A measuring device for drilling assemblies

Abstract

The present invention relates to a core drilling assembly, comprising an outer barrel assembly that includes a drill bit at one end and a coupling for connection to the drill rods at the other end thereof, the outer barrel assembly carrying an inner tube assembly that includes at least a core catcher, an inner tube and a head assembly, the core catcher being configured to grip and rotationally fix at least a section of the core sample relative to the core catcher thus also the inner tube and head assembly thereof, also including, - a measuring device being connected to the forward end of the head assembly, being mechanically and electromagnetically shielded from the outer environment, - the measuring device comprising at least a sensor and a data storage configured to measure and store the rotational orientation of the head assembly.

Description

[0001] A MEASURING DEVICE FOR DRILLING ASSEMBLIES

[0002] Technical Field of the Invention

[0003] The present invention relates to an electronic measuring system for a core drilling assembly and corresponding method for acquisition of data gathered by the said electronic measuring system.

[0004] Background of the Invention

[0005] Geological information about the sub surface can be obtained by means of a sampling device such as a core drilling assembly, providing core samples of the drilled formation. The geological information obtained could be related to e.g. composition of the drilled formation or orientation of the core sample as it was when situated in the sub surface e.g. before it was broken from the sub surface, to determine the orientation of e.g. layers or grains in the sub surface, relative to a known reference such as earth gravity or geographic north.

[0006] A core drilling assembly is typically driven by a drill rig at surface, wherein a set of hollow drill rods connected one after another is connecting the core drilling assembly with the drill rig at surface. The core drilling assembly typically comprises an outer barrel assembly having a drill bit at a first end and a coupling for connection to the drill rods at the other end thereof, wherein the inner bore of outer barrel assembly carries an inner tube assembly having an inner tube with a core catcher connected at one end close to the drill bit, and a head assembly at the other end thereof. The inner tube being adopted to collect core samples during drilling, while the core catcher is adopted to grip and rotationally fix at least a section of the core sample relative to the core catcher or any tube or coupling thereof, at the time the core sample is broken from the sub surface. The head assembly allows the inner tube to rotate freely relative to the outer barrel assembly. In one configuration the inner tube assembly is seated permanently inside the outer barrel assembly, thus the whole core drilling assembly need to be brought to surface for removal of the core sample. In another configuration inner tube assembly have a latching device connected to the head assembly, said latching device providing means for locking and releasing the inner tube assembly to / from the outer barrel assembly. A fishing device operated by a wire line can then be used to release the inner tube assembly from the outer barrel assembly and hoist the inner tube assembly thus also the core sample to surface, without bringing the whole core drilling assembly to surface. After the core sample is removed from the inner tube, the inner tube assembly is reseated downhole for continued drilling. The most common method for determining the orientation of a core sample, is to add an extension to the rear end of the inner tube at one end, and the head assembly at the other end thereof, said extension comprising a core orientation device. The core orientation device will typically have on one or more electronic sensors such as accelerometers measuring the orientation of the inner tube thus also the core catcher, as well as the section of the core sample that are rotationally fixed within the core catcher, relative to earth gravity at the time the core sample is broken from the sub surface. After the inner tube assembly is brought to surface, the operator will gain access to the core orientation device by means of an electronic communication interface at the circumference of the said extension to download the stored, measured data. At this point the inner tube assembly is typically placed horizontally on a stand, wherein the operator after downloading the stored data switches to real time reading of the rotational orientation of the core orientation device. The operator then rotates the core orientation device, thus also the core catcher and the core sample fixed within the core catcher, until the core orientation device shows the same rotational orientation as measured down hole. The high side of the core sample is then marked, typically on the fracture surface of the core sample, or if possible, any stick-out thereof. The core sample is then removed from the inner tube assembly and put into a core tray. The core orientation device is then restarted, and the inner tube assembly seated downhole to make the core barrel assembly ready for a new drilling run. The procedure is repeated each time the inner tube assembly are at surface for recovery of the core sample, typically each 3 or 6 meters.

[0007] There is however a major disadvantage with core orientation devices connected directly to the inner tube as an extension, in that the length of the inner tube assembly will be extended, thus the length outer barrel assembly must be extended accordingly. To extend the outer barrel assembly the assembly must be brought to surface, an operation that in most cases will involve many hours or even a 12h shift of rod handling, both for installation and later removal of the core orientation device.

[0008] Core orientation devices integrated into the head assembly are also known in prior art, such as the one described in WO2021 / 087558, wherein a bearing coupling at the rear end of the head assembly have a core orientation device integrated. There are also other prior art describing similar approaches where a tubular coupling in front of the bearing coupling described in EP4055246 / WO2021 / 087558 as well as in the publication cited against EP4055246: "Aziwell: "OriCORE STD uses 3-axis high-accuracy accelerometers to measure orientation, inclination, gravity vector as well additional sensors for temperature and battery status", 1 January 2017 (2017-01-01), pages 1-1, (below referred to as Aziwell Oricore) both having a core orientation device integrated. Both systems have the advantage that they don't extend the total length of the inner tube assembly, thus there is no need to bring the core drilling assembly to surface to adjust the overall length of the core drilling assembly whenever a core orientation is needed as otherwise known from prior art.

