WO2025259748A1

WO2025259748A1 - Self-contained pressure compensation for rotating control device seals

Info

Publication number: WO2025259748A1
Application number: PCT/US2025/033138
Authority: WO
Inventors: Jaakko Jalmari HALMARI
Original assignee: Schlumberger Canada Ltd; Services Petroliers Schlumberger SA; Schlumberger Technology BV; Schlumberger Technology Corp
Current assignee: Schlumberger Canada Ltd; Services Petroliers Schlumberger SA; Schlumberger Technology BV; Schlumberger Technology Corp
Priority date: 2024-06-14
Filing date: 2025-06-11
Publication date: 2025-12-18
Anticipated expiration: 2026-12-14

Abstract

A technique facilitates use of a rotating control device in a variety of wellbore operations. According to an embodiment, the rotating control device may comprise relative rotatable components, such as an outer housing and an inner rotatable system which is rotatable with respect to the outer housing. Additionally, the rotating control device may comprise a seal system disposed between the rotatable components. The rotating control device further comprises a pressure compensation system in communication with the seal system to provide pressure compensation against wellbore pressure acting on the seal system. The pressure compensation system is fully self-contained and powered by wellbore pressure.

Description

SELF-CONTAINED PRESSURE COMPENSATION FOR ROTATING CONTROL DEVICE SEALS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63/659,861, filed June 14, 2024, which is incorporated by reference herein in its entirety.

BACKGROUND

[0002] In many oil and gas well applications, a rotating control device is used to contain and isolate pressure while rotary drilling. The rotating control device comprises an outer housing and an inner rotating system. When used in offshore operations, e.g. subsea drilling, the rotating control device housing may be integral to a riser system extending up through the sea toward a surface facility from a seabed location. The inner rotating system is deployed within the outer housing and at least portions of the system rotate with the drill string during a drilling operation while maintaining a seal with the drill string via large elastomeric drill string seals. The inner rotating system may be mounted within the outer housing via a plurality of bearings. Additionally, a seal system is disposed between the inner rotating system and the outer housing so as to seal against wellbore pressure. The seal system is sealed with a single pressure compensation pressure applied against seals of the seal system in opposition to the wellbore pressure. The compensation pressure may be achieved via oil supplied under pressure to the rotating control device and its seal system through hoses routed down to the rotating control device from an external skid. Consequently, in various existing pressure compensation systems the maintenance of compensation pressure utilizes a relatively complex system for maintaining a single compensation pressure. SUMMARY

[0003] In general, a system and methodology facilitate use of a rotating control device in a variety wellbore operations. According to an embodiment, the rotating control device may comprise relative rotatable components, such as an outer housing and an inner rotatable system which is rotatable with respect to the outer housing. Additionally, the rotating control device may comprise a seal system disposed between the rotatable components. The rotating control device further comprises a pressure compensation system in communication with the seal system to provide pressure compensation against wellbore pressure acting on the seal system. The pressure compensation system is fully self-contained and powered by wellbore pressure.

[0004] However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

[0006] Figure 1 is a schematic illustration of an example of a rotating control device positioned along a riser deployed in a subsea well operation, according to an embodiment of the disclosure;

[0007] Figure 2 is a cross-sectional view of a portion of the rotating control device illustrated in Figure 1, according to an embodiment of the disclosure; [0008] Figure 3 is an orthogonal view of an example of an outer housing of the rotating control device combined with a self-contained pressure compensation system, according to an embodiment of the disclosure;

[0009] Figure 4 is an enlarged cross-sectional view of an example of the self- contained pressure compensation system, according to an embodiment of the disclosure;

[0010] Figure 5 is a view of the self-contained pressure compensation system in cross-section showing pressure porting for routing fluid through the outer housing and to appropriate regions of the seal system, according to an embodiment of the disclosure; and

[0011] Figure 6 is an illustration similar to that of Figure 5 but showing the self- contained pressure compensation system in a different operational configuration, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

[0012] In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0013] The disclosure herein generally involves a system and methodology which facilitate use of a rotating control device in a variety of wellbore operations. According to an embodiment, the rotating control device may comprise relative rotatable components, such as an outer housing and an inner rotatable system which is rotatable with respect to the outer housing. Depending on the application, the inner rotatable system may rotate within the outer housing via bearings and may comprise various features and components. For example, the inner rotatable system may comprise one or more large elastomeric drill string seals configured to seal against a drill string when the drill string is moved linearly through an interior passage of the inner rotatable system.

