Pressure-insensitive safety valve of the production column with hydrostatic compensation

Abstract

Safety valves (5) and methods of operation thereof. An exemplary safety valve includes a first piston (10) disposed within a safety valve body (15). The first piston forms a first seal (20) with the interior of the safety valve body. The first piston, the interior of the safety valve body, and the first seal define two chambers within the safety valve separated by the first seal. The first chamber is a control line pressure chamber (25) disposed upstream of the first seal, and the second chamber is a fluid compression chamber (30) disposed downstream of the first seal. The control line pressure chamber is pressurized to translate the first piston downstream in an axial direction. A second seal (45) is formed with an annular space outside and adjacent the safety valve.A biasing mechanism (40) translates the second piston (35) upstream in the axial direction. A fluid volume chamber (60) is in fluid communication with the fluid compression chamber. Abstract Figure: Figure 1.

Description

Title of the invention: Pressure-insensitive safety valve of the production column with hydrostatic compensation Technical field

[0001] The present disclosure relates generally to drilling operations, and more particularly, to the use of a safety valve that is insensitive to production string pressure and is configured to compensate for hydrostatic pressure in the wellbore.

[0002] CONTEXT

[0003] For certain drilling operations, it may be desirable to use a safety valve to prevent the uncontrolled release of wellbore fluids to the surface. If the surface or wellbore equipment experiences a failure, the fail-safe mechanism of the safety valve can force the safety valve to close, thereby preventing the uncontrolled release of wellbore fluids to the surface that could result in an environmental disaster and / or safety hazards to wellbore personnel. Safety valves may be impacted by tubing pressure and / or hydrostatic pressure in the wellbore.

[0004] Safety valves are an important element of drilling operations. The present invention provides improved apparatus and methods for using a safety valve that is insensitive to tubing pressure and is configured to compensate for hydrostatic pressure in the wellbore. Brief Description of the Drawings

[0005] Illustrative examples of the present disclosure are described in detail below with reference to the accompanying drawing figures, which are incorporated by reference herein, and in which:

[0006] [Fig.l] is a diagram illustrating an example of a safety valve according to one or more examples described herein;

[0007] [Fig.2] is a diagram of an enlarged portion of the safety valve of [Fig.l] according to one or more examples described herein;

[0008] [Fig.3] is another diagram of an enlarged part of the safety valve of the [Fig.l] according to one or more examples described herein;

[0009] [Fig.4] is a further diagram of an enlarged portion of the safety valve of [Fig.l] according to one or more examples described herein; and

[0010] [Fig.5] is another diagram of an enlarged part of the safety valve of the [Fig.l] according to one or more examples described herein.

[0011] The illustrated figures are examples only and are not intended to state or imply any limitation with respect to the environment, architecture, design or process in which the various examples may be implemented. DETAILED DESCRIPTION

[0012] The present disclosure relates generally to drilling operations, and more particularly, to the use of a safety valve that is insensitive to production string pressure and is configured to compensate for hydrostatic pressure in the wellbore.

[0013] In the following detailed description of several illustrative examples, reference is made to the accompanying drawings which are an integral part of this document and in which specific examples capable of being implemented are illustrated. These examples are described in sufficient detail to enable those skilled in the art to practice them, and it is understood that other examples may be used and that logical structural, mechanical, electrical, and chemical modifications may be made without departing from the spirit or scope of the disclosed examples. In order to avoid details which are not necessary to enable those skilled in the art to practice the examples described herein, the description may omit certain information known to those skilled in the art.The following detailed description should therefore not be taken in a limiting sense, and the scope of the illustrative examples is defined only by the appended claims.

[0014] Unless otherwise indicated, all numbers expressing amounts of ingredients, properties such as molecular weight, reaction conditions, etc., used in this specification and the associated claims are to be understood as being modified in all instances by the term "about." Therefore, unless otherwise indicated, the numerical parameters set forth in the following specification and the appended claims are approximations which may vary depending on the desired properties sought to be achieved by the examples of the present invention. At the very least, and without seeking to limit the application of the doctrine of equivalents to the scope of the claim, each numerical parameter should at least be interpreted in light of the number of significant figures reported and by applying ordinary rounding techniques.It should be noted that when "about" is at the beginning of a numerical list, "about" modifies each number in the numerical list. Furthermore, in some numerical lists of ranges, certain indicated lower limits may be greater than certain indicated upper limits. Those skilled in the art will recognize that the subset . selected will require the selection of an upper limit exceeding the selected lower limit.