[0009] Avoiding the need for adjusting the overall length of the core drilling assembly is un-doubtfully an improvement, yet there are major disadvantages with the described solutions.

[0010] One disadvantage is that the solutions require integration of the core orientation device into one or more system critical couplings needed for normal operation of the inner tube assembly. Thus, there will be limited space and conflict with the intended original functionality of the said coupling / s.

[0011] Another disadvantage is that the approach involves the need for time consuming disassembly of the head assembly to replace the original coupling / s with a modified coupling / s having a core orientation device integrated.

[0012] Yet another disadvantage is that the modified couplings carrying the core orientation device will typically differs between different bore hole sizes or even core sizes within the same bore hole size, thus many modified couplings / core orientation devices is needed to cover only a few common core drilling assemblies in the marked. The latter would also apply for core drilling assemblies from different manufacturers, as many manufacturers have their own unique geometry and threats on the involved coupling, thus one might need specific couplings for every manufacturer, or the approach might not be applicable at all for a given manufacturer due to lack of space for integration of the core orientation device.

[0013] In US11255156 a solution is shown where a sleeve is connected to the threads at the rear end of the inner tube, wherein the sleeve is carrying a valve member having a core orientation device integrated.

[0014] The main disadvantage with this solution is that the inner tube assembly in one configuration becomes longer, since the sleeve is screwed directly onto the treads at the rear end of the inner tube, thus the solution add extra length to the inner tube assembly and as so resembles older prior art where the core barrel assembly must be brought to surface to adjustment of the overall length of the core drilling assembly as well. In another configuration the tubular coupling known from the abovementioned Aziwell Oricore solution may be shortened to compensate for the added length caused by the sleeve, this approach will however involve modifying a system critical coupling, and thus meet similar problems as described for WO2021 / 087558 and the Aziwell Oricore orientation tool.

[0015] Another major disadvantage related to US11255156 is that the solution will have all the disadvantages described for Aziwell Oricore and WO2021 / 087558 when it comes to the need for many sizes and designs to cover only a few common core drilling assemblies on the marked, given that a sleeve is connected directly to the inner tube, said inner tube being both size and manufacturer specific

[0016] Yet another disadvantage is that the solution will add an extra pair of threads that need to be opened to gain access the core sample, wherein the short length of the described sleeve will require special tools.

[0017] Objects of the Invention

[0018] The main object of the present invention is to provide a considerably easier and more convenient and flexible solution for measuring and storing or logging at least the orientation of a core sample collected from the sub surface relative to a known reference such as but not limited to earth gravity, compared to prior art.

[0019] Another object of the present invention is to provide a measuring device capable of measuring and storing / logging the orientation of a core sample, without the need to replace or modify major system critical components of the inner tube assembly.

[0020] Another object of the present invention is to provide a measuring device capable of measuring and logging the orientation of a core sample, that fits any core drilling assembly, regardless of core and hole size as well as manufacturer of the core drilling assembly.

[0021] Yet another object of the present invention is to provide a measuring device compatible with a range of different sensors for downhole measurements, wherein capable of measuring and storing or logging the orientation of a core sample, that does not extend or in any way interfere with the total length of the inner tube assembly or the overall length of the core drilling assembly, thus core orientation can be implemented in any core drilling assembly, without the bringing the core drilling assembly to surface.

[0022] Finally, there is an object of the present innovation to provide a measuring device capable of measuring and logging the orientation of a core sample, that can provide accurate and reliable data representing the orientation for the core sample relative to a known reference.

[0023] The above-mentioned object of the invention is obtained as disclosed in the accompanying claims.

[0024] Summary of the Invention

[0025] The present invention relates to a drilling assembly being adopted to collect core samples from the sub surface, wherein the core drilling assembly is equipped with an electronic measuring device according to the disclosed claims. More specifically the present invention relates to a system and a method for measuring at least the orientation of a core sample, or a section of the core sample, as it was situated before it was broken from the sub surface, relative to a known reference such as but not limited to earth gravity or geographic north. The present invention provides a solution where the relative orientation between downhole and topside measurements may be provided even when the core is completely contained and protected inside the assembly.

[0026] It should be appreciated that present invention describes a measuring device being capable of measuring at least the orientation of the core sample obtained by any core drilling assembly, without the need to replace or modify system critical couplings, and without adding additional length to the inner tube assembly or the core drilling assembly as a whole.

