Compensation device of drilling system without marine riser and emergency release method of compensation device

Abstract

The invention discloses a compensation device of a drilling system without a marine riser and an emergency release method thereof, the device comprises a mud return pipeline marine riser, a blowout preventer trailer, an adapter, a shunt unit, a compensation module and a control system, and the compensation module comprises a compensation main body and a compensation cylinder connected with the compensation main body; a second vertical channel is formed in the compensation body, the second vertical channel is configured to receive and suspend a suspension joint of the mud return pipeline marine riser, and the compensation cylinder is configured to be operated in a switchable mode in at least two working modes including operation under a first operation pressure and operation under a second operation pressure. In the normal working mode, the heaving motion of the drilling ship is counteracted through the normal compensation stroke, and in the emergency recovery mode, the drilling ship operates under the second operation pressure higher than the first operation pressure, and additional pulling force is provided through the emergency recovery stroke, so that the seabed gravity anchor is pulled out of the seabed. The problems that an existing drilling system without the marine riser cannot compensate the dynamic load in real time and the emergency recovery efficiency is low are solved.

Description

Technical Field

[0001] This invention relates to the field of subsea drilling technology, and in particular to a compensation device for a riserless drilling system and its emergency release method. Background Technology

[0002] In deepwater and ultra-deepwater drilling operations, traditional technology relies on large marine riser systems to connect the subsea wellhead to the drilling platform. Although existing technology has achieved operating capabilities in water depths of up to 3,600 meters, the system is costly to install and maintain, and suffers from operational complexity and slow response times. To reduce operating costs, the industry has developed riserless drilling technology suitable for shallow water areas. This technology constructs a closed-loop system through a rotating control head atop the subsea blowout preventer, but its application depth is limited to depths exceeding 2,000 meters due to hydrostatic pressure.

[0003] Existing riserless systems have two key drawbacks: first, the drilling fluid return pipe lacks an effective dynamic compensation mechanism, failing to offset the impact loads caused by the heave of the drilling platform in real time; second, system components cannot be quickly recovered in emergencies, and existing recovery procedures require complex preparation steps, potentially delaying evacuation in emergencies such as typhoons. Particularly in deepwater operations, excessively long return pipes generate significant hydrostatic pressure, severely impacting well control safety. Existing systems cannot effectively compensate for such pressure changes, nor can they quickly release subsea anchoring devices in emergencies.

[0004] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a compensation device and emergency release method for a riserless drilling system, which has the advantages of being able to compensate for the impact load caused by the movement of the drilling vessel in real time and quickly recovering the seabed gravity anchor in emergency situations to improve operational safety.

[0006] This invention is achieved using the following technical solution: A compensation device for a riserless drilling system includes: The mud return pipeline riser is fixed to the seabed at its lower end by a seabed gravity anchor, and is equipped with a suspension joint at its upper end to withstand vertical and lateral loads. A blowout preventer trailer, which can be moved and installed in the moon pool of the drilling ship, is equipped with an adapter; A splitter unit, located on the adapter, is configured to form a first vertical channel that can be selectively opened and closed to allow the mud return line riser to move into the center of the compensation module. A compensation module is installed on the splitter unit. The compensation module includes a compensation body and a compensation cylinder connected to the compensation body. A second vertical channel is formed on the compensation body and is coaxially arranged with the first vertical channel. The second vertical channel is configured to receive and suspend the suspension joint of the mud return pipeline riser. The compensation cylinder is configured to operate switchably in at least two working modes. The at least two working modes include a normal working mode in which the drilling ship heaves and sags by operating at a first operating pressure and offsetting the heave motion of the drilling ship by normal compensation stroke, and an emergency recovery mode in which the drilling ship operates at a second operating pressure higher than the first operating pressure and provides additional pulling force by emergency recovery stroke to pull the seabed gravity anchor out of the seabed. The control system is electrically connected to the blowout preventer trailer, the splitter unit, and the compensation module, respectively.

[0007] Furthermore, the second vertical channel is provided with a load support shoulder that engages with the suspension joint.

[0008] Furthermore, it also includes a top joint and drill slips, the top joint being connected between the top drive and the suspension joint for suspending the mud return line riser below the top drive, and the drill slips being configured to selectively clamp or release the mud return line riser.

[0009] Furthermore, when the drilling rig slips clamp the mud return pipeline riser, the compensation cylinder switches to normal operating mode; when the drilling rig slips release the mud return pipeline riser, the compensation cylinder switches to emergency recovery mode.

[0010] Furthermore, the splitter unit includes two movable parts that can move relative to each other, and a drive mechanism that drives the two movable parts to move relative to each other; the two movable parts have a closed state that is close to each other and an open state that is far apart from each other; the two movable parts are respectively provided with a first mating part and a second mating part, and when in the closed state, the first mating part and the second mating part together define a first vertical channel that runs through the vertical direction.

[0011] Furthermore, the compensation body comprises two halves, each half being connected to one of the movable components.