[0015] In the following disclosure and in the claims, the terms "including" and "comprising" are used openly and should therefore be interpreted as meaning "including, but not limited to". Unless otherwise indicated, in this document, the term "or" does not imply mutual exclusivity.

[0016] The terms "upstream" and "downstream" may be used to refer to the location of various components relative to the bottom or end of a well. For example, a first component described as being upstream of a second component may be farther from the end of the well than the second component. Similarly, a first component described as being downstream of a well relative to a second component may be located closer to the end of the well than the second component.

[0017] The terms "upstream" and "downstream" may be used to refer to the location of various components relative to one another with respect to the flow of a sample through said components. For example, a first component described as being upstream of a second component will encounter a sample before the downstream second component encounters the sample. Similarly, a first component described as being downstream of a second component will encounter the sample after the upstream second component encounters the sample.

[0018] The present disclosure relates generally to drilling operations, and more particularly, to the use of a safety valve that is insensitive to tubing pressure and is configured to compensate for hydrostatic pressure in the wellbore. Advantageously, the safety valve may be used in wellbores having high hydrostatic pressure by balancing the hydrostatic pressure with the use of a fluid compression chamber and a fluid volume chamber to compensate for the force of the hydrostatic pressure. In addition, the safety valve is insensitive to tubing pressure because the tubing pressure is balanced on both sides of the first piston.Thus, there is no effect on the control line pressure when opening the safety valve and there is also no effect on the biasing mechanism when closing the safety valve. An additional advantage is that once the tubing pressure is balanced, operation of the safety valve only requires overcoming the force of the biasing mechanism (e.g., a spring) and, as such, the safety valve can be opened with a limited amount of differential pressure applied by a single control line. Another advantage is that the fail-safe mechanism can be operated by the release of the pressure applied by the control line. The release of the pressure applied by the . control allows the biasing mechanism to close the valve, and the tubing pressure exerted below further helps to seal the well pressure exerted below as well as the force of the biasing mechanism. Another advantage is that the safety valve can be equipped to have a radial flow inlet, thus providing the maximum cross-flow area for the safety valve. An additional advantage is that the safety valve forms a metal-to-metal seal against an adjacent surface until it is opened to allow flow through it.

[0019] The safety valves disclosed herein may be installed in wellbore conduits and used within a variety of drilling locations, including those comprising land-based or subsea drilling locations. The safety valves may be used in a variety of wellbores, including, but not limited to, horizontal wellbores, vertical wellbores, deviated wellbores, and the like. The safety valves may be used with a variety of well types, including, but not limited to, oil and gas wells, disposal wells, geothermal wells, water wells, and the like.

[0020] [Fig.l] is a perspective figure illustrating a safety valve 5 for use in a wellbore. The safety valve 5 includes a first piston 10 disposed within the body 15 of the safety valve 5. A raised seal 20 is formed from a raised element outside the first piston 10. This raised element may be a variable surface machined into the profile of the first piston 10 or may be a sealing element such as an O-ring or a stack of sealing elements attached to the outside of the first piston 10. The first piston 10, the raised seal 20 within the safety valve body 15 and the inner surface of the safety valve body 15 define two chambers within the safety valve 5. These two chambers are separated by the raised seal 20. The first chamber is a control line pressure chamber 25 and is disposed upstream of the raised seal 20.The second chamber is a fluid compression chamber 30 and is disposed downstream of the protruding seal 20.

[0021] As will be described in more detail below, the control line pressure chamber 25 may be pressurized with hydraulic fluid introduced via a single control line (not shown). Upon exceeding a desired pressure threshold, the pressurized hydraulic fluid translates the first downstream piston in the axial direction within the body 15 of the safety valve 5.

