Riser-less drilling mud recovery deck control device and control method

Abstract

The present invention discloses a riser-less drilling mud recovery deck control device and control method, specifically relating to the field of marine drilling technology. The device comprises: a drill pipe, a suction module, a mud level identification device, a mud return line, a mud lift pump, and a deck measurement and control manifold. The deck measurement and control manifold comprises an input pipeline, a mud output pipeline, a seawater output pipeline, a three-way valve I, and a sight glass. The input pipeline is connected and communicated with the mud return line. The sight glass is disposed on the input pipeline. The input pipeline, the mud output pipeline, and the seawater output pipeline are connected via a three-way valve I. The mud output pipeline is connected to a mud tank on the deck, and the seawater output pipeline is connected to the outside world. The present invention can maintain the continuous operation of the mud lift pump, avoiding damage to the motor caused by frequent starts and stops, and can also prevent rock debris settling caused by pump shutdown. It also prevents seawater from mixing with the mud and causing performance degradation, thereby ensuring the stable operation of the riser-less drilling mud recovery deck control device.

Description

Technical Field

[0001] The present invention relates to the field of marine drilling technology, and in particular to a riser-less drilling mud recovery deck control device and a control method. Background Art

[0002] During the riser-less mud recovery process, mud is injected into the bottom of the hole through the drill pipe, then returns to the seabed suction module carrying the cuttings cut by the drill bit, and finally is lifted back to the deck surface along the mud return pipeline by the mud lift pump, completing the entire mud recovery cycle.

[0003] However, as the borehole deepens, it is often necessary to add drill pipes, and the mud pump on the deck needs to be stopped at this time; if the underwater mud lift pump stops along with the mud pump on the deck, the rock cuttings in the mud return pipeline will settle and block the mud return pipeline and the mud lift pump, resulting in abnormal circulation; at the same time, frequent starting and stopping of the mud lift pump will affect the life of the underwater motor that drives the mud lift pump; if the mud lift pump is not stopped at this time, since the mud pump on the deck stops grouting into the hole, continuing to run the mud lift pump will cause seawater to enter the mud return pipeline from the suction module, and eventually be lifted back into the mud tank on the deck, causing seawater to mix with the mud, affecting the mud performance.

[0004] Moreover, the underwater motor that drives the mud lift pump currently adopts variable frequency control, which controls the flow of the mud lift pump by adjusting the motor speed through frequency conversion. However, due to the characteristics of the motor, the frequency cannot be reduced indefinitely. Therefore, the control of the small flow of returning mud needs to be solved urgently.

[0005] Finally, because the return mud contains rock debris, there is a risk of clogging the return mud pipeline under special circumstances. When the pipeline is blocked, a simple unblocking method that can be operated from the deck is required to avoid recovering the entire underwater equipment.

[0006] In summary, there is an urgent need for a riser-less drilling mud recovery deck control device and control method that can realize the functions of continuous circulation of the pump by adding drill pipes, small flow control of the returning mud, and unblocking, so as to ensure the stable operation of the riser-less drilling mud recovery deck control device. Summary of the Invention

[0007] The purpose of the present invention is to provide a riser-less drilling mud recovery deck control device and control method to solve the problems existing in the above-mentioned prior art. It can not only keep the mud lifting pump working continuously and avoid damage to the motor caused by frequent start and stop, but also avoid rock cuttings sedimentation caused by pump stop, and at the same time avoid seawater mixing into the mud to cause performance degradation, thereby ensuring the stable operation of the riser-less drilling mud recovery deck control device.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] The present invention provides a riser-less drilling mud recovery deck control device, comprising:

[0010] A drill pipe through which the mud in the mud tank on the deck is injected to the bottom of the hole;

[0011] A suction module, which is sleeved outside the drill pipe and is used to store mud returning from the bottom of the hole to the wellhead;

[0012] a mud level identification device, the mud level identification device being installed in the suction module and being used to detect the height of the mud level inside the suction module;

[0013] a mud return line, the mud return line being connected to and in communication with the suction module and being used for conveying the mud in the suction module back to the mud tank on the deck;

[0014] A mud lift pump, the mud lift pump being arranged on the mud return pipeline and used for providing power for the returning mud;

[0015] The deck measurement and control manifold includes an input pipeline, a mud output pipeline, a seawater output pipeline, a three-way valve I and a sight cup. The input pipeline is connected and communicated with the mud return pipeline. The sight cup is set on the input pipeline. The input pipeline, the mud output pipeline and the seawater output pipeline are connected through the three-way valve I. The mud output pipeline is connected to the mud tank on the deck, and the seawater output pipeline is communicated with the outside world.