[0014] Additionally, the rotating control device comprises a seal system disposed between the rotatable components to seal against wellbore fluids, such as drilling mud which is pumped downhole during a drilling operation. The wellbore fluids may be at relatively high wellbore pressures, and the seal system protects various components of the rotating control device against undesired exposure to these fluids. The rotating control device further comprises a pressure compensation system in communication with the seal system to provide pressure compensation against the wellbore pressure acting on the seal system. The pressure compensation system is fully self-contained and powered solely by wellbore pressure. This self-contained nature of the pressure compensation system enables its operation without routing hydraulic pressure lines down to the rotating control device and without employing a skid having pressure equipment for supplying compensation fluid under pressure through the hydraulic pressure lines. Instead, wellbore pressure is used to pressurize compensation fluid in the pressure compensation system and this pressurized compensation fluid is directed to appropriate seals of the seal system.

[0015] The actual configuration of the pressure compensation system may have several embodiments depending on, for example, the overall structure and intended use of the rotating control device. For example, the pressure compensation system may be formed as a block or module attached, e.g. bolted, to the outer housing of the rotating control device. However, the pressure compensation system may be wholly or partially integrally formed in the outer housing; or the pressure compensation may be internal with respect to the outer housing.

[0016] According to one embodiment, the pressure compensation system comprises a module having a housing formed with a plurality of cylinders, e.g., two or more cylinders. The module is bolted or otherwise attached to the outer housing of the rotating control device along one side of the rotating control device. The cylinders are exposed to wellbore pressures on one side and to compensation pressures on an opposite side.

[0017] In some embodiments, one of the cylinders is a full compensation pressure cylinder that uses a single diameter piston providing equal wellbore and compensation pressures. The single diameter piston provides active surface areas exposed to the wellbore pressure and the compensation fluid pressure, and those active surface areas are equal in area. In some applications, a spring may be added to slightly increase the compensation pressure above that provided by the single diameter piston and thus above the wellbore pressure.

[0018] Another one of the cylinders may be a reduced compensation pressure cylinder that reduces the pressure of the compensation fluid to a level less than the wellbore pressure, e.g., half the wellbore pressure. By way of example, the reduced compensation pressure cylinder may contain a compensation piston having two different diameters. The different diameters present two differently sized surface areas which create the desired reduction or step down in pressures. A section of the compensation piston between the two active surface areas may be connected to atmosphere.

[0019] It should be noted that additional cylinders and pistons may be added to the system to provide additional compensating pressures. Regardless, the system is fully self-contained and powered by the wellbore pressure so that no outside connections are needed.

[0020] Referring generally to Figure 1, a well system 20 is illustrated as employed in a subsea well operation, e.g., a subsea wellbore drilling operation. However, well system 20 also can be an on-shore system utilizing the pressure compensation system described herein. In the illustrated example, subsea equipment 22, including a blowout preventer (BOP) 24, is deployed at a subsea location along a seabed 26. A subsea well 28 comprises a borehole 30, e.g. a wellbore, extending down from the subsea equipment 22. During a drilling operation, the borehole 30 may be formed via continued drilling to a desired subsea depth and location.

[0021] The well system 20 further comprises a riser 32 extending through seawater 34 from the subsea equipment 22 to a surface facility 36. The surface facility 36 may comprise a variety of ships, platforms, rigs, or other types of facilities located along a sea surface 38. A rotating control device 40 may be positioned at a desired location along the riser 32 so as to facilitate, for example, a drilling operation. However, the rotating control device 40 may be positioned along other types of equipment for use in other types of applications with respect to borehole 30.