[0022] A second piston 35 is coupled to the first piston 10. The second piston 35 and the first piston 10 have a linked movement such that the movement of the first piston 10 also causes the movement of the second piston 35 in the same direction and at the same time. The second piston 35 comprises a mechanism biasing mechanism 40 to provide a biasing force to translate the second piston 35 upstream in the axial direction of the safety valve 5. The biasing mechanism 40 is shown as a spring, but any mechanism that biases the second piston 35 in the upstream direction with sufficient force may be used. Examples of biasing mechanisms 40 may include electrical, mechanical, hydraulic, and pneumatic mechanisms. The biasing mechanism 40 forces the safety valve 5 into the closed configuration, which is the configuration in which the second piston 35 and the linked first piston 10 are positioned in their upstream default position. Tubing pressure acting on the tubing downhole also helps maintain the safety valve 5 in the closed configuration.A metal-to-metal seal 45 is formed from the second piston 35 and the adjacent sleeve 50 to seal the flow path through the safety valve 5 from the surrounding annular space (e.g., the wellbore annulus or the casing annulus). To open the safety valve 5, the first piston 10 and the linked second piston 35 are forced to move downstream in the axial direction. This movement causes the metal-to-metal seal 45 to be withdrawn and the interior of the safety valve 5 to be opened to allow fluid flow through the opening 55 in the safety valve 5 from the surrounding annular space.

[0023] In order to open the safety valve 5 to allow flow therethrough, the force of the tubing pressure exerted on the safety valve 5 downstream at the bottom of the tubing may be balanced. To balance this force, pressure may be applied to the tubing above the safety valve 5, for example, at the wellhead to equalize the tubing pressure. The tubing may be pressurized by introducing a fluid into the tubing to a desired pressure. When the tubing pressure is equalized, the only force that must be overcome to open the safety valve 5 is the force provided by the biasing mechanism 40.This force produced by the biasing mechanism 40 can be overcome by applying a force from the pressurized hydraulic fluid introduced into the control line pressure chamber 25 as mentioned above. The pressurized hydraulic fluid can be introduced into the control line pressure chamber 25 via a control line coupled to the safety valve 5. When the pressure in the control line pressure chamber 25 increases, the first piston 10 and the linked second piston 35 translate downstream in the axial direction. This translation of the linked pistons occurs when the pressurized fluid in the line pressure chamber . control mechanism 25 generates sufficient force to overcome that of the biasing mechanism 40.

[0024] As the first piston 10 and the linked second piston 35 translate downstream in the axial direction, the fluid within the fluid compression chamber 30 is compressed as the available volume in the fluid compression chamber 30 decreases. The fluid in the fluid compression chamber 30 is a separate fluid from the fluid in the control line pressure chamber 25 and these two fluids do not come into physical contact with each other or mix. Examples of the fluid in the fluid compression chamber 30 may include, but are not limited to, silicon oil and / or gases such as atmospheric air. The fluid in the fluid compression chamber 30 functions as a cushion to resist the force of the hydrostatic pressure exerted on the safety valve 5 as well as to reduce uncontrolled movement of the first piston 10 and the second piston 35.When the fluid in the fluid compression chamber 30 is compressed, at least a portion of the fluid is transferred to the fluid volume chamber 60. The fluid volume chamber 60 is configured to contain at least a portion of the fluid present in the fluid compression chamber 30. The fluid compression chamber 30 and the fluid volume chamber 60 are in fluid communication such that fluid may flow from one to the other. The fluid compression chamber 30 and the fluid volume chamber 60 may be in fluid communication via the production tubing or any other fluid container sufficient to convey fluid from one chamber to the other and vice versa.

[0025] When the safety valve 5 is in the open configuration, fluid from the surrounding annular space may enter the safety valve 5 through the opening 55. The opening 55 is shown as a radial opening in the wall of the first piston 10. Other non-radial openings may be used for the opening 55 in alternative embodiments. The opening 55 allows fluid to enter the interior of the first piston 10 and flow upstream via the upstream connected production tubing and / or conduits to the surface of the well location.