[0016] Preferably, the deck measurement and control manifold further includes a proportional control valve and a flow meter, both of which are arranged on the input pipeline, and the flow meter is farther away from the mud return pipeline than the proportional control valve.

[0017] Preferably, the deck measurement and control manifold also includes a three-way valve II, a plugging pump and a plugging pipeline. The three-way valve II is provided on the seawater output pipeline. The two ends of the three-way valve II are respectively connected to the seawater output pipeline, and the other end is connected to the plugging pipeline. The other end of the plugging pipeline extends into the seawater. The plugging pump is provided on the plugging pipeline to provide power for the seawater entering the plugging pipeline.

[0018] The present invention also provides an operating method of the riser-less drilling mud recovery deck control device.

[0019] When the mud is recovered normally, the three-way valve I is adjusted to connect the input pipeline with the mud output pipeline, so that the lifting flow Q0 of the mud lifting pump is equal to the mud return flow of the suction module, the mud liquid level is dynamically stabilized at a certain height, and the mud can be stably recovered and recycled;

[0020] When the deck is adding drill pipes and the deck mud pump stops grouting, the operation steps are as follows:

[0021] Step 1: When the deck mud pump stops grouting, the time is recorded as T0. The lifting pump volume of the mud lifting pump is adjusted to Q1. Q1 is less than Q0 but greater than the minimum mud return flow. The mud level in the suction module decreases. When the mud level recognition device inside the suction module detects that the seawater reaches the height of the suction module outlet line, the time T1 is recorded.

[0022] Step 2: Continue to maintain the lift pump volume Q1 of the mud lift pump unchanged, and allow seawater to enter the mud return pipeline to displace the mud;

[0023] Step 3: Based on the volume V of the entire mud return line and the lifting capacity Q1 of the mud lift pump, the time T2 for the mud return line to be filled with seawater can be calculated, T2 = T1 + V / Q1. After T2, the mud return line is filled with seawater. At the same time, manual observation is performed through the sight glass. Then, the three-way valve I is adjusted to connect the input pipeline with the seawater output pipeline, and the seawater in the mud return line is discharged into the seawater.

[0024] Step 4: After the drill pipe is connected to the deck, the deck mud pump is restarted to inject mud into the drill pipe. The mud level inside the suction module rises. When the mud level recognition device inside the suction module detects that the mud has reached the height of the suction module outlet line, the time T3 is recorded.

[0025] Step 5: Adjust the lifting flow rate of the mud lift pump to Q2, where Q2 is greater than Q1, and the mud enters the mud return pipeline to displace the seawater;

[0026] Step six, based on the volume V of the entire mud return line and the lifting pump volume Q2 of the mud lifting pump, the time T4 when the mud fills the mud return line can be calculated, T4 = T3 + V / Q2. After T4 time, the mud fills the mud return line, and manual observation is performed through the sight glass. Then, the three-way valve I is adjusted to connect the input pipeline with the mud output pipeline, and the mud in the mud return line is circulated to the mud tank on the deck.

[0027] Preferably, when the mud lift pump needs to perform a small flow lift, the mud lift pump can achieve controllable small flow lift by controlling the opening of the proportional control valve and comparing the data of the flow meter.

[0028] Preferably, when the solid particles in the returned mud block the mud return pipeline, the three-way valve I is adjusted to connect the input pipeline with the seawater output pipeline, the three-way valve II is adjusted to connect the seawater output pipeline with the flushing pipeline, and the flushing pump is started to inject seawater into the mud return pipeline under high pressure through the flushing pump to flush out the blocked position, and then the three-way valve II is adjusted to connect the seawater output pipeline with the outside world, and the seawater in the mud return pipeline is discharged to the outside world. At the same time, manual observation is performed through the sight glass until the seawater in the mud return pipeline is emptied, and then the three-way valve I is adjusted to connect the input pipeline with the mud output pipeline, and the mud in the mud return pipeline is circulated to the mud tank on the deck again.

