Annulus pressure buildup mitigation device

Abstract

The invention relates to an annulus pressure buildup mitigation device (202) configured to be fitted on the outside of a casing string, the annulus pressure buildup mitigation device (202) comprising a tubular sleeve (203), an enclosed space within the tubular sleeve (203) and a pressure sensitive device (204), wherein the enclosed space is sealed by the pressure sensitive device (204) and the pressure sensitive device (204) is configured to unseal the enclosed space and thereby put the enclosed space in fluid communication with the outside of the tubular sleeve (203) if pressure outside of the tubular sleeve (203) exceeds a pressure threshold.

Description

[0001] ANNULUS PRESSURE BUILDUP MITIGATION DEVICE

[0002] Technical field

[0003] The present invention relates to the field of oil or gas production wells, and more specifically to an annulus pressure buildup mitigation device configured to be fitted on the outside of a casing of an oil or gas production well. The invention also relates to a casing segment having the annulus pressure buildup mitigation device fitted thereon. The invention further relates to a casing string comprising one or more of such casing segments having the annulus pressure buildup mitigation device fitted thereon. The invention finally relates to an oil or gas production well comprising the casing string comprising one or more of such casing segments having the annulus pressure buildup mitigation device fitted thereon.

[0004] Technical background

[0005] When an oil or gas production well is constructed, after the drilling step, there can be trapped annular volumes between casings. This will have consequences during production. Indeed, annulus pressure buildup (APB) may appear and can be a major issue. APB occurs when a trapped annular fluid is overheating. The trapped annular fluid generally heats up during production of hot oil or gas as described in Loder, Toni, Evans, Jason H., and James E. Griffith (2003), Prediction of and Effective Preventative Solution for Annular Fluid Pressure Buildup on Subsea Completed Wells-Case Study, 10.2118 / 84270-MS.

[0006] Too much annulus pressure buildup can cause an over pressurisation and potential irreversible damage to the casing, such as casing burst or casing collapse causing potential leakage. In some cases, the production can be deeply affected to the point that the well has to be abandoned.

[0007] Also known is Yin, Fei & Gao, Deli (2014), Improved Calculation of Multiple Annuli Pressure Buildup in Subsea HPHT Wells, 10.2118 / 170553-MS, which discloses a calculation method based on temperature increment that improves the calculation precision of annular pressure buildup.

[0008] Current options to mitigate against annulus pressure buildup exist. These different existing techniques all present advantages and drawbacks. A first option is to frac the casing shoe. This essentially consists of breaking the casing to release the pressure. Another option is to have a rupture disc, i.e. a metal disc which bursts when excess pressure is applied, thus allowing the pressure to vent from a first annulus, preferably farthest to the production tubing, to a second annulus, preferably closest to the production tubing. Another option is based on a nitrogen cap. It generally comprises injecting a certain volume fraction of nitrogen into the well to mitigate against the annulus pressure buildup. Another option is crushable plastic. Such an option involves the use of a crushable plastic or foam on the outside of the casing that can be compressed under high pressure to free more space and therefore reduce the pressure. A final option is vacuum insulated tubing. This kind of tubing reduces lateral heat loss from the production tubing to the wellbore. The vacuum insulation helps minimize heat transfer and thus prevents the annulus pressure buildup.

[0009] Within this context, there is still a need for an improved solution for mitigating against annulus pressure buildup, which in particular better fits different well design scenarios.

[0010] Summary of the invention

[0011] A first object of the invention is an annulus pressure buildup mitigation device configured to be fitted on the outside of a casing string, the annulus pressure buildup mitigation device comprising a tubular sleeve, an enclosed space within the tubular sleeve and a pressure sensitive device, wherein the enclosed space is sealed by the pressure sensitive device and the pressure sensitive device is configured to unseal the enclosed space and thereby put the enclosed space in fluid communication with the outside of the tubular sleeve if pressure outside of the tubular sleeve exceeds a pressure threshold.

[0012] In some variations, the annulus pressure buildup mitigation device is configured to be fitted on the outside of the casing string by at least one set screw.

[0013] In some variations, the enclosed space is filled with nitrogen or air, preferably at atmospheric pressure, when the enclosed space is sealed.