[0022] As explained in greater detail below, the rotating control device 40 comprises a pressure compensation system 42 which is fully self-contained and powered solely by wellbore pressure. In other words, the wellbore pressure resulting from wellbore fluids within riser 32 is used to establish the desired compensation pressures for compensation fluids directed to a seal system of the rotating control device 40. By using the wellbore pressure to establish the desired compensation pressures, the overall pressure compensation system is substantially simplified by avoiding the need for external connections to external hoses and additional pressure equipment.

[0023] Referring generally to Figure 2, a cross-sectional portion of one example of rotating control device 40 is illustrated. In this embodiment, the rotating control device 40 comprises an outer housing 44 which may be constructed for mounting to riser 32 in a rotationally stationary position. Additionally, a rotatable system 46 is mounted within the outer housing 44 and may be constructed in a variety of configurations with various components and features.

[0024] The rotatable system 46 and outer housing 44 are examples of components which may be rotatably mounted with respect to each other via, for example, bearings 48. Bearings 48 may comprise one or more sets of bearings with suitable constructions, e.g., roller bearings, tapered roller bearings, or other suitable types of bearings. The rotating control device 40 also comprises a seal system 50 disposed between the rotatable system 46 and the outer housing 44 so as to seal against the ingress of undesirable well fluids, e.g., drilling mud, into regions between rotatable system 46 and outer housing 44, e.g., regions containing bearings 48.

[0025] The seal system 50 comprises at least one seal 52, e.g., a plurality of seals 52, which may be mounted within a seal housing 54 secured within outer housing 44. (In some embodiments, the seals 52 could be fixed along their inside with the rotating/siding surface along their outside.) The seals 52 may be rotary seals or other suitable seals oriented for contact with an inner support housing 56 of rotatable system 46, as illustrated. In the illustrated example, the seal system 50 comprises three seals 52 although different numbers of seals 52 may be employed to provide the desired sealing.

[0026] In the embodiment of Figure 2, the seal system 50 is exposed to wellbore pressure, e.g., the pressure of the drilling mud, at a wellbore pressure region 58, and to atmospheric pressure at an atmospheric pressure region 60 located on an opposite side of the seals 52. One or more of the seals 52 experience wellbore pressure on one side, and this wellbore pressure is compensated via compensating pressure on an opposing side of the subject seals 52. The compensating pressure may be established via suitable compensating pressure fluids, e.g., compensating oil, directed to opposing sides of selected seals 52 as indicated by arrows 62.

[0027] It should be noted the rotating control device 40 may comprise many other components and features, such as various mounting structures for securing the bearings 48 and other components. Additionally, the rotatable system 46 of rotating control device 40 may comprise one or more large elastomeric drill string seal members 64. The drill string seal members 64 are sized and configured to seal against a well string 66, e.g., a drill string, as it is moved down through an interior passage 68 of rotating control device 40. This interior passage 68 may be oriented linearly through a central region of rotatable system 46. [0028] With additional reference to Figure 3, an example of pressure compensation system 42 is illustrated. In this embodiment, pressure compensation system 42 is in the form of a block or module 70 attached along an exterior of outer housing 44. By way of example, the module 70 may be bolted or otherwise secured along outer housing 44. It should be noted, however, the pressure compensation system 42 may be integrally formed within outer housing 44, positioned internally of outer housing 44, or located at other suitable positions along rotating control device 40.

[0029] In the example of Figure 3, the module 70 comprises a module housing 72 having cylinders 74 for receiving pistons 76. The number of cylinders 74 and pistons 76 may vary and may be used to achieve different levels of compensating fluid pressure. Similarly, the size and configuration of cylinders 74 and pistons 76 may be selected to achieve desired pressure compensation parameters with respect to seals 52.