[0029] Compared with the prior art, the present invention has achieved the following technical effects:

[0030] The present invention provides a riser-less drilling mud recovery deck control device and control method. When the deck is connecting drill pipes and the deck mud pump stops grouting, the mud lift pump can be kept in continuous operation by accurately switching the three-way valve I in the deck measurement and control manifold, thereby avoiding damage to the motor caused by frequent starts and stops and preventing rock cuttings settling caused by pump stoppage. At the same time, the mud in the mud return pipeline can be recovered and seawater can be discharged from the mud return pipeline, thereby avoiding performance degradation caused by seawater mixing with the mud and waste and pollution caused by mud discharged into the seawater. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is a schematic diagram of the structure of the riserless drilling mud recovery deck control system;

[0033] Figure 2 This is a structural diagram of the deck measurement and control manifold;

[0034] Figure 3 This is a schematic diagram of the normal mud recovery of the mud recovery deck control device for riserless drilling;

[0035] Figure 4 This is a schematic diagram of seawater entering the mud return pipeline;

[0036] Figure 5 This is a schematic diagram of the discharge of seawater in the mud return pipeline to the outside;

[0037] Figure 6 is a schematic diagram of the rising mud level inside the suction module;

[0038] Figure 7 This is a schematic diagram of the mud re-entering the mud return pipeline;

[0039] Figure 8 This is a schematic diagram of the mud returning pipeline being filled with mud again;

[0040] Figure 9 This is a schematic diagram of seawater blocking the mud return pipeline.

[0041] In the figure: 1. Drill pipe; 2. Suction module; 3. Mud level identification device; 4. Mud return pipeline; 5. Mud lifting pump; 6. Deck measurement and control manifold; 6-1. Input pipeline; 6-2. Proportional control valve; 6-3. Three-way valve I; 6-4. Mud output pipeline; 6-5. Three-way valve II; 6-6. Seawater output pipeline; 6-7. Plugging pump; 6-8. Plugging pipeline; 6-9. Flow meter; 6-10. Sight glass. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] The purpose of the present invention is to provide a riser-less drilling mud recovery deck control device and control method to solve the problems existing in the above-mentioned prior art. It can not only keep the mud lifting pump working continuously and avoid damage to the motor caused by frequent start and stop, but also avoid rock cuttings sedimentation caused by pump stop, and at the same time avoid seawater mixing into the mud to cause performance degradation, thereby ensuring the stable operation of the riser-less drilling mud recovery deck control device.

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] Example 1

[0046] This embodiment provides a riser-less drilling mud recovery deck control device, such as Figure 1-2As shown, it includes: a drill pipe 1, through which the mud in the mud tank on the deck is injected into the bottom of the hole; a suction module 2, which is sleeved on the outside of the drill pipe 1 and is used to store the mud returned from the bottom of the hole to the wellhead; a mud level identification device 3, which is installed in the suction module 2 and is used to detect the height of the mud level inside the suction module 2; a mud return pipeline 4, which is connected and communicated with the suction module 2 and is used to transport the mud in the suction module 2 back to the mud tank on the deck; a mud lift pump 5, which is set on the mud return pipeline 4, used to provide power for the returned mud; deck measurement and control manifold 6, which includes an input pipeline 6-1, a mud output pipeline 6-4, a seawater output pipeline 6-6, a three-way valve I 6-3, and a sight glass 6-10. Input pipeline 6-1 is connected and communicates with the mud return pipeline 4. Sight glass 6-10 is installed on input pipeline 6-1. Input pipeline 6-1, mud output pipeline 6-4, and seawater output pipeline 6-6 are connected via three-way valve I 6-3. Mud output pipeline 6-4 is connected to the deck mud tank, and seawater output pipeline 6-6 is connected to the outside world. Sight glass 6-10 is a transparent pipe that can be used to observe the fluid status within the pipe.

