CN110608005A - A gas lift reverse circulation drilling system and automatic control method - Google Patents

Abstract

The invention discloses a gas-lift reverse circulation drilling system and an automatic control method, which comprises a well head device, an inner drilling tool, a return pipeline, a gas injection pipeline, a drilling fluid injection pipeline and an automatic control system. Drilling tools in the well include drill bit, downhole electromagnetic PWD, drill collar, lower single-wall drill pipe, gas-water mixer, double-wall drill pipe, gas injection valve and upper single-wall drill pipe. Gas injection and drilling fluid injection pipelines are equipped with automatic throttle valves, pressure gauges, flow meters and automatic pressure relief valves. The automatic control system includes a signal receiver, computer, display, PLC controller, and parameter input module. During the gas lift reverse circulation drilling process, the bottom hole pressure is monitored in real time through the automatic control system, and the gas injection parameters and drilling fluid parameters are adjusted to realize well drilling. The bottom pressure is automatically and precisely controlled. The invention has the beneficial effects of: matching conventional wellhead well control equipment, reducing well control risk; accurately controlling bottom hole pressure, preventing well leakage and overflow.

Description

A gas lift reverse circulation drilling system and automatic control method

technical field

The invention relates to the technical field of oil and gas drilling, in particular to a gas lift reverse circulation drilling system and an automatic control method.

Background technique

During the drilling process, due to reasons such as unknown underground pressure system and complex geological conditions, lost circulation occurs from time to time, and even serious lost circulation occurs, which leads to complex downhole situations such as overflow, pipe sticking, and well wall collapse, causing a large number of Economic loss may also pollute the environment. There are many leakage prevention and control drilling technologies, including gas drilling technology, foam drilling technology, clear water strong drilling technology, mud cap drilling technology, etc. All these technologies have certain limitations: due to their own characteristics, gas drilling technology has a large water output. 1. The application of the stratum prone to collapse is limited; the foam drilling technology is difficult to recover the foam drilling fluid, which is easy to cause environmental pollution; the clear water strong drilling and mud cap drilling technologies are difficult to ensure that all the cuttings generated by drilling will leak into the formation, and the risk of pipe sticking is high.

Gas-lift reverse circulation drilling technology is a kind of leakage prevention and control drilling technology. It has unique advantages in dealing with serious leakage problems in low-pressure formations with developed fractures and karst caves. The main advantages are: it can establish circulation under the condition of loss of return; Annular pressure loss; high sand carrying efficiency. At present, this technology has been applied to drilling fields such as water wells, geothermal wells, mines, and gas discharge wells. However, the wellhead is open during the drilling process of conventional gas lift reverse circulation drilling technology, and there is a certain risk of well control, and the key construction parameters involved in this technology It is determined that it is still in the project summary stage, the bottom hole pressure control is not accurate, there are risks of well leakage and overflow during the construction process, and there are no risk control measures when the pressure is too high or the flow channel is blocked.

Contents of the invention

The purpose of the present invention is to solve the problem of difficult drilling in lossy formations, and to provide a gas lift reverse circulation drilling system and an automatic drilling system that reduces lost circulation and overflow, reduces well control risks, and is especially suitable for lossy formations with fractures and karst caves. Control Method.

The object of the present invention is achieved through the following technical solutions: a gas lift reverse circulation drilling system, which includes a wellhead device, a return pipeline, a drilling tool in a well, a gas injection pipeline, a drilling fluid injection pipeline and an automatic control system;

The wellhead device includes a drilling spool arranged on the top of the wellhead, and the top of the drilling spool is sequentially provided with a rising nipple, a ram blowout preventer and a rotary blowout preventer, and the bypass valve on the right side of the rotary blowout preventer An annular liquid level monitoring echo instrument is installed on the upper part, and an air-water isolation tube is arranged inside the raised sub-section, and the upper end of the air-water isolation tube is turned outward and fixed on the inner wall of the raised sub-joint, and the air-water isolation tube is The lower end of the isolation pipe runs through the drilling spool and extends into the well;

