A pressure control drilling system and method for sustainable full wellbore circulation

Abstract

The present invention discloses a pressure-controlled drilling system and method for sustainable full-wellbore circulation. The system includes a drilling assembly, a main mud injection mechanism, a bypass mud injection mechanism, and a mud return mechanism. The drilling assembly includes a blowout preventer group at the wellhead, drill pipes, drill collars, a drill bit, a top drive, and a circulation joint. The main mud injection mechanism includes a mud pit, a mud pump, a main injection pipe, and a main injection control valve group. The bypass mud injection mechanism includes a bypass injection pipe and a bypass injection control valve group. The mud return mechanism includes a return pipe and a throttle valve. The beneficial effect of the technical solution proposed by the present invention is that by adding a bypass mud injection mechanism to the traditional pressure-controlled drilling system, continuous full-wellbore circulation is achieved during the connection of drill collars in pressure-controlled drilling, which has a significant effect on improving wellbore cleaning, reducing sand sticking in the drill string, reducing the pressure fluctuation caused by the annulus profile pressure fitting during the full-wellbore / ground circulation switchover, and reducing the wellbore temperature drop.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure-controlled drilling, and particularly to a pressure-controlled drilling system and method capable of sustainable full-wellbore circulation. Background Art

[0002] With the gradual development of the proven conventional oil and gas blocks globally, major oil companies have started to engage in deeper and more complex horizons, and the exploration and development of high-temperature and high-pressure wells are becoming increasingly common. High-temperature and high-pressure wells generally have difficulties such as high formation pressure, narrow safety pressure windows, and high well control risks. Reducing the accidents and complexities in high-pressure wells and narrow density window wells, improving drilling efficiency, and ensuring safe drilling are currently urgent technical problems to be solved. The pressure-controlled drilling technology effectively solves the problem of safe drilling in narrow density windows by establishing a trapped pressure environment to control the annulus pressure profile.

[0003] However, during the operation of connecting a single drill pipe / stand (a single drill pipe is referred to as a single joint, and three drill pipes connected together are called a stand) in the conventional pressure-controlled drilling process, it is necessary to switch from the full-wellbore circulation in the drilling state to the surface short-circuit circulation, which increases the risk of bottom-hole pressure fluctuations; moreover, the pressure-controlled drilling process is relatively cumbersome, the operation time of connecting a single drill pipe / stand is long, the full-wellbore circulation is interrupted, the cuttings stop returning to the surface, and the risk of sand bridge also increases; at the same time, during the connection of the stand, the full-wellbore circulation is interrupted, the drilling fluid cannot be circulated out of the wellbore, and the temperature of the drilling fluid in the wellbore cannot be released. Summary of the Invention

[0004] In view of this, it is necessary to provide a pressure-controlled drilling system and method capable of sustainable full-wellbore circulation to solve the technical problems that during the operation of connecting a single drill pipe / stand in the existing pressure-controlled drilling process, it is necessary to switch from the full-wellbore circulation in the drilling state to the surface short-circuit circulation, the full-wellbore circulation is interrupted, resulting in bottom-hole pressure fluctuations, sand bridge risks, and the temperature of the drilling fluid in the wellbore cannot be released.

[0005] To achieve the above object, the present invention provides a pressure-controlled drilling system capable of sustainable full-wellbore circulation, including a drilling assembly, a main mud injection mechanism, a bypass mud injection mechanism, and a mud reflux mechanism;

[0006] The drilling assembly includes a wellhead blowout preventer group, drill pipes, drill collars, a drill bit, a top drive, and a circulation joint. The wellhead blowout preventer group is arranged at the wellhead. The drill pipes pass through the wellhead blowout preventer group, with one end inside the wellbore and the other end outside the wellbore. The drill collars are installed at the lower end of the drill pipes. The drill bit is installed at the lower end of the drill collars. The top drive is installed at the upper end of the drill pipes and is used to drive the drill pipes to rotate. The circulation joint includes a joint housing, and the joint housing is provided with a first interface, a second interface, and a third interface that communicate with each other. The first interface is connected to the top drive, and the second interface is connected to the upper end of the drill pipes;

