CA2853642C - Riser with internal rotating flow control device - Google Patents

Abstract

A riser pipe system is provided for releasably securing a rotating flow control device internally within a riser string for use in offshore drilling. The system includes a riser pipe section, a removable fastener assembly for releasably securing the RFCD, and upper and lower retaining members. The retaining members are disposed within the riser pipe section and axially restrain the fastener assembly axially therebetween. At least one of the retaining members is removably attached to the inner wall of the riser pipe section. The fastener assembly includes a latch and a seal element for engaging the RFCD, which are hydraulically or pneumatically actuated together.

Description

RISER WITH INTERNAL ROTATING FLOW CONTROL DEVICE
Field of the Invention 100011 The present invention relates to devices for managing downhole fluid pressures in offshore drilling, and more particularly to a riser pipe section with an internal rotating flow control device.
Background to the Invention

[0002] Oil and gas offshore drilling operations require the use of a "riser", or "riser string" as it is also known. The riser consists of a string of pipe that extends from a floating drilling platform down to the sea floor. The riser is comprised of riser components that are attached end-to-end by means of flanged or custom connections. Drilling mud, cuttings and hydrocarbon products from the borehole in the seafloor are returned to the drilling platform through the riser. The top of the riser is attached to the drilling platform while its lower end is secured to the wellhead on the seafloor. Immediately below the drilling platform, the riser has a "slip joint", or "tension joint" as it is also known, that is configured to telescope to compensate for the heave and swell that the floating drilling platform experiences in the sea.

[0003] It is conventional to use a subsurface blowout preventer (a "BOP") placed between the wellhead and the riser to provide protection against the sudden release of gas, which can arise if the drilling operations encounter pressurized formations.
To promote safety and control, a surface BOP is also frequently placed at the top of the riser proximate to the drilling platform.

[0004] It is also conventional to use a surface rotating flow control device (a "RFCD") at the level of the drilling platform in conjunction with the surface BOP. The surface RFCD
serves multiple purposes including the provision of a pressure seal around drill pipe that is being moved in and out of the riser and the wellbore while allowing rotation of same.
Conventional diverters are also placed at the head of the riser above the slip joint to divert wellbore returns to the surface separation and storage equipment.

[0005] While the use of a surface BOP and a surface RFCD provides a pressure seal and a barrier between the external environment and the wellbore returns, such a configuration can be problematic. If the subsurface BOP fails, or if there is a sudden release of gas or pressurized fluid into the riser for any other reason (for example, solution gas assuming gaseous form as it ascends the riser), control of the pressurized gas or fluid in the riser occurs at the level of the drilling platform using the surface BOP stack, the surface RFCD
and the diverter. This can result in exposure of the drilling platform to dangerous risk if the pressure and volume of the wellbore return within the riser exceeds the pressure rating of the riser, or if the capacity of the surface equipment to deal with this type of event is not adequate.

[0006] These problems may be mitigated by positioning the RFCD in the riser below the slip joint, which is the weakest pressure rated assembly in the riser string.
In this manner, the RFCD creates a pressure seal that isolates the pressurized wellbore returns in the riser below the drilling platform so that they can be contained and diverted if required at a subsurface level thereby substantially eliminating the exposure of the drilling platform to danger, and giving the riser greater than typical pressure integrity.

[0007] U.S. 2006/0102387 to Bourgoyne et al. describes a RFCD releasably positioned in a riser by a holding member that is threadably connected to the RFCD. In use, the assembled holding member and RFCD are run down the riser together, until their movement is resisted either by lugs on the holding member that engage an internal 1.5 shoulder of the riser, or a passive latching mechanism between the holding member and an internal formation of the riser. However, the holding member adds weight to the drill string, and a retractable seal is required between the holding member and the interior of the riser to permit passage of the holding member.

[0008] WO 2013006963 to Boyd et al. describes a RFCD integrated into the riser by a stationary housing having a flanged connector that is, in use, sandwiched between the flanges of two adjacent riser pipe sections. However, the flange connection of the stationary housing must be made complementary to the flanges of the adjacent riser pipe sections.

[0009] Accordingly, there is a need for a system to secure a RFCD in a riser to create an additional pressure seal between the wellbore and the external environment. It would also be preferable if the system avoided the need for components that added to the weight of the drill string, retractable seals, and extensive modification to standard riser pipe sections. Further, it would be preferable if the system allowed the RFCD to be remotely secured and released.
Summary of the Invention

[0010] In one aspect, there is described a system for securing and sealing a rotating flow control device ("RFCD") within a riser pipe section, the system comprising: a seal element which releasably seals against the RFCD; a seal piston which actuates the seal element; a latch which releasably secures the RFCD in the riser pipe section; and a latch piston which actuates the latch, wherein a first pressure applied to the latch piston causes the latch piston to displace, and wherein displacement of the latch piston applies a second pressure to the seal piston, thereby concurrently actuating the latch and the seal element.

