TIEBACK CEMENTING PLUG SYSTEM

Abstract

A method for casing a subsea wellbore includes running a tieback casing string into the subsea wellbore using a workstring including first, second, and third wiper plugs. The method further includes: launching a first release plug or tag into the workstring; pumping cement slurry into the workstring, thereby driving the first release plug or tag along the workstring; after pumping the cement slurry, launching a second release plug or tag into the workstring; and pumping chaser fluid into the workstring, thereby driving the release plugs or tags and cement slurry through the workstring. The release plugs or tags engage and release the respective wiper plugs from the workstring. The first wiper plug or release plug ruptures, thereby allowing the cement slurry to flow therethrough. The method further includes: stabbing the tieback casing string into a liner string; and retrieving the workstring, the workstring still including the third wiper plug.

Description

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure generally relates to a plug system for cementing a tieback casing string.

2. Description of the Related Art

Tieback casing strings are utilized to extend a production liner to a wellhead. Installation of a liner/tieback combination offers several advantages over a continuous casing, including delaying of expenses for uncertain or high risk well exploration, testing of isolation between the liner annulus and the open hole section, and a reduction of load-bearing requirements for derricks.

Many tieback strings are installed and cemented just before installation of completion equipment. However, issues with the cementing operation may necessitate removal of the tieback string and cement to correct the issues, a process which can be both expensive and time consuming.

Therefore, there is a need for an improved process for cementing a tieback casing string.

SUMMARY OF THE DISCLOSURE

The present disclosure generally relates to a plug system for cementing a tieback casing string. In one embodiment, a method for casing a subsea wellbore includes running a tieback casing string into the subsea wellbore using a workstring. The workstring includes a first wiper plug, a second wiper plug, and a third wiper plug. The method further includes: launching a first release plug or tag into the workstring; pumping cement slurry into the workstring, thereby driving the first release plug or tag along the workstring; after pumping the cement slurry, launching a second release plug or tag into the workstring; and pumping chaser fluid into the workstring, thereby driving the release plugs or tags and cement slurry through the workstring. The release plugs or tags engage and release the respective wiper plugs from the workstring. The first wiper plug or release plug ruptures, thereby allowing the cement slurry to flow therethrough and into an annulus formed between the tieback casing string and an outer casing string. The method further includes stabbing the tieback casing string into a liner string; and retrieving the workstring, the workstring still including the third wiper plug.

A method for casing a subsea wellbore includes running a tieback casing string into the subsea wellbore using a workstring. The workstring includes a first wiper plug, a second wiper plug, and a third wiper plug. The method further includes: launching a first release plug or tag into the workstring; pumping cement slurry into the workstring, thereby driving the first release plug or tag along the workstring; after pumping the cement slurry, launching a second release plug or tag into the workstring; and pumping chaser fluid into the workstring, thereby driving the release plugs or tags and cement slurry through the workstring. The release plugs or tags engage and release the respective wiper plugs from the workstring. The first wiper plug or release plug ruptures, thereby allowing the cement slurry to flow therethrough and into an annulus formed between the tieback casing string and an outer casing string. The method further includes: pumping conditioner fluid into the workstring, thereby rupturing the second wiper plug or release plug and flushing the cement slurry from the annulus; pumping remedial cement slurry into the workstring; after pumping the remedial cement slurry, launching a third release plug or tag into the workstring; pumping the chaser fluid into workstring, thereby driving the third release plug or tag and remedial cement slurry through the workstring. The third engages and releases the third wiper plug. The third wiper plug drives the remedial cement slurry into the annulus. The method further includes stabbing the tieback casing string into a liner string; and retrieving the workstring.

A plug release system includes a first wiper plug including a burst tube, the first burst tube adapted to burst at a pressure between 900 psi and 1100 psi; a second wiper plug including a burst tube, the second burst tube adapted to burst at a pressure between 3500 psi and 5000 psi; and a third wiper plug; wherein: the first wiper plug is coupled to the second wiper plug by a shearable fastener, the shearable fastener adapted to shear at a pressure between 500 psi and 700 psi; and the second wiper plug is coupled to the third wiper plug by a shearable fastener, the shearable fastener adapted to shear at a pressure between 1300 psi and 1700 psi.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

FIGS. 1A-1C illustrate a drilling system in a tieback casing deployment mode, according to one embodiment of this disclosure.

FIG. 2 illustrates a tieback deployment assembly, according to one embodiment of this disclosure.

FIGS. 3A-3C illustrate darts for releasing wiper plugs of the tieback deployment assembly.

FIG. 4 illustrates a lower portion of the tieback casing string.

FIGS. 5A-5G, 6A-6G and 7 illustrate a primary tieback cementing operation using the tieback deployment assembly.

FIGS. 8A-8D and 9A-9D illustrate a remedial tieback cementing operation using the tieback deployment assembly.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

FIGS. 1A-1C illustrate a drilling system 1 in a tieback casing deployment mode, according to one embodiment of this disclosure. The drilling system 1 may include a mobile offshore drilling unit (MODU) 1m, such as a semi-submersible, a drilling rig 1r, a fluid handling system 1h, a fluid transport system 1t, a pressure control assembly (PCA) 1p, and a workstring 9.

The MODU 1m may carry the drilling rig 1r and the fluid handling system 1h aboard and may include a moon pool, through which drilling operations are conducted. The semi-submersible MODU 1m may include a lower barge hull which floats below a surface (aka waterline) 2s of sea 2 and is, therefore, less subject to surface wave action. Stability columns (only one shown) may be mounted on the lower barge hull for supporting an upper hull above the waterline. The upper hull may have one or more decks for carrying the drilling rig 1r and fluid handling system 1h. The MODU 1m may further have a dynamic positioning system (DPS) (not shown) or be moored for maintaining the moon pool in position over a subsea wellhead 10.