[0007] The main mud injection mechanism includes a mud pit, a mud pump, a main injection pipe and a main injection control valve group. The inlet of the mud pump communicates with the mud pit, the outlet of the mud pump communicates with one end of the main injection pipe, the other end of the main injection pipe communicates with the top drive, and the main injection control valve group is installed on the main injection pipe;

[0008] The mud bypass injection mechanism includes a bypass injection pipe and a bypass injection control valve group. One end of the bypass injection pipe communicates with the outlet of the mud pump, the other end of the bypass injection pipe is used to communicate with the third interface, and the bypass injection control valve group is installed on the bypass injection pipe;

[0009] The mud reflux mechanism includes a reflux pipe and a throttle valve. One end of the reflux pipe communicates with the wellbore, the other end of the reflux pipe communicates with the mud pit, the throttle valve is arranged on the reflux pipe, and a pressure detection component is arranged on the reflux pipe.

[0010] In some embodiments, the circulation joint further includes a first valve plate and a first elastic member. The first valve plate is hinged to the first interface, one end of the first elastic member is connected to the first interface, and the other end of the first elastic member is connected to the first valve plate.

[0011] In some embodiments, the circulation joint further includes a second valve plate and a second elastic member. The second valve plate is hinged to the third interface, one end of the second elastic member is connected to the third interface, and the other end of the second elastic member is connected to the second valve plate.

[0012] In some embodiments, the main injection control valve group includes a first main injection control valve and a second main injection control valve. The first main injection control valve and the second main injection control valve are connected in parallel and then connected to the main injection pipe.

[0013] In some embodiments, the bypass injection control valve group includes a first bypass injection control valve and a second bypass injection control valve. The first bypass injection control valve and the second bypass injection control valve are connected in parallel and then connected to the bypass injection pipe.

[0014] In some embodiments, the main mud injection mechanism further includes a first pressure relief pipe and a first pressure relief valve. One end of the first pressure relief pipe communicates with the main injection pipe, the other end of the first pressure relief pipe communicates with the mud pit, and the first pressure relief valve is arranged on the first pressure relief pipe.

[0015] In some embodiments, the mud bypass injection mechanism further includes a second pressure relief pipe and a second pressure relief valve. One end of the second pressure relief pipe is communicated with the bypass injection pipe, the other end of the second pressure relief pipe is communicated with the mud pit, and the second pressure relief valve is arranged on the second pressure relief pipe.

[0016] In some embodiments, the main mud injection mechanism further includes an auxiliary pump and an auxiliary injection valve. The inlet of the auxiliary pump is communicated with the mud pit, the outlet of the auxiliary pump is communicated with one end of the auxiliary injection valve, and the other end of the auxiliary injection valve is communicated with the main injection pipe.

[0017] In some embodiments, it further includes a first switching valve, a second switching valve and a third switching valve. One end of the first switching valve is communicated with the outlet of the mud pump, the other end of the first switching valve is communicated with the top drive, one end of the second switching valve is communicated with the outlet of the mud pump, the other end of the second switching valve is communicated with one end of the main injection control valve group, one end of the third switching valve is communicated with the other end of the main injection control valve group, and the other end of the third switching valve is communicated with the main injection pipe.

[0018] The present invention also provides a pressure-controlled drilling method for sustainable full-wellbore circulation, which is applicable to the pressure-controlled drilling system for sustainable full-wellbore circulation, and includes the following steps:

[0019] S1. During normal drilling, close the bypass injection control valve group, open the main injection control valve group. The mud in the mud pit is sucked into the mud pump, then enters the main injection pipe from the mud pump, then enters the top drive, and then is discharged into the annulus of the wellbore in sequence through the circulation joint, drill pipe, drill collar and bit. After the annulus is filled with mud, it flows back to the mud pit through the return pipe to form a circulation. During this process, the pressure of the returned mud is detected by the pressure detection component, and by controlling the displacement of the mud pump and the opening degree of the throttle valve, the mud pressure is always kept within the preset range;