[0011] In another aspect, there is described a system for releasing a rotating flow control device ("RFCD") from a riser pipe section, the system comprising: a latch which releasably secures the RFCD in the riser pipe section; a latch piston which actuates the latch; a seal element which releasably seals against the RFCD; and a seal piston which actuates the seal element, wherein a first pressure applied to the seal piston causes the seal piston to displace, and wherein displacement of the seal piston applies a second pressure to the latch piston, and thereby concurrently releases the seal element and the latch from the RFCD.

[0011a1 In another aspect, there is described a method of securing a rotating flow control device ("RFCD") in a riser pipe section, the method comprising: lowering the RFCD into the riser pipe section, the riser pipe section comprising a latch which releasably secures the RFCD
in the riser pipe section, and the riser pipe section further comprising a seal element which releasably seals against the RFCD; applying a first pressure to a first port of the riser pipe section, thereby displacing a latch piston and actuating the latch; and applying a second pressure to a seal piston in response to displacement of the latch piston, thereby displacing the seal piston and actuating the seal element.
[0011b] In another aspect, there is described a method of releasing a rotating flow control device ("RFCD") from a riser pipe section, the method comprising: applying a first pressure to a first port of the riser pipe section, thereby displacing a seal piston and expanding a seal element configured to releasably seal against the RFCD; and applying a second pressure to a latch piston in response to displacement of the seal piston, thereby displacing the latch piston and releasing a latch configured to releasably secure the RFCD in the riser pipe section.
Brief Description of the Drawings

[0012] In the drawings, like elements are assigned like reference numerals.
The drawings are not necessarily to scale, with the emphasis instead placed upon the principles of the present invention. Additionally, each of the embodiments depicted are but one of a number of possible arrangements utilizing the fundamental concepts of the present invention. Any dimensions shown in the accompanying are intended to be illustrative only, and not limiting of the claimed invention. The drawings are briefly described as follows:

[0013] Figure 1 is a diagrammatic depiction of one embodiment of an offshore drilling operation including a system of the present invention.

[0014] Figure 2 is a three-dimensional perspective view through a vertical half-section one embodiment of the system of the present invention installed within a riser string, with a RFCD and drill pipe secured therein.
5a

[0015] Figure 3 is a three-dimensional perspective view through a vertical three-quarter section of the embodiment of the system shown in Figure 2, with a flow outlet attached,

[0016] Figure 4 is a three-dimensional perspective view through a vertical half-section of a portion of the embodiment of the system shown in Figure 2,

[0017] Figure 5 is a side elevation view through a vertical half-section of a portion of the embodiment of the system shown in Figure 2.

[0018] Figures 6A, 6B and 6C are side elevation views through a vertical half-section of a portion of the system shown in Figure 2, with an RFCD secured therein. In Figure 6A, the latch piston and seal piston are in a raised position. In Figure 6B, the latch piston is a lowered position and the seal piston in a raised position, In Figure 6C, the latch piston and the seal piston are in a lowered position.

[0019] Figure 7 is a three-dimensional perspective view through a vertical half-section of the embodiment of the RFCD shown in Figure 2, Detailed Description of Embodiments of the Invention

[0020] The invention relates to a system for securing a rotating flow control device ("RFCD") in a riser of an offshore drilling operation. When describing the present invention, all terms not defined herein have their common art-recognized meanings. To the extent that the following description is of a specific embodiment or a particular use of the invention, it is intended to be illustrative only, and not limiting of the claimed invention. The following description is intended to cover all alternatives, modifications and equivalents that are included in the spirit and scope of the invention, as defined in the appended claims.

[0021] Offshore oil and gas drilling operations conducted on the sea floor require the use of riser. In one embodiment, as shown in Figure 1, the riser (2) extends from the drilling platform (4) down to the sea floor (6). The drilling platform (4) may comprise a floating rig or a drill ship, or any like surface platform employed by the offshore drilling industry.
The riser (2) is comprised of a string of interconnected riser components, including riser pipe sections (30a, 30b, 30c, 30d), generally denoted as (30). Commonly, the riser pipe sections (30) have flanged ends. The flanged ends of the riser pipe sections (30) attach in a complementary manner and are secured by bolts passing through apertures formed in the flanged ends,

[0022] Once a wellbore (8) has been established in the sea floor (4) and a casing (10) has been cemented into place in the wellbore (8), a subsea BOP (12) is landed on and secured to the well head (not shown). The riser (2) connects to the subsea BOP (12) and extends to the drilling platform (4). In practice, the subsea BOP (12) is tested to ensure operational functionality following which, drilling operations commence through the riser (2) in an incremental manner, Drill pipe (not shown) is lowered down through the riser (2) and drilling mud is injected down through the drill pipe. Drilling mud, cuttings and hydrocarbon returns from the borehole travel up to the drilling platform (4) through the annular space between the drill pipe and the riser (2). Immediately below the drilling platform (4), the riser (2) has a slip joint (14) that is configured to telescope in an open and closed fashion to compensate for the heave and swell that the floating drilling platform (4) experiences in the sea. The slip joint (14) prevents the riser (2) from being pulled or pushed off the well head as the drilling platform (4) rises and falls with the movement of the sea.