[0030] Outer housing 44 may be constructed with suitable flat surfaces, seal surfaces, and other features to facilitate mounting module 70. It should also be noted that outer housing 44 may comprise various other features, such as connection ends 78 for coupling the outer housing 44 with riser 32. Outer housing 44 also may comprise a mud return passage 80 for directing returning drilling mud to an exterior of the riser 32.

[0031] In the illustrated example, there are two cylinders 74 as further shown in Figure 4. According to this embodiment, the cylinders 74 comprise a full compensation pressure cylinder 82 and the pistons 76 comprise a single diameter piston 84 disposed in the full compensation pressure cylinder 82. The single diameter piston 84 provides a compensation pressure equal to the wellbore pressure to which it is exposed.

[0032] Effectively, the single diameter of piston 84 results in a first active surface area 86 exposed to wellbore pressure and a second active surface area 88 providing the compensation fluid pressure (see also Figure 5). The active surface areas 86, 88 are equal in area and thus equalize the compensation fluid pressure with the wellbore fluid pressure. [0033] In some embodiments, a spring 90 may be added to slightly increase the compensation pressure above that provided by the single diameter piston 84 and thus above the wellbore pressure. Spring 90 may be a coil type spring disposed within an interior of piston 84, as illustrated. However, other types of springs 90 may be used to provide a compensation fluid pressure slightly greater than the wellbore pressure. The slightly greater compensation fluid pressure helps ensure that any leakage moves from the clean oil side to the wellbore side so the seals 52 and the clean oil remain clean.

[0034] Another one of the cylinders 74 may be a reduced compensation pressure cylinder 92. Similarly, another one of the pistons 76 may be a pressure reduction piston 94 in the form of a plural diameter, e.g., a double diameter, piston 94 configured for sliding actuation within the reduced compensation pressure cylinder 92. The reduced compensation pressure cylinder 92 and piston 94 cooperate to reduce the pressure of the compensation fluid acting on at least one of the seals 52 to a level less than the wellbore pressure. For example, the compensation fluid pressure may be reduced to half the wellbore pressure or to another desired lower pressure level.

[0035] The two diameters of illustrated piston 94 provide a first active surface area 96 exposed to wellbore pressure and a second active surface area 98 providing the reduced compensation fluid pressure. The active surface area 96 may have half the surface area relative to active surface area 98 to provide a reduced compensation pressure of approximately half the wellbore pressure. As discussed above, however, different ratios of active surface areas 96, 98 may be employed to achieve a desired pressure reduction. A section of the compensation pressure reduction piston 94 between the two active surface areas 96, 98 may be connected to atmosphere.

[0036] It should be noted that additional cylinders 74 and pistons 76 may be added to the pressure compensation system 42 to provide additional compensating pressures. Regardless, the system is fully self-contained and powered by the wellbore pressure so that no outside connections or extra pressure equipment are needed. [0037] In some embodiments, individual cylinders 74 may contain additional pistons positioned to provide an improved barrier between, for example, drilling mud and a compensation fluid 100 so as to avoid introducing foreign materials into the pressure compensation system 42. (It should be noted that with respect to the compensation fluid 100 illustrated in Figure 4, the compensation fluid 100 is effectively separated fluids with the compensation fluid 100 in the left cylinder 74 experiencing full compensating pressure while the compensation fluid 100 in the right cylinder 74 experiences the reduced compensating pressure. As noted below, the compensating oil 100 from the left cylinder 74 could be used to feed the right cylinder 74 in certain embodiments.) Various other techniques also may be employed to provide transfer barriers which limit and/or remove such foreign materials. Additionally, some embodiments may utilize clean compensation fluid 100 to provide the desired wellbore pressure on a given side of one of the pistons 76. If, for example, the configuration of full compensation pressure cylinder 82 is able to hold sufficient compensation fluid 100, that fluid could also be directed to the “wellbore pressure” side of piston 94 instead of exposing piston 94 directly to wellbore fluid. These are just a few examples of modifications that may be made with respect to pressure compensation system 42 while still achieving the desired results.