[0026] When it is desired to close the safety valve 5, it is possible to cut off the pressure to the control line supplying pressurized hydraulic fluid to the control line pressure chamber 25. When this pressure is released, the biasing mechanism 40 can translate the first piston 10 and the second piston 30 in the upstream direction to place the safety valve 5 in the closed configuration. In addition, it is not necessarily necessary to release the pressure applied to the surface to equalize the production column pressure, because the biasing mechanism 40 will close the safety valve 5. Once the valve safety valve 5 is open, the pressure exerted below and above the safety valve 5 is balanced and, therefore, it is not necessary to release the pressure from the production column applied above.

[0027] The safety valve 5 may be installed in the wellbore with a wireline or other mechanism. In some examples, the safety valve may be retrieved with a wireline or upon retrieval of the tie-in production string.

[0028] [Fig. 2] is a cross-sectional illustration of an enlarged portion of the safety valve 5 shown in [Fig. 1]. In the illustration of [Fig. 2], the safety valve 5 is in its closed configuration and the opening 55 is not aligned with the access port covered by the metal-to-metal seal 45 of the second piston 35 and the surrounding sleeve 50. The biasing mechanism 40, shown as a spring, is extended and the first piston 10 and the linked second piston 35 are deflected upstream when the force of the biasing mechanism 40 and the tubing pressure acting on the tubing are sufficient to overcome any force acting on the first piston 10 from the upstream direction.In order to open the safety valve 5, pressure exerted above the safety valve 5 may be applied to the drill string to balance the tubing pressure acting on the tubing at the downstream end of the tubing, for example, at the bottom hole assembly. This pressure exerted from the surface may be applied to the wellhead by introducing a fluid into the tubing to pressurize the tubing so that a desired pressure is applied to the tubing. If an equal or nearly equal amount of pressure is applied to the safety valve 5 upstream of the safety valve 5, the only force that must be overcome to open the safety valve 5 is the force applied by the biasing mechanism 40.As a result, a differential pressure with an applied force greater than that of the biasing mechanism 40 can be supplied via a single control line to the control line pressure chamber (i.e., reference 25 as illustrated in [Fig.l]) to pressurize the chamber and apply a force greater than that of the biasing mechanism 40 causing the first piston 10 and the second piston 35 to translate.

[0029] [Fig. 3] is a sectional illustration of an enlarged portion of the safety valve 5 shown in [Fig. 1]. In the illustration of [Fig. 3], the safety valve 5 is in its open configuration and the opening 55 is now aligned with the access port that was previously covered by the metal-to-metal seal (i.e., reference 45 as shown in [Fig. 2]). The biasing mechanism 40, shown as a spring, is compressed and the first piston 10 and the second piston 35 linked are pushed downstream when the force of the biasing mechanism 40 is overcome by the force of the pressurized hydraulic fluid applied to the control line pressure chamber (i.e., reference 25 as illustrated in [Fig. 1]). The translational movement in the downstream direction of the first piston 10 and the second piston 35 aligns the opening 55 with the orifice previously blocked by the metal-to-metal seal (i.e., reference 45 in [Fig. 2]). The opening 55 is now configured to allow fluid flow from a surrounding annular space, such as the wellbore annulus, into the safety valve 5 via the opening 55 and the throughbore of the first piston 10.

[0030] To close the safety valve 5, the flow of pressurized fluid pumped to the control line pressure chamber 25 can be interrupted, biasing the pressure difference in favor of the force applied by the biasing mechanism 40.