[0023] As further shown in Figure 1, a surface BOP (16) may be employed proximate to the drilling platform (4). It is also conventional to use a surface RFCD (18) at the head on the riser (2) on the drilling platform (4). The surface RFCD (18) serves multiple purposes including the provision of a pressure seal around tubular are being tripped in and out of the riser (2), and ultimately the wellbore (8) itself, while allowing rotation of the drill pipe, A conventional diverter (20) is also placed at the head of the riser (2) beneath the surface RFCD (16) to divert wellbore returns from the riser (2) to the surface separation and storage equipment (not shown).

[0024] The use of a conventional diverter (20) and a surface RFCD (18) at the head of a riser (2) provides a pressure seal and a barrier between the external environment and the wellbore returns. However, such configuration can be problematic. If the subsurface BOP
stack (12) fails, or if there is a sudden release of gas or pressurized fluid into the riser (2) for any other reason (for example, solution gas assuming gaseous form as it ascends), control of the pressurized gas or fluid in the riser (2) occurs at the level of the drilling platform (4) using the surface BOP (16), the surface RFCD (18), and the diverter (20), This can expose of the drilling platform (4) to dangerous risk if the pressure and volume of the wellbore return within the riser (2) exceeds the pressure rating of the riser (2), or if the capacity and pressure rating of the surface equipment to deal with this type of event is inadequate. For example, should the pressure in the riser (2) exceed the pressure capacity of its weakest component, which is typically a 500 psi maximum pressure rated slip joint (14) located immediately below the diverter (20) and drilling platform (4), then to preclude mechanical failure of the riser (2), the diverter (20) is usually configured to automatically open a control port to vent the wellbore returns to relieve pressure. This results in the sudden release of pressurized hydrocarbon product at surface level that can potentially ignite resulting in an explosion at surface, Further, if venting using the diverter (20) does not successfully reduce the pressure in the riser (2), mechanical failure in the riser (2) or the well head may occur, resulting in uncontrolled introduction of wellbore returns into the sea and external environment.

[0025] In one embodiment, the system (1) of the present invention seeks to mitigate these problems by securing a RFCD in the riser (2) at a position below both the drill platform (4) and the weakest pressure rated assembly in the riser string, namely the slip joint (14), thus giving the riser (2) a much greater typical pressure integrity. In one embodiment, a riser (2) employing the system (1) of the present invention may have a pressure integrity of up to 2000 psi. When so secured, the combination of the system (1) and the RFCD
create a pressure seal that isolates the pressurized wellbore returns in the riser (2) below the drilling platform (4) such that it can be contained and diverted if required at a subsurface level thereby substantially eliminating the exposure of the drilling platform to danger, In this manner, the system and the RFCD provide an effective additional safety system to complement the surface level conventional diverter (20), surface BOP
(16), and the surface RFCD (18).

[0026] One embodiment of the system (1) of the present invention is now described with reference to Figures 2 to 7. Referring to Figure 2, the system (1) secures a RFCD (100) that in conjunction with stripper elements (120, 122) form a pressure seal around a drill pipe (200) in a riser (2). In general, the system (1) includes a riser pipe section (30), a lower retaining member (40), an upper retaining member (50), and a removable fastener assembly (60), In the embodiment shown in the Figures, the system (1) also includes a collet locating member (130). As used herein, in describing the orientation of parts of the system (1), the term "axial" means a direction substantially parallel to the lengthwise direction of the drill pipe (200), and the term "radial" means a direction substantially perpendicular to the axial direction,

[0027] The riser pipe section (30) allows the system (1) to be installed axially within the riser string (2). Referring to Figure 2, in one embodiment, the riser pipe section (30) has an inner wall (32) that defines a bore, which de-fines an annular space between the riser (2) and the drill pipe (200). The lower end (34) of the riser pipe section (30) is formed into a flange with bolt holes, which are complementary to the bolt holes formed in the upper flange of adjacent lower riser pipe section (30b). Similarly, the upper end (36) of the riser pipe section (30) is formed into a flange with bolt holes, which are complementary to the bolt holes formed in the lower flange of adjacent upper riser pipe section (30d). The flanges can be standard American Petroleum Institute (API) flanges or custom-sized to match flanges of riser components, In other embodiments (not shown), the lower and upper ends (34, 36) may comprise other types of connection systems employed in the art for rigidly connecting riser pipe components, Referring to Figure 3, in one embodiment, the riser pipe section (30) also defines one or more ports (38) which can be used to relieve pressure downhole of the RECD (100) in to an attached flow outlet (140), which is positioned axially between the RFCD (100) and the wellbore (8),