[0012] Furthermore, a suction hose with a buoyancy element is connected between the upper part of the seabed gravity anchor and the wellhead suction module on the seabed.

[0013] Furthermore, an anchor chain is connected between the seabed gravity anchor and the lower end of the riser of the mud return pipeline.

[0014] An emergency release method for a riserless drilling system, employing the aforementioned compensation device for the riserless drilling system, the method comprising: In normal operating mode, the compensation cylinder is controlled to work within the normal compensation stroke to compensate for the load generated by the movement of the drilling vessel on the connected mud return pipeline riser. Upon receiving an emergency release signal, an emergency release mode is activated, which includes: The tension increase step is to increase the output tension of the compensation cylinder; Emergency release execution steps: Control the compensation cylinder to run to its emergency release stroke, the emergency release stroke being greater than the normal compensation stroke; In this mode, by executing the emergency release, the pulling force applied by the compensation cylinder is sufficient to pull the seabed gravity anchor out of the seabed.

[0015] Furthermore, the emergency release mode specifically refers to: the control system responding to the emergency release signal by opening a pressure supply valve to provide high-pressure hydraulic oil to the compensation cylinder; The pressure inside the compensation cylinder is increased by using the high-pressure hydraulic oil; The increased pressure drives the compensation cylinder to the emergency release stroke, thereby pulling the seabed gravity anchor out of the seabed.

[0016] Compared with the prior art, the beneficial effects of the present invention include at least the following: This invention, through the dual-mode switching design of the compensation module, dynamically offsets the impact of the drilling vessel's heave motion on the riser of the mud return pipeline in normal working mode, and rapidly increases the pulling force to recover the riser of the mud return pipeline in emergency mode. This solves the technical problems of existing systems being unable to compensate for dynamic loads in real time and having low emergency recovery efficiency, and has the advantages of improving the safety and emergency response capabilities of deepwater drilling operations. Attached Figure Description

[0017] Figure 1 This is a simplified schematic diagram of the compensation system for riserless drilling according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the compensation module according to an embodiment of the present invention; Figure 3 These are top and side views of the mud return pipeline riser in the initial position outside the blowout preventer trailer according to an embodiment of the present invention. Figure 4 These are top and side views of the splitter unit in an embodiment of the present invention, showing the movable parts of the splitter unit in a state where they are far apart from each other. Figure 5 These are top and side views of the mud return pipeline riser, which is suspended by the top drive of the wellbore, according to an embodiment of the present invention. Figure 6These are top and side views of an embodiment of the present invention, showing the blowout preventer trailer moved to a position directly below the drill rig slips. Figure 7 The above and side views show the suspension joint of the mud return pipeline riser in this embodiment of the invention, which is suspended and supported by the compensation module. Figure 8 These are top and side views of an embodiment of the present invention, showing the movement of the blowout preventer trailer from below the drill rig slips to an offset parking position within the moon pool of the drilling vessel. Figure 9 These are two side views of the emergency disconnection mode of the compensation module in an embodiment of the present invention; In the diagram: 1. Top drive; 2. Load support shoulder; 3. Power winch; 4. Pulley; 5. Subsea gravity anchor; 6. Adapter; 7. Blowout preventer trailer; 8a. Upper interface stress joint; 8b. Lower interface stress joint; 9. Mud return pump module; 10. Mud return pipeline riser; 11. Suction hose; 12. Drilling vessel; 13. Clamp; 14. Remotely operated vehicle; 15. Moon pool beam; 16. Umbilical cable; 17. Seabed; 18. Splitter unit; 19. Driver; 20. Compensation module; 21. Top joint; 22. Flow head; 23. Suspension joint; 24. Discharge hose; 25. Drilling platform slips; 26. Drill pipe; 27. Wellhead suction module; 28. Sea surface; 29. ​​Compensation cylinder; 30. Normal compensation stroke; 31. Emergency release stroke; 32. Anchor chain. Detailed Implementation

[0018] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided to make the invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted.

[0019] The terms used to express position and direction in this invention are illustrated with reference to the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of this invention.

[0020] like Figures 1 to 9 As shown, a compensation device for a riserless drilling system provided by the present invention includes: The mud return pipeline riser 10 is fixed to the seabed 17 at its lower end by a seabed gravity anchor 5, and is equipped with a suspension joint 23 at its upper end for bearing vertical and lateral loads. Blowout preventer trailer 7 is movably installed in the moon pool of the drilling vessel 12, and the blowout preventer trailer 7 is equipped with an adapter 6; The splitter unit 18 is disposed on the adapter 6 and is configured to form a first vertical channel that can be selectively opened and closed to allow the mud return pipeline riser 10 to move into the center position of the compensation module 20. The compensation module 20 is installed on the splitter unit 18. The compensation module 20 includes a compensation body and a compensation cylinder 29 connected to the compensation body. A second vertical channel is formed on the compensation body and is coaxially arranged with the first vertical channel. The second vertical channel is configured to receive and suspend the suspension joint 23 of the mud return pipeline riser 10. The compensation cylinder 29 is configured to switchably operate in at least two working modes. The at least two working modes include a normal working mode in which the drilling ship 12 heaves and sags by normal compensation stroke 30 is offset under a first operating pressure, and an emergency recovery mode in which the drilling ship 12 heaves and sags by emergency recovery stroke is provided to pull the seabed gravity anchor 5 out of the seabed 17 by operating under a second operating pressure higher than the first operating pressure. The control system is electrically connected to the blowout preventer trailer 7, the splitter unit 18, and the compensation module 20, respectively.