[0020] S2. Before making a connection of a single pipe / stand, connect the other end of the bypass injection pipe to the third interface of the joint housing, and then gradually open the bypass injection control valve group. At the same time, gradually close the main injection control valve group. At this time, the mud in the mud pit is sucked into the mud pump, then enters the bypass injection pipe from the mud pump, then enters the circulation joint, and then is discharged into the annulus of the wellbore in sequence through the drill pipe, drill collar and bit. After the annulus is filled with mud, it flows back to the mud pit through the return pipe to form a circulation. Continue to detect the pressure of the returned mud by the pressure detection component, and by controlling the displacement of the mud pump and the opening degree of the throttle valve, the mud pressure is always kept within the preset range;

[0021] S3. Conduct the single joint / stand operation, disconnect the top drive from the circulation sub, connect the new drill pipe to the upper end of the circulation sub. A new circulation sub is pre-installed on the new drill pipe, and then connect the upper end of the new circulation sub to the top drive;

[0022] S4. After the single joint / stand operation is completed, gradually open the main injection control valve group. At the same time, gradually close the bypass injection control valve group. At this time, the mud circulates according to the process in step S1. Then, disconnect the other end of the bypass injection pipe from the third interface of the joint housing, and then continue to drive the drill pipe and the bit through the top drive for drilling operations.

[0023] Compared with the prior art, the beneficial effects of the technical solution proposed by the present invention are as follows: By adding a mud bypass injection mechanism to the traditional pressure control drilling system, continuous full wellbore circulation is achieved during the connection of stands in pressure control drilling, which has a significant effect on improving wellbore cleaning, reducing sand sticking and jamming of the drill string, reducing the pressure fluctuations caused by the annulus pressure profile fitting during the switching between full wellbore / ground circulation, and reducing the wellbore temperature drop. Description of the Drawings

[0024] Figure 1 is a schematic diagram of the mud circulation process during normal drilling of an embodiment of the pressure control drilling system with sustainable full wellbore circulation provided by the present invention;

[0025] Figure 2 is Figure 1 a schematic diagram after connecting the bypass injection pipe to the third interface of the circulation sub in

[0026] Figure 3 is Figure 2 the structural schematic diagram of the circulation sub in

[0027] Figure 4 is Figure 2 a schematic diagram after opening the second bypass injection control valve in

[0028] Figure 5 is Figure 4 a schematic diagram after opening the first bypass injection control valve in

[0029] Figure 6 is Figure 5 a schematic diagram after sequentially closing the first main injection control valve and the second main injection control valve in

[0030] Figure 7 is Figure 6 a schematic diagram after installing a new drill pipe / stand pre-installed with a circulation sub after opening the first pressure relief valve to relieve pressure in

[0031] Figure 8 is Figure 7 a schematic diagram after opening the auxiliary pump and the auxiliary injection valve in

[0032] Figure 9 Yes Figure 8 Schematic diagram after closing the auxiliary pump and the auxiliary injection valve and then sequentially opening the first main injection control valve and the second main injection control valve in [specific context];

[0033] Figure 10 Yes Figure 9 Schematic diagram after sequentially closing the first bypass injection control valve and the second bypass injection control valve in [specific context];

[0034] In the figure: 1 - drilling assembly, 11 - drill pipe, 11` - new drill pipe, 12 - top drive, 13 - circulation joint, 131 - joint housing, 1311 - first interface, 1312 - second interface, 1313 - third interface, 132 - first valve plate, 133 - second valve plate, 13` - new circulation joint, 2 - main mud injection mechanism, 21 - mud pump, 22 - main injection pipe, 23 - main injection control valve group, 231 - first main injection control valve, 232 - second main injection control valve, 24 - first pressure relief pipe, 25 - first pressure relief valve, 26 - auxiliary injection valve, 3 - mud bypass injection mechanism, 31 - bypass injection pipe, 32 - bypass injection control valve group, 321 - first bypass injection control valve, 322 - second bypass injection control valve, 41 - first on - off valve, 42 - second on - off valve, 43 - third on - off valve. Detailed implementation manners

[0035] The following will specifically describe the preferred embodiments of the present invention in conjunction with the accompanying drawings. The accompanying drawings form a part of this application and are used together with the embodiments of the present invention to explain the principles of the present invention, and are not used to limit the scope of the present invention.