[0014] In some variations, the pressure sensitive device comprises:

[0015] - a shear pin;

[0016] - a shear plug; and

[0017] - a plug bypass;

[0018] wherein the shear plug is configured to break the shear pin and to move into the plug bypass if pressure outside of the tubular sleeve exceeds the pressure threshold.

[0019] In some variations, the pressure sensitive device comprises a rupture disc. In some variations, the annulus pressure buildup mitigation device comprises a plurality of enclosed spaces within the tubular sleeve and a plurality of pressure sensitive devices, wherein each enclosed space is sealed by a respective pressure sensitive device and each pressure sensitive device is configured to unseal the respective enclosed space and thereby put the respective enclosed space in fluid communication with the outside of the tubular sleeve if pressure outside of the tubular sleeve exceeds a pressure threshold.

[0020] In some variations, the or each enclosed space is sealed by a plurality of pressure sensitive devices.

[0021] In some variations, the or each enclosed space comprises a channel. In some variations, the or each channel is a helical channel extending around the longitudinal axis of the tubular sleeve.

[0022] In some variations, the or each channel is a longitudinal channel extending parallel to the longitudinal axis of the tubular sleeve.

[0023] In some variations, the annulus pressure buildup mitigation device comprises a gas test port associated with the or each enclosed space.

[0024] The invention further relates to a casing segment having the annulus pressure buildup mitigation device according to any one or any combination of the preceding variations fitted thereon.

[0025] In some variations, the casing segment is a production casing segment, or an intermediate casing segment, or a surface segment.

[0026] The invention further relates to a casing string comprising one or more casing segments.

[0027] The invention further relates to an oil or gas production well comprising the casing string.

[0028] Compared to the previously presented solutions, the Annulus Pressure Buildup Mitigation Device offers some benefits. Indeed, the present invention is non-destructive to the casing string contrary to the use of a rupture disc or to having to frac the casing shoe. The present invention is also simpler in operation compared to a nitrogen cap which may require complex intervention and additional tools. The present invention allows to reduce the cost compared to vacuum insulation tubing. The present invention finally is more effective than crushable plastic in mitigating APB.

[0029] More generally, the present invention requires fewer resources and a shorter rig time to prevent over pressurisation compared to previous known methods. The present invention offers better cost effectiveness, better useability, better operability and redundancy.

[0030] Brief description of the drawings

[0031] FIG. 1 shows an example of casing for an offshore subsea well.

[0032] FIG. 2 shows an embodiment of an annulus pressure buildup mitigation device fitted on the outside of a casing joint. FIG. 3A / 3B show details of the device of FIG. 2 in two different configurations.

[0033] FIG. 4 shows another example of an annulus pressure buildup mitigation device comprising longitudinal channels.

[0034] FIG. 5 shows another example of an annulus pressure buildup mitigation device comprising coiled tubing.

[0035] Detailed description

[0036] The invention will now be described in more detail without limitation in the following description.

[0037] A first object of the invention is an annulus pressure buildup mitigation device configured to be fitted on the outside of a casing string. The annulus pressure buildup mitigation device comprises a tubular sleeve. The annulus pressure buildup mitigation device further comprises one or more enclosed spaces within the tubular sleeve. The annulus pressure buildup mitigation device further comprises one or more pressure sensitive devices. In the annulus pressure buildup mitigation device, the or each enclosed space is sealed by at least one pressure sensitive device and the pressure sensitive device is configured to unseal the respective enclosed space and thereby put the respective enclosed space in fluid communication with the outside of the tubular sleeve if pressure outside of the tubular sleeve exceeds a pressure threshold.

[0038] “Annulus pressure buildup" (APB) refers to an annular pressure increase. The annular pressure is the pressure between two elements in a well, for example between the production tubing and a first casing or between two casings.

[0039] “Annulus pressure buildup mitigation device" (APBMD) refers to the device presented in the first object of the invention. This device is configured to mitigate against the annulus pressure buildup. In other words, this device is configured to reduce the annular pressure.