[0031] [Fig.4] is a sectional illustration of an enlarged portion of the safety valve 5 shown in [Fig.l]. The illustration of [Fig.4] shows the two chambers formed inside the safety valve 5 by the boundary defined by the outside of the first piston 10, the protruding seal 20 inside the safety valve body 15 and the inner surface of the safety valve body 15. The raised element forming the protruding seal 20 extends from the outside of the first piston 10 to seal against the inside of the safety valve 15 to form two chambers on either side of the protruding seal 20, the upstream chamber (i.e. the leftmost chamber in the figure) is the control line pressure chamber 25. The downstream chamber (i.e. the rightmost chamber in the figure) is the fluid compression chamber 30.A single control line is connected to the control line pressure chamber 25 via the illustrated port, or other sufficient connection, and pressurized hydraulic fluid may flow to the control line pressure chamber 25 to create a differential pressure to overcome the force exerted by the biasing mechanism (i.e., reference numeral 40 in [Fig. 1]). Pressurizing the control line pressure chamber 25 beyond this threshold will result in translation of the first piston 10 in the axial direction, causing the safety valve 5 to open. The fluid compression chamber 30 is a separate chamber from the control line pressure chamber 25, and fluid stored therein is transported into the safety valve 5 as it descends downhole. This fluid is not pumped into the fluid compression chamber 30 once the safety valve 5 is deployed.The fluid inside the fluid compression chamber 30 also does not contact or mix with the pressurized fluid inside the control line pressure chamber 25. The fluid inside . of the fluid compression chamber 30 functions as a cushion to resist pressure exerted on the safety valve 5 as well as to reduce uncontrolled movement of the first piston 10 and the second piston 35. When the first piston 10 is pushed downstream, the first piston 10 compresses the fluid within the fluid compression chamber 30 decreasing the available volume within the fluid compression chamber 30. At least a portion of the now compressed fluid is transferred to the fluid volume chamber (i.e., reference 60 in [Fig.l]). The transferred fluid may be delivered to the fluid volume chamber 60 using a tubing string, line, or even a separate flow path machined or otherwise formed within the bodies of the safety valve components, such as through the first piston 10 and the second piston 35 to connect the two chambers.

[0032] [Fig. 5] is a cross-sectional illustration of an enlarged portion of the safety valve 5 shown in [Fig. 1]. The illustration in [Fig. 5] shows an enlarged portion of the second piston 35 and a portion of the fluid volume chamber 60. In the illustration, a separate line 65 is shown for fluidly connecting the fluid volume chamber 60 to the fluid compression chamber 30. The fluid volume chamber 60 receives compressed fluid from the fluid compression chamber 30 for accommodation when the safety valve 5 is open. The stored fluid can return to the fluid compression chamber 25 when the pressure to the control line pressure chamber (i.e., reference 25 in [Fig. 1]) is cut off.

[0033] It should be understood that the exemplary system illustrated by [Fig.l]-5 is only a general application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Accordingly, the scope of this disclosure is not limited in any way to the details of [Fig.l]-5 as described herein.

[0034] The systems disclosed herein may directly or indirectly affect one or more components or pieces of equipment associated with or likely to come into contact with the safety valves disclosed herein, such as, but not limited to, wellbore casing, well liner, completion string, insert strings, drill string, coiled tubing, slickline, wireline, drill pipe, drill collars, mud motors, downhole motors and / or pumps, cement pumps, surface-mounted motors and / or pumps, centralizers, turbolizers, scrapers, floats (e.g., shoes, collars, valves, etc.), logging tools and associated telemetry equipment, actuators (e.g., electromechanical devices, hydromechanical devices, etc.), sliding sleeves, production sleeves, plugs, screens, filters, flow control devices (e.g., inflow control devices, stand-alone inflow control devices, outflow control devices, etc.), couplers (e.g., wet-connect electro-hydraulic coupler, dry-connect coupler, inductive coupler, etc.), control lines (e.g., electrical, fiber optic, hydraulic, etc.), monitoring lines, drill bits and reamers, sensors or distributed sensors, downhole heat exchangers, valves and corresponding actuation devices, tool seals, packers, cement plugs, bridge plugs and other wellbore isolation devices or components, and so on.