[0028] The lower and upper retaining members (40, 50) axially restrain the fastening member (60) therebetween within the riser pipe section (30). In one embodiment, as shown in Figure 3, the lower and upper retaining members (40, 50) also axially restrain the collet locating member (130) therebetween within the riser pipe section (30). At least one of the retaining members (40, 50) is removably attached to the inner wall of the riser pipe section (30) to allow for removal of the fastener assembly (60) and, if present, the collet locating member (130), from the riser pipe section (30). The other retaining member may also be removably attached to the inner wall of the riser pipe section (30), or may be permanently affixed or integrally formed with the riser pipe section (30). In one embodiment, the lower and upper retaining members (40, 50) have an inner diameter that is substantially equal to the drift (i.e., internal diameter) (D) of the riser pipe section (30),

[0029] Referring to Figure 4, in one embodiment, the lower retaining member (40) comprises a continuous annular ring. The ring is attached to the bottom of fastener assembly (60) by bolts. Each of four quarter snap rings (42) are received in a groove formed in the inner wall of the riser pipe section (30) to define a gap therebetween. The ring of the lower retaining member (40) has arms (41) that are received in one of the gaps and form a friction-fit with one of the snap rings (42) and the inner wall of the riser pipe section (30). When so assembled, the snap rings (42) resist downward axial movement of the ring and attached fastener assembly (60). In other embodiments (not shown), the lower retaining member (40) may have a different shape, such as a plurality of projections such as lugs. The lower retaining member (40) may also be attached to the inner wall of the riser pipe section (30) by other suitable means known in the art such as a threaded connection, or may be formed integrally with the inner wall of the riser pipe section (30).

[0030] Referring to Figure 4, in one embodiment, the upper retaining member (50) also comprises a continuous annular ring. A bolted connection removably secures the upper retaining member (50) to an annular shoulder (39) formed monolithically with the inner wall of the riser pipe section (30). The lower surface (52) of the upper retaining member (50) provides a downward facing bearing surface for the collet locating member (130).
An upper surface (54) of the upper retaining member (50) bears against the internal annular shoulder (39) of the riser pipe section (30). In other embodiments (not shown), the upper retaining member (50) may have a different shape. Also, the upper retaining member (50) may be removably attached to the inner wall of the riser pipe section (30) by other suitable means known in the art such as a threaded connection, or may be formed integrally with the inner wall of the riser pipe section (30).

[0031] The fastener assembly (60) releasably secures the RFCD (100) within the riser pipe section (30). Referring to Figure 4, in one embodiment, the fastener assembly (60) is retained within the riser pipe section (30) by direct engagement with the lower retaining member (40) and indirect engagement with the upper retaining member (50) via the collet locating member (130). In one embodiment, the fastener assembly (60) has an inner diameter that is substantially the same as the drift (D) of the riser pipe section (30).
However, the fastener assembly (60) includes a plurality of latches (62) which extend radially inward to engage the RFCD (100) when installed in the fastener assembly (60), and which retract to disengage from the RFCD (100) to allow for removal of the RFCD
(100). In one embodiment, springs (not shown) bias the latches (62) in the radial inward direction, but yield when compressed to allow the RFCD (100) to slide into the annulus (64) of the fastener assembly (60). The fastener assembly (60) also has a seal assembly (84) to sealingly engage the RFCD (100) and resist axial rotation of the RFCD
(100) as the drill pipe (200) rotates within the RFCD (100). Referring to Figure 6A, in one embodiment, the seal element (84) is attached to the inner surface of the inner member (70). The seal element (84) may be made of a compressible material so that when the RFCD (100) slides axially into the annulus (64) of the fastener assembly (60), the seal element (84) compresses radially to allow axial passage of the RFCD (100).

[0032] Referring to Figure 4, in one embodiment, the fastener assembly (60) comprises an annular outer member (66), intermediate member (68), inner member (70) and ring (72). The wall of the outer member (66) has a substantially L-shape cross-section in the axial plane, with a horizontal leg that is adjacent and attached to the lower retaining member (40), and a vertical leg that is complementary to the inner wall of the riser pipe section (30) so as to create a fluid-tight seal therebetween. The wall of the intermediate member (68) has a substantially T-shape cross-section in the axial plane. The wall of the 'inner member (70) has a substantially linear cross-section in the axial plane and is disposed between the horizontal leg of the outer member (66) and the horizontal arm of the intermediate member (68). The inner member (70) retains the latches (62) and defines apertures for radial extension and retraction of the latches (62). The ring (72) engages the vertical leg of the outer member (66), the top of the intermediate member (68) and the bottom of the collet locating member (130) so as to create a fluid-tight seal therebetween.
The ring (72) is secured to the vertical leg of the outer member (66) by bolts (not shown) through aligned screw holes (73).