[0027] A core drilling assembly according to the present invention involves an outer barrel assembly having a drill bit at one end and a coupling for connection to the drill rods at the other end thereof. It is to be emphasized that an outer barrel assembly may comprise a range of different couplings between the said drill bit and the coupling for connection to the drill rods, such as one or more reaming shells as well as adaptor and extension couplings, without this being relevant for the scope of the present invention. The inner bore of the outer barrel assembly is typically carrying an inner tube assembly that includes at least a core catcher, an inner tube, and a head assembly, said inner tube having threads at each end wherein the core catcher is connected to the end facing the drill bit the head assembly at the other end thereof. The inner tube stores the core sample during drilling, while the core catcher grip and rotationally fix at least a section of the core sample relative to the core catcher or any tube or coupling thereof, at the time the core sample is broken from the sub surface. As so, the orientation of the core catcher, thus also the inner tube and head assembly at this moment of time, represents the orientation of the core sample as it was situated before it was broken from the sub surface. The head assembly allows the inner tube to rotate freely relative to the outer barrel assembly, and is typically connected to at least a spindle, a bearing coupling and a tubular coupling having threaded ends, wherein one end is connected to the bearing coupling and the other end thereof is connected to the inner tube. A valve such as a check valve may also be connected to the forward end of the head assembly, said forward end being the end having a treaded connection to the inner tube. It's emphasized that a head assembly may have other couplings and configurations without this being relevant for the scope of the present invention. For example, the threaded connection between the inner tube and the head assembly may be exchanged to a bayonet, snap-on or other connection couplings being capable of maintaining the relative orientation between the two during the operation. It is also emphasized that the forward end of the head assembly may have either male or female threads and the inner tube corresponding threads.

[0028] According to the present invention a measuring device is connected to the forward end of the head assembly, more specifically internal to the treads or coupling connecting the head assembly to the inner tube and in such manner that the connection does not interfere with the said treads connecting the head assembly to the inner tube. As so, the total length of the inner tube assembly thus also the overall length of the core drilling assembly is unaffected. Thus, the measuring device is connected only to the head assembly, possibly through adapters or other equipment between the measuring instrument and head assembly and is not affected by the removal of the inner tube from the head assembly.

[0029] In one embodiment the measuring device is connected directly to the forward end of the head assembly, in another embodiment the measuring device is connected to the forward end of the head assembly by means of an adaptor, in a third embodiment the said adaptor may act as a valve or valve cap, or the measuring device is connected to the original valve or valve cap if present, the valve thus being between the head assembly and the measuring device. It's emphasized that the listed ways for connecting the measuring device to the forward end of the head assembly according to the invention is merely a selection of possible embodiments that falls within the objects of the present invention with the intention of having a flexibility in the type of measuring device without restrictions caused by the need to adapt the measuring unit to other parts of the head assembly. It will be apparent for a skilled professional that the described location of the measuring device inside the core tube and partially internal to the treads or coupling connecting the head assembly to the inner tube, implies that the measuring device will not have any access point / s reaching out to the circumference of the inner tube assembly that can be used for cable communication, likewise will the inner tube and head assembly act as a faraday cage that prevent radio communication with the measuring device as long as the inner tube is connected to the head assembly. Consequently, the measuring unit must include means for data storage as well as a local power supply and preferably processors, and the inner tube must be unscrewed or otherwise detached from the head assembly whenever data communication is needed. Unscrewing the inner tube will however break the rotational relationship between the measuring device and the core catcher holding the core sample, thus it will not be possible to determine the orientation of the core sample unless a set of steps is taken to circumvent this problem. A similar problem will arise with other mounting solutions requiring a relative rotation between the two parts, such as with a bayonet mount.

[0030] According to the present invention a measuring device is connected to the forward end of the head assembly, said measuring device being capable of at least measure and log or store the orientation of the core catcher relative to e.g. earth gravity, one or more times downhole within the timeframe between the end of a drill run i.e. the rotation has stopped, and the inner tube being released from the outer barrel assembly for retrieval to surface. During this time frame the core sample will be broken from the sub surface and in that process being wedged and rotationally fixed inside the core catcher, thus the orientation of the core catcher may be used in the process to determine the orientation of the core sample relative to e.g. earth gravity. It's emphasized that the core drilling assembly is kept non-rotational at least for a period of time related to the measurement / s of the core orientation to ensure consistent and reliable data. Using the measuring device to determine the orientation of the core sample implies that the measuring device have an internal reference typically being the axes or planes of one or more sensors, wherein the angular offset between the said axes or planes relative to an external reference such as earth gravity, is used to be determine the orientation of the sensor and any connected parts thereof such as the head assembly.

[0031] In the case the measuring device is configured to measure and log the orientation of the core sample relative to earth gravity by means of one or more gravity sensors such as accelerometers, the present invention will involve steps and features for performing the operation. The measuring device may periodically measure and log the orientation with corresponding time stamps, making it possible at a later stage to select the orientations measured in the period of time when the drilling operation has been stopped and before the inner tube assembly is released from the outer barrel assembly. As an alternative the measuring device may include sensors and processors being configured to detect that the drilling has stopped and measure and store the orientation as a result of that detection. Other solutions may also be possible to achieve one or more measurements at a relevant point of time, such as timers, magnet switches, microphones, or movement detectors.