[0021] refer to Figure 1-2 This system is applied to a drilling vessel 12 floating on the sea surface 28. A wellhead suction module 27 is installed at the borehole opening on the seabed to collect drilling fluid returned from the borehole. The drill pipe 26 is used to drill the borehole and supply drilling fluid into the well. A seabed gravity anchor 5 is installed near the wellhead suction module 27 to anchor the mud return riser 10 to the seabed 17. The drilling vessel 12 has two operating centers. The center of the mud return riser 10 is offset relative to the drilling center. This is to ensure the deployment and operation of the mud return riser 10. The distance between the two centers is large enough to effectively prevent interference between the drill pipe 26 and the mud return riser 10 when using the system in deep water and strong currents. The mud return line riser 10 includes a mud return pump module 9, which is installed at a certain depth underwater. Its purpose is to return drilling fluid to the drilling vessel 12 for recycling. Specifically, refer to... Figure 3The mud return pump module 9 is powered by an umbilical cable 16, which is fixed to the mud return line riser 10 by multiple clamps 13. The mud return pump module 9 is equipped with an upper interface stress joint 8a and a lower interface stress joint 8b. A power winch 3 and a pulley 4 are installed on the deck of the drilling vessel 12. The umbilical cable 16 passes around the pulley 4 and connects to the power winch 3, and the power winch 3 is used to raise and lower the umbilical cable 16. The upper end of the mud return line riser 10 is suspended by a compensation module 20 installed in the moon pool of the drilling vessel 12. When the drilling vessel 12 is moved by the waves, the compensation module 20 is used to provide vertical load support for the mud return line riser 10. A discharge hose 24 is connected to the top of the mud return line riser 10, which connects the mud return line riser 10 to the drilling fluid outflow line of the drilling vessel 12. The adapter 6 is mounted on top of the blowout preventer trailer 7 to form a load-bearing vertical support for the mud return line riser 10.

[0022] Figure 3 One of the side and top view arrangements of the system is shown, where the left top view shows the mud return line riser 10 initially located outside the BOP trailer 7. The right side view also shows the same location of the mud return line riser 10. A splitter unit 18 is mounted on top of the adapter 6 of the BOP trailer 7, which is movably mounted on the moon pool beam 15. The two movable parts of the splitter unit 18 are operated by independent actuators 19 (such as cylinders). The function of the splitter unit 18 is that when the BOP trailer 7 moves within the moon pool from an offset position (see left top view) to the mud return line riser 10's intended suspension position to enter the compensation module 20, the two movable parts are in the open state, creating space for the mud return line riser 10 to enter the center of the splitter unit 18. The side view on the right also shows that the mud return line riser 10 is suspended by the top drive 1, and the rig slips 25 are used to connect or disconnect the mud return line riser 10. A top joint 21 is used between the top drive 1 and the upper part of the mud return line riser 10, while the upper part of the mud return line riser 10 is a suspension joint 23 with vertical and lateral stress bearing characteristics.

[0023] Figure 4 This is the second example of the side and top view layout of the system. The two movable parts of the splitter unit 18 are in the open position, and a functional test was conducted in the open state. The mud return line riser 10 remains offset relative to the blowout preventer trailer 7.

[0024] Figure 5 The third illustration shows the layout of the system in side and top views. A compensation module 20 is assembled on top of the splitter unit 18. The compensation module 20 is divided into two identical halves for mounting onto the two movable parts of the splitter unit 18. Figure 5 The top-down view on the left shows the blowout preventer trailer 7 in an off-center position. Figure 5 The right-side side view shows that the mud return line riser 10 is suspended by the top drive 1.

[0025] Figure 6 This is the fourth illustration showing the arrangement of the system in side and top views. At this point, the blowout preventer trailer 7 has been moved to a position directly below the drill rig slip 25. The right side view shows that the splitter unit 18 and compensation module 20 are in the off state. The compensation module 20 closes synchronously with the splitter unit 18. The suspension joint 23 remains in a free-suspension state, its vertical load borne by the coupling 21 connected to the top drive.

[0026] Figure 7 The fifth arrangement is shown in the side and top views. The suspension joint 23 is lowered to the load support shoulder 2 via the top joint 21. At this time, the vertical and lateral loads acting on the mud return line riser 10 have been transferred from the top joint 21 to the suspension joint 23, which is now suspended by the compensation module 20.