[0033] In one embodiment, the latches (62) and seal element (84) are hydraulically or pneumatically actuated together to extend and retract radially to engage with or disengage from the RFCD (100). Referring to Figure 6A, in one embodiment, the outer member (66) and intermediate member (68) cooperate to form an annular chamber (74). A
sliding annular latch piston (76) divides the chamber (74) into a lower portion and an upper portion and scalingly isolates the portions from each other. A linear cam (82) tbnned on the latch piston (72) translates axial movement of the latch piston (76) into radial movement of the latches (62). The intermediate member (68) and the inner member (70) of the fastener assembly (60) cooperate to form an annular chamber (86). A
sliding annular seal piston (88) divides the chamber (86) into a lower portion and an upper portion by and sealingly isolates the lower portion from the upper portion. An upper port (61) in the intermediate member (68) allows fluid communication between the lower portion of the chamber (74) and the upper portion of chamber (86). A linear cam (90) formed on the seal piston (88) translates axial movement of the seal piston (88) into radial movement of the seal element (84) to engage with or disengage from the RFCD (100). A lower port (35) of the riser pipe section (30) is aligned with a lower port (63) of the outer member (66) and a port (65) of the intermediate member (68), which is in fluid communication with the lower portion of chamber (86). An upper port (33) of the riser pipe section (30) is aligned with an upper port (80) of the outer member (66) which is in fluid communication with the upper portion of chamber (74). The latches (62) and seal element (84) may be disengaged from the RFCD (100) remotely by pumping fluid through a line connected to the lower port (35) of the riser pipe section (30), while relieving fluid through a line connected to the upper port (33) of the riser pipe section (30). As shown in Figure 6A, when the fluid pressure at the lower port (35) is greater than the fluid pressure at the upper port (33), the fluid urges the seal piston (88) to move upwardly in the fluid chamber (86), thus allowing the seal element (84) to retract radially and disengage from the RFCD (100). As the seal piston (88) moves upwards in the chamber (86), it forces the fluid in the upper portion of chamber (86) through port (61) into the lower portion of chamber (74). This urges the latch piston (76) to move upwardly in the fluid chamber (74), thus allowing the latches (62) to retract radially and disengage from the RFCD (100). Conversely, the latches (62) and seal element (84) may be engaged with the RFCD (100) remotely by pumping hydraulic fluid through a line connected to the upper port (33) of the riser pipe section (30), while relieving hydraulic through a line connected to the lower port (35) of the riser pipe section (30). As shown in Figure 6B, a greater fluid pressure at the upper port (33) than at the lower port (35) urges the latch piston (76) to move downwardly in the fluid chamber (74), thus allowing the latches to extend radially and engage the RFCD (100). As shown in Figure 6C, when the latch piston (76) moves axially downward, it forces hydraulic fluid from the lower portion of chamber (74) through the port (61) and into the upper portion of chamber (86). This urges the seal piston (88) to move axially downward in chamber (86), thus driving the seal element (84) to extend radially and engage the RFCD (100). In this manner, the latches (62) and seal element (84) can, in unison, be selectively engaged with the RFCD (100) or disengaged from the RFCD
(100) as a result of fluid communication between chamber (74) and chamber (86).

[0034] An intermediate port (31) of the riser pipe section (30) allows the latches (62) to be disengaged, independently of the seal element (84), from the RFCD (100). The intermediate port (31) is connected to a high flow line of hydraulic or pneumatic fluid and is in fluid communication with the lower portion of the chamber (74) via intermediate port (78) of outer member (66). In the event of seal failure of the latch piston (76) wherein the latches (62) remains engaged with the RFCD (100), hydraulic or pneumatic fluid can be pumped through the intermediate port (31) at high volume flow rate to drive the latch piston (76) upwards, and thereby allow the latches (62) to sufficiently disengage from the RFCD (100) so that the RFCD (100) can be pulled upwards and out of the fastener assembly (60). Although the seal element (84) may remain engaged with the RFCD (100), the seal element (84) may be configured so that there is insufficient friction between the seal element (84) and the RFCD
(100) to prevent deliberate removal of the RFCD (100) when the latches (62) are disengaged from the RFCD (100).