Alternatively, the MODU may be a drill ship. Alternatively, a fixed offshore drilling unit or a non-mobile floating offshore drilling unit may be used instead of the MODU. Alternatively, the wellbore may be subsea having a wellhead located adjacent to the waterline and the drilling rig may be a located on a platform adjacent the wellhead. Alternatively, the wellbore may be subterranean and the drilling rig located on a terrestrial pad.

The drilling rig 1r may include a derrick 3, a floor 4, a top drive 5, a cementing head 7, and a hoist. The top drive 5 may include a motor for rotating the workstring 9. The top drive motor may be electric or hydraulic. A frame of the top drive 5 may be linked to a rail (not shown) of the derrick 3 for preventing rotation thereof during rotation of the workstring 9 and allowing for vertical movement of the top drive with a traveling block 11t of the hoist. The frame of the top drive 5 may be suspended from the derrick 3 by the traveling block 11t. The quill may be torsionally driven by the top drive motor and supported from the frame by bearings. The top drive 5 may further have an inlet connected to the frame and in fluid communication with the quill. The traveling block 11t may be supported by wire rope 11r connected at its upper end to a crown block 11c. The wire rope 11r may be woven through sheaves of the blocks 11c,t and extend to drawworks 12 for reeling thereof, thereby raising or lowering the traveling block 11t relative to the derrick 3. The drilling rig 1r may further include a drill string compensator (not shown) to account for heave of the MODU 1m. The drill string compensator may be disposed between the traveling block 11t and the top drive 5 (aka hook mounted) or between the crown block 11c and the derrick 3 (aka top mounted).

Alternatively, a Kelly and rotary table may be used instead of the top drive.

In the deployment mode, an upper end of the workstring 9 may be connected to the top drive quill, such as by threaded couplings. The workstring 9 may include a tieback deployment assembly (TDA) 9d and a deployment string, such as joints of drill pipe 9p connected together, such as by threaded couplings. An upper end of the TDA 9d may be connected a lower end of the drill pipe 9p, such as by threaded couplings. The TDA 9d may be connected to the tieback casing string 44, such as by engagement of a bayonet lug 45b with a mating bayonet profile formed in an upper end of the tieback casing string. The tieback casing string 44 may include a packer 44p, a casing hanger 44h, a mandrel 44m for carrying the hanger and packer and having a seal bore formed therein, joints of casing 44j, a float collar 44c, a seal stem 44s, and a guide shoe 44g. The tieback casing components may be interconnected, such as by threaded couplings.

Once deployment of the tieback casing string has concluded, the workstring 9 may be disconnected from the top drive 5 and the cementing head 7 may be inserted and connected between the top drive 5 and the workstring 9. The cementing head 7 may include an isolation valve 6, an actuator swivel 7h, a cementing swivel 7c, and one or more plug launchers, such as a first dart launcher 7a and a second dart launcher 7b. The isolation valve 6 may be connected to a quill of the top drive 5 and an upper end of the actuator swivel 7h, such as by threaded couplings. An upper end of the workstring 9 may be connected to a lower end of the cementing head 7, such as by threaded couplings.

The cementing swivel 7c may include a housing torsionally connected to the derrick 3, such as by bars, wire rope, or a bracket (not shown). The torsional connection may accommodate longitudinal movement of the swivel 7c relative to the derrick 3. The cementing swivel 7c may further include a mandrel and bearings for supporting the housing from the mandrel while accommodating rotation of the mandrel. An upper end of the mandrel may be connected to a lower end of the actuator swivel, such as by threaded couplings. The cementing swivel 7c may further include an inlet formed through a wall of the housing and in fluid communication with a port formed through the mandrel and a seal assembly for isolating the inlet-port communication. The cementing mandrel port may provide fluid communication between a bore of the cementing head and the housing inlet. The actuator swivel 7h may be similar to the cementing swivel 7c except that the housing may have three inlets in fluid communication with respective passages formed through the mandrel. The mandrel passages may extend to respective outlets of the mandrel for connection to respective hydraulic conduits (only one shown) for operating respective hydraulic actuators of the plug launchers 7a,b. The actuator swivel inlets may be in fluid communication with a hydraulic power unit (HPU, not shown).

Each dart launcher 7a,b may include a body, a diverter, a canister, a latch, and the actuator. Each body may be tubular and may have a bore therethrough. To facilitate assembly, each body may include two or more sections connected together, such as by threaded couplings. An upper end of the top dart launcher body may be connected to a lower end of the actuator swivel 7h, such as by threaded couplings and a lower end of the bottom dart launcher body may be connected to the workstring 9. Each body may further have a landing shoulder formed in an inner surface thereof. Each canister and diverter may each be disposed in the respective body bore. Each diverter may be connected to the respective body, such as by threaded couplings. Each canister may be longitudinally movable relative to the respective body. Each canister may be tubular and have ribs formed along and around an outer surface thereof. Bypass passages may be formed between the ribs. Each canister may further have a landing shoulder formed in a lower end thereof corresponding to the respective body landing shoulder. Each diverter may be operable to deflect fluid received from a cement line 14 away from a bore of the respective canister and toward the bypass passages. A release dart, such as a first dart 43a or a second dart 43b, may be disposed in the respective canister bore.

Each latch may include a body, a plunger, and a shaft. Each latch body may be connected to a respective lug formed in an outer surface of the respective launcher body, such as by threaded couplings. Each plunger may be longitudinally movable relative to the respective latch body and radially movable relative to the respective launcher body between a capture position and a release position. Each plunger may be moved between the positions by interaction, such as a jackscrew, with the respective shaft. Each shaft may be longitudinally connected to and rotatable relative to the respective latch body. Each actuator may be a hydraulic motor operable to rotate the shaft relative to the latch body.

Alternatively, the actuator swivel and launcher actuators may be pneumatic or electric. Alternatively, the dart launcher actuators may be linear, such as piston and cylinders.