[0032] Before or after the drilling operation the core catcher, inner tube and head assembly is be held in a fixed rotational orientation, preferably horizontally, wherein in a reference mark is made on the core catcher or the inner tube, said reference mark representing the high side of either of the items. Any suitable means can be used to find the high side, such as but not limited to a leveler or an electronic device measuring direction of earth gravity. While maintaining the same rotational orientation of the core catcher, inner tube, and head assembly, the measuring device is set to measure its own rotational orientation relative to earth gravity. It's emphasized that the reference mark as well as the measurement of the rotational orientation of the measuring device can be made in different order as long as the described tasks are fulfilled, alternatively a permanent mark is made, thus marking before or after the drill run can be skipped until any of the involved parts are replaced.

[0033] The operational procedure to perform a drill run that includes orientation of the core sample will then be as follows according to the present invention and the claims thereof.

[0034] After the drill run is completed the measuring device will measure the orientation of the core catcher thus also the core sample relative to e.g. earth gravity. The inner tube assembly is then hoisted to surface by means of a wire line. At surface the inner tube assembly is placed preferably horizontal on a stand. In one embodiment the marking of the high side as well a measurement was done before the drill run started, in another embodiment the marking of the high side as well a measurement is done at this moment of time. The inner tube is then unscrewed and detached from the head assembly, wherein the logged data can be accessed and downloaded in any suitable way, wherein the offset between the measured angular value downhole and the measured angular value at surface, will represent the offset between the reference mark and the high side of the core sample when situated in the bed rock. An angle protractor can be used to find the exact position of the core sample high side and the core sample marked accordingly. The core sample can now the removed from the inner tube and placed into the core tray, wherein the same procedure is repeated, and the inner tube assembly seated in the core drilling assembly downhole to continue the drilling operation. In an alternative approach the head assembly is kept in a fixed rotational orientation after it arrives to surface, wherein the measuring device is set to measure its own rotational orientation at this moment of time. The inner tube is then unscrewed and detached from the head assembly, to access the logged data before the inner tube screwed back onto the head assembly. A leveler or an electronic device measuring direction of earth gravity is now used to find the high side of the core catcher, wherein the head assembly thus also the inner tube and core catcher is rotated equal the offset between the first measurement downhole and the second measurement at the stand, with help of e.g. a protractor and a leveler. The high side of the new rotational orientation of the core catcher thus also to the core sample will now represent the rotational orientation of the core sample as it was before broken from the sub surface. The core sample can now the removed from the inner tube and placed into the core tray, wherein the same procedure is repeated, and the inner tube assembly seated in the core drilling assembly downhole to continue the drilling operation.

[0035] It's emphasized that core drilling assemblies are available either with a retrievable inner tube assembly or a fixed inner tube assembly. Even if the description in this patent is focused on core drilling assemblies having a retrievable inner tube, this is not meant to limit or define the scope of the patent, as the main principles described will be the same for both retrievable and fixed inner tube assemblies. It is however to be understood that a fixed inner tube assembly require the whole core drilling assembly to be brought to surface when the core sample is to be retrieved, and measurement of the core sample orientation downloaded.

[0036] Preferably the measuring device is adopted to measure the rotational orientation of the core sample as well as inclination, relative to earth gravity by means of one or more gravity sensors such as accelerometers, without this defining or limiting the scope of the present invention. The present invention provides a solution for an measuring device being suitable for using a wide range of available sensors, such as but not limited to accelerometers, magnetometers and gyros, thus the core sample may be orientated in a 3D space relative to any available reference, such as but not limited to magnetic north or any other detectable object or source, herein the outer barrel of the drilling assembly or any coupling or reference point thereof. This way the orientation may be monitored and controlled every time the inner tube assembly are retrieved to surface using an interface for reading the information stored by the measuring device being accessible first when the inner tube assembly has been retrieved to surface and the inner tube unscrewed and detached from the head assembly or any coupling thereof. The interface will usually be constituted by electric couplings being revealed when the inner tube is detached form the head assembly but may in some cases be constituted by wireless communication that is shielded from interference as long as the inner tube is connected to the forward end of the head assembly, but made available at the removal of the shield, e.g. represented by the inner tube.

[0037] It should also be emphasized that the word "core sample" is to be understood as any sample material collected from the sub surface such as but not limited to rock, gravel clay and ice.

[0038] Moreover, its emphasized that the word "orientation" relates to orientation of any object such as the core sample in a 3D space, wherein the orientation is relative to a known position or object such as earth gravity or geographic north.

[0039] Moreover, its emphasized that the word "high side" is to be understood as 12 o'clock on the circumference of the object, relative to an external reference such as earth gravity when looking along the center axis of the object such as the core sample.

[0040] It should be emphasized that the word "downhole" and "sub surface" is to be understood as any place below surface and in a location where the device or an object is not directly accessible by hand.

[0041] Moreover, its emphasized that the word "drilling" can be any method suitable for penetrating the sub surface, such as but not limited to rotational drilling, percussion drilling or just pressing, and wherein any suitable tool bit to obtain a hole may be used.