[0035] The removable RFCD (100) permits the drill pipe (200) to rotate within the riser pipe section (30). Referring to Figure 7, in one embodiment, the RFCD (100) is =
configured for a dual stripper arrangement. The RFCD (100) includes a robust lower housing (102) and a lower inner tubular shaft (104) for axial rotation therein. An intermediate housing (106) connects the lower outer housing (102) to a robust upper outer housing (108), which houses an upper inner tubular shaft (110) for axial rotation therein.
The housings (102, 106, 108), and the tubular shafts (104, 110) may be constructed from any suitable metallic material including, without limit, 41/30 alloy steel.
Each of the housings (102, 108) and their respective inner tubular shafts (104, 110) define therebetween an annular chamber (not shown) that contains bearing elements (not shown) and lubricating fluid. The annular chambers are sealed with respect to the lubricating fluid, thus avoiding the need for an external source of lubricating fluid and lubricating fluid lines. The bearing elements may comprise any suitable type used for like purposes by those skilled in the art, and may be arranged in any manner in the annular chambers to provide appropriate axial and radial support to the inner tubular shafts (104, 110). Any suitable lubricating fluid may be utilized in the annular chamber to cool and lubricate the bearing elements. Rotation of the inner tubular shafts (104, 110) within their respective outer housings (102, 108) is made possible by the bearing elements engaging an outer race that remains stationary with the housings (102, 108) and an inner race that rotates with the inner tubular shafts (104, 110).

[0036] Referring to Figure 7, in one embodiment, the lower outer housing (102) defines a circumferential lower recess (112) and upper recess (114). The lower recess (112) provides an engagement surface that is complementary in shape to the seal element (84) of the fastener assembly (60) to create a fluid-tight seal barrier between the lower outer housing (102) of the RFCD (100) and the inner member (70) of the fastener assembly (60). The upper recess (114) provides an engagement surface that is complementary in shape to the latches (62) of the fastener assembly (60).
10037] The stripper elements (120, 122) sealingly grip the drill pipe (200) to create a fluid tight seal with the drill pipe (200) and transfer axial rotation of the drill pipe (200) into axial rotation of the inner tubular shafts (104, 106) of the RFCD (100).
Referring to Figure 7, in one embodiment, a lower stripper element (120) is attached to the lower inner tubular shaft (104) and an upper stripper element (122) is attached to the upper inner tubular shaft (110) for a RFCD (100) with a dual stripper configuration. The stripper elements (120, 122) may be constructed from any suitable rubber, elastomer, or polymer substance.