In operation, when it is desired to launch one of the darts 43a,b, the HPU may be operated to supply hydraulic fluid to the appropriate launcher actuator via the actuator swivel 7h. The selected launcher actuator may then move the plunger to the release position (not shown). If one of the dart launchers 7a,b is selected, the respective canister and dart 43a,b may then move downward relative to the body until the landing shoulders engage. Engagement of the landing shoulders may close the respective canister bypass passages, thereby forcing fluid to flow into the canister bore. The fluid may then propel the respective dart 43a,b from the canister bore into a lower bore of the body and onward through the workstring 9.

The fluid transport system it may include an upper marine riser package (UMRP) 16u, a marine riser 17, a booster line 18b, and a choke line 18c. The riser 17 may extend from the PCA 1p to the MODU 1m and may connect to the MODU via the UMRP 16u. The UMRP 16u may include a diverter 19, a flex joint 20, a slip (aka telescopic) joint 21, and a tensioner 22. The slip joint 21 may include an outer barrel connected to an upper end of the riser 17, such as by a flanged connection, and an inner barrel connected to the flex joint 20, such as by a flanged connection. The outer barrel may also be connected to the tensioner 22, such as by a tensioner ring.

The flex joint 20 may also connect to the diverter 21, such as by a flanged connection. The diverter 21 may also be connected to the rig floor 4, such as by a bracket. The slip joint 21 may be operable to extend and retract in response to heave of the MODU 1m relative to the riser 17 while the tensioner 22 may reel wire rope in response to the heave, thereby supporting the riser 17 from the MODU 1m while accommodating the heave. The riser 17 may have one or more buoyancy modules (not shown) disposed therealong to reduce load on the tensioner 22.

The PCA 1p may be connected to the wellhead 10 located adjacent to a floor 2f of the sea 2. A conductor string 23 may be driven into the seafloor 2f. The conductor string 23 may include a housing and joints of conductor pipe connected together, such as by threaded couplings. Once the conductor string 23 has been set, a subsea wellbore 24 may be drilled into the seafloor 2f and a casing string 25 may be deployed into the wellbore. The casing string 25 may include a wellhead housing and joints of casing connected together, such as by threaded couplings. The wellhead housing may land in the conductor housing during deployment of the casing string 25. The casing string 25 may be cemented 26 into the wellbore 24. The casing string 25 may extend to a depth adjacent a bottom of the upper formation 27u. The wellbore 24 may then be extended into the lower formation 27b using a pilot bit and underreamer (not shown).

The lower formation 27b may be lined by deployment, hanging, cementing of lower annulus 48b, and sealing of a liner string 15. The liner string 15 may include, a packer 15p, a liner hanger 15h, a body 15v for carrying the hanger and packer (HP body), joints of liner 15j, a landing collar 15c, and a reamer shoe 15s. The HP body 15v, liner joints 15j, landing collar 15c, and reamer shoe 15s may be interconnected, such as by threaded couplings.

The upper formation 27u may be non-productive and a lower formation 27b may be a hydrocarbon-bearing reservoir. Alternatively, the lower formation 27b may be non-productive (e.g., a depleted zone), environmentally sensitive, such as an aquifer, or unstable.

The PCA 1p may include a wellhead adapter 28b, one or more flow crosses 29u,m,b, one or more blow out preventers (BOPs) 30a,u,b, a lower marine riser package (LMRP) 16b, one or more accumulators, and a receiver 31. The LMRP 16b may include a control pod, a flex joint 32, and a connector 28u. The wellhead adapter 28b, flow crosses 29u,m,b, BOPs 30a,u,b, receiver 31, connector 28u, and flex joint 32, may each include a housing having a longitudinal bore therethrough and may each be connected, such as by flanges, such that a continuous bore is maintained therethrough. The flex joints 21, 32 may accommodate respective horizontal and/or rotational (aka pitch and roll) movement of the MODU 1m relative to the riser 17 and the riser relative to the PCA 1p.

Each of the connector 28u and wellhead adapter 28b may include one or more fasteners, such as dogs, for fastening the LMRP 16b to the BOPs 30a,u,b and the PCA 1p to an external profile of the wellhead housing, respectively. Each of the connector 28u and wellhead adapter 28b may further include a seal sleeve for engaging an internal profile of the respective receiver 31 and wellhead housing. Each of the connector 28u and wellhead adapter 28b may be in electric or hydraulic communication with the control pod and/or further include an electric or hydraulic actuator and an interface, such as a hot stab, so that a remotely operated subsea vehicle (ROV) (not shown) may operate the actuator for engaging the dogs with the external profile.

The LMRP 16b may receive a lower end of the riser 17 and connect the riser to the PCA 1p. The control pod may be in electric, hydraulic, and/or optical communication with a rig controller (not shown) onboard the MODU 1m via an umbilical 33. The control pod may include one or more control valves (not shown) in communication with the BOPs 30a,u,b for operation thereof. Each control valve may include an electric or hydraulic actuator in communication with the umbilical 33. The umbilical 33 may include one or more hydraulic and/or electric control conduit/cables for the actuators. The accumulators may store pressurized hydraulic fluid for operating the BOPs 30a,u,b. Additionally, the accumulators may be used for operating one or more of the other components of the PCA 1p. The control pod may further include control valves for operating the other functions of the PCA 1p. The rig controller may operate the PCA 1p via the umbilical 33 and the control pod.

A lower end of the booster line 18b may be connected to a branch of the flow cross 29u by a shutoff valve. A booster manifold may also connect to the booster line lower end and have a prong connected to a respective branch of each flow cross 29m,b. Shutoff valves may be disposed in respective prongs of the booster manifold. Alternatively, a separate kill line (not shown) may be connected to the branches of the flow crosses 29m,b instead of the booster manifold. An upper end of the booster line 18b may be connected to an outlet of a booster pump (not shown). A lower end of the choke line 18c may have prongs connected to respective second branches of the flow crosses 29m,b. Shutoff valves may be disposed in respective prongs of the choke line lower end.

