A to 9C In this article, it can be collectively referred to as Figure 9.

[0078] Figure 10A 、 Figure 10B and Figure 10C 9 , respectively, a side view, an exploded side view, and a perspective view of the engagement mechanism when the cone is not shown. Figures 10A to 10C It may be collectively referred to as FIG10 in this article.

[0079] Figure 11A is a perspective view of a first support ring of the engagement mechanism of FIG. 8 , according to one embodiment.

[0080] Figure 11B is a perspective view of a first support ring of the engagement mechanism of FIG. 10 , according to one embodiment. Figure 11A and Figure 11B This may be collectively referred to herein as FIG11 .

[0081] Figure 12A is a perspective view of a second support ring of the engagement mechanism of FIG. 8 , according to one embodiment.

[0082] Figure 12B is a perspective view of a second support ring of the engagement mechanism of FIG. 10 , according to one embodiment. Figure 12A and Figure 12B This may be collectively referred to herein as FIG12.

[0083] Figure 13 is a flow chart of a method for determining a position of a dart in a wellbore according to one embodiment.

[0084] Figure 14 is a flow chart of a method for determining a position of a dart in a wellbore according to another embodiment.

[0085] Figure 15 is a flow chart of a method for determining a position of a dart in a wellbore according to yet another embodiment. DETAILED DESCRIPTION

[0086] In describing the present invention, all terms not defined herein have their generally accepted meanings in the art. To the extent that the following description is of specific embodiments or specific uses of the invention, it is intended to be illustrative only and not to limit the claimed invention. The following description is intended to encompass all alternatives, modifications, and equivalents within the spirit and scope of the present invention, as defined in the appended claims.

[0087] In general, the methods disclosed herein are used to deploy a device into a wellbore extending through a subsurface formation and use the autonomous operation of the device to perform downhole operations that may or may not involve the actuation of downhole tools. In some embodiments, the device is an unconstrained object sized to travel through a passage in a tubing string (e.g., the inner bore of the tubing string) and various tools. The device may also be referred to as a dart, a plug, a ball, or a stick and may take different forms. The device may be pumped into the tubing string (i.e., pushed into the well along with the fluid), but in some embodiments, pumping may not be required to move the device through the tubing string.

[0088] In some embodiments, the device is deployed into a channel and configured to autonomously monitor its position in real time as it travels through the channel and autonomously operate to initiate a downhole operation upon determining that it has reached a given target location in the channel. In some embodiments, the device is deployed into the channel in an initial inactive position and remains in this position until the device determines that it has reached a predetermined target location in the channel. Once it reaches the predetermined target location, the device is configured to selectively self-activate into an active position to perform the downhole operation. To name a few examples, the downhole operation can be one or more of: a stimulation operation (e.g., a fracturing operation or an acidizing operation); an operation performed by a downhole tool (e.g., operation of a downhole valve, operation of a packer, operation of a single-shot tool, or operation of a perforating gun); formation of a downhole obstruction; fluid diversion (e.g., diversion of fracturing fluid to the surrounding formation); pressurization of a specific stage of a multi-stage well; deflection of a downhole tool sleeve; actuation of a downhole tool; and installation of a check valve in a downhole tool. Stimulation operations involve stimulating the formation using a stimulation fluid (such as acid, water, oil, CO2 and / or nitrogen) with or without proppants.

[0089] In some embodiments, the preselected target location is a location in the passageway that is upward from the target tool in the passageway, thereby allowing the device to determine that it is about to reach the target tool. By determining its current location, the device can be self-activated when it is expected to reach the target tool downhole. In some embodiments, the target location can be a specific distance downward relative to the surface opening of, for example, a wellbore. In other embodiments, the target location is a downhole location in the passageway that is somewhere upward from the target tool.

[0090] As disclosed herein, in some embodiments, the device can monitor and / or determine its position based on physical contact and / or physical proximity to one or more features in the channel. Each of the one or more features may or may not be part of a tool in the channel. For example, a feature in the channel may be a change in geometry (e.g., a constriction), a change in a physical property (e.g., a material difference in the tubing string), a change in magnetism, a change in material density in the tubing string, etc. In alternative or additional embodiments, the device can monitor and / or determine its downhole position by detecting changes in magnetic flux as the device travels through the channel. In alternative or additional embodiments, the device can monitor and / or determine its position in the channel by calculating a distance the device has traveled based, at least in part, on acceleration data of the device.

[0091] In some embodiments, the device comprises a body, a control module, and an actuating mechanism. In the inactive position, the body of the device can be transmitted through the passage to reach the target position. The control module is configured to determine whether the device has reached the target position, and when this is determined, the actuating mechanism is operated to convert the device to the active position. In embodiments where the device is used to actuate a target tool, the device in its active position can engage with the target tool by deploying a coupling mechanism to actuate the target tool and / or form a seal in the tubing string adjacent to the target tool to prevent fluid from flowing, for example to divert fluid into an underground formation.

[0092] In some embodiments, when in the inactivated position, the device is configured to pass through a downhole constriction (e.g., a valve seat or pipe connector), thereby allowing the device to be used in conjunction with the same sized bases, for example in a multi-stage application in which the device is used, so that the device can be selectively configured to engage a specific base. The device and related methods can be used for staged injection of treatment fluids, wherein the fluids are injected into one or more selected layers of a wellbore while other layers are closed. In some embodiments, the tubing string has multiple port joints along its length, and the device is configured to contact and / or detect the presence of at least some features along the tubing string to determine that it is about to reach a target tool (e.g., a target port joint). Based on such a determination, the device self-activates to open a port of the target port joint so that the treatment fluid can be injected through the open port to treat the underground formation accessible through the port.

[0093] The apparatus and methods described herein may be used in a variety of drilling conditions, including open hole, cased hole, vertical well, horizontal well, vertical well, or deviated well.

[0094] See also Figure 1A According to some embodiments, a multi-stage ("multi-stage") well 20 includes a wellbore 22 that penetrates one or more subterranean formations (e.g., hydrocarbon-bearing formations). In some embodiments, the wellbore 22 may be lined or supported by a tubing string 24. The tubing string 24 may be secured to the wellbore 22 with cement (such a wellbore is often referred to as a "cased hole" wellbore); or the tubing string 24 may be secured to the formation with packers (such a wellbore is often referred to as an "open hole" wellbore). Typically, the wellbore 22 extends through one or more zones or stages. Figure 1A In the exemplary embodiment shown, wellbore 22 has five stages 26a, 26b, 26c, 26d, and 26e. In other embodiments, wellbore 22 may have fewer or more stages. In some embodiments, well 20 may include multiple wellbores, each having a tubing string similar to the illustrated tubing string 24. In some embodiments, well 20 may be an injection well or a production well.

[0095] In some embodiments, multi-stage operations may be performed sequentially in the well 20, in its stages 26a, 26b, 26c, 26d, 26e, along a particular direction (e.g., in a direction from the toe T of the wellbore 22 to the heel H of the wellbore 22), or may not be performed in a particular direction or sequence, depending on the particular multi-stage operation.

[0096] In the illustrated embodiment, the well 20 includes downhole tools 28a, 28b, 28c, 28d, 28e located in each stage 26a, 26b, 26c, 26d, 26e. Each tool 28a, 28b, 28c, 28d, 28e can be any of a variety of downhole tools, such as valves (circulation valves, casing valves, sleeve valves, etc.), valve seat assemblies, check valves, plug assemblies, etc., depending on the specific embodiment. In addition, all tools 28a, 28b, 28c, 28d, 28e may not necessarily be the same, and the tools 28a, 28b, 28c, 28d, 28e may include a mix and / or combination of different tools (e.g., casing valves, plug assemblies, check valves, etc.).

[0097] Each tool 28a, 28b, 28c, 28d, 28e can be selectively actuated by a device 10 that is deployed through the interior passage 30 of the tubular string 24 (a dart in the illustrated embodiment). Typically, the dart 10 has an inactive position that allows the dart to pass relatively freely through the passage 30 and through one or more of the tools 28a, 28b, 28c, 28d, 28e, and an active position in which, for example, the dart is transformed to engage a selected tool (the "target tool") among the tools 28a, 28b, 28c, 28d, or 28e or otherwise secure it at a selected downhole location, such as to perform a specific downhole operation. Engaging a downhole tool can include one or more of: making physical contact with the downhole tool, wireless communication, and landing (or being "captured").

[0098] exist Figure 1A In the illustrated embodiment shown, the dart 10 is deployed from the opening of the wellbore 22 at the surface E into the passage 30 of the tubing string 24 and travels downhole along the passage 30 in a direction F until the dart 10 determines that it is about to reach a target tool, such as tool 28d (described further below), and transitions from its initial inactive position to an active position (described further below) and engages the target tool 28d. It should be noted that the dart 10 can be deployed from locations other than the surface E. For example, the dart 10 can be released by a downhole tool. As another example, the dart 10 can be run downhole on a conveyor mechanism and then released downhole to travel further downhole unrestrained.

[0099] In some embodiments, each stage 26a, 26b, 26c, 26d, 26e has one or more features 40. Any feature 40 can be part of the tool itself 28a, 28b, 28c, 28d, 28e, or can be located elsewhere within the corresponding stage 26a, 26b, 26c, 26d, 26e, such as at a defined distance from the tools within that stage. In some embodiments, feature 40 can be another downhole tool, such as a port connector, that is separate from the tool 28a, 28b, 28c, 28d, 28e and located within the corresponding stage. In some embodiments, feature 40 can be located between adjacent tools or at an intermediate location between adjacent tools, such as at a junction between adjacent sections of a tubing string. In some embodiments, a stage 26a, 26b, 26c, 26d, 26e can include multiple features 40, while another stage can include no features 40. In some embodiments, features 40 can be evenly / regularly distributed or unevenly / irregularly distributed along the length of passage 30. As will be appreciated by those skilled in the art, other configurations are possible. In some embodiments, the downhole location of the feature 40 in the tubing string 24 is known prior to deploying the dart 10 , such as through a well map of the wellbore 22 .

[0100] In some embodiments, a dart 10 autonomously determines its downhole position in real time, maintains an inactive position while passing through the preceding tool(s) (e.g., 28a, 28b, 28c) of a target tool 28d, and transitions to an active position before reaching the target tool 28d. In some embodiments, the dart 10 determines its downhole position within the channel by physically contacting one or more features 40 preceding the target tool. In alternative or additional embodiments, the dart 10 determines its downhole position by detecting the presence of the one or more features 40 preceding the target tool when the dart 10 is in close proximity to the one or more features 40 preceding the target tool. In alternative or additional embodiments, the dart 10 determines its downhole position by detecting changes in the magnetic field and / or magnetic flux as the dart travels through the channel 30. In alternative or additional embodiments, the dart 10 determines its downhole position by calculating the distance the dart has traveled based on the dart's real-time acceleration data. The above embodiments can be used individually or in combination to determine the (real-time) downhole position of the dart. The results obtained from two or more of the above embodiments can be correlated to more accurately determine the downhole position of the dart. Various embodiments will be described in detail below.

[0101] Figure 2AAn exemplary embodiment of a dart 10 is shown in FIG. In the illustrated embodiment, the dart 10 includes a body 120, a control module 122, and an actuation mechanism 124. The body 120 has an engagement section 126. The body 120 has a leading end 140 and a trailing end 142, with the actuation mechanism 124, engagement section 126, and control module 122 positioned therebetween. The body 120 is configured to allow the dart (including the engagement section 126) to freely travel through the channel 30 and the feature 40 therein when the dart 10 is in an inactive position. In its inactive position, the maximum outer diameter D1 of the dart 10 is smaller than the inner diameter of the feature 40, allowing the dart 10 to pass therethrough. When the dart 10 is in the active position, the engagement section 126 is transformed by the actuation mechanism 124, for example, so that the next tool encountered (i.e., the target tool) engages the engagement section 126 to capture the dart 10. For example, when activated, the engagement section 126 is deployed such that its outer diameter is larger than D1 and the inner diameter of the seat in the target tool.