[0047] When the deck is adding drill pipes 1 and the deck mud pump stops grouting, the mud lift pump 5 can be kept in continuous operation by accurately switching the three-way valve I6-3 in the deck measurement and control manifold 6, avoiding damage to the motor caused by frequent starts and stops, and preventing rock cuttings settling caused by pump stoppage; at the same time, the mud in the mud return pipeline 4 can be recovered and the seawater in the mud return pipeline 4 can be discharged, avoiding performance degradation caused by seawater mixing with the mud, and waste and pollution caused by mud discharged into the seawater.

[0048] In this embodiment, the deck measurement and control manifold 6 preferably also includes a proportional control valve 6-2 and a flowmeter 6-9. Both valves are located on the inlet pipeline 6-1, with the flowmeter 6-9 located farther from the mud return line 4 than the proportional control valve 6-2. When low-flow lift is required in the mud return line 4 and the frequency conversion of the mud lift pump 5 alone is insufficient, throttling control can be implemented via the proportional control valve 6-2. By controlling the opening of the proportional control valve 6-2 and comparing the data from the flowmeter 6-9, controlled lift of low-flow mud can be achieved.

[0049] In the embodiment of this embodiment, it is further preferred that the deck measurement and control manifold 6 further includes a three-way valve II 6-5, a flushing pump 6-7, and a flushing pipeline 6-8. The three-way valve II 6-5 is provided on the seawater output pipeline 6-6. The two ends of the three-way valve II 6-5 are respectively connected to the seawater output pipeline 6-6, and the other end is connected to the flushing pipeline 6-8. The other end of the flushing pipeline 6-8 extends into the seawater. The flushing pump 6-7 is provided on the flushing pipeline 6-8 to provide power for the seawater entering the flushing pipeline 6-8. When the mud returned from the mud return pipeline 4 contains solid particles such as rock debris, there is a risk of solid particles clogging the pipeline. When the pipeline is blocked, adjust the three-way valve I 6-3 to connect the input pipeline 6-1 with the seawater output pipeline 6-6, adjust the three-way valve II 6-5 to connect the seawater output pipeline 6-6 with the flushing pipeline 6-8, and start the flushing pump 6-7 to perform reverse flushing operations, avoiding the need to recycle the entire set of underwater equipment and saving costs.

[0050] Example 2

[0051] This embodiment provides an operating method of the riserless drilling mud recovery deck control device of embodiment 1.

[0052] like Figure 3 As shown, when the mud is recovered normally, the three-way valve I 6-3 is adjusted to connect the input pipeline 6-1 with the mud output pipeline 6-4, so that the lifting flow Q0 of the mud lifting pump 5 is equal to the mud return flow of the suction module 2, the mud liquid level is dynamically stabilized at a certain height, and the mud can be stably recovered and recycled;

[0053] When the deck is connected to the drill pipe 1 and the deck mud pump stops grouting, the operation steps are as follows:

[0054] Step one, when the deck mud pump stops grouting, the time recorded at this time is T0. Since the specific gravity of the mud is greater than that of seawater, according to the U-tube effect, the mud in the drill pipe 1 will drop to a certain height. At this time, the mud lifting pump 5 can appropriately reduce the lifting pump volume, and adjust the lifting pump volume of the mud lifting pump 5 to Q1. Q1 is less than Q0 but must be greater than the minimum mud return flow rate to ensure that the mud can rise to the mud tank on the deck, wherein the lifting pump volume of the mud lifting pump 5, that is, the actual mud return flow rate, can be measured by the flow meter 6-9 to prevent rock chips from sinking. Since the suction module 2 is connected to the external seawater and there is no upward return mud, as the lifting pump continues to lift the mud, the mud height in the suction module 2 drops, and at the same time, seawater will flow into the suction module 2. When the mud level identification device 3 inside the suction module 2 detects that the seawater has reached the outlet line height of the suction module 2, the time T1 is recorded at this time;

[0055] Step 2, such as Figure 4 As shown, the lifting pump volume Q1 of the mud lifting pump 5 is maintained unchanged, and seawater enters the mud return pipeline 4 to replace the mud;

[0056] Step three, such as Figure 5 As shown, based on the volume V of the entire mud return line 4 and the lifting pump volume Q1 of the mud lifting pump 5, the time T2 when the seawater fills the mud return line 4 can be calculated. T2 = T1 + V / Q1. After T2, the seawater fills the mud return line 4. At the same time, manual observation is performed through the sight glass 6-10. In order to prevent seawater from mixing into the mud tank and reducing the mud performance, the three-way valve I 6-3 is adjusted in time to connect the input pipeline 6-1 with the seawater output pipeline 6-6, and the seawater in the mud return line 4 is discharged into the seawater.