A pressure sensor may be connected to a second branch of the upper flow cross 29u. Pressure sensors may also be connected to the choke line prongs between respective shutoff valves and respective flow cross second branches. Each pressure sensor may be in data communication with the control pod. The lines 18b,c and umbilical 33 may extend between the MODU 1m and the PCA 1p by being fastened to brackets disposed along the riser 17. Each shutoff valve may be automated and have a hydraulic actuator (not shown) operable by the control pod.

Alternatively, the umbilical may be extended between the MODU and the PCA independently of the riser. Alternatively, the shutoff valve actuators may be electrical or pneumatic.

The fluid handling system 1h may include one or more pumps, such as a cement pump 13 and a mud pump 34, a reservoir, such as a tank 35, a solids separator, such as a shale shaker 36, one or more pressure gauges 37c,m, one or more stroke counters 38c,m, one or more flow lines, such as cement line 14, mud line 39, and return line 40, and a cement mixer 42. In the drilling mode, the tank 35 may be filled with drilling fluid, such as mud (not shown). In the tieback deployment mode, the tank 35 may be filled with conditioner 70.

A first end of the return line 40 may be connected to the diverter outlet and a second end of the return line may be connected to an inlet of the shaker 36. A lower end of the mud line 39 may be connected to an outlet of the mud pump 34 and an upper end of the mud line may be connected to the top drive inlet. The pressure gauge 37m may be assembled as part of the mud line 39. An upper end of the cement line 14 may be connected to the cementing swivel inlet and a lower end of the cement line may be connected to an outlet of the cement pump 13. The shutoff valve 41 and the pressure gauge 37c may be assembled as part of the cement line 14. A lower end of a mud supply line may be connected to an outlet of the mud tank 35 and an upper end of the mud supply line may be connected to an inlet of the mud pump 34. An upper end of a cement supply line may be connected to an outlet of the cement mixer 42 and a lower end of the cement supply line may be connected to an inlet of the cement pump 13.

During deployment of the tieback casing string 44, the workstring 9 may be lowered 8a by the traveling block 11t and the conditioner 70 may be pumped into the workstring bore by the mud pump 34 via the mud line 39 and top drive 5. The conditioner 70 may flow down the workstring bore and the liner string bore and be discharged by the guide shoe 44g into an upper annulus 48u formed between the tieback string 44 and the casing string 25. The conditioner 70 may flow up the upper annulus 48u and exit the wellbore 24 and flow into an annulus formed between the riser 17 and the workstring 9/tieback string 44 via an annulus of the LMRP 16b, BOP stack, and wellhead 10. The conditioner 70 may exit the riser annulus and enter the return line 40 via an annulus of the UMRP 16u and the diverter 19. The conditioner 70 may flow through the return line 40 and into the shale shaker inlet. The conditioner 70 may be processed by the shale shaker 36 to remove any particulates therefrom.

FIG. 2 illustrates the TDA 9d. FIGS. 3A-3C illustrate darts 43a-c for releasing respective wiper plugs 50a-c of the TDA 9d. The TDA 9d may include a running tool 45, a plug release system 46, and a packoff 47. The packoff 47 may be disposed in a recess of a housing 45h of the running tool 45 and carry inner and outer seals for isolating an interface between the tieback casing string 44 and the TDA 9d by engagement with the seal bore of the mandrel 44m. The running tool housing 45h may be connected to a housing 46h of the plug release system 46, such as by threaded couplings.

The plug release system 46 may include an equalization valve 46e, a first wiper plug 50a, a second wiper plug 50b, and third wiper plug 50c. The equalization valve 46e may include a housing 46h, an outer wall 46w, a cap 46c, a piston 46p, a spring 46s, a collet 46f, and a seal insert 46i. The housing 46h, outer wall 46w, and cap 46c may be interconnected, such as by threaded couplings. The piston 46p and spring 46s may be disposed in an annular chamber formed radially between the housing and the outer wall and longitudinally between a shoulder of the housing 46h and a shoulder of the cap 46c. The piston 46p may divide the chamber into an upper portion and a lower portion and carry a seal for isolating the portions. The cap 46c and housing 46h may also carry seals for isolating the portions. The spring 46s may bias the piston 46p toward the cap 46c. The cap 46c may have a port formed therethrough for providing fluid communication between the upper annulus 48u and the chamber lower portion and the housing 46h may have a port formed through a wall thereof for venting the upper chamber portion. An outlet port may be formed by a gap between a bottom of the housing 46h and a top of the cap 46c. As pressure from the upper annulus 48u acts against a lower surface of the piston 46p through the cap passage, the piston 46p may move upward and open the outlet port to facilitate equalization of pressure between the annulus and a bore of the housing 46h to prevent surge pressure from prematurely releasing one or more of the plugs 50a-c.

Each wiper plug 50a-c may be made from a drillable material and include a respective finned seal 51a-c, a plug body 52a-c, a latch sleeve 53a-c, and a lock sleeve 54a-c. Each latch sleeve 53a-c may have a collet formed in an upper end thereof and the second and third latch sleeves 53b,c may each have a respective collet profile formed in a lower portion thereof. Each lock sleeve 53a-c may have a respective seat 55a-c and seal bore 56a-c formed therein. Each lock sleeve 53a-c may be movable between an upper position and a lower position and be releasably restrained in the upper position by a respective shearable fastener 57a-c. Each dart 43a-c may be made from a drillable material and include a respective finned seal 58a-c and dart body. Each dart body may have a respective landing shoulder 59a-c and carry a respective landing seal 60a-c for engagement with the respective seat 55a-c and seal bore 56a-c. A major diameter of the first landing shoulder 59a may be less than a minor diameter of the second seat 55b and a major diameter of the second landing shoulder 59b may be less than a minor diameter of the third seat 55c such that the first dart 43a may pass through the second 50b and third 50c wiper plugs and the second dart 43b may pass through the third wiper plug.