[0102] In some embodiments, the control module 122 includes a controller 123, a memory module 125, and a power supply 127 (for powering one or more components of the dart 10). In some embodiments, the control module 122 includes one or more of the following: a magnetometer 132, an accelerometer 134, and a gyroscope 136, the functions of which are described in detail below.

[0103] In some embodiments, the controller 123 includes one or more of the following: a microcontroller, a microprocessor, a field programmable gate array (FPGA), or a central processing unit (CPU), which receives feedback regarding the dart's position and generates appropriate signal(s) for transmission to the actuation mechanism 124. In some embodiments, the controller 123 uses a microprocessor-based device operating under stored program control (i.e., firmware or software stored or embedded in a program memory of a memory module) to perform the functions and operations associated with the dart described herein. According to other embodiments, the controller 123 may be in the form of a programmable device (e.g., an FPGA) and / or dedicated hardware circuitry. Specific implementation details of the above embodiments will be within the purview of those skilled in the art. In some embodiments, the controller 123 is configured to execute one or more software, firmware, or hardware components or functions to perform one or more of the following: analyzing acceleration data and gyroscope data; calculating distance using acceleration data and gyroscope data; and analyzing magnetic field signals and / or magnetic flux signals to detect, identify, and / or recognize features 40 in the pipe string based on physical contact with and / or proximity to the features.

[0104] In some embodiments, the dart 10 is programmable to allow an operator to select a target position downward at which the dart self-activates. The dart 10 is configured so that the controller 123 can be assigned and / or programmed with target position information by an operator on-site during manufacture or prior to deployment in a well. In some embodiments, the dart 10 can be pre-programmed during manufacture and subsequently reprogrammed on-site by an operator to have different target position information. In some embodiments, the control module 122 is configured to have a communication interface, such as a port for connecting a communication cable or a wireless port (e.g., a radio frequency or RF port) for receiving (sending) radio frequency signals, for programming or configuring the controller 123 with target position information. In some embodiments, when the controller 123 is disposed within an RF shielded enclosure, such as an aluminum and / or magnesium enclosure, modulation of the enclosure's magnetic field, sound, and / or vibration can be used to communicate with the controller 123 to program the target position. In some embodiments, the control module 122 is configured to have a communication interface and / or include a user interface that is connected (wirelessly or by cable) to an input device (e.g., a computer, tablet, smartphone, etc.), the user interface being configured to query an operator for information and process input from the operator to configure the dart and / or functions associated with the dart or the control module. For example, the control module 122 can be configured to have an input port that includes one or more user-settable switches that are set using target position information. Other configurations of the control module 122 are possible.

[0105] In some embodiments, the target location information includes a specific number of features 40 in the string 24 that the dart 10 passes through before self-activating. For example, the dart 10 can be programmed with target location information specifying the number "five" so that the dart remains inactive until the controller 123 records five counts, indicating that the dart has passed through five features 40, and the dart self-activates before reaching the next (sixth) feature in its path. In this embodiment, the sixth feature is the target tool. In an alternative embodiment, the target location information includes the actual number of features of the target tool in the string. For example, if the target tool is the sixth feature in the string, the dart 10 can be programmed with target location information specifying the number "six", and in this case, the controller 123 is configured to subtract one from the number of target location information and self-activate after the dart 10 passes through five features.

[0106] In some embodiments, the controller maintains a count of each recorded feature (e.g., via an electronically based counter), and this count can be stored in the memory 125 (volatile or non-volatile memory) of the dart 10. Thus, the controller 123 records when the dart 10 passes through a feature 40 and updates the count accordingly, thereby determining the downhole position of the dart based on the count. When the dart 10 determines that the count (based on the number of recorded features 40) matches the target position information programmed into the dart, the dart self-activates.

[0107] In other embodiments, the target location information includes a specific distance from the ground surface E at which the dart 10 will self-activate. For example, the dart can be programmed with target location information specifying a distance of "100 meters," thereby causing the dart to remain inactive until the controller 123 determines that the dart 10 has traveled 100 meters in the channel 30. When the controller 123 determines that the dart has reached the target location, the dart 10 self-activates. In this embodiment, the target tool is the next tool in the dart's path after self-activation.

[0108] In some embodiments, a well map may be stored in memory 125 and controller 123 may reference the well map to help determine the real-time location of the dart.

[0109] physical contact

[0110] Figure 1B Shown with Figure 1A The multi-stage well 20a is similar to the multi-stage well 20 of FIG. 20 , but at least one feature of each stage 26a, 26b, 26c, 26d, 26e of well 20a is a constriction 50, i.e., an axial segment having an inner diameter smaller than that of the surrounding segments of the tubing string. The inner diameter of constriction 50 is sized so that a dart can pass through it when in its inactive position, but at least a portion of the dart physically contacts constriction 50 to pass through it. The inner diameter of each constriction 50 can be substantially the same throughout the tubing string. In some embodiments, constriction 50 can be a valve seat or a connection between adjacent segments of the tubing string or adjacent tools.

[0111] Figure 2B An exemplary embodiment of a dart 100 is shown that is configured to physically contact one or more features in a channel to determine the downhole position of the dart relative to a target location. The dart 100 has a body 120, a control module 122, an actuation mechanism 124, and an engagement section 126, which are similar to those described above with respect to Figure 2A The same numbered parts as those described in the dart 10 are the same or similar. Figure 1B and Figure 2BIn some embodiments, the dart 100 includes one or more retractable protrusions 128 located on the body 120 to be acted upon, e.g., depressed by, the constriction 50 in the channel 30 as the dart passes through the constriction. In the illustrated embodiment, the protrusions 128 are shown in an extended (or undepressed) position, in which they extend radially outward from the outer surface of the body 120 to provide an effective outer diameter D2 that is greater than the maximum outer diameter D1 of the body 120 when the dart 100 is in the inactive position. The maximum outer diameter D1 is less than the inner diameter of the constriction 50 to allow the dart 100 to pass through the constriction when the dart 100 is inactive. The dart 100 is configured such that the outer diameter D2 is slightly greater than the inner diameter of the constriction 50 in the channel 30. When the dart 100 passes through the constriction 50, the protrusion 128 is pressed by the inner surface of the constriction into a retracted position, thereby allowing the dart 100 to pass through the constriction 50 unimpeded. In an embodiment, the protrusion 128 is spring-biased or otherwise configured to extend radially outward from the body 120 (i.e., the extended position), retract when pressed by the constriction as it passes through the constriction (i.e., the retracted position), and rebound radially outward from the body 120 after passing through the constriction and re-extend back to the extended position. In some embodiments, the protrusion 128 allows the control module 122 to record and count each instance of the dart 100 passing through the constriction 50, as will be described in more detail below.

[0112] The protrusion 128 is positioned somewhere between the leading end 140 and the trailing end 142 on the body 120. In an embodiment, the leading end 140 has a diameter smaller than D1, which allows the dart 100 to initially pass through the constriction 50 more easily, thereby allowing the dart 100 to be more centrally positioned and substantially coaxial with the constriction as the protrusion 128 approaches the constriction. Although the protrusion 128 is shown in FIG. 2 as being axially spaced from the engagement section 126, it will be appreciated that in other embodiments, the dart 100 can be configured such that the protrusion 128 coincides with or overlaps the engagement section 126.

[0113] In some embodiments, the dart 100 uses electronic sensing based on physical contact with one or more constrictions 50 in the channel 30 to determine whether the dart has reached the target location. In this embodiment, each protrusion 128 has a magnet 130 embedded therein, and the control module 122 is configured to detect changes in the magnetic field and / or flux associated with the magnet 130, the changes caused by the movement of the magnet.

[0114] In some embodiments, the magnet 130 can be made of a material that is magnetized and produces its own persistent magnetic field. In some embodiments, the magnet 130 can be a permanent magnet formed at least in part from one or more ferromagnetic materials. Suitable ferromagnetic materials that can be used for the magnet 130 described herein can include, for example, iron, cobalt, rare earth metal alloys, ceramic magnets, aluminum nickel cobalt alloys, rare earth magnets (e.g., neodymium magnets and / or samarium-cobalt magnets). Various materials that can be used for the magnet 130 can include what is known as Co-netic 2 and 3 , the magnets 130 are rare earth magnets. Each magnet 130 can have any shape, including, for example, a cylinder, a rectangular prism, a cube, a sphere, combinations thereof, or an irregular shape. In some embodiments, all magnets in the dart 100 are substantially identical in shape and size.

[0115] exist Figure 2B In the embodiment shown in FIG3 , the control module 122 includes a magnetometer 132 (which may be a three-axis magnetometer) configured to detect the amplitude of magnetic flux along three axes (i.e., the x-axis, the y-axis, and the z-axis). A three-axis magnetometer is a device that can measure changes in anisotropic magnetoresistive properties caused by an external magnetic field. Using a magnetometer to measure magnetic fields and / or magnetic flux allows for directional and vector-specific sensing. Furthermore, because it does not operate according to the principles of Lenz's law, the magnetometer does not need to move to measure magnetic fields and / or magnetic flux. The magnetometer can detect magnetic fields even when stationary. In some embodiments, as best shown in FIG3 , the magnetometer 132 is positioned on or around the central longitudinal axis of the dart 100 so that the z-axis of the magnetometer is substantially parallel to the direction of travel of the dart (i.e., direction F). In the embodiment shown, the x-axis and y-axis of the magnetometer are substantially orthogonal to direction F, and the x-axis and y-axis are substantially orthogonal to the z-axis and to each other. In the illustrated embodiment, the y-axis is substantially parallel to the direction in which the magnets 130 move when the protrusions 128 are depressed. In further embodiments, the magnetometers 132 are positioned substantially equidistant from each magnet 130 when the protrusions 128 are not depressed.

[0116] While the dart 100 can operate with only one protrusion 128, in some embodiments, the dart may include two or more protrusions 128 spaced azimuthally apart on the outer surface of the dart, i.e., at approximately the same axial position on the dart body 120, to provide corroborative data to help the controller 123 distinguish between a dart passing through a constriction 50 and a simple irregularity in the channel 30. For example, when the dart passes through a constriction 50, depression of two or more protrusions 128 may occur nearly simultaneously, causing the controller 123 to register the event as a constriction because all protrusions are depressed nearly simultaneously. Conversely, when the dart passes through an irregularity on the inner surface of the string (e.g., a bump or bump), only one or two of the multiple protrusions may be depressed, causing the controller 123 to not register the event as a constriction 50 because not all protrusions are depressed nearly simultaneously. Thus, including multiple protrusions 128 in the dart can help the controller 123 distinguish between irregularities in the channel and actual constrictions.

[0117] See also Figure 2B In the exemplary embodiment shown in FIG3 , the dart 100 has two protrusions 128, each having a magnet 130 embedded therein. The magnets 130 are azimuthally spaced approximately 180° apart and positioned at approximately the same axial position on the body 120 of the dart 100. Each magnet 130 is a permanent magnet having two opposing magnetic poles (a north pole (N) and a south pole (S)) and a corresponding magnetic field M. In some embodiments, the magnets 130 in the dart 100 are positioned such that like poles of the magnets 130 face each other. For example, as shown in the illustrated embodiment, the magnets 130 are positioned in the dart 100 such that the north pole N of the magnets faces radially inward, while the south pole S of the magnets 130 faces radially outward. In other embodiments, the north pole N may face radially outward, while the south pole S faces radially inward. It will be appreciated that in other embodiments, the dart 100 may have fewer or more protrusions and / or magnets, and each protrusion may have more than one magnet embedded therein, and other polarity orientations of the magnets 130 are possible.