The return pipeline includes a top drive, a hose, a standpipe, a sand discharge pipeline and a vibrating screen, and a hose, a riser and a sand discharge pipeline are sequentially connected between the liquid outlet of the top drive and the inlet of the vibrating screen;

The drilling tool in the well includes a drill bit, a downhole electromagnetic PWD, a drill collar, a lower single-wall drill pipe, a gas-water mixer, a double-wall drill pipe, a gas injection valve and an upper single-wall drill pipe arranged in the well and connected sequentially from bottom to top. Rod, the upper single-wall drill pipe extends on the drill floor and is connected with the top drive;

The double-walled drill pipe includes an outer tube and an inner tube, and the inner tube is axially arranged inside the outer tube;

The gas injection valve includes an inner tube of the gas injection valve, an outer tube of the gas injection valve and a partition A, the partition A is welded in the outer tube of the gas injection valve, a through hole A is opened in the center of the partition A, and the inside of the through hole A is welded There is an inner tube of the gas injection valve, the upper end of the inner tube of the gas injection valve extends upwards and is threadedly connected with the lower end of the upper single-wall drill pipe, the lower end of the inner tube of the gas injection valve is threaded with the upper end of the inner tube, and the gas injection valve There are a plurality of side holes A located below the partition A on the outer pipe, and the outer pipe of the gas injection valve is threadedly connected with the upper end of the outer pipe, and the gas injection valve moves within the range of the gas-water isolation pipe when it is working;

The gas-water mixer includes an inner tube of the gas-water mixer, an outer tube of the gas-water mixer and a partition B, the partition B is welded in the outer tube of the gas-water mixer, and a through hole B is opened in the center of the partition B through which The inner pipe of the air-water mixer is welded in the hole B, and there are a plurality of side holes B located above the partition B on the inner pipe of the air-water mixer. The lower end of the inner pipe of the air-water mixer extends downward and is threadedly connected with the upper end of the lower single-wall drill pipe. The outer pipe of the air-water mixer is threadedly connected to the lower end of the outer pipe, and the air-water mixer works submerged below the liquid level in the annular space;

The gas injection pipeline includes an air compressor, a supercharger, and a rotary blowout preventer, and an automatic throttle valve I and a pressure gauge I are sequentially connected between the air outlet of the supercharger and the bypass valve on the left side of the rotary blowout preventer. , flow meter I and automatic pressure relief valve I;

The drilling fluid injection pipeline includes a mud tank, a mud pump, a kill manifold, and a drilling spool. An automatic pressure relief valve II and an automatic throttle valve II are sequentially connected between the mud pump and the inlet of the kill manifold. , pressure gauge II and flow meter II, the mud pump is communicated with the mud tank through pipelines;

Described automatic control system comprises signal receiver, display, parameter input module, PLC controller and computer, and described signal receiver, display, parameter input module, PLC controller are connected with computer by wire respectively;

The signal receiver is connected with the downhole electromagnetic PWD and the annular liquid level monitoring echo instrument through radio signals, and the signal receiver is connected with the pressure gauge I, flowmeter I, pressure gauge II, and flowmeter II through wired electrical signals ;

The PLC controller is connected with the automatic throttle valve I, the automatic pressure relief valve I, the automatic throttle valve II, and the automatic pressure relief valve II through wired electrical signals.

The upper end of the gas injection valve and the lower end of the gas-water mixer are equal in diameter to the single-wall drill pipe, and the lower end of the gas injection valve and the upper end of the gas-water mixer are equal in diameter to the double-wall drill pipe.

Both the left and right sides of the rotary blowout preventer are provided with bypass valves.

The kill manifold is connected with the flat valve on the left side of the drilling spool.

The downhole electromagnetic PWD and annular space liquid level monitoring echometer have the function of radio signal transmission.