[0057] Step 4: Figure 6 As shown, when the deck is connected to the drill pipe 1, the deck mud pump restarts and injects mud into the drill pipe 1. The mud level inside the suction module 2 rises. When the mud level recognition device 3 inside the suction module 2 detects that the mud reaches the height of the outlet line of the suction module 2, the time T3 is recorded.

[0058] Step five, such as Figure 7 As shown, the lifting flow rate of the mud lifting pump 5 is adjusted to Q2, Q2 is greater than Q1, and the mud enters the mud return pipeline 4 to replace the seawater;

[0059] Step six, such as Figure 8 As shown, based on the volume V of the entire mud return line 4 and the lifting pump volume Q2 of the mud lifting pump 5, the time T4 when the mud fills the mud return line 4 can be calculated, T4 = T3 + V / Q2. After T4 time, the mud fills the mud return line 4 again. At the same time, manual observation is carried out through the sight glass 6-10. In order to prevent the mud from continuing to be discharged into the sea and causing waste and environmental pollution, the three-way valve I 6-3 is adjusted in time to connect the input pipeline 6-1 with the mud output pipeline 6-4, and the mud in the mud return line 4 is circulated to the mud tank on the deck.

[0060] The above method completes the operational control of deck measurement and control manifold 6 during pump shutdown and drill pipe 1 connection. Throughout this process, three-way valve I6-3 is switched according to times T2 and T4. This ensures continuous operation of the lift pump, preventing motor damage from frequent starts and stops, and reduces rock debris settling caused by pump shutdowns. Furthermore, precise switching of three-way valve I6-3 enables mud recovery and seawater discharge, avoiding performance degradation caused by seawater mixing with the mud, as well as waste and pollution caused by mud discharge into the seawater.

[0061] Example 3

[0062] This embodiment provides an operating method for a riser-less drilling mud recovery deck control device of embodiment 1. When the mud lift pump 5 needs to perform small-flow lifting, the opening of the proportional control valve 6-2 can be controlled and the data of the flow meter 6-9 can be compared to achieve controllable lifting of the mud lift pump 5 at a small flow rate.

[0063] Example 4

[0064] This embodiment provides an operating method of the riser-less drilling mud recovery deck control device of embodiment 1, such as Figure 9 As shown, when solid particles in the returning mud clog the mud return line 4, three-way valve I 6-3 is adjusted to connect the input line 6-1 with the seawater output line 6-6. Three-way valve II 6-5 is adjusted to connect the seawater output line 6-6 with the flushing line 6-8. The flushing pump 6-7 is activated to inject seawater into the mud return line 4 at high pressure, clearing the blockage. Three-way valve II 6-5 is then adjusted to connect the seawater output line 6-6 with the outside world, draining the seawater in the mud return line 4. Simultaneously, manual observation is performed through sight glass 6-10. Once the seawater in the mud return line 4 is drained, three-way valve I 6-3 is adjusted to connect the input line 6-1 with the mud output line 6-4, allowing the mud in the mud return line 4 to be recirculated to the mud tank on deck. This avoids the need to recycle the entire underwater equipment, saving costs.

[0065] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A riserless drilling mud recovery deck control device, characterized by: include: A drill pipe through which the mud in the mud tank on the deck is injected to the bottom of the hole; A suction module, which is sleeved outside the drill pipe and is used to store mud returning from the bottom of the hole to the wellhead; a mud level identification device, the mud level identification device being installed in the suction module and being used to detect the height of the mud level inside the suction module; a mud return line, the mud return line being connected to and in communication with the suction module and being used for conveying the mud in the suction module back to the mud tank on the deck; A mud lift pump, the mud lift pump being arranged on the mud return pipeline and used for providing power for the returning mud; The deck measurement and control manifold includes an input pipeline, a mud output pipeline, a seawater output pipeline, a three-way valve I and a sight cup. The input pipeline is connected and communicated with the mud return pipeline. The sight cup is set on the input pipeline. The input pipeline, the mud output pipeline and the seawater output pipeline are connected through the three-way valve I. The mud output pipeline is connected and communicated with the mud tank on the deck, and the seawater output pipeline is communicated with the outside world.