[0042] Moreover, its emphasized that the words "connected" is to be understood as one part connected to another part, wherein the parts are at least rotationally fixed to each other by means of the connection in any suitable way, preferably by threads, but non-screwed connection may also be feasible for some connections.

[0043] In addition, it should be emphasized that the words "storing" and "logging" of the measured data are both referring to the fact that the measurements are stored in a memory in the measuring device for being downloaded through an electronic interface when available.

[0044] Moreover, its emphasized that the "reference mark" given to the core catcher or the inner tube can be made by any suitable means proving a mark that can be recognized by the operator over a sufficient period of time, such as but not limited to a pencil or paint brush mark, a notch or a device clamped or otherwise attached to the marked object.

[0045] It's emphasized that there are many feasible methods for initiating a measurement at a relevant moment of time, such as a timer, a switch e.g. a magnet switch, an event, time stamp or counting of measurements having start or stop of a measuring cycle as reference, an event or a given moment in time as reference, without this defining or being relevant for the scope of the patent.

[0046] Moreover, its emphasized that after unscrewing the inner tube the data collected by the measuring device, can be accessed and / or downloaded in any suitable way, or visualized on the measuring device its selves, without this being relevant or limiting the scope of the present invention.

[0047] BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention will be described below with reference to the accompanying drawings, illustrating the invention by way of examples.

[0049] Figure 1 illustrates a partially cross sectioned core drilling assembly according to the prior art.

[0050] Figure 2 illustrates a partially cross sectioned outer barrel assembly according to the prior art.

[0051] Figure 3 illustrates an inner tube assembly according to the prior art.

[0052] Figure 4 illustrates an inner tube assembly having the inner tube separated from the head assembly according to the prior art.

[0053] Figure 5 illustrates a partially cross sectioned rear end of an inner tube assembly having a measuring device capable of measuring and logging the orientation of a core sample connected in front of the head assembly according to the invention.

[0054] Figure 6 similar to figure but wherein the measuring device capable of measuring and logging the orientation of a core sample is connected to a feature in front of the head assembly according to the invention.

[0055] Figure 7 illustrates a partially cross sectioned inner tube assembly having a measuring device capable of measuring and logging the orientation of a core sample according to the invention, said inner tube carrying a core sample.

[0056] Figure 8 similar to figure 7 but wherein the inner tube is separated from the head assembly according to the invention.

[0057] Figure 9-12 illustrates the process of calculating the core orientation according to the invention.

[0058] Figure 13 illustrates the method according to a preferred embodiment of the invention. DETAILED DESCRIPTION OF THE DRAWINGS

[0059] As illustrated in fig. 1-4 the present invention relates to a drilling assembly. More specifically a core drilling assembly used for collecting core samples of the sub surface, wherein the rear end of the core drilling assembly is connected to a set of drill rods (not shown) extending up to surface, where the final rod is connected to the drill rig (not shown).

[0060] The core drilling assembly (3) constitutes of two major sub-assemblies wherein one being the outer barrel assembly (7) and the other being the inner tube assembly (10) seated in the inner bore of the outer barrel assembly (7). The inner tube assembly (10) can be retrieved to surface by means of a wire line (not shown), for removal of the core sample within the inner tube (9). After the inner tube

[0061] (9) being emptied the inner tube assembly (10) may be seated again in the outer barrel assembly (7) and the drilling operation may continue.

[0062] More in detail referring to figures 1-4 the core drilling assembly (3) comprises an outer barrel assembly (7) that includes at least a drill bit (1), an extension barrel (2) and a coupling (5) for connection to the drill rods (not shown). The outer body assembly (7) may also include one or more reaming shells (not shown) as well as adaptor and extension couplings (not shown). The outer barrel assembly (7) may comprise a landing shoulder (4) and a locking shoulder (6) to facilitate locking and releasing of the inner tube assembly (10) within the outer barrel assembly (7).

[0063] The inner tube assembly (10) is shown to include at least a core catcher (8) adopted to wedge and thus fixate the core sample (22) relative to the core catcher (8), an inner tube (9) and a head assembly (11). The core catcher (8) being connected to the inner tube (9) at the end facing the drill bit (1), wherein said inner tube (9) is adopted to store the core sample (22) during drilling and transport to surface. At the other end thereof the inner tube (9) is connected by means of threads (16 / 17) to the head assembly (11), said head assembly (11) allowing the core catcher (8) and the inner tube assembly (8) to rotate freely relative to the outer barrel assembly (7) and latching device (14). The latching device (14) is shown to be connected to the rear end of the head assembly (11), said latching device (14) having a landing shoulder (12) that rest on the landing shoulder (4) in the outer barrel assembly (7), when the inner tube assembly is seated. The latching device (14) is also shown to include one or more hooks or pads (13) that can engage the locking shoulder (6), when the inner tube assembly (10) is seated inside the outer barrel assembly (7), thus the inner tube assembly

[0064] (10) will be locked in a fixed axial position inside the outer barrel assembly (7). A connection point (15) at the rear end of the latch assembly (14) is adopted to facilitate release of the inner tube assembly (10) from the outer barrel assembly (7) when pulled. As so, the inner tube assembly (10) thus also the core sample (22) may be retrieved to surface, without bringing the whole core drilling assembly (3) to surface. In another embodiment (not shown) the inner tube assembly (10) is seated permanently inside the outer barrel assembly (7), thus the inner tube assembly (10) will not have a latching device (14) and consequently the whole core drilling assembly (3) must be brought to surface when the core sample (22) is to be recovered. It's emphasized that the core drilling assembly (3) may also include a liner (not shown), said liner being inserted inside the inner tube (9) to facilitate recovery of the core sample (22) without having to collect the core sample (22) piece by piece from the inner tube (9). The latter is often used if the drilled formation is very soft or fractured.