The third shearable fastener 57c may releasably connect the third lock sleeve 53c to the valve housing 46h and the third lock sleeve may be engaged with the valve collet 46f in the upper position, thereby locking the valve collet into engagement with the collet of the third latch sleeve 53c. The second shearable fastener 57b may releasably connect the second lock sleeve 53b to the third lock sleeve 53c and the second lock sleeve may be engaged with the collet of the second latch sleeve 53b, thereby locking the collet into engagement with the collet profile of the third latch sleeve. The first shearable fastener 57a may releasably connect the first lock sleeve 53a to the second lock sleeve 53b and the second lock sleeve may be engaged with the collet of the first latch sleeve 53a, thereby locking the collet into engagement with the collet profile of the second latch sleeve. A release pressure necessary to fracture the first shearable fastener 57a may be substantially less than the release pressure necessary to fracture the second shearable fastener 57b which may be substantially less than the release pressure necessary to fracture the third shearable fastener 57c.

The first 50a and second 50b wiper plugs may each include one or more (pair shown) bypass ports formed through a wall of the respective lock sleeves 54a,b initially sealed by respective burst tubes 61a,b to prevent fluid flow therethrough. The burst tubes 61a,b are adapted to rupture when a predetermined pressure is applied thereto and a rupture pressure of the first burst tube 61a may be substantially less than a rupture pressure of the second burst tube 61b. The rupture pressure of the first burst tube 61a may also be substantially greater than the release pressure of the first wiper plug 50a and substantially less than the release pressure of the second wiper plug 50b. The rupture pressure of the second burst tube 61b may also be substantially greater than the release pressure of the second wiper plug 50b and substantially greater than the release pressure of the third wiper plug 50b.

The first wiper plug 50a may be released at a pressure ranging between 500 psi to 700 psi, the second wiper plug 50b may be released at a pressure ranging between 1300 psi to 1700 psi, and the third wiper plug 50c at a pressure ranging between 2000 psi to 2400 psi. The first burst tube 61a may rupture at a pressure ranging between 900 psi to 1100 psi and the second burst tube 61b may rupture at a pressure ranging between 3500 psi to 5000 psi.

Alternatively, the first dart 43a and the second dart 43b may include rupture disks or burst tubes rather than or in addition to the burst tubes 61a,b of the wiper plugs 50a,b. Thus, rupturing the of the burst tube within the first dart 43a or the second dart 43b would allow fluid flow therethrough when seated within a respective wiper plug.

To facilitate subsequent drill-out, each plug body 50a-c may further have a portion of an auto-orienting torsional profile 62m,f formed at a longitudinal end thereof. The first and second plug bodies 50a,b may each have the female portion 62f and male portion 62m formed at respective upper and lower ends thereof (or vice versa). The third plug body 50c may have only the male portion formed at the lower end thereof.

FIG. 4 illustrates a lower portion of the tieback casing string 44. The float collar 44c may include a housing 63h, a check valve 63v, and a body 63b. The body 63b and check valve 63v may be made from drillable materials. The body 63b may have a bore formed therethrough and the torsional profile female portion 62f formed in an upper end thereof for receiving the first wiper plug 50a. The check valve 63v may include a seat 64s, a poppet 64p disposed within the seat, a seal 64e disposed around the poppet and adapted to contact an inner surface of the seat to close the body bore, and a rib 64r. The poppet 64p may have a head portion and a stem portion. The rib 64r may support a stem portion of the poppet 64p. A spring 64g may be disposed around the stem portion and may bias the poppet 64p against the seat 64s to facilitate sealing. The poppet 64p may have a bypass slot 64b formed therein to prohibit the occurrence of hydraulic lock when stabbing the seal stem 44s into the PBR 15r by allowing fluid to pass around the closed poppet.

During deployment of the tieback casing string 44, the conditioner 70 may be pumped to prepare the upper annulus 48u for cementing. The conditioner 70 may be pumped down at a sufficient pressure to overcome the bias of the spring 64g, actuating the poppet 62s downward to allow conditioner 70 to flow through the bore of the body 63b.

The seal stem 44s may include a gland 65, one or more (three shown) seals 66, and a pair of wipers 67 straddling the seals. During stabbing of the seal stem 44s, the seals 66 may engage an inner surface of the PBR 15r while the wipers 67 displace particulates therefrom to ensure proper sealing. The wipers 67 and seals 66 may be positioned in grooves formed within an outer surface of the gland 65 to fix the wipers and the seals in place. During stabbing, the seals 66 initially engage the PBR 15r and change configuration to occupy an interface between the gland 65 and the PBR. The seals 66 may each include a protrusion for contact with the PBR 15r and energization thereof in response to the contact. The gland 65 may have a guide shoulder that is adapted to facilitate guidance of the tieback casing 44 in to the PBR 15r.

The guide shoe 44g may include a housing 68h and a nose 68n made from a drillable material. The nose 68n may have a rounded distal end to guide the tieback casing 44 down the casing 25 and into the PBR 15r.

FIGS. 5A-5G, 6A-6G and 7 illustrate a primary tieback cementing operation using the TDA 9d. As illustrated in FIGS. 5A and 6A, the tie back casing string 44 is lowered 8a until the packer 44p, hanger 44h, and mandrel 44m thereof are positioned proximately above the subsea wellhead 10 and the guide shoe 44g is positioned proximately above the PBR 15r to form a gap 69 therebetween. The gap 69 provides a fluid path from the bore of the tieback casing string 44 to the upper annulus 48u for the tieback cementing operation.