2. The riserless drilling mud recovery deck control device according to claim 1, characterized in that: The deck measurement and control manifold further includes a proportional control valve and a flow meter. Both the proportional control valve and the flow meter are arranged on the input pipeline. The flow meter is farther away from the mud return pipeline than the proportional control valve.

3. The riserless drilling mud recovery deck control device according to claim 2, characterized in that: The deck measurement and control manifold also includes a three-way valve II, a plugging pump and a plugging pipeline. The three-way valve II is provided on the seawater output pipeline. The two ends of the three-way valve II are respectively connected to the seawater output pipeline, and the other end is connected to the plugging pipeline. The other end of the plugging pipeline extends into the seawater. The plugging pump is provided on the plugging pipeline to provide power for the seawater entering the plugging pipeline.

4. An operating method for a riserless drilling mud recovery deck control device according to claim 3, characterized in that: When the mud is recovered normally, the three-way valve I is adjusted to connect the input pipeline with the mud output pipeline, so that the lifting flow Q0 of the mud lifting pump is equal to the mud return flow of the suction module, the mud liquid level is dynamically stabilized at a certain height, and the mud can be stably recovered and recycled; When the deck is adding drill pipes and the deck mud pump stops grouting, the operation steps are as follows: Step 1: When the deck mud pump stops grouting, the time is recorded as T0. The lifting pump volume of the mud lifting pump is adjusted to Q1. Q1 is less than Q0 but greater than the minimum mud return flow. The mud level in the suction module decreases. When the mud level recognition device inside the suction module detects that the seawater reaches the height of the suction module outlet line, the time T1 is recorded. Step 2: Continue to maintain the lift pump volume Q1 of the mud lift pump unchanged, and allow seawater to enter the mud return pipeline to displace the mud; Step 3: Calculate the time T2 for the mud return line to be filled with seawater based on the volume V of the entire mud return line and the lifting capacity Q1 of the mud lift pump, where T2 = T1 + V / Q1. After T2, the mud return line is filled with seawater, and manual observation is performed through the sight glass. Then, adjust the three-way valve I to connect the input pipeline with the seawater output pipeline, and discharge the seawater in the mud return line into the seawater. Step 4: After the drill pipe is connected to the deck, the deck mud pump is restarted to inject mud into the drill pipe. The mud level inside the suction module rises. When the mud level recognition device inside the suction module detects that the mud has reached the height of the suction module outlet line, the time T3 is recorded. Step 5: Adjust the lifting flow rate of the mud lift pump to Q2, where Q2 is greater than Q1, and the mud enters the mud return pipeline to displace the seawater; Step six, based on the volume V of the entire mud return line and the lifting pump volume Q2 of the mud lifting pump, calculate the time T4 when the mud fills the mud return line, T4=T3+V / Q2. After T4 time, the mud fills the mud return line, and manual observation is performed through the sight glass. Then adjust the three-way valve I to connect the input pipeline with the mud output pipeline, and circulate the mud in the mud return line to the mud tank on the deck.

5. The operating method of the riserless drilling mud recovery deck control device according to claim 4, characterized in that: When the mud lift pump needs to perform small flow lift, the mud lift pump can achieve controllable small flow lift by controlling the opening of the proportional control valve and comparing the data of the flow meter.

6. The method for operating the riserless drilling mud recovery deck control device according to claim 4, characterized in that: When the solid particles in the returned mud clog the mud return pipeline, adjust the three-way valve I to connect the input pipeline with the seawater output pipeline, adjust the three-way valve II to connect the seawater output pipeline with the flushing pipeline, start the flushing pump, and inject seawater into the mud return pipeline under high pressure through the flushing pump to flush the clogged position, then adjust the three-way valve II to connect the seawater output pipeline with the outside world, discharge the seawater in the mud return pipeline to the outside world, and perform manual observation through the sight glass at the same time until the seawater in the mud return pipeline is emptied, then adjust the three-way valve I to connect the input pipeline with the mud output pipeline, and circulate the mud in the mud return pipeline to the mud tank on the deck again.

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