[0035] A safety valve for a wellbore is provided in accordance with the disclosure and the illustrated FIGS. An exemplary safety valve includes a first piston disposed within a safety valve body. The safety valve body has an interior. The first piston forms a first seal with a surface of the interior of the safety valve body. The first piston, the interior of the safety valve body, and the first seal define two chambers within the safety valve. The two chambers are separated by the first seal. A first chamber of the two chambers is a control line pressure chamber and is disposed upstream of the first seal. A second chamber of the two chambers is a fluid compression chamber and is disposed downstream of the first seal.The control line pressure chamber is configured to be pressurized to translate the first piston downstream in an axial direction. The safety valve further includes a second piston coupled to the first piston such that the two pistons comprise a linked movement. The second piston forms a second seal with an annular space outside and adjacent the safety valve. The second piston includes a biasing mechanism to provide a force to translate the second piston upstream in the axial direction. The safety valve is in a closed configuration when the second piston translates in the upstream direction. The safety valve is in an open configuration when the second piston translates in the downstream direction.The open configuration causes the second seal to retract, thereby allowing fluid flow from the annular space to an interior of the first piston. The safety valve also includes a fluid volume chamber in fluid communication with the fluid compression chamber of the first piston.

[0036] Additionally or alternatively, the safety valve may include one or more of the following features, individually or in combination. The first piston may include a radial opening such that removal of the second seal exposes the radial opening to the annulus. The biasing mechanism may include a spring. A connecting flow path may fluidly connect the volume chamber to the fluid compression chamber. The connecting flow path may be a flow line. The connecting flow path may at least partially include a flow path disposed through the body of the second piston. The volume chamber and the fluid compression chamber may be configured to contain a compressible fluid when the safety valve is transported into the wellbore. The safety valve may be insensitive to tubing pressure. The safety valve may be configured to be installed with a wireline. The first seal may be formed by an O-ring or a stack of sealing elements.

[0037] Methods of using a safety valve are provided in accordance with the disclosure and the illustrated FIGS. An exemplary method includes providing a safety valve. The safety valve includes a first piston disposed within a safety valve body. The safety valve body has an interior. The first piston forms a first seal with a surface of the interior of the safety valve body. The first piston, the interior of the safety valve body, and the first seal define two chambers within the safety valve. The two chambers are separated by the first seal. A first chamber of the two chambers is a control line pressure chamber and is disposed upstream of the first seal. A second chamber of the two chambers is a fluid compression chamber and is disposed downstream of the first seal.The control line pressure chamber is configured to be pressurized to translate the first piston downstream in an axial direction. The safety valve further includes a second piston coupled to the first piston such that the two pistons comprise a linked movement. The second piston forms a second seal with an annular space outside and adjacent the safety valve. The second piston includes a biasing mechanism to provide a force to translate the second piston upstream in an axial direction. The safety valve is in a closed configuration when the second piston translates in the upstream direction. The safety valve is in an open configuration when the second piston translates in the downstream direction.The open configuration causes the second seal to retract, thereby allowing fluid flow from the annular space into the first piston. The safety valve further includes a fluid volume chamber in fluid communication with the fluid compression chamber of the first piston.

[0038] The method further comprises applying pressure from the production tubing to the upstream safety valve, applying hydraulic pressure to the control line pressure chamber by pumping hydraulic fluid into the control line pressure chamber; wherein the applied hydraulic pressure is sufficient to overcome the force of the biasing mechanism, thereby translating the second piston in the downstream direction to open the safety valve.

[0039] Additionally or alternatively, the method may include one or more of the following features, individually or in combination. The first piston may include a radial opening such that removal of the second seal exposes the radial opening to the annulus. The biasing mechanism may include a spring. A connecting flow path may fluidly connect the volume chamber to the fluid compression chamber. The connecting flow path may be a flow line. The connecting flow path may at least partially include a flow path disposed through the body of the second piston. The volume chamber and the fluid compression chamber may be configured to contain a compressible fluid when the safety valve is transported into the wellbore. The safety valve may be insensitive to tubing pressure.The safety valve may be configured to be installed with a wire rope. The first seal may be formed by an O-ring or a stack of sealing elements. The method may further include releasing the applied hydraulic pressure; wherein releasing the applied hydraulic pressure allows the biasing mechanism to close the safety valve. The volume chamber and the fluid compression chamber may contain a compressible fluid and applying hydraulic pressure to the control line pressure chamber translates the first piston in the downstream direction and compresses the compressible fluid in the fluid compression chamber. At least a portion of the compressible fluid may be transferred to the fluid volume chamber. The compressible fluid may include silicon oil or atmospheric air.