The signal receiver has wireless and wired signal receiving functions.

The automatic control method of the gas lift reverse circulation drilling system, it comprises the following steps:

S1. Set the pressure relief thresholds of automatic pressure relief valve I and automatic pressure relief valve II on the parameter input module of the automatic control system according to the pressure bearing capacity of the wellhead equipment, gas injection pipeline, and drilling fluid injection pipeline. According to the adjacent well data, The prediction data is input into the formation pore pressure, formation collapse pressure, formation leakage pressure and formation fracture pressure on the parameter input module;

S2. The specific steps of gas lift reverse circulation drilling are:

S21. Start the air compressor and mud pump, and drive the upper single-wall drill pipe to rotate through the top drive, the upper single-wall drill pipe to drive the double-wall drill pipe to rotate, and the double-wall drill pipe to drive the lower single-wall drill pipe, drill collar and drill bit to rotate , the drill bit penetrates into the formation;

S22. The air compressor produces compressed gas, and the compressed gas enters the rotary blowout preventer through the supercharger, automatic throttle valve I, pressure gauge I, flow meter I, and bypass valve in sequence. Secondary through the side hole A, the annular space between the inner tube of the gas injection valve and the outer tube of the gas injection valve, the annular space of the double-walled drill pipe, the annular space between the inner tube of the gas-water mixer and the outer tube of the gas-water mixer, and side hole B into the In the inner tube, the high-pressure gas lifts the drilling fluid in the inner tube toward the wellhead;

S23. The mud pump pumps out the drilling fluid in the mud tank, and the drilling fluid enters the drilling spool through the automatic throttle valve II, pressure gauge II, flow meter II, kill manifold, and flat valve sequentially under the action of the pump pressure , the drilling fluid is blocked by the gas-water isolation tube, and falls to the bottom of the well along the annulus between the well wall and the gas-water isolation tube, and the annulus between the well wall and the outer tube. The single-wall drill pipe and the through hole B enter into the inner tube of the double-wall drill pipe;

S24. The lifted drilling fluid passes through the inner pipe of the double-wall drill pipe, the through hole A, the upper single-wall drill pipe, the water hose, the riser, and the sand discharge pipeline in sequence, and finally enters the vibrating screen, and enters the mud tank after separation , and finally completed gas lift reverse circulation drilling;

S3. During the drilling process in step S1, monitor gas injection parameters and drilling fluid parameters in real time through flowmeter I, pressure gauge I, flowmeter II, and pressure gauge II, and monitor annular fluid in real time through an annular liquid level monitoring echo instrument Surface height, real-time monitoring of bottomhole pressure and drilling fluid flow drilling parameters through bottomhole electromagnetic MWD;

S4. During the drilling process in step S1, the bottom hole safety pressure window is calculated by computer, and it is judged whether the bottom hole pressure monitored by PWD in real time is within the safety pressure window. If not, new gas injection parameters and drilling fluid injection parameters are calculated. parameter, and transmit the signal to the PLC controller to control the automatic throttle valve I and automatic throttle valve II to adjust, change the gas injection volume and drilling fluid displacement, keep the bottom hole pressure within the safe pressure window range, and prevent overflow flow, leakage;

S5. During the drilling process in step S1, the gas injection pressure and the injection drilling fluid pressure are monitored in real time by the automatic control system. When the pressure exceeds the pressure relief threshold, the PLC controller controls the automatic pressure relief valve I and the automatic pressure relief valve II to perform relief. Pressure, to prevent high pressure pressure hazards caused by blockage of the flow channel;

S6. During the drilling process in step S1, the bottom hole safety pressure window, annular liquid level height, bottom hole pressure, gas injection parameters, drilling fluid parameters, automatic throttle valve opening, Drilling parameters such as pressure valve switch status can be monitored in real time to control gas lift reverse circulation drilling performance.