[0118] Figure 3A The positions of the magnets 130 relative to each other are shown when the protrusion (with at least a portion of the magnet disposed therein) is in an extended position in which the protrusion is not depressed. Figure 3B and Figure 3C The positions of the magnets 130 relative to each other are shown when the protrusion is in a retracted position, for example when the protrusion is pressed by the constriction 50. For the sake of clarity, a portion of the dart 100 has been omitted from Figure 3 .

[0119] See also Figure 2B 3 , when the protrusion 128 is pressed and the magnet 130 therein moves radially inward a certain distance (e.g. Figure 3B and Figure 3C As shown in FIG. 1 , the movement of the magnet 130 changes the gradient of the magnetic field vector within the dart 100. When the relative position of the magnet 130 changes, the magnetic field M associated with the magnet 130 also changes. For example, when the protrusion 128 and the magnet 130 therein are moved from the extended position ( Figure 3A ) moves to the retracted position ( Figure 3B and Figure 3C ), the positions of the magnets 130 change relative to each other (ie, the distance between the magnets 130 decreases). Figure 3B and Figure 3C In the illustrated embodiment shown, when the protrusion is pressed, the north poles N of the magnets 130 move closer together. The shortened distance between the magnets 130 causes the corresponding magnetic field M to change, and in this case, the magnetic field is distorted. The change (e.g., distortion) in the magnetic field of the magnets 130 can be detected by measuring the magnetic flux in each of the x-axis, y-axis, and z-axis using the magnetometer 132.

[0120] Based on the magnetic flux detected by the magnetometer 132, the magnetometer can generate one or more signals. In some embodiments, the controller 123 is configured to process the signals generated by the magnetometer 132 to determine whether the change in the magnetic field and / or magnetic flux detected by the magnetometer 132 is caused by a constriction 50. Based on this determination, the controller 123 can determine the downhole position of the dart relative to the target position and / or the target tool by counting the number of constrictions 50 encountered by the dart and / or by referring to the known location of the constrictions 50 in a well map of the reference string and the number of constrictions counted. In some embodiments, the controller 123 uses a counter to maintain a count of the number of constrictions recorded by the controller.

[0121] Figure 4An exemplary graph 400 of signals generated by the magnetometer 132 is shown. In graph 400, the x-axis component, y-axis component, and z-axis component of the magnetic flux measured over time as the dart 100 travels down the string are represented by lines 402, 404, and 406, respectively, corresponding to the x-axis, y-axis, and z-axis directions indicated in FIG3 . In some embodiments, the magnetometer 132 continuously measures the magnetic flux components along these three axes as the dart 100 travels. When the dart 100 moves freely in the channel without any interference, the magnetometer 132 detects baseline magnetic flux 402a, 404a, and 406a for each of the x-axis, y-axis, and z-axis, respectively. In the illustrated embodiment, the baseline 402a for the x-axis component is approximately -10,500.0 μT; the baseline 404a for the y-axis component is approximately 300.0 μT; and the baseline 406a for the z-axis component is approximately -21,300.0 μT. In some embodiments, each of the x-axis component 402 , the y-axis component 404 , and the z-axis component 406 of the magnetic flux detected by the magnetometer 132 may provide different types of information to the controller 123 .

[0122] In one example, a change in the magnitude of the z-axis component 406 of the magnetic flux relative to the baseline 406a can indicate that the dart has passed through the constriction 50. In some embodiments, the z-axis component 406 is correlated with the distance the magnet 130 has moved, which helps the controller 123 determine whether a change in the magnetic flux in the z-axis is caused by the constriction 50 or a simple irregularity (e.g., a random bump or bump) in the pipe string based on the magnitude of the detected magnetic flux relative to the baseline 406a.

[0123] In another example, the y-axis component 404 of the detected magnetic flux can help the controller 123 distinguish between a dart 100 passing through a constriction 50 and simple downhole noise. In some embodiments, the y-axis component 404 helps the controller 123 identify and ignore signals caused by asymmetric magnetic field fluctuations. Asymmetric magnetic field fluctuations occur when the protrusions are not pressed nearly simultaneously, which is likely to occur when the dart 100 encounters an irregularity in the channel. When the magnetic field fluctuations are asymmetric, the magnetic flux detected on the y-axis 404 deviates from the baseline 404a. Conversely, when the dart 100 passes through a constriction, all protrusions are pressed nearly simultaneously, resulting in substantially synchronized radial inward movement of the magnets 130 and substantially symmetric magnetic field fluctuations in the magnets 130. When the resulting magnetic field fluctuations are substantially symmetric, the y-axis component of the measured magnetic flux 404 is the same as or close to the baseline 404a because the magnetic field distortions of the magnets 130 substantially cancel each other out along the y-axis.

[0124] The z-axis component 406 and the y-axis component 404 together provide the controller 123 with the necessary information to determine whether the dart 100 has passed through the constriction 50 or is simply an irregularity in the channel. Based on the change in the magnetic flux detected in the z-axis and y-axis relative to the baseline values 406a, 404a, the controller 123 can determine whether the magnet 130 has moved a sufficient distance to consider any noise downhole (e.g., asymmetric magnetic field fluctuations) to recognize the change as being caused by the constriction rather than by an irregularity.

[0125] In some embodiments, the detected x-axis component 402 of the magnetic flux is not attributable to movement of the magnet 130, but rather to any residual magnetization of the material in the pipe string. Residual magnetization has a similar effect on the y-axis component 404 of the magnetic flux and can move the y-axis component outside its detection threshold window. By monitoring the x-axis component 402, the controller 123 can use the x-axis component signal to dynamically adjust the baseline 404a of the y-axis component to compensate for the effects of residual magnetization and / or correct any magnetic flux reading errors associated with residual magnetization.

[0126] In some embodiments, the controller 123 monitors the magnetic flux signal to indicate that the dart has passed through the constriction 50. Figure 4 3 , i.e., when at least one of the protrusions is pressed, a change in the magnetic flux of the z-axis component 406 relative to the baseline 406a can be detected by the magnetometer, and such a change in the z-axis magnetic flux is shown, for example, by pulses 410, 412, 414, and 416. When a change in the z-axis component is detected, the controller 123 checks when the change in the z-axis component is at its maximum value (i.e., a peak or valley value of a pulse in the z-axis signal, e.g., Figure 4 404a) to determine whether the two tabs are pressed substantially simultaneously, as described above. In some embodiments, the controller 123 may only examine the y-axis magnetic flux signal 404 if the maximum value of the z-axis pulse is greater than a predetermined threshold amplitude. The controller 123 may ignore any changes in the z-axis magnetic flux signal below the predetermined threshold amplitude as noise.

[0127] Figure 4Points 420 and 422 in FIG. 4 are examples of baseline readings of the y-axis component 404 of the detected magnetic flux (occurring substantially simultaneously with the maximum values of the z-axis pulses (i.e., points 410 and 412, respectively). A "baseline reading" in the y-axis component refers to a signal at or near baseline 404a (i.e., within a predetermined window around baseline 404a). It should be noted that a positive or negative change in the y-axis magnetic flux 404 detected immediately before or after baseline readings 420, 422 may be caused by one or more protrusions being pressed just before other protrusions, as the dart 100 may not be perfectly centered in the channel when passing through the constriction.

[0128] In some embodiments, when a pulse maximum in the z-axis signal coincides with a baseline reading in the y-axis signal (e.g., the combination of point 420 in y-axis signal 404 and a pulse 410 trough in z-axis signal 406; and the combination of point 422 in y-axis signal 404 and a pulse trough 412 in z-axis signal 406), controller 123 can infer that dart 100 has passed through constriction 50. In some embodiments where the baseline reading on the y-axis substantially coincides with the magnetic flux change detected on the z-axis, controller 123 can be configured to accept the baseline reading only if it persists for at least a predetermined threshold time span (e.g., 10 μs), and to reject the baseline reading as noise if it is shorter than the predetermined time span. This can help controller 123 distinguish noise from actual readings obtained by the dart passing through the constriction.

[0129] When the dart 100 passes through an irregularity in the channel other than the constriction 50, typically only one protrusion is depressed, which results in an asymmetric magnetic field fluctuation. Such an event is indicated by a change in the z-axis magnetic flux signal 406, such as shown by each of pulses 414 and 416, which coincides with a positive or negative change in the y-axis magnetic flux 404 relative to the baseline 404a, such as shown by each of pulses 424 and 426, respectively. Therefore, when the controller 123 detects a change in the z-axis magnetic flux relative to the baseline 406a and sees that the y-axis magnetic flux deviates from the baseline 404a by more than a predetermined window at substantially the same time, the controller 123 can ignore such a change in the y-axis and z-axis signals and treat the event as noise.

[0130] Figure 13is a flow chart illustrating an exemplary process 500 for determining the real-time position of a dart 100 via physical contact, according to one embodiment. In step 502, the controller 123 of the dart 100 is programmed with a desired target position, which can be a number or a distance. In step 504, the dart 100 is deployed into the string. In step 506, as the dart 100 travels down the string, the magnetometer 132 continuously measures the magnetic flux along the x-, y-, and z-axes and sends these signals to the controller 123, allowing the controller 123 to monitor the magnetic flux along all three axes.

[0131] In some embodiments, in step 508, the controller 123 uses the detected x-axis magnetic flux signal to adjust the baseline of the y-axis signal, as described above. In step 510, the controller 123 continuously checks for changes in the z-axis magnetic flux signal. If the z-axis signal has not changed, the controller continues to monitor the magnetic flux signal (step 506). If the z-axis signal has changed, the controller 123 compares the change to a predetermined threshold magnitude (step 512). If the change in the z-axis signal is below the threshold magnitude, the controller 123 ignores the event (step 514) and continues to monitor the magnetic flux signal (step 506).

[0132] If the change in the z-axis signal is equal to or greater than the threshold amplitude, the controller 123 checks whether the y-axis signal is at a baseline reading (i.e., the y-axis signal is within a predetermined baseline window) when the z-axis signal pulse change is at its maximum value (step 516). If the y-axis signal is not within the baseline window, the controller 123 ignores the event (step 514) and continues to monitor the magnetic flux signal (step 506). If the y-axis signal is within the baseline window, the controller 123 checks whether the y-axis baseline reading has persisted for at least a threshold time span (step 518). If the y-axis baseline reading persists for less than the threshold time span, the controller 123 ignores the event (step 514) and continues to monitor the magnetic flux signal (step 506). If the y-axis baseline reading persists for at least the threshold time span, the controller 123 records the event as a passage through the constriction 50 and increments a counter (e.g., by one) (step 520). In step 520, the controller 123 may also determine the current downhole position of the dart based on the number in the counter and the known location of the constriction 50 on the well map.

[0133] The controller 123 then proceeds to step 522, where it checks whether the updated counter number or the determined current position of the dart has reached the pre-programmed target position. If the controller determines that the dart has reached the target position, the controller 123 sends a signal to the actuation mechanism 124 to activate the dart 100 (step 524). If the controller determines that the dart has not yet reached the target position, the controller 123 continues to monitor the magnetic flux signal (step 506).