As illustrated in FIGS. 5B and 6B, the first dart 43a may be released from the first launcher 7a by operating the first plug launcher actuator. Cement slurry 71 may be pumped from the mixer 42 into the cementing swivel 7c via the valve 41 by the cement pump 13. The cement slurry 71 may flow into the second launcher 7b and be diverted past the second dart 43b via the diverter and bypass passages. The cement slurry 71 may flow into the first launcher 7a and be forced behind the first dart 43a by closing of the bypass passages, thereby propelling the first dart into the workstring bore.

Once the desired quantity of cement slurry 71 has been pumped, the second dart 43b may be released from the second launcher 7b by operating the second plug launcher actuator. Chaser fluid 72 may be pumped into the cementing swivel 7c via the valve 41 by the cement pump 13. The chaser fluid 72 may flow into the second launcher 7b and be forced behind the second dart 43b by closing of the bypass passages, thereby propelling the second dart into the workstring bore. Pumping of the chaser fluid 72 by the cement pump 13 may continue until residual cement in the cement line 14 has been purged. Pumping of the chaser fluid 72 may then be transferred to the mud pump 34 by closing the valve 41 and opening the valve 6. The train of darts 43a,b and cement slurry 71 may be driven through the workstring bore by the chaser fluid 72. The first dart 43a may reach the first wiper plug 50a and the landing shoulder 59a and seal 60a of the first dart may engage the seat 55a and seal bore 56a of the first wiper plug.

As shown in FIGS. 5C and 6C, continued pumping of the chaser fluid 72 may increase pressure in the workstring bore against the seated first dart 43a until the first release pressure is achieved, thereby fracturing the first shearable fastener 57a. The first dart 43a and lock sleeve 54a of the first wiper plug 50a may travel downward until reaching a stop of the first wiper plug, thereby freeing the collet of the first latch sleeve 53a and releasing the first wiper plug from the second wiper plug 50b. The released first dart 43a and first wiper plug 50a may travel down the bore of the tieback casing string 44 wiping the inner surface thereof and forcing the conditioner 70 therethrough. The second dart 43b may then reach the second wiper plug 50b and the landing shoulder 59b and seal 60b of the second dart may engage the seat 55b and seal bore 56b of the second wiper plug.

As shown in FIGS. 5D and 6D, continued pumping of the chaser fluid 72 may increase pressure in the workstring bore against the seated second dart 43b until the second release pressure is achieved, thereby fracturing the second shearable fastener 57b. The second dart 43b and lock sleeve 54b of the second wiper plug 50b may travel downward until reaching a stop of the second wiper plug, thereby freeing the collet of the second latch sleeve 53b and releasing the second wiper plug from the third wiper plug 50c. Continued pumping of the chaser fluid 72 may drive the train of darts 43a,b, wiper plugs 50a,b, and cement slurry 71 through the tieback casing bore until the first wiper plug 50a bumps the float collar 44c.

As illustrated in FIGS. 5E and 6E, continued pumping of the chaser fluid 72 may increase pressure in the tieback casing bore against the seated first dart 43a and first wiper plug 50a until the first rupture pressure is achieved, thereby rupturing the first burst tube 61a and opening the bypass ports of the first wiper plug. The cement slurry 71 may flow around the first dart 43a and through the first wiper plug, the seal stem 44s, and the guide shoe 44g, and upward into the upper annulus 48u via the gap 69. The cement slurry 71 may be prohibited from flowing down the liner string 15 by the seated liner dart 15d and packer 15p and a column of incompressible chaser fluid (not shown) in the liner bore.

As shown in FIGS. 5F and 6F, pumping of the chaser fluid 72 may continue to drive the cement slurry 71 into the upper annulus 46u until the second wiper plug 50b bumps the seated first wiper plug 50a. Pumping of the chaser fluid 72 may be halted prior to reaching the second rupture pressure, thereby leaving the second burst tube 61b intact. The check valve 62v may close in response to halting of the pumping. Acceptability of the primary cementing operation may be determined. If acceptable, the workstring 9 may be lowered 74 until a shoulder of the tieback hanger 44h engages a seat of the wellhead 10, thereby stabbing the seal stem 44s into the PBR 15r. Pressure 75 may be relieved upward through the bypass slot of the poppet 64p and the first wiper plug 50a, and around the directional fins of the second wiper plug 50b, thereby avoiding hydraulic lock due to the incompressible cement slurry 71.

As illustrated in FIGS. 5G and 6G, the workstring 9 may continued to be lowered 74, thereby releasing a shearable connection of the tieback hanger 44h and driving a cone thereof into dogs thereof, thereby extending the dogs into engagement with a profile of the wellhead 10 and setting the hanger. Continued lowering 74 of the workstring may drive a wedge of the tieback packer 44p into a metallic seal ring thereof, thereby extending the seal ring into engagement with a seal bore of the wellhead 10 and setting the packer.

As shown in FIG. 7, with the tieback casing string 44 secured in place, the bayonet connection between the TDA 9d and the tieback casing 44 may be released and the workstring 9 retrieved to the rig 1r. Since the primary cementing operation was deemed successful, the third wiper plug 50c remains part of the TDA 9d and may be retrieved to the rig 1r.

FIGS. 8A-8D and 9A-9D illustrate a remedial tieback cementing operation using the tieback deployment assembly. If the cement slurry 71 does not meet one or more requirements, such as location, composition, or uniformity, the primary cementing operation may be deemed unsuccessful. If not for the presence of the third wiper plug 50c, the tieback casing string 44 would need to be removed, the cement slurry 71 would need to be drilled or flushed, and the tieback casing string would then need to be reinserted to allow the cementing operation to be performed again. Such a process would be extremely time consuming and could take on the order of days to complete at considerable expense.