[0036] Please refer to Figures 1-8 , the present invention provides a pressure - controlled drilling system for sustainable full - wellbore circulation, including a drilling assembly 1, a main mud injection mechanism 2, a mud bypass injection mechanism 3, and a mud reflux mechanism (not shown).

[0037] The described drilling assembly 1 includes a blowout preventer group at the wellhead, drill pipes 11, drill collars, a drill bit, a top drive 12 and a circulation joint 13. The blowout preventer group at the wellhead is arranged at the wellhead, and its function is to seal the gap between the drill pipe 11 and the annulus when the drill string rotates or is tripped in and out, so as to prevent the mud from overflowing from the wellhead. The drill pipe 11 passes through the blowout preventer group at the wellhead, with one end located inside the wellbore and the other end located outside the wellbore. The drill collar is installed at the lower end of the drill pipe, and the drill bit is installed at the lower end of the drill collar. A check valve is arranged at the outlet of the drill bit, which can prevent the mud from flowing back into the drill bit. The top drive is installed at the upper end of the drill pipe and is used to drive the drill pipe to rotate. The circulation joint 13 includes a joint housing 131, and the joint housing 131 is provided with a first interface 1311, a second interface 1312 and a third interface 1313 that are interconnected. The first interface 1311 is connected to the top drive 12, and the second interface 1312 is connected to the upper end of the drill pipe 11. It should be noted that the first interface 1311 and the third interface 1313 are one-way interfaces, that is, they are opened during forward flow and closed during reverse flow.

[0038] The main mud injection mechanism 2 includes a mud pit, a mud pump 21, a main injection pipe 22 and a main injection control valve group 23. The inlet of the mud pump 21 is communicated with the mud pit, the outlet of the mud pump 21 is communicated with one end of the main injection pipe 22, the other end of the main injection pipe 22 is communicated with the top drive 12, and the main injection control valve group 23 is installed on the main injection pipe 22.

[0039] The mud bypass injection mechanism 3 includes a bypass injection pipe 31 and a bypass injection control valve group 32. One end of the bypass injection pipe 31 is communicated with the outlet of the mud pump 21, the other end of the bypass injection pipe 31 is used to be communicated with the third interface 1313, and the bypass injection control valve group 32 is installed on the bypass injection pipe 31.

[0040] The mud reflux mechanism includes a reflux pipe and a throttle valve. One end of the reflux pipe is communicated with the annulus of the wellbore, the other end of the reflux pipe is communicated with the mud pit, the throttle valve is arranged on the reflux pipe, and a pressure detection member is arranged on the reflux pipe.