[0040] With reference to FIG. 1, an oil or gas production well, in this case an offshore subsea well, is presented. In this case, the well is positioned under the sea level 101 and extends from the seabed 103. The well comprises a casing which protects a production tubing 105 transporting production fluid 104. The casing may comprise a production casing 107 surrounding the production tubing 105, an intermediate casing 109 surrounding the production casing 107, and a surface casing 111 surrounding the intermediate casing 109. The production tubing 105 may extend deeper than the production casing 107. The production casing 107 may extend deeper than the intermediate casing 109. The intermediate casing 109 may extend deeper than the surface casing 111. Each casing is protected by a surrounding envelope made of cement 102.

[0041] A first annulus A 106 may be present between the production tubing 105 and the production casing 107. A second annulus B 108 may be present between the production casing 107 and the intermediate casing 109. A third annulus C 110 may be present between the intermediate casing 109 and the surface casing 111. Each annulus A, B, C may comprise annular fluid 112, comprising for instance drilling mud. The annular fluid 112 may heat up during production in the production tubing, causing an annulus pressure buildup.

[0042] A “casing" refers to a system of protective pipes or shells protecting well integrity and avoiding fluid displacement within the well.

[0043] A “casing string" refers to a long section of connected pipes in a casing. A “casing segment’ or “casing joint’ refers to an individual pipe; the casing segments are connected to form a casing string.

[0044] The annulus pressure buildup mitigation device may be configured to be fitted on the outside of a casing string by at least one set screw, preferably by a plurality of set screws. The annulus pressure buildup mitigation device may be fitted on the outside of a casing segment or on the outside of a casing coupling between two casing segments, the casing segment or casing coupling belonging for example to the production casing 107, intermediate casing 109 or surface casing 111.

[0045] Another object of the invention is a casing segment having the annulus pressure buildup mitigation device fitted thereon. Such a casing segment may be a segment of the production casing 107. Such a casing segment may be a segment of the intermediate casing 109. Such a casing segment may be a segment of the surface casing 111.

[0046] Another object of the invention is a casing string comprising one or more casing segments having an annulus pressure buildup mitigation device fitted thereon. The annular pressure buildup mitigation device ensures the integrity of the casing string. This casing string may be installed in a conventional way, with the one or more annulus pressure buildup mitigation device already preinstalled on the relevant casing segments.

[0047] Another object of the invention is an oil or gas production well comprising a casing string comprising one or more casing segments having the annulus pressure buildup mitigation device fitted thereon. More than one casing strings in the well may comprise one or more casing segments having the annulus pressure buildup mitigation device fitted thereon. Such an oil or gas production well may efficiently mitigate annulus pressure buildup in a non-destructive way for the well. The tubular sleeve of the annulus pressure buildup mitigation device may be slid onto and fixed to the casing string.

[0048] The length of an annulus pressure buildup mitigation device along the longitudinal axis of the casing string may be between 5% and 15% of the length of a casing segment. Multiple consecutive annulus pressure buildup mitigation devices can be fitted on the outside of a casing string, along the longitudinal axis of the casing string. For example, one annulus pressure buildup mitigation device may be present on each casing segment, or one annulus pressure buildup mitigation device may be present every N casing segments, N being for example 2, 3, 4, 5, 6, 7, 8, 9, 10 or more than 10. The total number of annulus pressure buildup mitigation devices on the casing string may be from 1 to 1500, preferably from 50 to 1000, more preferably from 100 to 500, by way of example from 150 to 250. A relatively large number of such devices on the casing string may be more reliable as there is more redundancy in the overall system; besides, only the necessary number of devices will shear to protect the casing string, depending on the pressure buildup.

[0049] The annulus pressure buildup mitigation device may be scalable in size to suit different casing string sizes. The annulus pressure buildup mitigation device may be scalable in length or scalable in diameter. For this purpose, the annulus pressure buildup mitigation device may be 3D printed (for example in carbon steel) to suit any annular space and combination of casing for example of different diameters. This also helps achieve rigidity and integrity of the annulus pressure buildup mitigation device.