As illustrated in FIGS. 8A and 9A, after recognition of a failed primary cementing operation, the third dart 43c may be loaded into one of the launchers 7a,b and conditioner 70 may be injected into the workstring 9 to increase pressure in the tieback casing bore against the seated second dart 43b and second wiper plug 50b until the second rupture pressure is achieved, thereby rupturing the second burst tube 61b and opening the bypass ports of the second wiper plug. The conditioner 70 may flow around the second dart 43a and through the second wiper plug 50b, around the first dart 43a, and through the first wiper plug 50a, the seal stem 44s, and the guide shoe 44g, and upward into the upper annulus 48u via the gap 69, thereby flushing the failed cement slurry 71 from the upper annulus 48u.

As shown in FIGS. 8B and 9B, after flushing the failed cementing slurry 71 from the upper annulus 48u, remedial cement slurry 76 may be pumped from the mixer 42 into the cementing swivel 7c via the valve 41 by the cement pump 13. Once the desired quantity of remedial cement slurry 76 has been pumped, the third dart 43c may be released from the loaded launcher 7a,b by operating the respective plug launcher actuator. Chaser fluid 72 may be pumped into the cementing swivel 7c via the valve 41 by the cement pump 13. The chaser fluid 72 may flow into the loaded launcher 7a,b, thereby propelling the third dart into the workstring bore. Pumping of the chaser fluid 72 by the cement pump 13 may continue until residual cement in the cement line 14 has been purged. Pumping of the chaser fluid 72 may then be transferred to the mud pump 34 by closing the valve 41 and opening the valve 6. The third dart 43c and remedial cement slurry 76 may be driven through the workstring bore by the chaser fluid 72. The third dart 43c may reach the third wiper plug 50c and the landing shoulder 59c and seal 60c of the third dart may engage the seat 55c and seal bore 56c of the third wiper plug.

As shown in FIGS. 8C and 9C, continued pumping of the chaser fluid 72 may increase pressure in the workstring bore against the seated third dart 43c until the third release pressure is achieved, thereby fracturing the third shearable fastener 57c. The third dart 43c and lock sleeve 54c of the third wiper plug 50c may travel downward until reaching a stop of the third wiper plug, thereby freeing the collet 46f and releasing the third wiper plug 50c from the equalization valve 46e. Continued pumping of the chaser fluid 72 may drive the third dart 43c, third wiper plug 50c, and remedial cement slurry 76 through the tieback casing bore. The remedial cement slurry 76 may flow around the second dart 43a and through the second wiper plug 50b, around the first dart 43a, and through the first wiper plug 50a, the seal stem 44s, and the guide shoe 44g, and upward into the upper annulus 48u via the gap 69.

As shown in FIGS. 8D and 9D, pumping of the chaser fluid 72 may continue to drive the remedial cement slurry 76 into the upper annulus 46u until the third wiper plug 50c bumps the seated second wiper plug 50b. Pumping of the chaser fluid 72 may then be halted. The workstring 9 may then be lowered 74, thereby stabbing the seal stem 44s into the PBR 15r and setting the tieback hanger 44h and packer 44p against the wellhead 10. The workstring 9 may then be retrieved to the rig 1r.

Alternatively, the primary cementing job may be successful but a problem may occur during stabbing of the seal stem 44s/landing of the tieback hanger 44h. If such problem occurs, the workstring 9 may be raised to reform the gap 69 and then the remedial cementing operation may be performed.

In another embodiment (not shown), the cement head 7 may be omitted and the cement line 14 instead connected to the top drive 5. Further, instead of darts, the release plugs may be balls. Alternatively, RFID tags may be used instead of the balls and gel plugs or foam plugs may be used to separate the fluids. In either instance, launchers may be assembled as part of the cement line 14 and the wiper plugs may each have a flapper valve biased toward a closed position and held in an open position by a single prop sleeve extending through the wiper plugs. The first and second flappers may each have a rupture disk therein to serve the purpose of the burst sleeves, discussed above.

For the tag alternative, a first tag launcher may be operated to release an RFID tag into the cement line 14 and a first foam or gel plug may be launched/injected into the cement line 14. Alternatively, the first foam or gel plug may be omitted. Cement slurry 71 may then be pumped from the mixer 42, through the cement line and top drive, and into the workstring 9 by the cement pump 13. After a desired amount of cement slurry 71 has been pumped, a second RFID tag and a foam/gel plug may be launched/pumped into the cement line 14, through the top drive, and propelled down the workstring 9 by chaser fluid 72. As the first and second RFID tags travel down the workstring, the first RFID tag will travel near an RFID antenna of an electronics package located within mandrel of the plug launch assembly. The first RFID tag sends a signal to the RFID antenna as the tag passes thereby. An MCU may receive the first command signal from the first tag and may operate an actuator controller to energize an actuator to move the prop sleeve upward from engagement with the first wiper plug. Once the upward stroke has finished, the prop sleeve may also be clear of the first wiper plug collet. The flapper of the first wiper plug may then close and pressure may increase thereon until the first plug is released from the second plug. The released first wiper plug may then be propelled through the tieback casing, as described above. The second RFID tag similarly instructs actuation of the prop sleeve to move clear of the second flapper and collet, thereby releasing the second wiper plug. If necessary, a third RFID tag may be used to launch the third wiper plug. A more detailed discussion of plug launching using RFID tags can be found in U.S. patent application Ser. No. 14/083,021, filed Nov. 18, 2013, which is herein incorporated by reference.