The present invention has the following advantages:

1. The required equipment can be modified on the basis of the existing equipment. The on-site operation is simple, the process conversion is convenient, and the principle of gas lift reverse circulation is used for drilling, which is suitable for the leakage formation with fractures and caves.

2. Gas is injected into the outer tube of the double-wall drill pipe through the rotary blowout preventer and the gas injection valve. The wellhead uses a single-wall drill pipe, which fully matches the conventional wellhead well control equipment and reduces the risk of well control.

3. During the drilling process, the bottom hole pressure is monitored in real time by the downhole electromagnetic PWD, and the gas injection parameters and drilling fluid injection parameters are adjusted through the automatic control system to realize automatic and precise control of the bottom hole pressure and prevent lost circulation and overflow.

Description of drawings

Fig. 1 is a flow chart of an embodiment of the automatic control method for gas lift reverse circulation drilling of the present invention;

Figure 2 is a schematic diagram of the connection of the gas injection valve, the double-walled drill pipe and the gas-water mixer;

Fig. 3 is a schematic diagram of the flow of fluid in the drilling tool in the well;

Figure 4 is a schematic diagram of the structure of the partition;

Figure 5 is a schematic diagram of the structure of the gas-water isolation tube;

In the figure, 1-drilling spool, 2-rising nipple, 3-ram blowout preventer, 4-rotary blowout preventer, 5-top drive, 6-water hose, 7-standpipe, 8-vibrating screen , 9-drill bit, 10-downhole electromagnetic PWD, 11-drill collar, 12-lower single-wall drill pipe, 13-air-water mixer, 14-double-wall drill pipe, 15-gas injection valve, 16-upper single-wall drill Rod, 17-inner tube of gas injection valve, 18-outer tube of gas injection valve, 19-side hole A, 20-baffle A, 21-inner tube, 22-outer tube, 23-inner tube of gas-water mixer, 24 - side hole B, 25 - outer tube of air-water mixer, 26 partition B, 27 - air compressor, 28 - supercharger, 29 - automatic throttle valve I, 30 - pressure gauge I, 31 - flow meter I , 32-Automatic pressure relief valve Ⅰ, 33-Mud tank, 34-Automatic pressure relief valve II, 35-Automatic throttle valve II, 36-Pressure gauge II, 37-Flow meter II, 38-Kill manifold, 39 -Automatic control system, 40-display device, 41-computer, 42-PLC controller, 43-signal receiver, 44-parameter input module, 45-air-water isolation pipe, 46-mud pump, 47-bypass valve , 48-echo instrument, 49-sand discharge pipeline, 50-flat valve, 51-well.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing, protection scope of the present invention is not limited to the following:

As shown in Figures 1 to 5, a gas lift reverse circulation drilling system includes a wellhead device, a return pipeline, an in-hole drilling tool, a gas injection pipeline, a drilling fluid injection pipeline and an automatic control system 39;

The wellhead device includes a drilling spool 1 arranged on the top of the wellhead, and the top of the drilling spool 1 is provided with a rising nipple 2, a ram blowout preventer 3 and a rotating blowout preventer 4 in sequence, and the rotating blowout preventer 4 An annular liquid level monitoring echo instrument 48 is installed on the bypass valve on the right side, and an air-water isolation pipe 45 is arranged in the rising joint 2, and the upper end of the air-water isolation pipe 45 is flanged outwards and fixed on the On the inner wall of the rising sub 2 , the lower end of the gas-water isolation pipe 45 runs through the drilling spool 1 and extends into the well 51 .

The return pipeline includes a top drive 5, a water hose 6, a riser 7, a sand discharge pipeline 49 and a vibrating screen 8, and a water hose 6, Standpipe 7 and sand discharge pipeline 49; the well drilling tool includes drill bit 9, downhole electromagnetic PWD10, drill collar 11, lower single-wall drill pipe 12, and gas-water mixer arranged in the well 51 and connected sequentially from bottom to top 13. Double-wall drill pipe 14, gas injection valve 15 and upper single-wall drill pipe 16, the upper single-wall drill pipe 16 extends on the drill floor and is connected with top drive 5.