[0041] During normal drilling, the bypass injection control valve group 32 is closed, and the main injection control valve group 23 is opened. The mud in the mud pit is sucked into the mud pump 21, then enters the main injection pipe 22 from the mud pump 21, then enters the top drive 12, and then is discharged into the annulus of the wellbore in sequence through the circulation joint 13, the drill pipe 11, the drill collar and the drill bit (as Figure 1), after the annulus is filled with mud, it flows back to the mud pit through the return pipe, forming a circulation. During this process, the pressure of the returned mud is detected by the pressure detection component, and by controlling the displacement of the mud pump and the opening degree of the throttle valve, the mud pressure is always maintained within the preset range, thereby realizing pressure control drilling; before making a connection of a single joint / stand, the other end of the bypass injection pipe 31 is connected to the third interface 1313 of the joint housing 131 (such as Figure 2 ), then gradually open the bypass injection control valve group 32. At the same time, gradually close the main injection control valve group 23. At this time, the mud in the mud pit is sucked into the mud pump 21, then enters the bypass injection pipe 31 from the mud pump 21, then enters the circulation joint 13, and then is discharged into the annulus of the wellbore through the drill pipe 11, drill collar and bit in sequence (such as Figure 4 ), after the annulus is filled with mud, it flows back to the mud pit through the return pipe, forming a circulation. Continue to detect the pressure of the returned mud by the pressure detection component, and by controlling the displacement of the mud pump and the opening degree of the throttle valve, the mud pressure is always maintained within the preset range; then disconnect the connection between the top drive 12 and the circulation joint 13, connect a new drill pipe 11` (or a new stand) to the upper end of the circulation joint 13, a new circulation joint 13` is pre-installed on the new drill pipe 11`, and then connect the upper end of the new circulation joint 13` to the top drive 12 (such as Figure 7 ); after the operation of making a connection of a single joint / stand is completed, gradually open the main injection control valve group 23. At the same time, gradually close the bypass injection control valve group 32 (such as Figure 8 ), then disconnect the connection between the other end of the bypass injection pipe 31 and the third interface 1313 of the joint housing 131, and then continue to drive the drill pipe 11 and the bit for drilling operation through the top drive 12.

[0042] The present invention realizes continuous full-wellbore circulation during the connection of stands in pressure control drilling by adding a mud bypass injection mechanism 3 to the traditional pressure control drilling system, which has a significant effect on improving wellbore cleaning, reducing sand sticking and jamming of the drill string, reducing the pressure fluctuation caused by the annulus profile pressure fitting during the switching between full-wellbore / ground circulation and wellbore cooling.

[0043] In order to specifically realize the function of the circulation joint 13, please refer to Figure 2 and Figure 3 , in a preferred embodiment, the circulation joint 13 further includes a first valve plate 132 and a first elastic member. The first valve plate 132 is hinged to the first interface 1311. One end of the first elastic member is connected to the first interface 1311, and the other end of the first elastic member is connected to the first valve plate 132. When there is mud input above the first interface 1311, the first valve plate 132 opens. Otherwise, under the action of the first elastic member, the first valve plate 132 closes the first interface 1311.

[0044] To specifically implement the function of the circulation joint 13, please refer to Figure 2 and Figure 3 , in a preferred embodiment, the circulation joint 13 further includes a second valve plate 133 and a second elastic member. The second valve plate 133 is hinged to the third interface 1313. One end of the second elastic member is connected to the third interface 1313, and the other end of the second elastic member is connected to the second valve plate 133. When mud is input from the side of the third interface 1313, the second valve plate 133 opens. Otherwise, under the action of the second elastic member, the second valve plate 133 closes the third interface 1313.

[0045] To buffer the process of switching the flow channel, please refer to Figure 4 and Figure 5 , in a preferred embodiment, the main injection control valve group 23 includes a first main injection control valve 231 and a second main injection control valve 232. The first main injection control valve 231 has a larger flux. The first main injection control valve 231 and the second main injection control valve 232 are connected in parallel and then connected to the main injection pipe 22. When it is necessary to close the main injection control valve group 23, first close the second main injection control valve 232, and then close the first main injection control valve 231. Similarly, when it is necessary to open the main injection control valve group 23, first open the first main injection control valve 231, and then open the second main injection control valve 232.

[0046] To buffer the process of switching the flow channel, please refer to Figure 4 and Figure 5 , in a preferred embodiment, the bypass injection control valve group 32 includes a first bypass injection control valve 321 and a second bypass injection control valve 322. The first bypass injection control valve 321 has a larger flux. The first bypass injection control valve 321 and the second bypass injection control valve 322 are connected in parallel and then connected to the bypass injection pipe 31. When it is necessary to close the bypass injection control valve group 32, first close the second bypass injection control valve 322, and then close the first bypass injection control valve 321. Similarly, when it is necessary to open the bypass injection control valve group 32, first open the first bypass injection control valve 321, and then open the second bypass injection control valve 322.