[0027] Figure 8 shows the sixth layout of the system in side and top views. The blowout preventer trailer 7 with the suspended mud return line riser 10 has been moved from its position below the rig slip 25 to an off-center parking position in the rig's December pool. Figure 8 The top and side views also show that a flow head 22 with a pipeline leading to the drilling fluid outlet on board has been connected to the top of the suspension joint 23.

[0028] Figure 9 Two side views illustrate the system's emergency disconnect function. The left view depicts the normal operating condition, in which the seabed gravity anchor 5 provides lateral compensation and also vertical compensation during normal operation. The compensation cylinder 29 works in conjunction with the seabed gravity anchor 5 chain during the normal compensation stroke 30 to counteract the vertical and lateral loads generated by the heave and roll of the drilling vessel 12. The right view illustrates that when rapid retrieval of the seabed gravity anchor 5 is required, the compensation cylinder 29 operates via an automatic emergency disconnect procedure. First, the pulling force of the compensation cylinder 29 is increased; second, it moves upward to the emergency release stroke 31 to pull the seabed gravity anchor 5 out of the seabed 17.

[0029] In this invention, the compensation module 20 integrates dynamic compensation and emergency recovery functions to construct a complete safety assurance system for the riserless drilling system. The mud return riser 10 is fixed to the seabed 17 by a seabed gravity anchor 5. In normal operation, the cooperation between the suspension joint 23 and the compensation module 20 enables load transfer between the riserless drilling system and the drilling vessel 12. The splitter unit 18, through its openable first vertical channel design, allows the mud return riser 10 to be precisely positioned at the center of the compensation module 20, ensuring alignment between the riser 10 and the compensation module 20. The compensation module 20 adopts a dual-channel coaxial structure; the cooperation between the second vertical channel and the suspension joint 23 forms a stable load transfer path. The dual-mode design of the compensation cylinder 29 achieves heave compensation under normal operating conditions and active recovery in emergency situations through pressure switching. The control system's coordinated control of each execution unit enables the system to switch operating modes in real time according to the operational status, meeting both the stability requirements of daily drilling operations and the emergency response capability for rapid response to sudden events.

[0030] It should be noted that the mud return riser 10 will be deployed from the center of the well on the floating drillship 12, below the top drive 1. A mud return pump module 9 is mounted on the entire mud return riser 10. A splitter unit 18 and a compensation module 20 are mounted on the blowout preventer trailer 7, surrounding the mud return riser 10. The entire weight of the mud return riser 10 will then be transferred from the top drive 1 to the blowout preventer trailer 7. Next, the mud return riser 10, with the mud return pump module 9 mounted, will be moved off-center to allow space for the drill pipe 26 to extend through the water to the wellhead suction module 27 located on the seabed 17. The compensation module 20 includes a set of retractable load-bearing profiles that mate with corresponding load-bearing profiles on the suspension joint 23 of the mud return riser 10. When the compensation module 20 is closed and pressure is applied to the compensation cylinder 29, the compensation module 20 will bear the load of the mud return pipeline riser 10.

[0031] In a preferred embodiment, the second vertical channel is provided with a load support shoulder 2 that engages with the suspension joint 23.

[0032] In this embodiment, a load support shoulder 2 is provided in the second vertical channel of the compensation module 20. This load support shoulder 2 forms a mechanical connection with the suspension joint 23 at the upper end of the mud return pipeline riser 10, thus constructing a stable load transfer interface. This structural design allows the suspension joint 23 and the compensation module 20 to form a surface contact support, which can evenly distribute vertical and lateral loads during normal operation, ensuring the continuity of load transfer during dynamic compensation. In emergency recovery mode, when the compensation cylinder 29 applies additional tension, the rigid connection between the load support shoulder 2 and the suspension joint 23 can withstand the sudden increase in axial tension, avoiding stress concentration caused by point or line contact, and ensuring the integrity of the tension transfer path during the removal of the seabed gravity anchor 5. The load support shoulder 2 also solves the problem of displacement deviation that conventional suspension mechanisms are prone to under complex load conditions. By limiting the axial degree of freedom of the suspension joint 23, the structural stability of the system is enhanced when switching between the two working modes.

[0033] It can be understood that the load support shoulder 2 is an annular protrusion structure set on the inner wall of the second vertical channel. Specifically, it can be realized by welding or machining a continuous annular step, the inner diameter of which is smaller than the outer diameter of the suspension joint 23, for mechanical contact with the lower end face of the suspension joint 23. Among them, the suspension joint 23 refers to the flange-type connection structure at the upper end of the mud return pipeline riser 10, which can be made of forged steel.

[0034] In a preferred embodiment, the system also includes a top joint 21 and a slip 25. The top joint 21 is connected between the top drive 1 and the suspension joint 23 and is used to suspend the mud return line riser 10 below the top drive 1. The slip 25 is configured to selectively clamp or release the mud return line riser 10.