[0040] Systems for operating a safety valve in a wellbore are provided in accordance with the disclosure and illustrated FIGS. An exemplary method includes a safety valve. The safety valve includes a first piston disposed within a safety valve body. The safety valve body has an interior. The first piston forms a first seal with a surface of the interior of the safety valve body. The first piston, the interior of the safety valve body, and the first seal define two chambers within the safety valve. The two chambers are separated by the first seal. A A first chamber of the two chambers is a control line pressure chamber and is disposed upstream of the first seal. A second chamber of the two chambers is a fluid compression chamber and is disposed downstream of the first seal. The control line pressure chamber is configured to be pressurized to translate the first piston downstream in an axial direction. The safety valve further includes a second piston coupled to the first piston such that the two pistons comprise a linked motion. The second piston forms a second seal with an annular space outside and adjacent the safety valve. The second piston includes a biasing mechanism to provide a force to translate the second piston upstream in an axial direction. The safety valve is in a closed configuration when the second piston translates in the upstream direction.The safety valve is in an open configuration when the second piston translates in the downstream direction. The open configuration causes the second seal to retract, thereby allowing fluid flow from the annular space into the interior of the first piston. The safety valve further includes a fluid volume chamber in fluid communication with the fluid compression chamber of the first piston. The system further includes a conduit on which the safety valve is installed.

[0041] Additionally or alternatively, the system may include one or more of the following features, individually or in combination. The system may further include a control line coupled to the safety valve and in fluid communication with the control line pressure chamber. The control line may be a single control line and wherein the safety valve is not coupled to another control line. The first piston may include a radial opening such that removal of the second seal exposes the radial opening to the annulus. The biasing mechanism may include a spring. A connecting flow path may fluidly connect the volume chamber to the fluid compression chamber. The connecting flow path may be a flow line.The connecting flow path may at least partially include a flow path disposed through the body of the second piston. The volume chamber and the fluid compression chamber may be configured to contain a compressible fluid when the safety valve is transported into the wellbore. The safety valve may be insensitive to tubing pressure. The safety valve may be configured to be installed with a wireline. The first seal may be formed by an O-ring or a stack of sealing elements.

[0042] The foregoing description provides various examples of systems and methods of use disclosed herein, which may contain different method steps and alternative combinations of components. It is to be understood that, although individual examples may be discussed herein, the present disclosure covers all combinations of the disclosed examples, including, but not limited to, different combinations of components, combinations of method steps, and system properties. It is to be understood that the compositions and methods are described in terms of "comprising," "containing," or "including" various components or steps. The systems and methods may also "consist essentially of" or "consist of" different components and steps.

[0043] For brevity, only certain ranges are explicitly disclosed herein. However, ranges of any lower bound may be combined with any upper bound to form a range not explicitly cited, just as ranges of any lower bound may be combined with any other lower bound to form a range not explicitly cited. Similarly, ranges of any upper bound may be combined with any other upper bound to form a range that is not explicitly cited. In addition, whenever a numerical range with a lower bound and an upper bound is disclosed, any numbers and ranges within the range are specifically disclosed.In particular, each range of values ​​(of the form "from about a to about b" or, equivalently, "from approximately a to b" or, equivalently, "from approximately ab") disclosed herein should be taken to state every number and range within the broader range of values, even if not explicitly cited. Thus, each individual point or value may constitute its own lower or upper bound combined with any other individual point or value or with any other lower or upper bound, to constitute a range not explicitly cited.

[0044] One or more illustrative examples incorporating the examples disclosed herein are presented. For clarity, not all features of a physical implementation are described or illustrated in this application. Accordingly, the disclosed systems and methods are well adapted to achieve the stated objectives and advantages as well as those inherent therein. The particular examples disclosed above are given for illustration purposes only, and the teachings of the present disclosure may be modified and practiced in different but equivalent ways, obvious to those skilled in the art and having the benefit of the teachings contained herein. Furthermore, no limitations are intended with respect to the construction or design details presented herein, other than those described in the claims below. It is therefore obvious that the particular illustrative examples disclosed above may be modified, combined or varied, and all such variations are considered within the scope of this disclosure. The systems and methods illustratively disclosed herein may be implemented in the absence of any element not specifically disclosed herein and / or any optional element disclosed herein.