[0038] The collet locating member (130) cooperates with a collet (116) attached to the RFCD (100) to properly position the RFCD (100) within the fastener assembly (60) for engagement by the latches (62) and seal element (84). Referring to Figure 4, in one embodiment, the collet locating member (130) is an annular member formed separately and retained axially within the riser pipe section (30) by engagement with the upper retaining member (50) and the fastener assembly (60). In other embodiments, the collet locating member (130) may have different shapes and may be positioned elsewhere within the riser pipe section (30). The collet locating member (130) may also be formed integrally with the inner wall of the riser pipe section (30), the lower retaining member (40), or the upper retaining member (50).
[0039] Referring to Figure 4, in one embodiment, the inner wall of the collet locating member (130) includes a vertical frustum-shaped surface (132) that terminates at the lower end with a horizontal annular land (134). The collet locating member (130) defines an inner diameter that is equal to the drift (i.e., internal diameter) (D) of the riser pipe section (30). Referring to Figure 7, in one embodiment, the collet (116) attached to the RFCD (100) is made of spring steel, and is a generally tubular member with a plurality of kerfs (not shown) cut in the axial direction to define a plurality, of fingers. The fingers have a lower chamfer (117) that is similar to an upper chamfer (56) of the upper retaining member (50). When the lower chamfer (70) of the fingers is forced downwardly against the upper chamfer (56) of the upper retaining member (50), the upper chamfer (56) squeezes together the fingers to allow the collet (116) and attached RFCD
(100) to pass through the upper retaining member (50) and the annulus (64) of the fastener assembly (60). As the collet (116) continues to move downwards through the frustum-shaped surface (132) of the collet locating member (130), the fingers of the collet (116) expand radially outwardly and engage the land (134), thus preventing further downward movement of the RFCD (100) as shown in Figure 6A. The collet (116) is dimensioned so that when it engages the land (134), the recesses (112, 114) of the RFCD (100) are axially aligned with the seal element (84) and the latches (62), respectively, of the fastener assembly (60). The fingers also have an upper chamfer (118) that is similar to the frustum-shaped surface (132) of the riser collet locating member (130). When the RFCD
(100) is pulled upwards, the frustum-shaped surface (132) engages the upper chamfer (118) of the collet (130), thereby squeezing them together and allowing the collet (116) to pass through the annulus (64) of the fastener assembly (60) and the upper retaining member (50).
[0040] The use and operation of the embodiment of the system (1) shown in Figure 2 is now described. The riser pipe section (30), the lower retaining member (40), the upper retaining member (50), the fastener assembly (60) and the collet locating member. (130) are assembled at the surface prior to installation in the riser string (2).
Hydraulic or pneumatic fluid lines are connected to each of ports (31, 33, 35) of the riser pipe section (30). A dual valve flow outlet (140) (as shown in Figure 3) for equalizing fill, and purge operations is connected to one of the ports (38). The flow outlet (140) is connected to pipes or hoses (142) (as shown in Figure 1) which travel to the surface for the selective discharge of well fluids and gases. The valves in the flow outlet (140) may be opened and closed remotely using surface controls to facilitate the selective venting and diversion of the well bore returns. Once assembled in this manner, the riser pipe section (30) is installed into the riser (2) as riser pipe section (30c) between adjacent riser pipe sections (30b, 30cI) as shown in Figures 1 and 2.
[0041] The RFCD (100) and associated stripper elements (120, 122) are also assembled at the surface. When required, the drill pipe (200) is inserted through the stripper elements (120, 122). As shown in Figure 2, the RFCD (100) rides the drill pipe (200) as the drill pipe (200) is lowered into the riser (2). Eventually, the collet (116) engages the land (134) of the collet locating member (130) to prevent further downward movement of the RFCD (100) when the recesses (112, 114) of the RFCD (100) are axially aligned with the seal element (84) and latches (62) of the fastener assembly (60). When the RFCD
(100) is so positioned, hydraulic or pneumatic fluid is pumped from the surface through the upper port (33) of the riser pipe section (30) into the upper portion of chamber (74) and relieved from the lower portion of chamber (86) through lower port (35) of the riser pipe section (30). This urges the latches (62) into engagement with the recess (114) of the RFCD (100) to secure the RFCD (100) in place. As the latch piston (76) moves downwards and drives fluid into the upper portion of chamber (86), the seal element (84) is urged into sealing engagement with the recess (112) of the RFCD (100). The RFCD
(100) may be removed by reversing the foregoing steps. If the stripper elements (120, 122) are not too compromised, the RIVE) (100) may be removed by pulling the drill pipe (200) upwards. However, if the stripper elements (120, 122) are unable to form an adequate seal on the drill pipe (200), then a recovery tool may be used for removal of the RFCD (100).
[0042] Once secured in the riser (2), the system (1) in conjunction with the RFCD (100) provides a seal on drill pipe (200) that is being run into or out of the wellbore (8) and provides an additional pressure barrier between the external environment and the wellbore (8) at a subsea level below the drilling platform (4). It also isolates the slip joint (14) from pressurized well bore returns. In the event of failure of the lower BOP stack (12) or the introduction of pressurized gas or fluid into the riser (2), the system (1) and RFCD (100) form a pressure seal thus precluding exposure of the slip joint (14) and the drilling platform (4) components to the pressurized fluid or gas. If venting is required to reduce the pressure in the riser (2) beneath the system (1), ports in the flow outlet (140) may be opened and the associated hose or pipe (142) will conduct the vented substances to a location that is a safe distance from the drilling platform. As such, the system (1) and RFCD (100) may be employed for well control operations, to promote safety and to mitigate environmental concerns and to manage high pressure drilling activities.
[0043] As will be apparent to those skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the scope of the invention claimed herein.

Claims (38)

EMBODIMENTS IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS
CLAIMED ARE DEFINED AS FOLLOWS:

1. A system for securing and sealing a rotating flow control device ("RFCD") within a riser pipe section, the system comprising:
a seal element which releasably seals against the RFCD;
a seal piston which actuates the seal element;
a latch which releasably secures the RFCD in the riser pipe section; and a latch piston which actuates the latch, wherein a first pressure applied to the latch piston causes the latch piston to displace, and wherein displacement of the latch piston applies a second pressure to the seal piston, thereby concurrently actuating the latch and the seal element.

2. The system of claim 1, wherein the latch displaces radially inward, and thereby secures the RFCD within the riser pipe section.

3. The system of claim 2, wherein the latch engages a first circumferential groove in an outer housing of the RFCD.

4. The system of claim 1, wherein the latch piston comprises a linear cam which converts axial movement of the latch piston into radial movement of the latch.

5. The system of claim 1 or 2, wherein the seal element seals radially inward against an outer housing of the RFCD when the second pressure is applied.

6. The system of claim 5, wherein the seal element engages a second circumferential groove in the outer housing of the RFCD.

7. The system of claim 1, 2 or 3, wherein the seal piston comprises a linear cam which converts axial movement of the seal piston into a compressive force of the seal element against the RFCD.

8. The system of claim 1, wherein the riser pipe section comprises first and second ports, and wherein the latch piston displaces in response to a differential in fluid pressure between the first and second ports.

9. The system of any one of claims 1 to 8, further comprising a collet locating member, wherein the collet locating member comprises a land which engages a collet disposed on an exterior of the RFCD, and thereby prevents further downward movement of the RFCD, but allows upward movement of the RFCD.

10. The system of claim 9, wherein the collet comprises a plurality of collet fingers separated by axial kerfs, each finger having a fixed end and a free end having an upper chamfer and a lower chamfer.