[0134] Environmental Sensing

[0135] In some embodiments, the dart does not require physical contact to monitor its position in the channel 30. As the dart travels through the tubing string, the magnetic field surrounding the dart changes due to a variety of reasons: for example, residual magnetization in the tubing string, variations in the thickness of the tubing string, different types of formations (e.g., ferrous soil) traversing the tubing string, etc. In some embodiments, by monitoring the changes in the magnetic field surrounding the dart, the downhole position of the dart can be determined in real time.

[0136] Figure 1C Shown with Figure 1A 20 , but at least one feature in each level 26a, 26b, 26c, 26d, 26e of the well 20b is a magnetic feature 60. The magnetic feature 60 comprises a ferromagnetic material or is otherwise configured to have a magnetic property that is different from the magnetic property of the surrounding segments of the tubular string 24. "Different" magnetic properties can refer to a weaker magnetic field (or other magnetic properties) or a stronger magnetic field (or other magnetic properties). In one example, the magnetic feature 60 can include a magnet so that the magnetic property of the magnetic feature 60 is different from the magnetic property of the surrounding tubular segments. In another example, the magnetic feature 60 can include a "thicker" feature in the tubular string 24, such as a tie, because the tie is typically thicker than the surrounding segments and therefore contains more metallic material than the surrounding segments. The tubular string ties are spaced apart a known distance because they are intermittently positioned along the tubular string 24 to connect adjacent tubular segments. In yet another example, the magnetic feature 60 may include any of tools 28a, 28b, 28c, 28d, 28e because the tool may contain more metallic material (i.e., the tool may have a thicker metallic material than its surrounding sections) or be formed of a material having different magnetic properties than the surrounding sections of the tubing string.

[0137] In some embodiments, see Figure 1C and 2A As shown, the magnetometer 132 of the dart 10 is configured to continuously sense the ambient magnetic field and / or magnetic flux of the magnetometer as the dart 10 travels down the pipe string 24, and accordingly send one or more signals to the controller 123. As the dart 10 travels down the pipe string, the strength of the magnetic field and / or magnetic flux measured by the magnetometer 132 changes due to the influence of the magnetic features 60 in the pipe string as the dart 10 approaches, coincides with, and passes through each magnetic feature 60. In some embodiments, a magnet may be provided in one or more of the magnetic features 60 to help further distinguish the magnetism of the magnetic feature 60 from the magnetism of the surrounding pipe string segments, which may enhance the magnetic field and / or magnetic flux detectable by the magnetometer 132.

[0138] Based on the signal generated by the magnetometer 132, the controller 123 detects and records when the dart 10 approaches a magnetic feature 60 in the tubing string, so that the controller 123 can determine the downhole position of the dart at any given time. For example, a change in the magnetometer signal can indicate the presence of a magnetic feature 60 near the dart 10. In some embodiments, the magnetometer 132 measures directional magnetic fields and is configured to measure magnetic fields in the x-axis direction and the y-axis direction when the dart 10 travels in the direction F. Figure 2A In the illustrated embodiment shown, the magnetometer 132 is positioned at the central longitudinal axis of the dart 10, which can help minimize directional asymmetry in the magnetometer's measurement sensitivity. The x-axis and y-axis of the magnetometer 132 are substantially orthogonal to the direction F and to each other.

[0139] In some embodiments, the magnetic field M of the environment surrounding the magnetometer (“ambient magnetic field”) can be determined by:

[0140]

[0141] Wherein x is the x-axis component of the magnetic field detected by the magnetometer 132, c is the adjustment constant for the x-axis component, y is the y-axis component of the magnetic field detected by the magnetometer 132, and d is the adjustment constant for the y-axis component. The purpose of the constants c and d is to compensate for the influence of any components and / or materials in the dart on the ability of the magnetometer to sense uniformly in the xy plane around the periphery of the magnetometer. The values of the constants c and d depend on the components and / or configuration of the dart 10 and can be determined experimentally. When the appropriate constants c and d are used in equation 1, the calculated ambient magnetic field M is independent of any rotation of the dart 10 relative to the column 24 around its central longitudinal axis because any imbalance in the measurement sensitivity between the x-axis and y-axis of the magnetometer is taken into account. Considering only the x-axis component and the y-axis component of the magnetic field detected by the magnetometer when calculating the ambient magnetic field M can help reduce the noise in the calculated ambient magnetic field M (for example, minimizing any influence of the z-axis component).

[0142] The controller 123 interprets the magnetic field and / or magnetic flux signals provided by the magnetometer 132 on the x-axis and y-axis to detect magnetic features 60 in the dart's environment as the dart 10 travels. In some embodiments, each magnetic feature 60 is configured to provide a magnetic field strength detectable by the magnetometer between a predetermined minimum value ("minimum M threshold") and a predetermined maximum value ("maximum M threshold"). Furthermore, the magnetic strength and / or length of the magnetic features 60 can be selected so that, when the dart 10 travels at a given speed in the string, the magnetometer 132 can detect a magnetic field of the magnetic feature 60 whose value remains between the minimum M threshold and the maximum M threshold for a period of time between a predetermined minimum value ("minimum time span") and a predetermined maximum value ("maximum time span"). For example, for a magnetic feature, the minimum M threshold is 100 mT, the maximum M threshold is 200 mT, the minimum time span is 0.1 seconds, and the maximum time span is 2 seconds. Collectively, the minimum Mthreshold, maximum Mthreshold, minimum time span, and maximum time span of each magnetic signature 60 constitute a parameter distribution curve for that particular magnetic signature.

[0143] When the dart 10 is not near the magnetic feature 60, the magnitude of the magnetic field M determined by the controller 123 based on the x-axis signal and the y-axis signal from the magnetometer 132 may fluctuate but be below the minimum M threshold. When the dart 10 approaches an object in the pipe string with different magnetic properties (e.g., the magnetic feature 60), the magnitude of the detected magnetic field M changes and may rise above the minimum M threshold. In some embodiments, when the detected magnetic field M falls between the minimum M threshold and the maximum M threshold for a time period between the minimum time span and the maximum time span, the controller 123 identifies the event as being within the parameter distribution curve of the magnetic feature 60 and records the event as the dart passing through the magnetic feature 60. The controller 123 may use a timer to track the time that elapses when the magnetic field M remains between the minimum and maximum M thresholds.

[0144] In some embodiments, all magnetic features 60 in the string 24 have the same parameter profile. In other embodiments, one or more magnetic features 60 have different parameter profiles, such that when a dart 10 passes through one or more magnetic features 60, the changes and variations in the magnetic field and / or magnetic flux detected by the magnetometer 132 can be distinguished from the changes detected when the dart passes through other magnetic features in the string. In some embodiments, at least one magnetic feature in the string has a first parameter profile, and at least one of the remaining magnetic features in the string has a second parameter profile, wherein the first parameter profile is different from the second parameter profile.

[0145] By recording the presence of magnetic features 60 in the tubing string, the controller 123 can determine the downhole position of the dart in real time by cross-referencing the detected magnetic features 60 with their known positions on a well map, or by counting the number of magnetic features (or the number of magnetic features having a specific parameter distribution curve) encountered by the dart 10. In some embodiments, a counter of the controller 123 maintains a count of the detected magnetic features 60. The controller 123 compares the current position of the dart 10 with the target position, and upon determining that the dart has reached the target position, the controller 123 sends a signal to the actuator 124 to transition the dart to the activated position.

[0146] Figure 14 is a flow chart illustrating an exemplary process 600 for determining the downhole position of a dart 10 in a multi-stage well 20b. In step 602, the dart 10 is programmed with a desired target location. The dart 10 is then deployed in the tubing string (step 604). The magnetometer 132 of the dart 10 continuously measures the magnetic field and / or magnetic flux along the x-, y-, and z-axes (step 606) and transmits the x-axis signal, the y-axis signal, and (optionally) the z-axis signal to the controller 123. Based on at least the x-axis signal, the y-axis signal, and constants c and d, the controller 123 determines the ambient magnetic field M using Equation 1 above (step 608). If the dart 10 is not near a magnetic feature, the magnitude of the ambient magnetic field M may fluctuate, but will generally be below a minimum M threshold. As the ambient magnetic field M is continuously updated based on the signal received from the magnetometer 132, the controller 123 monitors the real-time value of the ambient magnetic field M to see if it rises above the minimum M threshold (step 610).

[0147] If ambient magnetic field M remains below minimum M threshold value, then controller 123 does nothing and continues to explain x-axis signal and y-axis signal (step 608) from magnetometer 132. If ambient magnetic field M rises to and is higher than minimum M threshold value, then controller 123 starts timer (step 612). Controller 123 continues to run timer (step 614), monitors magnetic field M to check whether real-time ambient magnetic field M is between minimum M threshold value and maximum M threshold value (step 616) simultaneously. If ambient magnetic field M rests between minimum M threshold value and maximum M threshold value, then controller 123 continues to run timer (step 614). If ambient magnetic field M falls outside minimum and maximum M threshold value, then controller 123 deactivates timer (step 618). Then, controller 123 checks whether the time that passes between the start time of timer in step 612 and the end time of timer in step 618 is between minimum time span and maximum time span (step 620). If the elapsed time is not between the minimum time span and the maximum time span, the controller 123 ignores the event (step 622) and continues to monitor the magnetic field M (step 608). If the elapsed time is between the minimum time span and the maximum time span, the controller 123 records the event as a dart passing through a magnetic feature and increments a counter (step 624). In step 624, the controller 123 can also determine the current downhole position of the dart 10 based on the number in the counter and the known position of the magnetic feature on the well map.

[0148] The controller 123 then proceeds to step 626, where it checks whether the updated counter number or the determined current position of the dart 10 has reached the pre-programmed target position. If the controller determines that the dart has reached the target position, the controller 123 sends a signal to the actuator 124 to activate the dart 10 (step 628). If the controller determines that the dart 10 has not yet reached the target position, the controller 123 continues to monitor the ambient magnetic field M (step 608).

[0149] Proximity sensing

[0150] Figure 2C An exemplary embodiment of a dart 200 is shown that is configured to determine its downhole position relative to a target location without physical contact with the tubing string. The dart 200 has a body 120, a control module 122, an actuation mechanism 124, and an engagement section 126, which are similar to those described above with respect to Figure 2A The same numbered components as those described for the dart 10 in FIG. 1 are the same or similar. In some embodiments, the dart 200 includes a magnet 230, and the magnet 230 may have the same properties as those described above with respect to FIG. Figure 2BIn the illustrated embodiment, the magnet 230 is embedded in the body 120 of the dart 200 and is rigidly mounted therein such that the magnet 230 is stationary relative to the body 120 regardless of the movement of the dart.

[0151] Figure 1D Shown with Figure 1A The multi-stage well 20c is similar to the multi-stage well 20 of the embodiment of the present invention, but at least one feature in each stage 26a, 26b, 26c, 26d, 26e of the well 20c is a thicker feature 70. The thicker feature 70 is a section of the tubing string 24 with increased thickness (or increased amount of metal material), such as a tubing string joint and / or any of the tools 28a, 28b, 28c, 28d, 28e. The downhole location of the feature 70 is known, for example, from a well map before deploying the dart 200. In other embodiments, the feature 70 is a thicker feature as described above with respect to the tubing string 24. Figure 1C The magnetic characteristics 60 described are the same or similar magnetic characteristics.