[0038] Referring again to Figures 4 and 5, the cylinders 74 each provide a region for receiving compensating fluid 100, e.g., compensating oil. The compensating fluid 100 may be directed to appropriate seals 52 of seal system 50 via a porting network 102 having compensation fluid ports 104 provided at appropriate locations in cylinders 74. As a result, the appropriate seals 52 are exposed to the intended compensation pressure. The porting network 102 also may comprise wellbore pressure ports 106 exposing different regions of cylinders 74 to wellbore fluid pressure. For example, the ports 104 may be located on opposite sides of the corresponding pistons 76 relative to the ports 106 (see also Figure 6).

[0039] According to one example, the porting network 102 provides a pathway for compensating fluid 100 between full compensation pressure cylinder 82 and an upper side of the lowest seal 52 illustrated in Figure 2. This exposes the upper side of lowest seal 52 to a compensation pressure equal to wellbore pressure (or slightly above if spring 90 is employed). The lower side of this lowest seal 52 is exposed to drilling mud and the associated wellbore pressure, thus placing both the upper and lower sides of this lowest seal 52 at approximately wellbore pressure.

[0040] The compensating fluid 100 at wellbore pressure also acts against a lower side of the next sequential seal 52, i.e., the middle seal in Figure 2. However, the porting network 102 routes compensating fluid 100 at a reduced pressure, e.g. half of the wellbore pressure, between the reduced compensation pressure cylinder 92 and an upper side of this middle seal 52.

[0041] This reduced pressure compensating fluid 100 also acts against a lower side of the next sequential seal 52, i.e., the upper seal in Figure 2, while the upper side of this upper seal 52 is exposed to atmosphere. However, different numbers of seals 52, different numbers of cylinders 74/pistons 76, and different configurations/routing with respect to porting network 102 may be utilized to achieve multiple compensation pressure levels in desired patterns with respect to seal system 50.

[0042] As illustrated in Figure 6, the pistons 76 are able to move along their corresponding cylinders 74 to accommodate for loss of compensating fluid 100. If sufficient compensating fluid 100 is lost during operation, the pistons 76 may ultimately reach the extent of their travel. However, the size and capacities of cylinders 74 can be selected to ensure sufficient volumes of compensating fluid for anticipated well operations, e.g., drilling operations. In some embodiments, a reservoir of the compensating fluid 100 can be connected to desired cylinders 74 via ports and/or hoses so the compensating fluid 100 could be replaced if the cylinders run low or run out of the compensating fluid. The reservoir could be located subsea or at the surface.

[0043] Effectively, the pressure compensation system 42 provides a self- contained system which utilizes wellbore fluid pressure to establish desired compensation pressures for seal system 50. As a result, the desired pressure compensation can be achieved without the added expense and complexity of hydraulic lines and pressure equipment for providing the pressure compensation fluid to the seal system. Additionally, the use of two or more cylinders 74/pistons 76 with appropriate similar and/or dissimilar active surface areas enables a multi-level pressure compensation system 42 by which multiple levels of pressure compensation can be achieved.

[0044] Depending on the specific well operation and well equipment, the overall well system 20 may be adjusted and various additional or alternate components may be utilized. For example, the features, size, shape, and configuration of the rotating control device 40 may be adjusted. Similarly, the configuration of the seal system 50 may vary and may contain an individual seal 52 or multiple seals 52, e.g., three or more seals 52. As discussed above, the configuration and location of the pressure compensation system 42 also may be changed without detrimentally affecting the self-contained pressure compensation capability or the ability to provide multiple levels of compensation pressure.

[0045] Language of degree used herein, such as the terms “approximately,” “about,” “generally,” and “substantially” as used herein represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately,” “about,” “generally,” and “substantially” may refer to an amount that is within less than 10% of, within less than 5% of, within less than 1% of, within less than 0.1% of, and/or within less than 0.01% of the stated amount. As another example, in certain embodiments, the terms “generally parallel” and “substantially parallel” or “generally perpendicular” and “substantially perpendicular” refer to a value, amount, or characteristic that departs from exactly parallel or perpendicular, respectively, by less than or equal to 15 degrees, 10 degrees, 5 degrees, 3 degrees, 1 degree, or 0.1 degree.