[0035] In this embodiment, the connecting joint 21 refers to the transition component connecting the top drilling drive 1 and the suspension joint 23. Specifically, it can be implemented as a rigid pipe section with a flange or threaded joint, and its internal channel communicates with the mud return line riser 10. This connecting joint 21 can transmit the vertical load applied by the top drilling drive 1 to the suspension joint 23, ensuring the axial stability of the mud return line riser 10 under dynamic loads. The drilling platform slips 25 are clamping devices installed on the drilling platform deck. Specifically, they can be implemented using a hydraulically driven or mechanically locked wedge-shaped slip structure, with their clamping surface contacting the outer wall of the mud return line riser 10. By actively controlling the closing and opening of the slips, the fixing or releasing operation of the mud return line riser 10 is achieved. Specifically, when the drilling platform slips 25 clamp the mud return pipeline riser 10, the compensation cylinder 29 switches to normal operating mode; when the drilling platform slips 25 releases the mud return pipeline riser 10, the compensation cylinder 29 switches to emergency recovery mode. In normal operating mode, the lifting and lowering movement of the top drive 1 acts directly on the mud return pipeline riser 10 through the connecting top joint 21, keeping the mud return pipeline riser 10 in a vertically tensioned state, ensuring the stable suspension of the mud return pipeline riser 10 during normal operation. In emergency recovery mode, the drilling platform slips 25 release the mud return pipeline riser 10 to instantly detach from the platform constraint in an emergency. At this time, the tension applied by the compensation module 20 acts directly on the seabed gravity anchor 5 through the suspension joint 23. Combined with the tension output of the compensation module 20, rapid anchor removal is achieved, significantly shortening the operation time for gravity anchor recovery. Existing mud return risers without risers rely solely on the platform suspension system for fixation, lacking an active release mechanism. Emergency retrieval requires manual disassembly of connecting components, resulting in response delays. This invention achieves dynamic suspension and rapid release of the mud return riser 10 through the synergistic action of the top joint 21 and the drilling platform slips 25. The top joint 21 connects the top drive 1 to the suspension joint 23, suspending the mud return riser 10 below the top drive. Its structural design can transmit the vertical load of the top drive 1, ensuring the vertical stability of the mud return riser 10 during normal operation and preventing pipeline displacement or detachment caused by the movement of the drilling vessel 12. The drilling platform slips 25 provide active control capabilities by selectively clamping or releasing the mud return riser 10: clamping the mud return riser 10 during normal operation to maintain system connection, and rapidly releasing the mud return riser 10 in emergency situations, coordinating with the emergency retrieval mode of the compensation module 20 to achieve the extraction of the seabed gravity anchor 5. The combination of the two ensures the reliable fixation of the pipeline during the operation and provides a direct operation interface for emergency release, solving the shortcomings of the existing technology in terms of complex recovery process and insufficient response speed.

[0036] In a preferred embodiment, the splitter unit 18 includes two movable parts that can move relative to each other and a drive mechanism that drives the two movable parts to move relative to each other; the two movable parts have a closed state that is close to each other and an open state that is far apart from each other; the two movable parts are respectively provided with a first mating part and a second mating part, and when in the closed state, the first mating part and the second mating part together define a first vertical channel that runs through the vertical direction.

[0037] In this embodiment, reference Figure 3A splitter unit 18 is installed on top of the adapter 6 of the blowout preventer trailer 7. The two movable parts of the splitter unit 18 are operated by independent actuators 19 (e.g., cylinders). The function of the splitter unit 18 is to open the two movable parts when the blowout preventer trailer 7 moves from the offset position (see left top view) within the moon pool to the position where the mud return line riser 10 is to enter the suspension position of the compensation module 20, creating space for the mud return line riser 10 to enter the center of the splitter unit 18. The right side view also shows that the mud return line riser 10 is suspended by the top drive 1, and the rig slips 25 are used to connect or disconnect the mud return line riser 10. A coupling 21 is used between the top drive 1 and the upper part of the mud return line riser 10, while the upper part of the mud return line riser 10 is a suspension joint 23 with vertical and lateral stress bearing characteristics.

[0038] This invention achieves dynamic control of the first vertical channel through the structural design of the splitter unit 18. The relative movement design of the two movable parts allows the splitter to have both closed and open states, with the drive mechanism providing the power source for state switching. In the closed state, the mating parts on the two movable parts together form a vertically penetrating first vertical channel. This mating structure ensures the integrity of the first vertical channel and provides precise guidance for the positioning of the subsequent mud return pipeline riser 10. By controlling the relative position of the movable parts through the drive mechanism, the working state of the splitter unit 18 can be quickly switched when needed. The synergistic effect of the first and second mating parts ensures the structural stability of the first vertical channel in the closed state and provides a precise axial alignment reference for the subsequent docking of the compensation module 20. Preferably, the drive mechanism includes two independent actuators 19, with each movable part equipped with one actuator 19. The actuator 19 is preferably a linear module, such as a cylinder or an electric push rod. The first and second mating parts are groove structures provided on the opposite surfaces of the two movable parts.