[0152] See also Figure 1D and Figure 2C The magnetometer 132 of the dart 200 is configured to continuously measure the magnetic field and / or magnetic flux of the magnet 230 as the dart 200 travels down the pipe string 24, and to send one or more signals accordingly to the controller 123. As the dart 200 travels down the pipe string, the magnetic field strength and / or magnetic flux of the magnet 230 may be affected by the dart's environment (e.g., proximity to different materials and / or the thickness of the materials in the pipe string). In some embodiments, the magnetometer 132 of the dart 200 is configured to detect changes (e.g., distortions) in the strength of the magnet's magnetic field and / or magnetic flux due to the influence of the magnetic features 70 in the pipe string as the dart 200 approaches, coincides with, and passes through each feature 70. In other embodiments, in addition to or in lieu of increased thickness, one or more features 70 may be magnetic, which may enhance the magnetic field and / or magnetic flux detectable by the magnetometer 132 when the dart 200 approaches such features. By monitoring changes in the magnetic field and / or magnetic flux of the magnet 230 as the dart 200 travels along the channel 30 , the downhole position of the dart 200 can be determined in real time.

[0153] In some embodiments, based on the signal generated by the magnetometer 132, the controller 123 detects and records when the dart 200 is near a feature 70 in the tubing string, so that the controller 123 can determine the downhole location of the dart at any given time. For example, a change in the magnetometer's signal can indicate the presence of a feature 70 near the dart 200. In some embodiments, the magnetometer 132 is configured to measure the x-axis component, y-axis component, and z-axis component of the magnetic field and / or magnetic flux of the magnet 230 seen by the magnetometer 132 as the dart 200 travels in the F direction. Figure 2CIn the illustrated embodiment shown, magnetometer 132 is positioned at the central longitudinal axis of dart 200 with its z-axis parallel to direction F and its x- and y-axes substantially orthogonal to the z-axis and to each other.

[0154] In this embodiment, the magnetic field M of the magnet 230 sensed by the magnetometer 132 can be determined as follows:

[0155]

[0156] Where x is the x-axis component of the magnetic field detected by magnetometer 132; p is the adjustment constant for the x-axis component; y is the y-axis component of the magnetic field detected by magnetometer 132; q is the adjustment constant for the y-axis component; Z is the z-axis component of the magnetic field detected by magnetometer 132; and r is the adjustment constant for the z-axis component. The magnetic field M calculated using Equation 2 provides a measure of the vector-specific magnetic field and / or magnetic flux seen by magnetometer 132 in the direction of magnet 230. In the illustrated embodiment, the vector from magnetometer 132 to magnet 230 is represented by arrow Vm. In some embodiments, constants p, q, and r are determined at least in part based on one or more of: the magnetic strength of magnet 230; the dimensions of dart 200; the configuration of components within dart 200; and the penetrability of the dart material. In some embodiments, constants p, q, and r are determined by calculation and / or experimentation.

[0157] By monitoring the magnetic field strength at magnetometer 132 (i.e., in direction Vm), distortions in the magnet's magnetic field can be detected. In some embodiments, controller 123 interprets the magnetic field and / or flux signals provided by magnetometer 132 in the x-, y-, and z-axes to detect features 70 in the dart's environment (i.e., near magnet 230) as dart 200 travels. In some embodiments, based on the signals from the magnetometer, the controller determines the value of magnetic field M in real time using Equation 2 and examines changes in the value of magnetic field M. In some embodiments, when dart 200 coincides with feature 70, the magnetic field of magnet 230 detected by the magnetometer is stronger because the dart 200 absorbs and / or deflects less of the magnet's magnetic field when it is in the feature than when it is in the surrounding, thinner section of the string 24. As dart 200 leaves feature 70 and enters the thinner section of the string, the magnetic field of magnet 230 becomes weaker. In this embodiment, the controller 123 may detect an increase in the magnetic field M to indicate that the dart has entered the feature 70, and a corresponding decrease in the magnetic field M to confirm that the dart has exited the feature and entered a thinner section of the tubular string. In other embodiments, the controller 123 may detect a further increase in the magnetic field M from the initial increase, which may indicate that the dart has exited the feature 70 and entered a thicker section of the tubular string.

[0158] Depending on its material and configuration, each feature 70 can increase the magnetic intensity of magnet 230, where the magnitude of the increased magnetic field is between a minimum value ("minimum M threshold") and a maximum value ("maximum M threshold"). Furthermore, the length of feature 70 can be selected so that, when dart 200 travels at a given speed in the string, the increase in magnetic field caused by feature 70 is detectable for a period of time between the minimum value ("minimum time span") and the maximum value ("maximum time span"). For example, for feature 70, the minimum M threshold is 100 mT, the maximum M threshold is 200 mT, the minimum time span is 0.1 seconds, and the maximum time span is 2 seconds. Collectively, the minimum M threshold, maximum M threshold, minimum time span, and maximum time span of each feature 70 constitute the parameter profile for that particular feature.

[0159] When dart 200 is not near feature 70, the magnitude of magnetic field M determined by controller 123 based on the x-axis signal, y-axis signal, and z-axis signal from magnetometer 132 may fluctuate but remain below a minimum M threshold. When dart 200 approaches feature 70 in the pipe string, the magnitude of the detected magnetic field M rises above the minimum M threshold. In some embodiments, when the detected magnetic field M falls between the minimum M threshold and the maximum M threshold for a period of time between a minimum time span and a maximum time span, controller 123 identifies the event as within the parameter distribution curve for feature 70 and records the event as the dart passing through feature 70. Controller 123 may use a timer to track the time that elapses while magnetic field M remains between the minimum and maximum M thresholds.

[0160] In some embodiments, all features 70 in the string 24 have the same parameter profile. In other embodiments, one or more features 70 have different parameter profiles, such that changes in the magnetic field and / or magnetic flux detected by the magnetometer 132 when the dart 200 passes through one or more features 70 can be distinguished from changes detected when the dart passes through other features in the string. In some embodiments, at least one feature 70 in the string has a first parameter profile, and at least one feature 70 among the remaining features in the string has a second parameter profile, wherein the first parameter profile is different from the second parameter profile.

[0161] By recording the dart's passage through one or more features 70 in the tubing string, the controller 123 can determine the downhole position of the dart 200 in real time by cross-referencing the detected features 70 with their known locations on a well map, or by counting the number of features 70 (or the number of features 70 having a particular parameter distribution curve) encountered by the dart 200. In some embodiments, a counter in the controller 123 maintains a count of the detected features 70. The controller 123 compares the current position of the dart 200 with the target position, and upon determining that the dart has reached the target position, the controller 123 sends a signal to the actuator 124 to transition the dart to the activated position.

[0162] Figure 15 is a flow chart illustrating an exemplary process 700 for determining the downhole position of a dart 200 in a multi-stage well 20c. In step 702, the dart 200 is programmed with a desired target position. The dart 200 is then deployed in the tubing string (step 704). The magnetometer 132 of the dart 200 continuously measures the magnetic field and / or flux along the x-, y-, and z-axes (step 706) and transmits the x-, y-, and z-axis signals to the controller 123. Based on the x-, y-, and z-axis signals and the constants p, q, and r, the controller 123 determines the magnetic field M using Equation 2 above (step 708). If the dart 200 is not near a feature 70, the magnitude of the magnetic field M may fluctuate but will generally be below a minimum M threshold. As the magnetic field M is continuously updated based on the signal received from the magnetometer 132, the controller 123 monitors the real-time value of the magnetic field M to see if it rises above the minimum M threshold (step 710).

[0163] If magnetic field M keeps lower than minimum M threshold value, then controller 123 does nothing and continues to explain x-axis signal, y-axis signal and z-axis signal (step 708) from magnetometer 132.If magnetic field M rises to and is higher than minimum M threshold value, then controller 123 starts timer (step 712).Controller 123 continues to run timer (step 714), monitors magnetic field M to check whether real-time magnetic field M is between minimum M threshold value and maximum M threshold value simultaneously (step 716).If magnetic field M rests between minimum M threshold value and maximum M threshold value, then controller 123 continues to run timer (step 714).If magnetic field M falls outside minimum and maximum M threshold value, then controller 123 deactivates timer (step 718).Then, controller 123 checks whether the time that passes between the start time of timer in step 712 and the end time of timer in step 718 is between minimum time span and maximum time span (step 720). If the elapsed time is not between the minimum time span and the maximum time span, the controller 123 ignores the event (step 722) and continues to monitor the magnetic field M (step 708). If the elapsed time is between the minimum time span and the maximum time span, the controller 123 records the event as a dart passing through feature 70 and increments the counter (step 724). In step 724, the controller 123 can also determine the current downhole position of the dart 200 based on the number in the counter and the known position of the feature 70 on the well map.

[0164] The controller 123 then proceeds to step 726, where the controller 123 checks whether the updated counter number or the determined current position of the dart 200 has reached the pre-programmed target position. If the controller determines that the dart has reached the target position, the controller 123 sends a signal to the actuation mechanism 124 to activate the dart 200 (step 728). If the controller determines that the dart 200 has not yet reached the target position, the controller 123 continues to monitor the magnetic field M (step 708).

[0165] Distance calculation based on acceleration

[0166] In some embodiments, the real-time downhole position of the dart can be determined by analyzing the dart's acceleration data. Referring to FIG. 2 , according to one embodiment, the dart 10 , 100 , 200 can include an accelerometer 134 , which can be a three-axis accelerometer. The accelerometer 134 measures the acceleration of the dart as it passes through the channel 30 . Using the collected acceleration data, the distance traveled by the dart 10 , 100 , 200 can be calculated by quadratically integrating the acceleration of the dart at any given time. For example, generally speaking, the distance s at any given time t can be calculated using the following equation:

[0167] s(t)=s0+∫ tν(t)dt=s0+ν0t+∫ t ∫ τ a(τ)dτdt (Equation 3)

[0168] where v is the velocity of the dart, a is the acceleration of the dart, and τ is time.

[0169] Equation 3 can be used when the dart travels in a straight line and the acceleration a of the dart is measured along the straight path. However, the dart typically does not travel in a straight line through the channel 30, so that the measured acceleration is affected by the earth's gravity (1g). If the influence of gravity is not taken into account, the distance s calculated using Formula 3 based on the detected acceleration may be inaccurate. In some embodiments, the dart 10, 100, 200 includes a gyroscope 136 to help compensate for the influence of gravity by measuring the rotation of the dart. Before deploying the dart 10, 100, 200, when the dart is stationary, the reading of the gyroscope 136 is obtained and the initial gravity vector (e.g., 1g) is determined based on the gyroscope reading. After deployment, the gyroscope 136 continuously measures the rotation of the dart 10, 100, 200 as the dart travels downhole, and uses the initial gravity vector to adjust the rotation measurement value. The real-time acceleration measured by the accelerometer 134 is then corrected with the adjusted rotation measurement to account for gravity to provide a corrected acceleration. The corrected acceleration is used instead of the detected acceleration to calculate the distance traveled by the dart.

[0170] For example, to simplify calculations, the initial gravity vector is set to a constant to adjust the rotation measurements made by the gyroscope 136 as the dart moves. Furthermore, when the dart 10, 100, 200 moves in the direction F, the z-axis component of the acceleration measured by the accelerometer 134 (where the z-axis is parallel to the F direction) is compensated by the adjusted rotation measurements to generate a corrected acceleration a. C Using the corrected acceleration a C , the velocity v of the dart at a given time t can be calculated as follows:

[0171] ν(t)=ν0+∫ t a c (t)dt (Equation 4)

[0172] where a C (t) is the corrected acceleration at time t, and v o is the initial velocity of the dart. In some embodiments, v o is zero. Then based on the velocity v calculated using Formula 4, the distance s traveled by the dart at time t can be calculated as follows:

[0173] s(t)=s0+∫ τ ν(τ)dτ (Equation 5)

[0174] Furthermore, the corrected acceleration a is used C The error in the distance s calculated using Equations 4 and 5 may increase as the magnitude of the acceleration increases. Therefore, in some embodiments, the changes in the magnetic field and / or magnetic flux detected by the magnetometer 132 as described above may be used for corroboration purposes to correct any errors in the distance s calculated using data from the accelerometer 134 and the gyroscope 136 in order to more accurately determine the real-time downhole position of the dart.