[0047] To facilitate the pressure relief of the main injection pipe 22, please refer to Figure 6 and Figure 7, in a preferred embodiment, the main mud injection mechanism 2 further includes a first pressure relief pipe 24 and a first pressure relief valve 25. One end of the first pressure relief pipe 24 is communicated with the main injection pipe 22, and the other end of the first pressure relief pipe 24 is communicated with the mud pit. The first pressure relief valve 25 is arranged on the first pressure relief pipe 24. Before disconnecting the connection between the top drive 12 and the circulation joint 13, it is necessary to first open the first pressure relief valve 25 to relieve the pressure of the main injection pipe 22 to ensure operation safety.

[0048] To relieve the pressure of the bypass injection pipe 31, please refer to Figure 9 and Figure 10 , in a preferred embodiment, the mud bypass injection mechanism 3 further includes a second pressure relief pipe 33 and a second pressure relief valve 34. One end of the second pressure relief pipe 33 is communicated with the bypass injection pipe 31, and the other end of the second pressure relief pipe 33 is communicated with the mud pit. The second pressure relief valve 34 is arranged on the second pressure relief pipe 33. Before disconnecting the connection between the bypass injection pipe 31 and the circulation joint 13, it is necessary to first open the second pressure relief valve 34 to relieve the pressure of the bypass injection pipe 31 to ensure operation safety.

[0049] To improve the bottom hole pressure stability, please refer to Figure 8 , in a preferred embodiment, the main mud injection mechanism 2 further includes an auxiliary pump and an auxiliary injection valve 26. The inlet of the auxiliary pump is communicated with the mud pit, the outlet of the auxiliary pump is communicated with one end of the auxiliary injection valve 26, and the other end of the auxiliary injection valve 26 is communicated with the main injection pipe 22. As Figure 8 shown, after installing a new drill pipe 11`, before opening the main injection control valve group 23, first open the auxiliary pump and the auxiliary injection valve 26 to fill the new drill pipe 11` with mud, so as to avoid the bottom hole pressure fluctuation that may be caused by directly opening the main injection control valve group 23.

[0050] To facilitate maintenance, please refer to Figure 1 , in a preferred embodiment, the pressure control drilling system capable of sustainable full wellbore circulation further includes a first switching valve 41, a second switching valve 42 and a third switching valve 43. One end of the first switching valve 41 is communicated with the outlet of the mud pump 21, and the other end of the first switching valve 41 is communicated with the top drive 12. One end of the second switching valve 42 is communicated with the outlet of the mud pump 21, and the other end of the second switching valve 42 is communicated with one end of the main injection control valve group 23. One end of the third switching valve 43 is communicated with the other end of the main injection control valve group 23, and the other end of the third switching valve 43 is communicated with the main injection pipe 22. Under normal circumstances, the first switching valve 41 is always closed, and the second switching valve 42 and the third switching valve 43 are always open. When the system needs to be maintained, the second switching valve 42 and the third switching valve 43 can be closed.

[0051] The present invention also provides a pressure-controlled drilling method with sustainable full-wellbore circulation, which is applicable to the pressure-controlled drilling system with sustainable full-wellbore circulation, and includes the following steps:

[0052] S1. During normal drilling, close the bypass injection control valve group 32, open the main injection control valve group 23. The mud in the mud pit is sucked into the mud pump 21, then enters the main injection pipe 22 from the mud pump 21, then enters the top drive 12, and then is discharged into the annulus of the wellbore through the circulation joint 13, drill pipe 11, drill collar and bit in sequence (as Figure 1 ), after the annulus is filled with mud, it flows back to the mud pit through the return pipe, forming a circulation. During this process, the pressure of the returned mud is detected by the pressure detection component, and by controlling the displacement of the mud pump and the opening degree of the throttle valve, the annulus pressure is always maintained within the preset range, so as to achieve pressure-controlled drilling;