[0039] In a preferred embodiment, the compensation body includes two halves, each half being connected to one of the movable components.

[0040] In this embodiment, reference Figure 5 and Figure 6By designing the compensation body as two independent half-structures, each half directly connected to a corresponding movable part in the splitter unit 18, mechanical linkage between the splitter unit 18 and the compensation module 20 is achieved. This structural design allows the two halves of the compensation module 20 to move synchronously when the two movable parts of the splitter unit 18 move relative to each other, ensuring that the second vertical channel of the compensation module 20 remains coaxially aligned with the first vertical channel of the splitter unit 18 whether the splitter unit 18 is open or closed. By dividing the compensation body into two halves and connecting them one-to-one with the movable parts of the splitter unit 18, interference with the overall structure of the compensation module 20 during the operation of the splitter unit 18 is avoided, and the coordinated movement of the compensation module 20 with that of the splitter unit 18 during dynamic compensation is ensured. This split connection method also enhances the structural reliability of the system under additional tension in emergency recovery mode, allowing the tension applied by the compensation cylinder 29 to be directly transmitted to the half-structure of the compensation module 20 through the movable parts of the splitter unit 18.

[0041] In a preferred embodiment, a suction hose 11 with a buoyancy element is connected between the upper part of the seabed gravity anchor 5 and the wellhead suction module 27 on the seabed.

[0042] In this embodiment, reference Figure 1 By installing a suction hose 11 with buoyancy elements between the seabed gravity anchor 5 and the wellhead suction module 27, the optimization of the mud return path and the emergency recovery function are combined. Specifically, the introduction of buoyancy elements can effectively reduce the self-weight load of the suction hose 11 in the water, thereby reducing the vertical load on the seabed gravity anchor 5. This design allows the suction hose 11 to maintain a stable mud return channel during normal operation, while avoiding an increase in the embedment depth of the seabed gravity anchor 5 due to the hose's own weight. In emergency recovery scenarios, the buoyancy provided by the buoyancy elements can assist the compensation module 20 in quickly lifting the seabed gravity anchor 5, significantly reducing the tensile force threshold required for emergency recovery by offsetting part of the weight of the hose and the gravity anchor system. In addition, as a key component connecting the seabed gravity anchor 5 and the wellhead suction module 27, the suction hose 11's flexible connection characteristics can adapt to changes in seabed topography, and the distributed design of the buoyancy elements can further prevent the hose from excessively bending or local stress concentration due to its own weight, thereby ensuring the reliability of the system under complex sea conditions. Figure 2 Specifically, the inhalation hose 11 is connected to the remotely operated vehicle 14.

[0043] In a preferred embodiment, an anchor chain 32 is connected between the seabed gravity anchor 5 and the lower end of the mud return pipeline riser 10.

[0044] In this embodiment, reference Figure 9In normal operation mode, the flexible connection characteristics of the anchor chain 32 allow the riser 10 of the mud return pipeline to undergo slight displacement with the heave and sway of the drilling vessel 12, while maintaining vertical positional constraint. When the emergency recovery mode is activated, the pulling force output by the compensation cylinder 29 is transmitted to the anchor chain 32 through the riser 10 of the mud return pipeline. The axial tensile strength of the anchor chain 32 can withstand the sudden increase in load and concentrate the pulling force on the top connection point of the seabed gravity anchor 5. Because there are rotational degrees of freedom between the links of the anchor chain 32, local stress concentration will not occur when transmitting large tensile forces, thereby avoiding the breakage of the connection structure.

[0045] This invention establishes a physical connection capable of transmitting tensile force between the seabed gravity anchor 5 and the mud return pipeline riser 10 through a flexible connection structure of anchor chain 32. As a load-bearing component, anchor chain 32 maintains the vertical positioning of the mud return pipeline riser 10 during normal operation and effectively transmits the tensile force applied by the compensation module 20 to the seabed gravity anchor 5 in emergency recovery mode. This connection method specifically considers the recovery requirements of the seabed gravity anchor 5. When the compensation cylinder 29 switches to emergency recovery mode, anchor chain 32 can withstand sudden, large tensile forces without breaking, ensuring that the seabed gravity anchor 5 can be pulled out as a whole. The flexibility of anchor chain 32 also avoids stress concentration problems that may occur with rigid connections, providing structural redundancy for the transmission of force under different operating modes.

[0046] The present invention also provides an emergency release method for a riserless drilling system, which utilizes the aforementioned compensation device for a riserless drilling system, the method comprising: In normal operating mode, the compensation cylinder 29 is controlled to work within the normal compensation stroke 30 to compensate for the load generated by the movement of the drilling vessel 12 on the connected mud return pipeline riser 10. Upon receiving an emergency release signal, an emergency release mode is activated, which includes: The tension increase step is to increase the output tension of the compensation cylinder 29; Emergency release execution steps: Control the compensation cylinder 29 to run to its emergency release stroke 31, the emergency release stroke 31 being greater than the normal compensation stroke 30; In this mode, by executing the emergency release mode, the pulling force applied by the compensation cylinder 29 is sufficient to pull the seabed gravity anchor 5 out of the seabed 17.