[0175] In some embodiments, the real-time downhole position of the dart, determined at least in part by the controller 123 based on the acceleration and rotation data, is compared to the target position. When the controller 123 determines that the dart 10, 100, 200 has reached the target position, the controller 123 sends a signal to the actuation mechanism 124 to activate the dart, for example, to perform downhole operations.

[0176] Dart actuation mechanism

[0177] Figure 5A One embodiment of a dart 300 is shown having an actuation mechanism configured to transition the dart to an activated position when a controller of the dart determines that the dart has reached a target position. Figure 5A and Figure 5B In FIG, the dart 300 is shown in an inactive position. For simplicity, Figure 5A Some components of the dart 300, such as the control module and magnets, are not shown. The dart 300 includes an actuation mechanism 224 having a first housing 250 and a second housing 254. The first housing defines a hydrostatic chamber 260 and a piston 252, and the second housing defines an atmospheric chamber 264. The hydrostatic chamber 260 contains an incompressible fluid, while the atmospheric chamber 264 contains a compressible fluid (e.g., air) at approximately atmospheric pressure. In other embodiments, the atmospheric chamber is a vacuum.

[0178] One end of the piston 252 extends axially into the hydrostatic chamber 260, and the interface between the outer surface of the piston 252 and the inner surface of the chamber 260 is fluidically sealed, for example, by an O-ring 262. The piston 252 is configured to be axially slidable relative to the first housing 250 in a telescopic manner; however, when the hydrostatic chamber 260 is filled with an incompressible fluid, such axial movement of the piston 252 is restricted. The piston 252 has an internal flow path 256, and as shown in FIG. Figure 5B As more clearly shown in FIG. 1 , when the dart 300 is in the inactive position, one end of the flow path 256 is fluidly sealed by a valve 258. The valve 258 controls the fluid communication between these chambers 260, 264. In the embodiment shown, the valve 258 is a burst disk. The burst disk 258 is in good condition (e.g., Figure 5B ) prevents fluid communication between chambers 260, 264 by preventing fluid from flowing through flow path 256. Figure 5A In the exemplary embodiment shown, the actuation mechanism 224 includes a piercing member 270 operable to rupture the burst barrier 258. When the dart 300 is not activated, as shown in FIG. Figure 5B As shown, piercing member 270 is adjacent to, but not in contact with, burst disk 258 .

[0179] exist Figure 5A In the illustrated embodiment, the dart 300 includes an engagement mechanism 266 positioned at the engagement section 226 of the dart. The engagement mechanism 266 is actuatable from an inactive position to an active position. The actuating mechanism 224 is configured to selectively actuate the engagement mechanism 266 to convert the mechanism 266 to the active position, thereby placing the dart in the active position. In the illustrated embodiment, the engagement mechanism 266 includes an expandable slider 266 supported on an outer surface of the piston 252. The first housing 250 has a frustoconical end 268 adjacent to the slider 266 for matingly engaging the slider. The frustoconical end 268 is also referred to herein as the cone 268. When the slider 266 is in the position shown, the slider 266 is in the active position. Figure 5A In the inactive (or "home") position shown, the slider 266 is retracted and not engaged with the cone 268. When activated, the slider 266 expands radially outward by engaging the cone 268, as described in more detail below.

[0180] Upon receiving an activation signal from the dart controller, the actuation mechanism 224 operates to actuate the engagement mechanism 266 by opening the valve 258. In some embodiments, the actuation mechanism 224 includes an exploding foil initiator (EFI) that is activated upon receiving the activation signal and a propellant that is activated by the EFI to drive the piercing member 270 into the burst disk 258 to rupture it. As will be appreciated by those skilled in the art, other ways of driving the piercing member 270 to rupture the burst disk 258 are possible.

[0181] Figure 6A The dart 300 is shown in its activated position according to one embodiment. Figure 6A and Figure 6BAs shown, burst disk 258 is ruptured by piercing member 270. Once burst disk 258 is ruptured, flow path 256 is unobstructed. The unobstructed flow path 256 establishes fluid communication between hydrostatic chamber 260 and atmospheric chamber 264, whereby incompressible fluid from chamber 260 can flow to chamber 264 via flow path 256 and port 272 to equalize the pressures in chambers 260 and 264. This equalization of pressure causes piston 252 to extend further axially into hydrostatic chamber 260, which in turn causes first housing 250, along with cone 268, to deflect axially toward slider 266, causing the cone to slide (further) beneath the slider, thereby forcing the slider to expand radially outward, placing engagement mechanism 266 in an activated (or "expanded") position. In some embodiments, once engagement mechanism 266 is activated, dart 300 is placed in the activated position.

[0182] In some embodiments, the engagement mechanism 266 is configured so that its effective outer diameter in the inactive (or initial) position is less than the inner diameter of the tubing string and the features in the tubing string. In the activated (or expanded) position, the effective outer diameter of the engagement mechanism 266 is greater than the inner diameter of the features (e.g., the narrowing 50) in the tubing string 24. When activated, the engagement mechanism 266 can engage the feature so that the activated dart 300 can be captured by the feature. In the case where the feature is a downhole tool and the dart 300 is captured by the tool, the dart can act as a plug, and the tool can be actuated by the dart by applying fluid pressure to the tubing string from the surface E so that the pressure above the dart 300 increases enough to move a component of the tool (e.g., deflect the sleeve).

[0183] Although in some embodiments, the activated dart 300 is configured to operate as a plug in the tubing string 24, which may be useful for wellbore treatment, the continued presence of the dart downhole may adversely affect the return flow of fluid (e.g., production fluid) through the tubing string 24. Therefore, in some embodiments, the dart 300 can be removed as the return flow is directed toward the surface E. In alternative embodiments, the dart 300 can include a valve (e.g., a one-way valve) that can be opened in response to the return flow, or a bypass port that can be opened at some time after the dart's plug function is completed. In other embodiments, at least a portion of the dart 300 is formed of a material that can dissolve under downhole conditions. For example, a portion of the dart (e.g., the body 120) can be formed of a material that is soluble in hydrocarbons, such that the portion dissolves when exposed to the return flow of the production fluid. In another example, the soluble portion of the dart may fail above a certain temperature or after prolonged contact with water. In this embodiment, for example, after a certain residence time during hydrocarbon production, most of the darts are dissolved leaving only small components, such as control modules, magnets, etc., which can float to the surface with the backflowing production fluid. Alternatively, the activated darts 300 can be drilled out.

[0184] Figures 7-10 illustrate an alternative engagement mechanism 366. Instead of a slider, engagement mechanism 366 includes a seal 310 (e.g., an elastomeric seal), a first support ring 330, and a second support ring 350, all of which are supported on the outer surface of cone 268 or, alternatively, on the outer surface of piston 252 (as shown in Figure 5). For simplicity, engagement mechanism 366 is shown in Figures 7-10 without other components of dart 300. Engagement mechanism 366 has an initial position, shown in Figures 7 (with cone 268) and 8 (without cone 268), and an expanded position, shown in Figures 9 (with cone 268) and 10 (without cone 268). In some embodiments, engagement mechanism 366 is in the initial position when dart 300 is in the inactive position and in the expanded position when the dart is in the active position.

[0185] In the illustrated embodiment, the seal 310 is an annular seal having an outer surface 312 and an inner surface 314, the inner surface defining a central opening for receiving a portion of the cone 268 therethrough. In some embodiments, the inner surface of the seal 310 is frustoconical for matingly abutting the outer surface of the cone 268. The seal 310 is radially expandable to allow the seal 310 to be slidably moved from a first axial position on the cone 268 to a second axial position on the cone 268, wherein the outer diameter of the second axial position is greater than the outer diameter of the first axial position. In some embodiments, the seal 310 is formed of an elastomeric material that can expand to accommodate the larger outer diameter of the second axial position while maintaining abutting engagement with the outer surface of the cone 268 (e.g., Figure 9A In the illustrated embodiment, the first support ring 330 is disposed between the seal 310 and the second support ring 350 .

[0186] With further reference to Figures 11 and 12, each support ring 330, 350 has a respective outer surface 332, 352 and a respective inner surface 334, 354 defining a central opening for receiving a portion of cone 268 therethrough. In some embodiments, the inner surface 334, 354 of each ring 330, 350 can be frusto-conical for matingly abutting the outer surface of cone 268. The first and second support rings 330, 350 are radially expandable to allow the rings to slidably move from a first axial position on cone 268 to a second axial position having a larger outer diameter than the first axial position. To allow for radial expansion to accommodate the larger outer diameter of the second axial position, the first and second support rings 330, 350 each have a respective gap 336, 356 that widens when a radially outward force is applied to the inner surfaces 334, 354, respectively, thereby increasing the size of the central opening and the effective outer diameter of each ring 330, 350. When the gaps 336, 356 widen (e.g. Figure 11B and Figure 12B ), the inner surfaces 334, 354 may be maintained in abutting engagement with the outer surface of the cone 268 (e.g. Figure 9A In some embodiments, the first support ring 330 and the second support ring 350 are positioned on the cone 268 such that the gaps 336, 356 are azimuthally offset from each other. In one embodiment, for example Figure 8C and Figure 10C As shown, the gaps 336, 356 are azimuthally spaced approximately 180° apart.

[0187] In some embodiments, the axial length of first support ring 330 and / or second support ring 350 is substantially uniform around the circumference of the ring. In some embodiments, the axial length of first support ring 330 can be less than, approximately equal to, or greater than the axial length of second support ring 350.

[0188] In the illustrated embodiment, the axial length of the first support ring 330 varies around its circumference. In the illustrated embodiment, as best shown in Figures 8, 10, and 11, the first support ring 330 has a short side 338 and a long side 340, with the long side 340 having a longer axial length than the short side 338. A first end of the first support ring 330 has a first face 342 extending between the short side 338 and the long side 340; and a second end of the first support ring 330 has an elliptical face 344 extending between the short side 338 and the long side 340. In some embodiments, the axial length of the first ring 330 around its circumference gradually increases from the short side 338 to the long side 340 and correspondingly decreases from the long side 340 to the short side 338, defining a first face 342 on one end and an elliptical face 344 on the other end. In an exemplary embodiment, the plane of the elliptical face 344 is tilted at an angle of approximately 1° to approximately 30° relative to the plane of the first face 342. In some embodiments, the elliptical face 344 is tilted approximately 5° relative to the plane of the first face 342. In some embodiments, the gap 336 of the first ring 330 is positioned at or near the short side 338 to minimize the axial length of the gap 336. Although the first face 342 is shown as being generally circular in the illustrated embodiment, the shape of the first face 342 may be non-circular in other embodiments.