[0050] The or each enclosed space within the tubular sleeve is configured to provide additional available volume for the annular fluid, so that when the pressure outside the tubular sleeve exceeds a pressure threshold, at least a part of the annular fluid outside the tubular sleeve can enter the enclosed space and therefore reduce the annular pressure.

[0051] When the or each enclosed space is sealed, it can be filled with gas, for example nitrogen or air, preferably at atmospheric pressure.

[0052] The annulus pressure buildup mitigation device may contain a total volume of enclosed space(s) from 0.0030 to 0.03 m3, preferably from 0.0040 to 0.02 m3, even more preferably from 0.0049 to 0.016 m3Multiple annulus pressure buildup mitigation devices may be combined to increase the available volume.

[0053] The or each enclosed space of the annulus pressure buildup mitigation device may comprise a channel. When the pressure exceeds the pressure threshold, the or each enclosed space is unsealed by the pressure sensitive device and so the annular fluid is displaced inside the channel. The channel may be a helical channel extending around the longitudinal axis of the tubular sleeve of the annulus pressure buildup mitigation device or a longitudinal channel extending parallel to the longitudinal axis of the tubular sleeve of the annulus pressure buildup mitigation device.

[0054] In some embodiments, the annulus pressure buildup mitigation device comprises a plurality of enclosed spaces within the tubular sleeve and a plurality of pressure sensitive devices. Each enclosed space is sealed by a respective pressure sensitive device and each pressure sensitive device is configured to unseal the respective enclosed space and thereby put the respective enclosed space in fluid communication with the outside of the tubular sleeve if pressure outside of the tubular sleeve exceeds a pressure threshold. This may provide more additional available volume for the annular fluid when the pressure exceeds the pressure threshold. The objective is to maximise the useful volume within the tubular sleeve.

[0055] Now referring to FIG. 2, an annulus pressure buildup mitigation device 202 is attached to a casing segment 201, for example thanks to set screws 207. The annulus pressure buildup mitigation device 202 may be slid into position on the outside of the casing segment 201 before being attached. The annulus pressure buildup mitigation device 202 comprises a tubular sleeve 203 (having a central longitudinal axis) and a pressure sensitive device 204 configured to unseal an enclosed space comprising a helical channel 205. There may be for example 2, 3, 4, 5, 6 or more than 6 helical channels, each helical channel having a substantially helical configuration around the central longitudinal axis of the tubular sleeve. The coils of the various helical channels may alternate along the tubular sleeve. Each helical channel may be arranged between an inner wall and an outer wall of the tubular sleeve, within the thickness of the tubular sleeve. Each helical channel 205 may be associated with its own pressure sensitive device 204 (or there may be two or more pressure sensitive devices per helical channel, for redundancy reasons).

[0056] The annulus pressure buildup mitigation device may further comprise a gas test port 206. There may be one such gas test port 206 per channel 205. A gas test port is configured to test (during manufacturing of the annulus pressure buildup mitigation device and / or during manufacturing of the casing string) that there is no risk leak in the annulus pressure buildup mitigation device, by applying pressure at this gas test port. After such testing, the gas test port may be closed so as to ensure sealing of the enclosed space.

[0057] Now referring to FIG. 4, another annulus pressure buildup mitigation device 202 is presented. The annulus pressure buildup mitigation device 202 is to be attached to a casing segment (not presented here) thanks to set screws 207. The annulus pressure buildup mitigation device 202 comprises a tubular sleeve 203 (having a central longitudinal axis) and a pressure sensitive device 204 configured to unseal an enclosed space comprising a longitudinal channel 205.

[0058] There may be for example 2, 3, 4, 5, 6 or more than 6 longitudinal channels, each longitudinal channel having a substantially linear orientation parallel to the central longitudinal axis of the tubular sleeve. Each longitudinal channel may be arranged between an inner wall and an outer wall of the tubular sleeve, within the thickness of the tubular sleeve. Each longitudinal channel 205 may be associated with its own pressure sensitive device 204 (or there may be two or more pressure sensitive devices per longitudinal channel, for redundancy reasons). Part or all of the longitudinal channels may be fluidically interconnected.

[0059] The annulus pressure buildup mitigation device may further comprise a gas test port 206, preferably one gas test port 206 per longitudinal channel, as described above in connection with FIG. 2.