[0047] In this embodiment, during normal operation, the compensation cylinder 29 absorbs the heave energy of the drilling vessel 12 through the dynamic extension and retraction of its normal compensation stroke 30, maintaining the stable suspension state of the mud return pipeline riser 10. When the drilling vessel 12 is unable to maintain its position above the wellhead suction module 27 due to a positioning thruster malfunction or other reasons, the mud return pipeline riser 10 connected to the sea must be retrieved immediately to avoid catastrophic damage to the drilling equipment and wellbore on the seabed and sea surface 28. The pressure inside the compensation cylinder 29 is increased by the drilling personnel or by activating the emergency release mode, causing the compensation cylinder 29 to exceed its normal stroke limit and enter the emergency release stroke 31. During this process, the pulling force generated by the compensation cylinder 29 increases linearly with the extension of the stroke. When a critical value is reached, the static friction between the seabed gravity anchor 5 and the seabed 17 is overcome, and the seabed gravity anchor 5 detaches from the seabed 17 under continuous pulling force. The synergistic effect of the two steps enables the transition from conventional compensation to emergency release. The tension increase step provides energy reserves for the system, while the emergency release execution step transforms mechanical advantages through stroke extension, ultimately forming a composite force capable of rapidly lifting the seabed gravity anchor 5.

[0048] Traditional methods rely on segmented disassembly to recover the riser 10 of the mud return pipeline, a process that is time-consuming and unable to handle unforeseen circumstances. This invention establishes a dual-mode compensation mechanism, integrating an emergency release function while maintaining routine operational capabilities, eliminating the need for additional dedicated recovery equipment. In existing technologies, the mud return pipe relies solely on static platform support, while this invention achieves a seamless switch from routine compensation to emergency release through the dynamic stroke extension of the compensation cylinder 29. This allows for rapid removal of the seabed gravity anchor 5 within a short time (30 seconds) through the synergistic effect of hydraulic system pressurization and stroke extension when the drilling vessel 12 encounters severe sea conditions or equipment failure, overcoming the limitation of traditional riserless systems in rapidly recovering seabed anchoring devices.

[0049] As a preferred embodiment, the emergency release mode specifically involves the control system responding to an emergency release signal by opening a pressure supply valve to provide high-pressure hydraulic oil to the compensation cylinder 29. The pressure inside the compensation cylinder 29 is increased by using the high-pressure hydraulic oil. Using the increased pressure, the compensation cylinder 29 is driven to the emergency release stroke 31, thereby pulling the seabed gravity anchor 5 out of the seabed 17.

[0050] In this embodiment, the pressure supply valve refers to the switching device that controls the flow of hydraulic oil to the compensation cylinder 29. Specifically, it can be implemented using an electromagnetic proportional valve, which regulates the oil flow by controlling the valve opening through an electrical signal. High-pressure hydraulic oil refers to a hydraulic medium with a pressure value higher than the normal working pressure. Specifically, it can be implemented using hydraulic oil output from a booster pump, and its pressure range can be set according to the embedding resistance of the seabed gravity anchor 5. The emergency release stroke 31 refers to the extended displacement of the piston rod of the compensation cylinder 29 relative to the normal working stroke. Specifically, it can be monitored by a hydraulic cylinder stroke sensor, and its function is to generate a greater traction force on the anchor chain 32 by increasing the mechanical stroke. Upon receiving an emergency release signal, the control system immediately activates the opening command of the pressure supply valve. After the pressure supply valve opens, high-pressure hydraulic oil generated by the booster pump is rapidly injected into the hydraulic chamber of the compensation cylinder 29 through the oil circuit. As the pressure in the hydraulic chamber continues to rise, the piston of the compensation cylinder 29, driven by high pressure, breaks through the normal working stroke limit and enters the preset emergency release stroke 31 range. During this process, the compensation cylinder 29 generates additional pulling force through the extension of the piston rod. This pulling force is transmitted to the mud return pipeline riser 10 through the suspension joint 23, and finally acts on the seabed gravity anchor 5. When the pulling force exceeds the static friction between the seabed gravity anchor 5 and the seabed 17, the seabed gravity anchor 5 is pulled up and detached from the seabed 17, realizing the rapid detachment and recovery of the seabed gravity anchor 5 in emergency situations, effectively avoiding the risk of pipeline rupture caused by the sudden displacement of the drilling vessel 12.

[0051] Traditional riprapless systems rely solely on the drilling platform to support the return pipe, lacking an active release mechanism. Emergency retrieval requires time-consuming, multi-step manual operations. This invention establishes an automated hydraulic drive system by integrating a pressure supply valve and an adjustable stroke compensation cylinder 29. Upon triggering an emergency signal, the system directly amplifies the pulling force through a pressure surge, enabling the extraction and retrieval of the seabed gravity anchor 5 without manual intervention. This solves the technical shortcomings of traditional systems, such as excessively long retrieval times and inability to handle emergencies.