[0189] In the illustrated embodiment, the axial length of second support ring 350 varies around its circumference. In the illustrated embodiment, as best shown in Figures 8, 10, and 12, second support ring 350 has a short side 358 and a long side 360, with long side 360 having a longer axial length than short side 358. A first end of second support ring 350 has a second face 362 extending between short side 358 and long side 360; and a second end of second support ring 350 has an elliptical face 364 extending between short side 358 and long side 360. In some embodiments, the axial length of second ring 350 around its circumference gradually increases from short side 358 to long side 360 and correspondingly decreases from long side 360 to short side 358, defining second face 362 on one end and elliptical face 364 on the other end. In an exemplary embodiment, the plane of elliptical face 364 is tilted at an angle of approximately 1° to approximately 30° relative to the plane of second face 362. In some embodiments, the elliptical face 364 is tilted approximately 5° relative to the second face 362. In some embodiments, the gap 356 of the second ring 350 is positioned at or near the short side 358 to minimize the axial length of the gap 356. Although the second face 362 is shown as being generally circular in the illustrated embodiment, the shape of the second face 362 may be non-circular in other embodiments.

[0190] In some embodiments, the axial length of the long side 360 of the second ring 350 is greater than, approximately equal to, or less than the axial length of the long side 340 of the first ring 330. In some embodiments, the axial length of the short side 358 of the second ring 350 is greater than, approximately equal to, or less than the axial length of the short side 338 of the first ring 330. In some embodiments, the axial length of the short side 358 of the second ring 350 can be less than, approximately equal to, or greater than the axial length of the long side 340 of the first ring 330. In an exemplary embodiment, the axial length of the short side 338 of the first support ring 330 is approximately 10% to approximately 30% of the axial length of the long side 340; approximately 18% to approximately 38% of the axial length of the short side 358 of the second support ring 350; and approximately 3% to approximately 23% of the axial length of the long side 360 of the second support ring 350. In an exemplary embodiment, the axial length of the short side 338 of the first support ring 330 is approximately 6% to approximately 26% of the axial length of the seal 310. In some embodiments, the axial length of the long side 360 of the second support ring 350 is between about 109% and about 129% of the axial length of the seal 310. In other embodiments, the axial length of the short side 358 of the second support ring 350 is between about 10% and about 30% of the axial length of the long side 360; between about 18% and about 38% of the axial length of the short side 338 of the first support ring 330; and between about 3% and about 23% of the axial length of the long side 340 of the first support ring 330. As will be appreciated by those skilled in the art, other configurations are possible.

[0191] 7-10 , in some embodiments, the elliptical surfaces 344, 364 are configured to cooperatively abut against each other when the first and second rings are engaged with each other to define an elliptical interface 380 between the first and second rings. In some embodiments, the first and second rings 330, 350 are arranged in the engagement mechanism 366 such that the short side 338 of the first ring 330 is positioned adjacent to the long side 360 of the second ring 350; and the short side 358 of the second ring 350 is positioned adjacent to the long side 340 of the first ring 330. In some embodiments, as Figure 8C and Figure 10C As illustrated, gaps 336, 356 are positioned at short sides 338, 358 of first support ring 330 and second support ring 350, respectively, such that gaps 336, 356 are azimuthally aligned with long sides 360, 340, respectively, and are azimuthally offset by approximately 180°.

[0192] When the dart 300 is in the inactive position, the engagement mechanism is in the initial position, as shown in FIG7 and FIG8 , wherein the seal 310, the first support ring 330 and the second support ring 350 are supported on the piston 252 ( Figure 5A), or supported on the first axial position of the cone 268. In some embodiments, the second ring 350 is positioned to align with the shoulder 274 ( Figure 5A ) is adjacent to (and can abut) the second face 362 such that the second face 362 faces the shoulder 274. The shoulder 274 limits axial movement of the engagement mechanism 366 in a direction toward the leading end 140. In some embodiments, at least a portion of the inner surface 314 of the seal 310, the inner surface 334 of the first ring 330, and / or the inner surface 354 of the second ring 350 can each abut the outer surface of the cone 268. In some embodiments, the seal 310 and the rings 330, 350 are concentrically positioned relative to each other on the cone. In an initial position, the effective outer diameter of the engagement mechanism 366 is less than the inner diameter of a feature (i.e., a constriction) in the tubing string, thereby allowing the dart 300 to travel down the tubing string undisturbed. In some embodiments, in the initial position, the outer surface 312 of the seal 310 has an outer diameter Di, and the outer surface 332 of the first ring 330 and the outer surface 352 of the second ring 350 each have an effective outer diameter Dir. The outer diameters Dir of the first ring 330 and the second ring 350 can be the same in some embodiments and different in other embodiments. In some embodiments, the outer diameter Di of the seal 310 is slightly larger than the outer diameters Dir of the first ring 330 and the second ring 350. In some embodiments, the outer diameters Di and Dir are smaller than the inner diameter of the feature in the tubing string. In the inactive position, the gaps 336 and 356 each have an initial width.

[0193] To convert the engagement mechanism 366 to the expanded position, the cone 268 is pushed axially toward the engagement mechanism, for example by operating the actuation mechanism 224 as described above with respect to the dart 300. When the second ring 350 abuts against the shoulder 274 ( Figure 5A ), axial movement of cone 268 relative to engagement mechanism 366 slidably displaces engagement mechanism 366 from the cone's first axial position to the cone's second axial position, wherein the second axial position has an outer diameter greater than the outer diameter of the first axial position. As engagement mechanism 366 engages the larger outer diameter of cone 268, the increase in the cone's outer diameter from the first axial position to the second axial position applies forces to inner surface 314 of seal 310, inner surface 334 of first ring 330, and inner surface 354 of second ring 350, respectively. Due to the frusto-conical outer surface of cone 268 and the form-fitting inner surfaces 314, 334, 354, the forces applied to seal 310 and rings 330, 350 can be a combination of radially outward and axially compressive forces. In some embodiments, the applied forces cause seal 310 to radially expand, and gaps 336 of first ring 330 and gaps 356 of second ring 350 widen to accommodate the larger diameter portion of the cone, thereby placing engagement mechanism 366 in the expanded position.

[0194] 9 and 10 , the seal 310, the first support ring 330, and the second support ring 350 are supported in a second (larger outer diameter) axial position on the cone 268. In some embodiments, at least a portion of the inner surface 314 of the seal 310, the inner surface 334 of the first ring 330, and / or the inner surface 354 of the second ring 350, respectively, can abut against the outer surface of the cone 268. In the expanded position, the effective outer diameter of the engagement mechanism 366 is larger than the inner diameter of a feature (i.e., a constriction) in the tubular string, thereby allowing the dart 300 to be captured by the next feature in the dart's path.

[0195] In some embodiments, in the expanded position, the outer diameter De of the outer surface 312 of the seal 310 is larger than the outer diameter Di in the initial position. In the expanded position, the gaps 336, 356 of the rings 330, 350 are widened, such as Figure 10C 、 Figure 11B and Figure 12B As best shown in FIG. 1 , the width of each gap 336, 356 is made larger than their respective initial widths (e.g., Figure 8C 、 Figure 11A and Figure 12A ). Widening the gaps 336, 356 can increase the effective outer diameter of the first ring 330 and the second ring 350. The effective outer diameter of the first ring 330 and the second ring 350 in the expanded state is represented by "Der". The outer diameter Der of the rings 330, 350 is greater than the outer diameter Dir in the initial position. The outer diameters Der of the first ring 330 and the second ring 350 can be the same in some embodiments and different in other embodiments. In some embodiments, the outer diameter De of the seal 310 is slightly larger than the outer diameter Der of the first ring 330 and the second ring 350. In the expanded position, one or both of the outer diameters De, Der are greater than the inner diameter of at least one feature in the tubing string.

[0196] In some embodiments, as Figure 10A As best shown in FIG, the offset toward the larger outer diameter portion of the cone 268 forces the seal 310 against the first face 342 of the first ring 330, and / or forces the elliptical face 344 of the first ring 330 against the elliptical face 364 of the second ring 350. The engagement of the elliptical faces 344, 364 forms an elliptical interface 380 between the rings 330, 350. When under axial compression, the elliptical interface 380 can cause the rings 330, 350 to radially deflect relative to each other, which can help maximize the effective outer diameter Der across the long side 340 to the long side 360 of the rings. The radial offset of the rings 330, 350 can cause the rings to become eccentrically positioned relative to each other. Figure 10CAs best shown in FIG, the rings 330, 350 together provide structural support for the seal 310, particularly when in the expanded position. In some embodiments, the seal 310 is supported around a majority of its circumference by the combined axial length of material of the first and second rings 330, 350. The portion of the seal 310 that is not supported by the combination of the first and second rings is the area of the seal that is azimuthally aligned with the gaps 336, 356. The area of the seal 310 that is aligned with the gap 356 of the second ring 350 is supported by the first ring 330 (e.g., the long side 340 of the first ring 330).

[0197] 10 , where gaps 336, 356 are located at or near short sides 338, 358 of rings 330, 350, respectively, and where rings 330, 350 are arranged so that each short side 338, 358 is positioned adjacent to a long side 360, 340 of the other ring, the longest axial section of each ring 330, 350 provides structural support to the other ring at the widened gaps 356, 336. When the rings are so arranged, the areas of seal 310 azimuthally aligned with gaps 336, 356 are also aligned with the longest axial sections of rings 330, 350 (i.e., long sides 360, 340, respectively).

[0198] In some embodiments, where the length of short side 338 is less than the length of short side 358, widened gap 336 is axially shorter than widened gap 356, even though the circumferential widths of gaps 336 and 356 may be substantially the same. Thus, gap 336 has a smaller volume than gap 356. By configuring and arranging rings 330 and 350 as described above and placing seal 310 on first ring 330, the amount of space into which expanded seal 310 can be squeezed can be minimized without compromising the overall support provided to the seal by rings 330 and 350. Minimizing the amount of squeezed-out expanded seal 310 can help reduce structural damage to the seal that could affect its sealing function.

[0199] In some embodiments, the first support ring 330 and / or the second support ring 350 can be made of one or more of the following: a metal, such as aluminum; and an alloy, such as brass, steel, or a magnesium alloy. In some embodiments, the first support ring 330 and / or the second support ring 350 are at least partially made of a dissolvable material, such as a dissolvable magnesium alloy.

[0200] Although the coupling mechanisms 266, 366 have been described above with respect to untethered darts, it will be appreciated that the coupling mechanisms disclosed herein may also be used in other downhole tools, including tethered devices delivered into the tubing string via wireline, continuous tubing, or other methods known to those skilled in the art.

[0201] In other embodiments, the dart's engagement mechanism may be a retractable stopper, an elastomeric bladder, a packer, or the like. For example, instead of a slider or an annular seal, the dart may include a retractable stopper that projects radially outward from the body 120 but collapses when the dart is inactive to allow the dart to squeeze through a non-target constriction. When the dart is activated, the back support (e.g., Figure 5A 250 ) moves against the stopper so that the stopper can no longer collapse. The effective outer diameter of the stopper when not collapsed is greater than the inner diameter of the constriction. Thus, when the dart is inactive, the stopper can collapse to allow the dart to pass through the constriction and can re-extend radially outward after passing through the constriction. When the dart is activated, the stopper does not collapse and the dart can therefore engage the constriction of the target tool because the dart cannot pass through it. In this way, fluid pressure can be applied to the dart to actuate the target tool, as described above. In some embodiments, the protrusion 128 of the dart (see Figure 2B ) is used as a retractable stop. In other embodiments, the retractable stop is separated from the protrusion 128.