11. The system of claim 9 or 10, wherein the latch is aligned with a first circumferential recess on the RFCD when the collet engages the land.

12. The system of claim 9, 10 or 11, wherein the seal element is aligned with a second circumferential recess on the RFCD when the collet engages the land.

13. A system for releasing a rotating flow control device ("RFCD") from a riser pipe section, the system comprising:
a latch which releasably secures the RFCD in the riser pipe section;
a latch piston which actuates the latch;
a seal element which releasably seals against the RFCD; and a seal piston which actuates the seal element, wherein a first pressure applied to the seal piston causes the seal piston to displace, and wherein displacement of the seal piston applies a second pressure to the latch piston, and thereby concurrently releases the seal element and the latch from the RFCD.

14. The system of claim 13, wherein the seal element expands radially outward away from an outer housing of the RFCD when the first pressure is applied.

15. The system of claim 13 or 14, wherein the seal piston comprises a linear cam which converts axial movement of the seal piston into radial expansion of the seal element away from the RFCD.

16. The system of claim 13, 14 or 15, wherein the latch displaces radially outward, and thereby releases the RFCD from the riser pipe section.

17. The system of claim 13 or 14, wherein the latch piston comprises a linear cam which converts axial movement of the latch piston into radial movement of the latch.

18. The system of any one of claims 13 to 17, wherein the riser pipe section comprises first and second ports, and wherein the seal piston displaces in response to a differential in fluid pressure between the first and second ports.

19. The system of any one of claims 13 to 18, wherein the riser pipe section comprises a third port, and wherein pressure applied to the third port releases the latch independent of the seal element.

20. A method of securing a rotating flow control device ("RFCD") in a riser pipe section, the method comprising:
lowering the RFCD into the riser pipe section, the riser pipe section comprising a latch which releasably secures the RFCD in the riser pipe section, and the riser pipe section further comprising a seal element which releasably seals against the RFCD;

applying a first pressure to a first port of the riser pipe section, thereby displacing a latch piston and actuating the latch; and applying a second pressure to a seal piston in response to displacement of the latch piston, thereby displacing the seal piston and actuating the seal element.

21. The method of claim 20, wherein the riser pipe section is positioned in a riser string below a slip joint.

22. The method of claim 20 or 21, wherein the latch displaces radially inward, thereby securing the RFCD within the riser pipe section.

23. The method of claim 22, wherein the latch engages a first circumferential groove in an outer housing of the RFCD.

24. The method of any one of claims 20 to 23, wherein the latch piston comprises a linear cam which converts axial movement of the latch piston into radial movement of the latch.

25. The method of claim 20, 21 or 22, wherein the seal element seals radially inward against an outer housing of the RFCD when the second pressure is applied.

26. The method of claim 25, wherein the seal element engages a second circumferential groove in the outer housing of the RFCD.

27. The method of any one of claims 20 to 23, wherein the seal piston comprises a linear cam which converts axial movement of the seal piston into a compressive force of the seal element against the RFCD.

28. The method of any one of claims 20 to 27, wherein the riser pipe section further comprises a second port, and wherein the latch piston displaces in response to a differential in fluid pressure between the first and second ports.

29. The method of any one of claims 20 to 28, wherein the RFCD comprises a collet and the riser pipe section comprises a collet locating member, and wherein the RFCD is lowered until the collet engages the collet locating member.

30. The method of claim 29, wherein the RFCD comprises a latch receiving groove which is axially aligned with the latch when the collet engages the collet locating member.

31. The method of claim 29 or 30, wherein the RFCD comprises a seal receiving groove which is axially aligned with the seal element when the collet engages the collet locating member.

32. A method of releasing a rotating flow control device ("RFCD") from a riser pipe section, the method comprising:
applying a first pressure to a first port of the riser pipe section, thereby displacing a seal piston and expanding a seal element configured to releasably seal against the RFCD; and applying a second pressure to a latch piston in response to displacement of the seal piston, thereby displacing the latch piston and releasing a latch configured to releasably secure the RFCD in the riser pipe section.

33. The method of claim 32, wherein the seal element expands radially outward away from an outer housing of the RFCD when the first pressure is applied.

34. The method of claim 32 or 33, wherein the seal piston comprises a linear cam which converts axial movement of the seal piston into radial expansion of the seal element away from the RFCD.

35. The method of claim 32, 33 or 34, wherein the latch displaces radially outward, thereby releasing the RFCD from the riser pipe section.

36. The method of claim 32 or 33, wherein the latch piston comprises a linear cam which converts axial movement of the latch piston into radial movement of the latch.

37. The method of any one of claims 32 to 36, wherein the riser pipe section further comprises a second port, and wherein the seal piston displaces in response to a differential in fluid pressure between the first and second ports.

38. The method of any one of claims 32 to 37, wherein the riser pipe section further comprises a third port, and wherein pressure applied to the third port releases the latch independent of the seal element.