[0046] Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

Claims

CLAIMS What is claimed is:

1. A system for use in a well operation, comprising: a rotating control device comprising: an outer housing; a rotatable system mounted within the outer housing, the rotatable system having a drill string seal member sized to seal along an exterior of a drill string; a bearing to facilitate rotation of the rotatable system relative to the outer housing; a seal system having a plurality of seals positioned between the outer housing and the rotatable system to provide sealing against wellbore pressure; and a pressure compensation system in communication with the seal system to provide pressure compensation against the wellbore pressure acting on the seal system, the pressure compensation system being self- contained and powered solely by wellbore pressure.

2. The system as recited in claim 1, wherein the pressure compensation system comprises a plurality of pistons mounted in a pressure compensation system housing, at least one piston of the plurality of pistons being exposed to wellbore fluid and thus to wellbore pressure.

3. The system as recited in claim 2, wherein the plurality of pistons comprises a single diameter piston in a full compensation pressure cylinder such that the single diameter piston provides a compensation pressure equal to the wellbore pressure.

4. The system as recited in claim 3, wherein the plurality of pistons further comprises at least one pressure reducer piston which provides a reduced seal compensation pressure relative to wellbore pressure.

5. The system as recited in claim 4, wherein the reduced seal compensation pressure is approximately half of the wellbore pressure.

6. The system as recited in claim 2, wherein the pressure compensation system housing is positioned along an exterior of the outer housing of the rotating control device.

7. The system as recited in claim 3, wherein the single diameter piston is combined with a spring such that the spring acts on the single diameter piston to provide an increased compensation pressure which is higher than the compensation pressure provided by the single diameter piston and thus above the wellbore pressure.

8. The system as recited in claim 1, further comprising a riser, the rotating control device being mounted along the riser.

9. The system as recited in claim 8, wherein the riser is connected to subsea equipment having a blowout preventer.

10. The system as recited in claim 9, wherein the riser is connected to a surface facility.

11. A system, comprising: a rotating control device comprising: a seal system disposed between components able to undergo relative rotation; and a pressure compensation system in communication with the seal system to provide pressure compensation against the wellbore pressure acting on the seal system, the pressure compensation system being self- contained and powered by wellbore pressure.

12. The system as recited in claim 11, wherein the pressure compensation system comprises a plurality of pistons mounted in a pressure compensation system housing.

13. The system as recited in claim 12, wherein the components able to undergo relative rotation include an outer housing, the pressure compensation system housing being positioned along an exterior of the outer housing.

14. The system as recited in claim 12, wherein the plurality of pistons comprises a single diameter piston in a full compensation pressure cylinder such that the single diameter piston provides a compensation pressure equal to the wellbore pressure.

15. The system as recited in claim 12, wherein the plurality of pistons further comprises at least one pressure reducer piston which provides a reduced compensation pressure relative to the wellbore pressure.

16. The system as recited in claim 15, wherein the pressure reducer piston comprises piston sections of differing diameters which provide different active surface areas relative to each other.

17. The system as recited in claim 15, further comprising a riser, the rotating control device being mounted along the riser.

18. A method, comprising: constructing a rotating control device with a rotatable system mounted within an outer housing for rotation with respect to the outer housing; providing a seal system between the rotatable system and the outer housing to seal against wellbore fluids; and employing a pressure compensation system in communication with the seal system to provide pressure compensation against the wellbore pressure acting on the seal system, the pressure compensation system being self-contained and powered by wellbore pressure.

19. The method as recited in claim 18, wherein employing comprises utilizing a plurality of pistons mounted in a pressure compensation system housing, at least one piston of the plurality of pistons being exposed wellbore pressure.

20. The method as recited in claim 19, further comprising positioning the rotating control device along a riser employed in a subsea well operation.