[0045] Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and modifications may be made herein without departing from the spirit and scope of the disclosure as defined by the following claims.

Claims

Claims

1. A safety valve (5) for a wellbore comprising: a first piston (10) disposed within a safety valve body (15), the safety valve body having an interior; wherein the first piston forms a first seal (20) with a surface of the interior of the safety valve body; wherein the first piston, the interior of the safety valve body, and the first seal define two chambers within the safety valve; wherein the two chambers are separated by the first seal; wherein a first chamber of the two chambers is a control line pressure chamber (25) and is disposed upstream of the first seal; wherein a second chamber of the two chambers is a fluid compression chamber (30) and is disposed downstream of the first seal;wherein the control line pressure chamber is configured to be pressurized to translate the first piston downstream in an axial direction; a second piston (35) coupled to the first piston such that the two pistons comprise a linked motion; wherein the second piston forms a second seal (45) with an annular space outside and adjacent the safety valve; wherein the second piston comprises a biasing mechanism (40) for providing a force to translate the second piston upstream in the axial direction; wherein the safety valve is in a closed configuration when the second piston translates in the upstream direction; wherein the safety valve is in an open configuration when the second piston translates in the downstream direction;wherein the open configuration causes the second seal to retract, thereby allowing fluid flow from the annular space to an interior of the first piston; a fluid volume chamber (60) in fluid communication with the fluid compression chamber of the first piston.;

2. A safety valve according to claim 1, wherein the first piston includes a radial opening such that removal of the second seal exposes the radial opening to the annular space.

3. A safety valve according to claim 1 or 2, wherein the biasing mechanism is a spring.

4. A safety valve according to any one of claims 1 to 3, wherein a connecting flow path fluidly connects the volume chamber to the fluid compression chamber.

5. A safety valve according to claim 4, wherein the connecting flow path is a flow line.

6. A safety valve according to claim 4, wherein the connecting flow path at least partially comprises a flow path disposed through the body of the second piston.

7. A safety valve according to any one of claims 1 to 6, wherein the volume chamber and the fluid compression chamber are configured to contain a compressible fluid when the safety valve is transported into the wellbore.

8. A safety valve according to any one of claims 1 to 7, wherein the safety valve is insensitive to production column pressure.

9. A safety valve according to any one of claims 1 to 8, wherein the safety valve is configured to be installed with a wire rope.

10. A safety valve according to any one of claims 1 to 9, wherein the first seal is formed by an O-ring or a stack of sealing elements.

11. A method of operating the safety valve (5) according to any one of claims 1 to 10, the method comprising: providing the safety valve, applying tubing pressure to the upstream safety valve, and applying hydraulic pressure to the control line pressure chamber by pumping hydraulic fluid into the control line pressure chamber; wherein the applied hydraulic pressure is sufficient to overcome the force of the biasing mechanism, thereby translating the second piston in the downstream direction to open the safety valve.

12. The method of claim 11, further comprising: releasing the applied hydraulic pressure; wherein releasing the applied hydraulic pressure allows the biasing mechanism to close the safety valve.

13. The method of claim 11 or 12, wherein the volume chamber and the fluid compression chamber contain a compressible fluid; wherein applying hydraulic pressure to the control line pressure chamber translates the first piston in the downstream direction and compresses the compressible fluid in the fluid compression chamber.

14. The method of claim 13, wherein at least a portion of the compressible fluid is transferred to the fluid volume chamber.

15. The method of claim 13, wherein the compressible fluid comprises silicon oil or atmospheric air.

16. An operating system of the safety valve (5) according to any one of claims 1 to 10, the system comprising: the safety valve, and a conduit on which the safety valve is installed.

17. The system of claim 16, further comprising a control line coupled to the safety valve and in fluid communication with the control line pressure chamber.

18. The system of claim 17, wherein the control line is a single control line and wherein the safety valve is not coupled to another control line.

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