[0052] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the invention without departing from the principles and spirit of the invention, and all such changes should fall within the protection scope of the claims of the present invention.

Claims

1. A compensation device for a riserless drilling system, characterized in that, include: The mud return pipeline riser (10) is fixed to the seabed (17) by a seabed gravity anchor (5) at its lower end and is provided with a suspension joint (23) at its upper end for bearing vertical and lateral loads. A blowout preventer trailer (7) is movably installed in the moon pool of the drilling vessel (12), and the blowout preventer trailer (7) is equipped with an adapter (6); A splitter unit (18) is provided on the adapter (6), the splitter unit (18) being configured to form a first vertical channel that can be selectively opened and closed to allow the mud return line riser (10) to move into the center of the compensation module (20); The compensation module (20) is installed on the splitter unit (18). The compensation module (20) includes a compensation body and a compensation cylinder (29) connected to the compensation body. A second vertical channel is formed on the compensation body and is coaxially arranged with the first vertical channel. The second vertical channel is configured to receive and suspend the suspension joint (23) of the mud return pipeline riser (10). The compensation cylinder (29) is configured to switchably operate in at least two working modes. The at least two working modes include a normal working mode that operates at a first operating pressure and offsets the heave motion of the drilling ship (12) through a normal compensation stroke (30) and an emergency recovery mode that operates at a second operating pressure higher than the first operating pressure and provides additional pulling force through an emergency recovery stroke to pull the seabed gravity anchor (5) out of the seabed (17). The control system is electrically connected to the blowout preventer trailer (7), the splitter unit (18), and the compensation module (20), respectively.

2. The compensation device for a riserless drilling system according to claim 1, characterized in that, The second vertical channel is provided with a load support shoulder (2) that engages with the suspension joint (23).

3. The compensation device for a riserless drilling system according to claim 1, characterized in that, It also includes a top joint (21) and a rig slip (25), the top joint (21) being connected between the top drive (1) and the suspension joint (23) for suspending the mud return line riser (10) below the top drive (1), and the rig slip (25) being configured to selectively clamp or release the mud return line riser (10).

4. The compensation device for a riserless drilling system according to claim 3, characterized in that, When the drilling platform slip (25) clamps the mud return pipeline riser (10), the compensation cylinder (29) switches to normal working mode. When the drilling platform slip (25) releases the mud return pipeline riser (10), the compensation cylinder (29) switches to emergency recovery mode.

5. The compensation device for a riserless drilling system according to claim 1, characterized in that, The splitter unit (18) includes two movable parts that can move relative to each other and a drive mechanism that drives the two movable parts to move relative to each other; the two movable parts have a closed state that is close to each other and an open state that is far apart from each other; the two movable parts are respectively provided with a first mating part and a second mating part, and when in the closed state, the first mating part and the second mating part together define a first vertical channel that runs through the vertical direction.

6. The compensation device for a riserless drilling system according to claim 5, characterized in that, The compensation body comprises two halves, each half being connected to one of the movable components.

7. The compensation device for a riserless drilling system according to claim 1, characterized in that, The upper part of the seabed gravity anchor (5) is connected to the seabed wellhead suction module (27) by a suction hose (11) with a buoyancy element.

8. The compensation device for a riserless drilling system according to claim 1, characterized in that, An anchor chain (32) is connected between the lower end of the seabed gravity anchor (5) and the riser pipe (10) of the mud return pipeline.

9. An emergency release method for a riserless drilling system, characterized in that, The method of using the compensation device for a riserless drilling system according to any one of claims 1-8 includes: In normal operating mode, the compensation cylinder (29) is controlled to work within the normal compensation stroke (30) to compensate for the load generated by the movement of the drilling vessel (12) on the connected mud return pipeline riser (10); Upon receiving an emergency release signal, an emergency release mode is activated, which includes: The tension increase step is to increase the output tension of the compensation cylinder (29); Emergency release execution steps: Control the compensation cylinder (29) to run to its emergency release stroke (31), the emergency release stroke (31) being greater than the normal compensation stroke (30); In this mode, by executing the emergency release mode, the pulling force applied by the compensation cylinder (29) is sufficient to pull the seabed gravity anchor (5) out of the seabed (17).

10. The emergency release method for a riserless drilling system according to claim 9, characterized in that, The emergency release mode is specifically as follows: the control system responds to the emergency release signal by opening a pressure supply valve to provide high-pressure hydraulic oil to the compensation cylinder (29); The pressure inside the compensation cylinder (29) is increased by the high-pressure hydraulic oil; Using the increased pressure, the compensation cylinder (29) is driven to the emergency release stroke (31), thereby pulling the seabed gravity anchor (5) out of the seabed (17).

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