For the ball alternative, the prop sleeve may have each ball seat disposed within and releasably connected thereto, such as by a shearable fastener. Each ball seat may close one or flow ports providing fluid communication between the prop sleeve bore and a respective flapper chamber of the respective wiper plug. The first wiper plug may also be releasably connected to the prop sleeve by a shearable fastener. A first ball launcher may be operated to release a first ball into the cement line 14 and cement slurry 71 may then be pumped from the mixer 42, through the cement line and top drive and into the workstring 9 by the cement pump 13. After a desired amount of cement slurry 71 has been pumped, a second ball may be launched into the cement line 14, through the top drive, and propelled down the workstring 9 by chaser fluid 72. The first ball may land in the first seat and release the first seat from the prop sleeve, thereby moving the first sleeve down the prop sleeve until a stop shoulder of the prop sleeve is engaged. The first ports may be opened by the movement of the first seat, thereby allowing the cement slurry to flow into the first flapper chamber and exert pressure on a first piston in the flapper chamber, thereby exerting a downward force on the first wiper plug until the shearable fastener fractures. The downward force may drive the first wiper plug off of the prop sleeve, thereby allowing the first flapper to close. The released first wiper plug may then be propelled through the tieback casing by pressure of the cement slurry acting on the closed flapper. The second ball may release the second wiper plug in a similar fashion and if necessary, a third ball may be launched to release the third wiper plug.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the invention is determined by the claims that follow.

Claims

1. A method for casing a subsea wellbore, comprising: running a tieback casing string into the subsea wellbore using a workstring, the workstring including a first wiper plug, a second wiper plug, and a third wiper plug;launching a first release plug or tag into the workstring;pumping cement slurry into the workstring, thereby driving the first release plug or tag along the workstring;after pumping the cement slurry, launching a second release plug or tag into the workstring;pumping chaser fluid into the workstring, thereby driving the release plugs or tags and cement slurry through the workstring, wherein: the release plugs or tags engage the respective wiper plugs and release the respective wiper plugs from the workstring, andthe first wiper plug or first release plug ruptures, thereby allowing the cement slurry to flow therethrough and into an annulus formed between the tieback casing string and an outer casing string;stabbing the tieback casing string into a liner string; andretrieving the workstring, the workstring still including the third wiper plug.

2. The method of claim 1, wherein: the second wiper plug has a bypass port and burst tube closing the bypass port, andthe burst tube is intact when retrieving the workstring.

3. The method of claim 2, wherein a rupture pressure of the burst tube is substantially greater than release pressures of the wiper plugs.

4. The method of claim 1, wherein: the tieback casing string includes a float collar, andthe first wiper plug ruptures after bumping the float collar.

5. The method of claim 2, wherein the float collar includes a poppet having a bypass slot formed therein for preventing hydraulic lock during stabbing.

6. The method of claim 1, wherein: the tieback casing string includes a guide shoe and a seal stem,the tieback casing string is run until the guide shoe is proximately above a polished bore receptacle of the liner string, thereby forming a gap therebetween, andthe cement slurry flows into the annulus via the gap.

7. The method of claim 1, wherein: the tieback casing string includes a hanger and a packer, andthe method further comprises setting the hanger and packer after stabbing.

8. The method of claim 1, wherein: the tieback casing string includes an equalization valve, andthe third wiper plug is releasably connected to the equalization valve.

9. The method of claim 1, wherein the release plug or tag is a dart.

10. A method for casing a subsea wellbore, comprising: running a tieback casing string into the subsea wellbore using a workstring, the workstring including a first wiper plug, a second wiper plug, and a third wiper plug;launching a first release plug or tag into the workstring;pumping cement slurry into the workstring, thereby driving the first release plug or tag along the workstring;after pumping the cement slurry, launching a second release plug or tag into the workstring;pumping chaser fluid into the workstring, thereby driving the release plugs or tags and cement slurry through the workstring, wherein: the release plugs or tags engage the respective wiper plugs and release the respective wiper plugs from the workstring, andthe first wiper plug or first release plug ruptures, thereby allowing the cement slurry to flow therethrough and into an annulus formed between the tieback casing string and an outer casing string;pumping conditioner fluid into the workstring, thereby rupturing the second wiper plug or second release plug and flushing the cement slurry from the annulus;pumping remedial cement slurry into the workstring;after pumping the remedial cement slurry, launching a third release plug or tag into the workstring;pumping the chaser fluid into workstring, thereby driving the third release plug or tag and remedial cement slurry through the workstring, wherein: the third release plug or tag engages the third wiper plug and releases the third wiper plug, andthe third wiper plug drives the remedial cement slurry into the annulus;stabbing the tieback casing string into a liner string; andretrieving the workstring.

11. The method of claim 10, wherein the second wiper plug is ruptured before stabbing.

12. The method of claim 10, wherein: the method further comprises attempting to stab the tieback casing string into the liner string, andthe second wiper plug is ruptured after the attempted stabbing.

13. The method of claim 10, wherein a rupture pressure of the burst tube is substantially greater than release pressures of the wiper plugs.

14. The method of claim 10, wherein: the tieback casing string includes a float collar, andthe first wiper plug ruptures after bumping the float collar.

15. The method of claim 14, wherein the float collar includes a poppet having a bypass slot formed therein for preventing hydraulic lock during stabbing.

16. The method of claim 10, wherein: the tieback casing string includes a guide shoe and a seal stem,the tieback casing string is run until the guide shoe is proximately above a polished bore receptacle of the liner string, thereby forming a gap therebetween, andthe cement slurry flows into the annulus via the gap.

17. The method of claim 10, wherein: the tieback casing string includes a hanger and a packer, andthe method further comprises setting the hanger and packer after stabbing.

18. The method of claim 10, wherein: the tieback casing string includes an equalization valve, andthe third wiper plug is released from the equalization valve.

19. The method of claim 10, wherein the release plug or tag is a dart.

20. A plug release system, comprising: a first wiper plug including a burst tube, the first burst tube adapted to burst at a pressure between 900 psi and 1100 psi;a second wiper plug including a burst tube, the second burst tube adapted to burst at a pressure between 3500 psi and 5000 psi; anda third wiper plug;wherein: the first wiper plug is coupled to the second wiper plug by a shearable fastener, the shearable fastener adapted to shear at a pressure between 500 psi and 700 psi; andthe second wiper plug is coupled to the third wiper plug by a shearable fastener, the shearable fastener adapted to shear at a pressure between 1300 psi and 1700 psi.