[0065] Figure 5 illustrates the rear end of an inner tube assembly (10 according to the invention and includes an inner tube (9) connected to the forward end of the head assembly (11) by means of a pair of threads (16 / 17). The treaded section (17) typically being seated on a tubular sleeve (19) of the head assembly, wherein the other end of tubular sleeve (19) is connected to a bearing coupling (20). A measuring device 18 is shown connected to the forward end of the treaded section (17), said measuring device may comprise sensors such as but not limited to accelerometers, magnetometers, and gyros. It is emphasized that measuring device (18) is not engaging or interfering with the treaded section (16 / 17), thus the overall length of the inner tube assembly (9) will stay unaffected of the measuring device (18) being installed. It will however be apparent for a professional that the location of the measuring device (18) inside the core tube (9) at the forward end of the head assembly (11), will make the measuring device (18) mechanically and electronically isolated relative to the circumference of the inner tube assembly (10), thus it will be impossible to establish wire or radio wave communication with the measuring device (18) to download logged data, unless the inner tube (9) is unscrewed and detached from the head assembly (11). As so, a series of steps are needed whenever the measuring device (18) is set to be used for orientation of a core sample (22).

[0066] Figure 6 is similar to figure 5, but wherein the measuring device is connected to a valve or valve cap (21) being a part of the head assembly. In another embodiment not shown, the measuring device or adaptor coupling thereof is acting as a valve cap (21). Other configurations may also be feasible for attaching the measuring device to the forward end of the head assembly without engaging or interfering with the treaded section (16 / 17). Figure 7 illustrates an inner tube assembly (10) according to the invention wherein the inner tube (9) is partially sectioned. A core sample (22) can be seen sticking out of the core catcher (8), said core sample (22) stretching all the way back to the forward end of the head assembly (11) and the measuring device (18) thereof. The illustration shows the measuring device (18) being mechanically and electronically isolated inside the inner tube (9) relative to the circumference of the inner tube assembly (10), when the said inner tube (9) is connected to the head assembly (11), thus it will be impossible to establish wire or radio wave communication with the measuring device (18) to download logged data at this moment of time. Furthermore, a reference mark (23) is shown on the core catcher. It's emphasized that the core catcher (8), inner tube (9) and the head assembly (11) is screwed together tightly, thus having a fixed rotational orientation relative to each other and that the mark can be either on the core catcher (8) or the inner tube (9).

[0067] Figure 8 is similar to figure 7, but wherein he inner tube (9) is unscrewed and detached from the head assembly (11) thus the measuring device (18) is now exposed and accessible for download of logged data.

[0068] Figure 9 illustrates a schematic visualization of a reference mark (23) on the core catcher (8), said reference mark (23) representing the high side at this moment of time. The core catcher (8), inner tube (9) and head assembly (11) being held fixed in this position, and the rotational orientation of the measuring device, more precisely an axis or plane within the measuring device is measured relative to a known reference such as earth gravity. In this specific example the measurement shows that the rotational orientation of the measuring device is position (24a), thus it will have an angular offset (25), relative to the reference mark (23). Said offset (25) may kept as is, or the operator may set the current rotational orientation of the head assembly thus also the measuring device as artificial zero.

[0069] Figure 10 illustrates a schematic visualization of an example measurement (24b) done by the measuring device down hole, said measurement representing the rotational orientation of the core catcher (8) at the time the core sample (22) was broken from the sub surface.

[0070] Figure 11 illustrates a schematic visualization of the measurement (24a) and (24b), said measurements being accessible for the operator first after the inner tube is unscrewed and detached from the head assembly, given the location of the measuring device inside the inner tube where it's both mechanically and electrically isolated. As shown the measurement (24b) indicates that the core catcher had an angular offset (26) equal to approx. -90 degree relative to the measurement (24a). A calculation can be done to get the exact numbers. It's emphasized that any type of data logged by the measuring device such as but not limited to inclination may be downloaded at the same time.

[0071] Figure 12 illustrates a schematic visualization wherein in the reference mark (23) of core catcher (8) is placed 12'oclock. From the downloaded data the operator will know that the angular offset between measurement (24a) done at surface and measurement (24b) done downhole is approx. 90 degrees in this specific example, thus the high side of the core sample (22) will have 90 degrees offset relative to the current rotational orientation of core catcher (8). An angle protractor can now be used to mark the high side of the core sample as it was at the time it was broken from the sub surface accordingly. Said high side of the core sample 8 being designated (27). Alternatively, the core catcher (8) thus also the core sample (22) can be rotated until high side (27) of the core sample (22) is at 12'oclock, wherein the high side is marked accordingly.