[0060] Alternatively, the channel may be provided by seamless small diameter tubing which may be coiled and slid onto the outside of the casing string. Multiple channels may be provided by a plurality of tubes which are coiled and slid onto the outside of the casing string. This may mitigate any manufacturing difficulties which may be encountered when large volumes are sought.

[0061] FIG. 5 shows an example of a buildup mitigation device 202 comprising tubing 205’ coiled around a casing segment 201, one end of the tubing 205’ being associated with a pressure sensitive device 204.

[0062] Pressure sensitive device

[0063] The pressure sensitive device is configured to unseal the enclosed space when the pressure on the outside of the tubular sleeve exceeds a certain pressure threshold. Exceeding a certain pressure threshold means that the pressure sensitive device is pressure-calibrated to unseal the enclosed space. The pressure sensitive device may be a one way opening device, that is it can unseal the enclosed space only once. After the enclosed space is unsealed, it cannot be sealed again by the pressure sensitive device.

[0064] The pressure threshold may be more than 300 bars, more than 400 bars or more than 500 bars. By way of example, the pressure threshold may be from 300 to 700 bars, preferably from 400 to 600 bars.

[0065] The or each enclosed space of the annulus pressure buildup mitigation device may be sealed by a plurality (two or more) of pressure sensitive devices. This may be helpful if at least one pressure sensitive device fails to unseal the enclosed space, as the further pressure sensitive devices may then operate as backup devices. The pressure threshold for each of these pressure sensitive devices may be the same or different.

[0066] In some embodiments, the pressure sensitive device comprises a shear pin, a shear plug and a plug bypass. The shear plug may be maintained by the shear pin in a fixed position when the pressure outside of the tubular sleeve is less than the pressure threshold. The shear plug is configured to break the shear pin and to move into the plug bypass if pressure outside of the tubular sleeve exceeds the pressure threshold.

[0067] Now referring to FIG. 3A and 3B, an exemplary pressure sensitive device 204 comprising a calibrated shear pin 301 and a shear plug 302 is shown. In FIG.

[0068] 3A, the enclosed space comprising the channel 205 is sealed. The shear plug 302 is maintained by the shear pin 301 in a fixed position, wherein the shear plug 302 sealingly obstructs a passageway between the enclosed space and the outside of the tubular sleeve 203. The plug bypass 303 may be aligned with the passageway. The enclosed space may be a channel having an entry between the passageway and the plug bypass 303. The shear pin 301 may be fixedly attached to the tubular sleeve 203. The shear pin 301 may be engaged with a corresponding pin hole in the shear plug 302. In the illustration, the shear pin 301 is provided as a protrusion on the outer periphery of a holding member 304 which is itself fixedly attached to the tubular sleeve 203. The holding member 304 in inserted in a recess of the shear plug 302 and the shear pin 301 engages a pin hole within the recess. The pressure differential between the outside of the tubular sleeve 203 and the enclosed space tends to push the shear plug 302 away from the passageway and into the plug bypass 303, but the shear plug 302 is maintained in fixed position owing to the pin engaged in the pin hole.

[0069] When the pressure on the outside of the tubular sleeve 203 reaches or exceeds the pressure threshold, the shear pin 301 may bend or break thus releasing the shear plug 302. The shear plug 302 may then move away from the holding member 304 and into the plug bypass 303, as shown on FIG. 3B. As a result, fluid communication may be established between the outside of the tubular sleeve 203 and the enclosed space, via the abovementioned passageway which is now unobstructed, so that the annular fluid may enter into the enclosed space.

[0070] Many variations of this mechanism are possible. For example, more than one shear pin may be provided. The shear pin may be present on the shear plug itself and may then engage a pin hole on a fixed holding member.

[0071] Instead of a shear pin I shear plug I plug bypass, the pressure sensitive device may comprise other configurations. For example, a shear plug and a plug bypass may be implemented as described above, except that the shear plug is maintained in fixed position (before the pressure threshold is reached or exceeded) by other attachment means, such as by friction fit, by an adhesive, by one or more screws, etc.