[0202] In another exemplary embodiment, the deployment element may be an elastic bladder with an outer diameter greater than the inner diameter of the constriction. In one embodiment, the outer diameter of the bladder is larger than the rest of the dart body 120, so that only the bladder must squeeze through each constriction as the dart passes through it. The bladder can elastically collapse inward to allow the dart to pass through the constriction and can restore its shape after passing through the constriction. The bladder can be formed from various elastic materials known to those skilled in the art for use in downhole conditions. When the dart is activated, the bladder can no longer collapse. For example, this can be achieved by the bladder defining an atmospheric chamber for the dart, and by incompressible fluid entering the bladder from the hydrostatic chamber after the actuation mechanism is activated, rendering the bladder non-collapsible. When the bladder is deployed (i.e., non-collapsed), the dart can then engage the constriction of its downhole target tool because the deployed bladder can no longer squeeze through the constriction. In this way, fluid pressure can be applied to the dart to actuate the target tool, as described above. In some embodiments, the bladder serves as the dart's protrusion 128 (see FIG. 2 ), and a rare earth magnet 130 is embedded in the bladder. In other embodiments, the bladder is separate from the protrusion 128 .

[0203] It should be noted that the aforementioned devices, systems, and methods do not require any electronics or power within the tubing string or wellbore to operate. Thus, the tubing string can be entered into the wellbore before the device is deployed, as there are no issues with battery charging, component damage, or the like. Furthermore, the tubing string itself requires little special preparation prior to installation, as all features therein (i.e., tools, sleeves, etc.) can be substantially identical, interchangeable, and / or installed in any particular order within the string. Furthermore, the number of features can be readily determined even after the string is installed downhole, although it may be known prior to running.

[0204] According to a broad aspect of the present disclosure, a method is provided that includes: measuring an initial rotation of a dart while the dart is at rest; measuring the acceleration and rotation of the dart as it travels through a downhole passage defined by a tubing string; adjusting the rotation using the initial rotation to provide a corrected rotation; adjusting the acceleration using the corrected rotation to provide a corrected acceleration; and integrating the corrected acceleration twice to obtain a distance value.

[0205] In some embodiments, the method includes comparing the distance value to a target location and activating the dart if the distance value and the target location are the same.

[0206] According to another broad aspect of the present disclosure, a method is provided that includes detecting changes in a magnetic field or flux as a dart travels through a downhole passage defined by a tubing string; and determining a position of the dart relative to a target location based on the changes in the magnetic field or flux.

[0207] In some embodiments, the change in magnetic field or flux is caused by movement of a magnet in the dart.

[0208] In some embodiments, the change in magnetic field or flux is caused by the dart approaching or passing through a feature in the string.

[0209] In some embodiments, the change in magnetic field or flux has an x-axis component, a y-axis component, and a z-axis component.

[0210] In some embodiments, movement of the magnet is caused by a constriction in the tubing string.

[0211] In some embodiments, the method includes activating the dart upon determining that the position of the dart is the same as the target position.

[0212] In some embodiments, the method includes engaging the activated dart with a downhole tool.

[0213] In some embodiments, activating the dart includes deploying a deployment element of the dart.

[0214] In some embodiments, the method includes forming a fluid seal within the passageway by engaging the deployed expansion element with a constriction in the downhole tubular string downwardly from the target location.

[0215] According to another broad aspect of the present disclosure, there is provided a dart comprising: a body; a control module in the body; an accelerometer in the body, the accelerometer in communication with the control module and configured to measure an acceleration of the dart; and a gyroscope in the body, the gyroscope in communication with the control module and configured to measure a rotation of the dart; wherein the control module is configured to determine a position of the dart relative to a target position based on the acceleration and rotation of the dart.

[0216] According to another broad aspect of the present disclosure, there is provided a dart comprising: a body; a control module within the body; and a magnetometer within the body, the magnetometer in communication with the control module and configured to measure a magnetic field or magnetic flux; wherein the control module is configured to identify a change in the magnetic field or magnetic flux based on the measured magnetic field or magnetic flux, and to determine a position of the dart relative to a target location based on the change.

[0217] In some embodiments, the magnetic field or flux has an x-axis component, a y-axis component, and a z-axis component.

[0218] In some embodiments, the dart comprises a rare earth magnet in the body.

[0219] In some embodiments, the dart comprises one or more retractable protrusions extending radially outward from the body; and a rare earth magnet embedded in each of the one or more retractable protrusions.

[0220] In some embodiments, the dart includes an actuation mechanism, and the control module is configured to activate the actuation mechanism when the position is the same as the target position.

[0221] In some embodiments, the actuation mechanism includes a deployment element that is deployable upon activation of the actuation mechanism.

[0222] In some embodiments, the deployment element is configured to expand radially when deployed.

[0223] In some embodiments, the deployment element is collapsible when not deployed and non-collapsible when deployed.

[0224] Explanation of terms

[0225] Unless the context clearly requires otherwise, throughout the description, the words "include", "comprises", etc. should be understood as inclusive rather than exclusive or exhaustive; that is, in the sense of "including but not limited to"; "connected", "coupled" or any variation thereof means any direct or indirect connection or connection between two or more elements; the connection or connection between these elements may be physical, logical or a combination thereof; "herein", "above", "below" and words of similar meaning when used to describe this specification refer to the specification as a whole and not to any specific part of this specification; "or" when referring to a list with two or more items covers all the following interpretations of the word: any item in the list, all items in the list and any combination of items in the list; the singular forms "a", "an" and "the" also include the meaning of any appropriate plural form.

[0226] Where a component is mentioned above, unless otherwise specified, reference to that component should be interpreted as including any component that is an equivalent (i.e., functionally equivalent) to that component and that performs the function of the described component, including components that are structurally different from the disclosed structure that performs that function in the exemplary embodiments shown.

[0227] The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown herein, but should be given the full scope consistent with the claims. All structural and functional equivalents of the elements of the various embodiments described throughout the text (known or later known to those of ordinary skill in the art) are intended to be covered by the elements of the claims. In addition, nothing disclosed herein is intended to be dedicated to the public, regardless of whether such disclosure is explicitly stated in the claims. Therefore, it is intended that the following appended claims and claims introduced thereafter be interpreted as including all such modifications, arrangements, additions, omissions, and sub-combinations that can be reasonably inferred. The scope of the claims should not be limited to the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the overall description.

Claims

1. A downhole tool for deployment within a passage of a tubular string disposed within a wellbore, the passage being defined by a passage-defining surface of the tubular string, comprising: cone; Ring seals; A first support ring, the first support ring comprising: a first face at the first end; a first elliptical surface at the second end; a first free end; a second free end; and a first gap extending from the first face to the first elliptical face and having a width extending from the first free end to the second free end; and A second support ring, the second support ring comprising: a second face at the first end; a second elliptical surface at the second end; a first free end; a second free end; and a second gap extending from the second face to the second elliptical face and having a width extending from the first free end to the second free end; and in: The first support ring is disposed between the annular seal and the second support ring; The first support ring and the second support ring are arranged such that the second elliptical surface is adjacent to the first elliptical surface and is configured to matingly abut the first elliptical surface, and The downhole tool is configurable in an inactive, retracted configuration and an active, expanded configuration. In an activated, expanded configuration, the downhole tool is configured to cooperate with the tubing string to establish a sealing interface within the tubing string, wherein the sealing interface is established by sealing engagement between an annular seal and a conduit-defining surface, wherein at least the cone and the first and second support rings cooperate to support the annular seal and establish the sealing interface, And, when activated and expanded: The first gap defines a first expanded configuration gap that is wider relative to the first gap in the inactive, retracted configuration; The second gap defines a second expanded configuration gap that is wider relative to the second gap in the inactive, retracted configuration; The first expanded configuration gap is offset relative to the second expanded configuration gap such that the long side of the second support ring is located adjacent to the first expanded configuration gap; The second support ring includes a short side, wherein the short side is arranged closer to one of the first free end belonging to the second support ring and the second free end belonging to the second support ring relative to the long side of the second support ring; An axial length of the long side measured along the longitudinal axis of the downhole tool is greater than an axial length of the short side measured along the longitudinal axis of the downhole tool.

2. The downhole tool of claim 1 , wherein: The first support ring comprises: a first short side having a first short side length; and a first long side having a first long side length that is greater than the first short side length, and the first face and the first elliptical face each extending from the first short side to the first long side; and The second surface and the second elliptical surface each extend from a short side of the second support ring to a long side of the second support ring.

3. The downhole tool of claim 2, wherein: The length of the long side of the second supporting ring is equal to or greater than the length of the first long side.

4. The downhole tool of claim 2 or 3, wherein there is one or both of the following: the first gap is located at or near the first short side; and the second gap is located at or near the second short side.

5. The downhole tool of claim 4, wherein: The second short side is located adjacent to the first long side; and the second long side is located adjacent to the first short side.

6. The downhole tool of claim 5, wherein: The first gap is offset from the second gap in azimuth.

7. The downhole tool of claim 1, wherein: The arrangement of the second support ring's long side adjacent the first expanded configuration gap of the first support ring in the activated, expanded configuration has the effect that the long side of the second support ring minimizes extrusion of the annular seal through the first expanded configuration gap.

8. The downhole tool of claim 2, wherein: One or both of the first face and the second face are circular.

9. The downhole tool of claim 2, wherein: The first elliptical surface is inclined relative to the first surface by an angle in a range of about 1° to about 30°.

10. The downhole tool of claim 1 , wherein: The axial length of the short side of the second support ring is in a certain ratio to the axial length of the long side of the second support ring. The ratio is within a certain range, and the range is 10% to 30%.

11. The downhole tool of claim 1 , wherein: In the activated, expanded configuration, at least a portion of the first support ring is radially offset from the second support ring.

12. The downhole tool of claim 1, wherein: The first support ring, the second support ring and the annular seal are supported on the outer surface of the cone.

13. The downhole tool of claim 12, wherein: In this inactive, retracted configuration: The annular seal and the first and second support rings are in a first axial position of the cone; as well as Transitioning the downhole tool from an inactive, retracted configuration to an active, expanded configuration results in: The annular seal and the first support ring and the second support ring are in a second axial position of the cone; and For the first support ring, the conversion includes: Relative displacement between the first free end and the second free end causes the first gap to widen into a first expanded configuration gap; and For the second support ring, the conversion includes: The relative displacement between the first free end and the second free end causes the second gap to widen into a second expanded configuration gap.

14. The downhole tool of claim 13, wherein: In the activated, expanded configuration, the first support ring and the second support ring are in a second axial position of the cone; wherein the outer diameter of the second axial position is greater than the outer diameter of the first axial position, such that the transition from the inactive, retracted configuration to the active, expanded configuration comprises: radial expansion of the annular seal; radial expansion of the first support ring; and Radial expansion of the second support ring.

15. The downhole tool of claim 2, wherein: The first short side of the first support ring has an axial length of about 6% to about 26% of the axial length of the annular seal.

16. The downhole tool of claim 2, wherein: The axial length of the long side of the second support ring is about 109% to about 129% of the axial length of the annular seal.

17. The downhole tool of claim 1, wherein: The first and second support rings each have a respective frustoconical inner surface for matingly abutting the outer surface of the cone.

18. The downhole tool of claim 1, wherein: One or both of the first support ring and the second support ring include a dissolvable material.

19. The downhole tool of claim 1, wherein: One or both of the first support ring and the second support ring include one or more of the following: aluminum, brass, steel, and a magnesium alloy.

20. The downhole tool of claim 14, wherein: The cone defines a frustoconical surface; at least the cone and the first and second support rings are cooperatively configured such that during transition from the retracted configuration to the expanded configuration, the first and second support rings are each arranged in contacting engagement with a frustoconical surface of the cone; and The conversion is responsive to relative movement between the first and second support rings and the cone along an axis parallel to the longitudinal axis of the wellbore passage.

21. The downhole tool of claim 1, in: Each of the first support ring and the second support ring is an independent open ring.

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