[0072] The method performed using the drilling assembly and system discussed above is schematically illustrated in figure 13, where the retrieval of a core sample using a drilling assembly according to the present invention may include the steps of:

[0073] 31 Catching and containing the core in the inner tube assembly, using the core catcher which thus secures that the core is rotationally fixed to the core catcher and thus to the forward end of the head assembly.

[0074] 32 Measuring and storing the orientation of the core sample using the measuring device in the position where the core is fixed to the core catcher,

[0075] 33 Retrieving the inner barrel assembly with the core to surface,

[0076] 34 Measuring and registering or storing the orientation of the inner tube assembly at the surface, thus providing a first, downhole measurement and a second topside measurement.

[0077] 35 Establishing a reference point by means of a marker or a reference device such as a clamp.

[0078] 36 Removing the inner tube from the head assembly to access the communication interface of the measuring device and download the stored data, wherein the angular difference between the reference point made in connection with the surface measurement representing the orientation of the core catcher at surface, and the down hole measurement representing the orientation of the core sample when situated in the subsurface, is used to find the orientation of the core sample when situated in the subsurface and 37 Marking the high side of the core sample according to the downloaded, stored data and obtaining the downhole orientation of the core sample.

[0079] This way the downhole orientation of the core sample can be provided based on the two registered measurements. It should be noted that the order of the measurements may be changed as the topside measurement providing a known reference orientation of the inner tube and core catcher relative to the forward end of the head assembly, may be performed before lowering the assembly into the borehole and catching the core. In other words, the first and second measurements may be made in the opposite order.

[0080] To summarize the present invention relates to a core drilling assembly comprising an outer barrel assembly that includes a drill bit at the forward end and a coupling for connection to the drill rods at the other end thereof. The core drilling assembly thus define a central core extending into a central space in the outer barrel assembly. The core drilling assembly also comprises a retrievable inner tube assembly, preferably being retrievable to a surface position independently of the outer tube assembly, wherein the inner tube assembly includes at least a core catcher at the forward end, connected to an inner tube having a head assembly at the aft end, the inner tube being configured to receive and hold the core sample, and the core catcher being configured to grip and rotationally fix at least a section of the core sample relative to the core catcher thus also the inner tube and head assembly thereof, when the drill bit is lifted off the hole bottom to break the core sample from the sub surface, as is well known in the art.

[0081] According to the present invention the inner tube assembly also includes a measuring device being connected or mounted on the forward end of the head assembly thus being enclosed by the inner tube and without the measuring device or any couplings or adaptors thereof engaging the inner tube, thus measuring device being mechanically and electromagnetically shielded from the outer environment of the inner tube assembly.

[0082] The measuring device may be of any suitable type being suitable for connecting to the forward end of the inner assembly, directly or through an adapter, and comprises at least a sensor and a data storage configured to measure and store a first measurement of the rotational orientation of the head assembly, thus also the inner tube and core catcher connected to the head assembly. The measurements being relative to a known reference such as the direction of earth gravity of magnetic field. The sensor is configured to measure and store the orientation at least within the timeframe between the end of a drill run i.e. the rotation has stopped, and the inner tube being released from the outer barrel assembly for retrieval to surface. The rotational orientation of the core catcher representing the rotational orientation of the core sample as it was situated in the sub surface before it was broken from the sub surface. The measuring device is also configured to measure and store a second measurement of the orientation of the head assembly and core catcher in a topside, surface position.

[0083] The measuring device also includes a computer interface configured for downloading the stored data to a topside computer or similar through a wired or wireless connection. As the measuring device is positioned inside the inner tube and being electromagnetically isolated from the environment it is only accessible when the inner tube with the samples has been unscrewed and / or detached from the head assembly.

[0084] Preferably the measuring device also includes an energy source, timing device and data storage, the measurements being retrievable from the data storage first after retrieval of the inner tube assembly and the inner tube unscrewed and detached from the head assembly.

[0085] The orientation measuring device may be configured to measure the orientation in a time sequence, possibly with a time or number stamp identifying the time or number of each measurement, so as to allow an operator to identify at which time or number the correct sample orientation has been measured, for example based on the known time when the drilling stopped or detecting from the sampled data when the orientation was stabilized and the rotation stopped. Alternatively, the measuring device is set to measure the orientation at a predetermined time or includes a sensor unit being configured to detect a downhole event such as the core catcher gripping the core sample and measure the orientation after detection the breaking operation or activation of the core catcher, that the drilling has stopped etc.