[0053] S2. Before making a connection of a single joint / stand, connect the other end of the bypass injection pipe 31 to the third interface 1313 of the joint housing 131 (as Figure 2 ), then gradually open the bypass injection control valve group 32, and at the same time, gradually close the main injection control valve group 23. At this time, the mud in the mud pit is sucked into the mud pump 21, then enters the bypass injection pipe 31 from the mud pump 21, then enters the circulation joint 13, and then is discharged into the annulus of the wellbore through the drill pipe 11, drill collar and bit in sequence (as Figure 4 ), after the annulus is filled with mud, it flows back to the mud pit through the return pipe, forming a circulation. Continue to detect the pressure of the returned mud by the pressure detection component, and by controlling the displacement of the mud pump and the opening degree of the throttle valve, keep the mud pressure always within the preset range;

[0054] S3. Disconnect the connection between the top drive 12 and the circulation joint 13, connect the new drill pipe 11` to the upper end of the circulation joint 13, a new circulation joint 13` is pre-installed on the new drill pipe 11`, and then connect the upper end of the new circulation joint 13` to the top drive 12 (as Figure 7 );

[0055] S4. After the connection of a single joint / stand is completed, gradually open the main injection control valve group 23, and at the same time, gradually close the bypass injection control valve group 32 (as Figure 8 ), then, disconnect the connection between the other end of the bypass injection pipe 31 and the third interface 1313 of the joint housing 131, and then continue to drive the drill pipe 11 and the bit for drilling operation through the top drive 12.

[0056] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A pressure-controlled drilling method for sustainable full-wellbore circulation, characterized in that, The pressure-controlled drilling device corresponding to this method for sustainable full-wellbore circulation includes a drilling assembly, a main mud injection mechanism, a bypass mud injection mechanism, and a mud reflux mechanism; The drilling assembly includes a blowout preventer group at the wellhead, drill pipes, drill collars, a drill bit, a top drive, and a circulation joint. The blowout preventer group is arranged at the wellhead. The drill pipes pass through the blowout preventer group, with one end inside the wellbore and the other end outside the wellbore. The drill collars are installed at the lower end of the drill pipes, the drill bit is installed at the lower end of the drill collars, the top drive is installed at the upper end of the drill pipes and is used to drive the drill pipes to rotate. The circulation joint includes a joint housing, and the joint housing is provided with a first interface, a second interface, and a third interface that are interconnected. The first interface is connected to the top drive, and the second interface is connected to the upper end of the drill pipes; The main mud injection mechanism includes a mud pit, a mud pump, a main injection pipe, and a main injection control valve group. The inlet of the mud pump is communicated with the mud pit, the outlet of the mud pump is communicated with one end of the main injection pipe, the other end of the main injection pipe is communicated with the top drive, and the main injection control valve group is installed on the main injection pipe; The bypass mud injection mechanism includes a bypass injection pipe and a bypass injection control valve group. One end of the bypass injection pipe is communicated with the outlet of the mud pump, and the other end of the bypass injection pipe is used to be communicated with the third interface. The bypass injection control valve group is installed on the bypass injection pipe; The mud reflux mechanism includes a reflux pipe and a throttle valve. One end of the reflux pipe is communicated with the wellbore, the other end of the reflux pipe is communicated with the mud pit, the throttle valve is arranged on the reflux pipe, and a pressure detection element is arranged on the reflux pipe; The main injection control valve group includes a first main injection control valve and a second main injection control valve. The first main injection control valve and the second main injection control valve are connected in parallel and then connected to the main injection pipe. The first main injection control valve has a larger flow rate. When it is necessary to close the main injection control valve group, first close the second main injection control valve, and then close the first main injection control valve. When it is necessary to open the main injection control valve group, first open the first main injection control valve, and then open the second main injection control valve; The pressure-controlled drilling method for sustainable full-wellbore circulation includes the following steps: S1. During normal drilling, close the bypass injection control valve group and open the main injection control valve group. The mud in the mud pit is sucked into the mud pump, then enters the main injection pipe from the mud pump, then enters the top drive, and then is discharged into the annulus of the wellbore in sequence through the circulation joint, drill pipes, drill collars, and drill bit. After the annulus is filled with mud, it flows back to the mud pit through the reflux pipe to form a circulation. During this process, the pressure of the returned mud is detected by the pressure detection element, and by controlling the displacement of the mud pump and the opening degree of the throttle valve, the mud pressure is always maintained within a preset range; S2. Before the operation of connecting a single drill pipe / stand, connect the other end of the bypass injection pipe to the third interface of the joint housing, and then gradually open the bypass injection control valve group. At the same time, gradually close the main injection control valve group. At this time, the mud in the mud pit is sucked into the mud pump, then enters the bypass injection pipe from the mud pump, then enters the circulation joint, and then is discharged into the annulus of the wellbore through the drill pipe, drill collar and bit in sequence. After the annulus is filled with mud, it flows back to the mud pit through the reflux pipe to form a circulation. Continue to detect the pressure of the returned mud through the pressure detection component, and by controlling the displacement of the mud pump and the opening degree of the throttle valve, keep the mud pressure within the preset range at all times; S3. Conduct the operation of connecting a single drill pipe / stand. Disconnect the connection between the top drive and the circulation joint, connect a new drill pipe to the upper end of the circulation joint. A new circulation joint is pre-installed on the new drill pipe, and then connect the upper end of the new circulation joint to the top drive; S4. After the operation of connecting a single drill pipe / stand is completed, gradually open the main injection control valve group. At the same time, gradually close the bypass injection control valve group. At this time, the mud circulates according to the process in step S1. Then, disconnect the connection between the other end of the bypass injection pipe and the third interface of the joint housing, and then continue to drive the drill pipe and bit for drilling operations through the top drive.