[0072] For example, the pressure sensitive device may comprise a rupture disc sealingly obstructing a passageway between the enclosed space and the outside of the tubular sleeve. When the pressure outside of the tubular sleeve reaches or exceeds the pressure threshold, the rupture disc may break, thus establishing fluid communication between the enclosed space and the outside.

[0073] Experimental results

[0074] The following table results from WellCat numerical simulations, assuming a volume of enclosed space (bypass volume) for each APBMD of 0.35 m3.

[0075] Number of Total Bypass Estimated Change in APB compared Total change in APBMDs Volume (m3) APB (bar) to n-1 APBMD (bar) APB (bar) 0 0 611.2893 0 0 37 0.35 538.8254 72.4639 72.4639 73 0.70 467.1889 71.6365 144.1004 131 1.05 396.5176 70.6713 214.7717

[0076]

[0077] 175 1.40 326.4668 70.0508 284.8225 Table 1: Pressure reduction as a function of bypass volume Therefore, in this example, providing 175 annulus pressure buildup mitigation devices reduces the annulus pressure buildup by almost 50%.

Claims

Claims1. An annulus pressure buildup mitigation device (202) configured to be fitted on the outside of a casing string, the annulus pressure buildup mitigation device (202) comprising a tubular sleeve (203), an enclosed space within the tubular sleeve (203) and a pressure sensitive device (204), wherein the enclosed space is sealed by the pressure sensitive device (204) and the pressure sensitive device (204) is configured to unseal the enclosed space and thereby put the enclosed space in fluid communication with the outside of the tubular sleeve (203) if pressure outside of the tubular sleeve (203) exceeds a pressure threshold.

2. The annulus pressure buildup mitigation device (202) of claim 1 which is configured to be fitted on the outside of the casing string by at least one set screw (207).

3. The annulus pressure buildup mitigation device (202) of claim 1 or 2, wherein the enclosed space is filled with nitrogen or air, preferably at atmospheric pressure, when the enclosed space is sealed.

4. The annulus pressure buildup mitigation device (202) of any one of claims 1-3, wherein the pressure sensitive device (204) comprises:- a shear pin (301);- a shear plug (302); and- a plug bypass (303);wherein the shear plug (302) is configured to break the shear pin (301) and to move into the plug bypass (303) if pressure outside of the tubular sleeve (203) exceeds the pressure threshold.

5. The annulus pressure buildup mitigation device (202) of any one of claims 1-4, wherein the pressure sensitive device (204) comprises a rupture disc.

6. The annulus pressure buildup mitigation device (202) of any one of claims 1-5, which comprises a plurality of enclosed spaces within the tubular sleeve (203) and a plurality of pressure sensitive devices(204), wherein each enclosed space is sealed by a respective pressure sensitive device (204) and each pressure sensitive device (204) is configured to unseal the respective enclosed space and thereby put the respective enclosed space in fluid communication with the outside of the tubular sleeve (203) if pressure outside of the tubular sleeve (203) exceeds a pressure threshold.

7. The annulus pressure buildup mitigation device (202) of any one of claims 1-6, wherein the or each enclosed space is sealed by a plurality of pressure sensitive devices (204).

8. The annulus pressure buildup mitigation device (202) of any one of claims 1-7, wherein the or each enclosed space comprises a channel (205).

9. The annulus pressure buildup mitigation device (202) of claim 8, wherein the or each channel (205) is a helical channel extending around the longitudinal axis of the tubular sleeve (203).

10. The annulus pressure buildup mitigation device (202) of claim 8, wherein the or each channel (205) is a longitudinal channel extending parallel to the longitudinal axis of the tubular sleeve (203).

11. The annulus pressure buildup mitigation device (202) of any one of claims 1-10, comprising a gas test port (206) associated with the or each enclosed space.

12. A casing segment (201) having the annulus pressure buildup mitigation device (202) according to any one of claims 1-11 fitted thereon.

13. The casing segment (201) according to claim 12, which is a production casing segment, or an intermediate casing segment, or a surface segment.

14. A casing string comprising one or more casing segments (201) according to claim 12 or 13.

15. An oil or gas production well comprising the casing string according to claim 14.

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