[0086] The releasable connection between the head assembly and the inner tube may be a threaded connection, bayonet coupling etc. The head assembly may include additional parts such as valves between the measuring device and the head assembly. The present invention also relates to a system including the drilling assembly discussed above. The system also includes a computer configured to be connected to said interface of the measuring device when detached form the inner tube from the forward end of the head assembly, wherein the computer being configured to determine the difference between the rotational orientation of the core sample when situated in the sub surface, and the rotational orientation of the core sample at surface, and is configured to use such data after the inner tube is detached from the forward end of the head assembly to determine and mark the rotational orientation of the core sample when situated in the sub surface relative to a known reference, such as earth gravity

[0087] The method for retrieving a core sample using a drilling assembly according to the present invention may include the steps of: catching and containing the core in the inner tube assembly, registering and storing the orientation of the core sample using the measuring device, retrieving the inner barrel assembly to surface, registering the orientation of the inner tube assembly at the surface, removing the inner tube from the head assembly to access the communication interface of the measuring device and download the stored data, and marking the high side of the core sample according to the downloaded, stored data.

[0088] Alternatively, the step of registering and measuring the orientation of the inner tube assembly may be performed before it is lowered into the outer tube assembly and the drilling has been started.

Claims

Claims1. A core drilling assembly, comprising an outer barrel assembly that includes a drill bit at one end and a coupling for connection to the drill rods at the other end thereof, the outer barrel assembly carrying a retrievable inner tube assembly that includes at least a core catcher, an inner tube and a head assembly, said core catcher, inner tube and forward end of the head assembly being in a fixed rotational relationship relative to each other, and wherein the core catcher being configured to grip and rotationally fix at least a section of the core sample relative to the core catcher thus also the inner tube and forward end of the head assembly thereof.W h e r e i n core drilling assembly also includes, a measuring device being connected to the forward end of the head assembly, mechanically and electromagnetically shielded and isolated from the outer environment of the inner tube assembly, the measuring device comprising at least a sensor and a data storage configured to measure and store the rotational orientation of the core catcher, relative to a known reference at least two moments in time, wherein a first stored measurement being when the core catcher has gripped and rotationally fixed the core sample relative to the core catcher, thus representing the rotational orientation of the core catcher thus also the core sample when situated in the sub surface, and a second stored measurement being when the inner tube assembly is at surface, thus representing the rotational orientation of the core catcher at surface the measuring device being exposed and accessible for download of logged data by unscrewing and detach the inner tube from the forward end of the head assembly a computer interface being configured to communicate the stored information to a computer the stored measurements being used to determine the rotational orientation of the core sample when situated in the sub surface, after the inner tube and core catcher thereof, is unscrewed and / or detached from the front end of the head assembly.

2. Core drilling assembly according to claim 1, wherein the measuring device includes an energy source, timing device and data storage, the measurements being retrievable from the data storage after retrieval of the inner core barrel assembly.

3. Core drilling assembly according to claim 1, wherein the measured data is acquired by means of a time stamp or a number stamp and a corresponding measured orientation.

4. Core drilling assembly according to claim 1, wherein the measuring device is configured to measure the orientation in a time or number sequence or where the measurement is triggered by a downhole event.

5. Drilling assembly according to claim 1, wherein the orientation measuring device is set to measure the orientation at a predetermined time or a predetermined number in a sequence.

6. Drilling assembly according to claim 1, wherein the measuring device includes a sensor unit being configured to detect the core catcher gripping the core and measure the orientation after the detection.

7. Drilling assembly according to claim 1, wherein the connection is a threaded connection.

8. Drilling assembly according to claims 1, wherein the inner tube assembly is retrievable independently of the outer tube assembly.

9. Method for retrieving a core sample using a core drilling assembly according to one of the preceding claims, including the steps of: catching and containing the core sample in the inner tube, measuring and storing the downhole orientation of the core sample as it was situated before it was broken from the sub surface using the measuring device, retrieving the inner tube assembly to surface, the inner tube assembly being held rotationally fixed while the high side is marked, and the orientation of the measuring device measured, removing the inner tube from the front end of the head assembly carrying the measuring device and downloading the stored data, and marking the core sample according to the stored data.

10. Method for retrieving a core sample using a drilling assembly according to one of the preceding claims 1-8, including the steps of: before drilling, the inner tube assembly being held rotationally fixed while the high side is marked and the orientation of the measuring device measured,catching and containing the core sample in the inner tube, measuring and storing the downhole orientation of the core sample as it was situated before it was broken from the sub surface using the measuring device, retrieving the inner tube assembly to surface, removing the inner tube from the forward end of the head assembly carrying the measuring device and downloading the measured data, and marking the core sample according to the stored data.

11. System including a drilling assembly according to claim 1, wherein the system also includes a computer configured to be connected to said interface of the measuring device when detached form the inner tube from the forward end of the head assembly, and the computer being configured to determine the difference between the rotational orientation of the core sample when situated in the sub surface, as represented by the first measurement, and the rotational orientation of the core sample at surface, as represented by the second measurement, and being configured to use such data after the inner tube is detached from the forward end of the head assembly to determine and mark the rotational orientation of the core sample when situated in the sub surface relative to a known reference, such as earth gravity.

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