2. The pressure control drilling method for sustainable full wellbore circulation according to claim 1, wherein The circulation joint further includes a first valve plate and a first elastic member. The first valve plate is hinged to the first interface. One end of the first elastic member is connected to the first interface, and the other end of the first elastic member is connected to the first valve plate.

3. The pressure control drilling method for sustainable full wellbore circulation according to claim 1, characterized in that, The circulation joint further includes a second valve plate and a second elastic member. The second valve plate is hinged to the third interface. One end of the second elastic member is connected to the third interface, and the other end of the second elastic member is connected to the second valve plate.

4. The pressure control drilling method for sustainable full wellbore circulation according to claim 1, characterized in that, The bypass injection control valve group includes a first bypass injection control valve and a second bypass injection control valve. The first bypass injection control valve and the second bypass injection control valve are connected in parallel and then connected to the bypass injection pipe.

5. The pressure control drilling method for sustainable full wellbore circulation according to claim 1, wherein, The main mud injection mechanism further includes a first pressure relief pipe and a first pressure relief valve. One end of the first pressure relief pipe is communicated with the main injection pipe, and the other end of the first pressure relief pipe is communicated with the mud pit. The first pressure relief valve is arranged on the first pressure relief pipe.

6. The pressure control drilling method for sustainable full wellbore circulation according to claim 1, characterized in that, The mud bypass injection mechanism further includes a second pressure relief pipe and a second pressure relief valve. One end of the second pressure relief pipe is communicated with the bypass injection pipe, and the other end of the second pressure relief pipe is communicated with the mud pit. The second pressure relief valve is arranged on the second pressure relief pipe.

7. The pressure control drilling method for sustainable full wellbore circulation according to claim 1, wherein The main mud injection mechanism further includes an auxiliary pump and an auxiliary injection valve. The inlet of the auxiliary pump is communicated with the mud pit, the outlet of the auxiliary pump is communicated with one end of the auxiliary injection valve, and the other end of the auxiliary injection valve is communicated with the main injection pipe.

8. The pressure control drilling method for sustainable full wellbore circulation according to claim 1, characterized in that, It further includes a first switching valve, a second switching valve and a third switching valve. One end of the first switching valve is communicated with the outlet of the mud pump, and the other end of the first switching valve is communicated with the top drive. One end of the second switching valve is communicated with the outlet of the mud pump, and the other end of the second switching valve is communicated with one end of the main injection control valve group. One end of the third switching valve is communicated with the other end of the main injection control valve group, and the other end of the third switching valve is communicated with the main injection pipe.

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