The double-wall drill pipe 14 includes an outer tube 22 and an inner tube 21, and the inner tube 21 is arranged in the outer tube 22 along the axial direction; the gas injection valve 15 includes an inner tube 17 of the gas injection valve, an outer tube 18 of the gas injection valve and Separator A20, said separator A20 is welded in the outer tube 18 of the gas injection valve, a through hole A is opened in the center of the separator A20, and the inner tube 17 of the gas injection valve is welded in the through hole A, and the upper end of the inner tube 17 of the gas injection valve part extends upwards and is threadedly connected with the lower end of the upper single-wall drill pipe 16, the lower end of the inner tube 17 of the gas injection valve is screwed with the upper end of the inner tube 21, and the outer tube 18 of the gas injection valve is provided with a plurality of The side hole A19 below A20 is threadedly connected to the upper end of the gas injection valve outer tube 18 and the outer tube 22, and the gas injection valve 15 moves within the range of the gas-water isolation tube 45 when it works; the gas-water mixer 13 includes gas-water mixing The inner pipe 23, the outer pipe 25 of the gas-water mixer and the partition B26, the partition B26 is welded in the outer pipe 25 of the gas-water mixer, the center of the partition B26 is provided with a through hole B, and the through hole B is welded with a gas The inner pipe 23 of the water mixer and the inner pipe 23 of the air-water mixer are provided with a plurality of side holes B24 located above the partition B26. The upper end of the inner pipe 23 of the air-water mixer extends upward and is threaded with the lower end of the inner pipe 21 Connection, the lower end of the inner pipe 23 of the air-water mixer extends downward and is threadedly connected with the upper end of the lower single-wall drill pipe 12, and the outer pipe 25 of the air-water mixer is threadedly connected to the lower end of the outer pipe 22, and the air-water mixing The device 13 is submerged below the liquid level of the annulus during operation.

The gas injection pipeline includes an air compressor 27, a supercharger 28, and a rotary blowout preventer 4, and an automatic throttle valve is sequentially connected between the air outlet of the supercharger 28 and the bypass valve on the left side of the rotary blowout preventer 4 I29, pressure gauge I30, flow meter I31 and automatic pressure relief valve I32; the drilling fluid injection pipeline includes mud tank 33, mud pump 46, kill manifold 38, drilling spool 1, the mud pump 46 and kill well An automatic pressure relief valve II34, an automatic throttle valve II35, a pressure gauge II36 and a flow meter II37 are sequentially connected between the inlet ports of the manifold 38, and the mud pump 46 communicates with the mud tank 33 through a pipeline.

Described automatic control system 39 comprises signal receiver 43, display 40, parameter input module 44, PLC controller 42 and computer 41, and described signal receiver 43, display 40, parameter input module 44, PLC controller 42 are connected with computer respectively 41 wired connections.

The signal receiver 43 is connected with the downhole electromagnetic PWD10 and the annular space liquid level monitoring echo instrument 48 by radio signal, and the signal receiver 43 is connected with the pressure gauge I30, flowmeter I31, pressure gauge II36, and flowmeter II37 by wired Electrical signal connection; the PLC controller 42 is connected with the automatic throttle valve I29, the automatic pressure relief valve I32, the automatic throttle valve II35, and the automatic pressure relief valve II34 through wired electrical signals. The upper end of the gas injection valve 15 and the lower end of the gas-water mixer 13 are equal in diameter to the single-wall drill pipe, and the lower end of the gas injection valve 15 and the upper end of the gas-water mixer 13 are equal in diameter to the double-wall drill pipe 14 . The left and right sides of the rotary blowout preventer 4 are provided with bypass valves. The kill manifold 38 is connected to the plate valve on the left side of the drilling spool 1 . The downhole electromagnetic PWD10 and the annular liquid level monitoring echo instrument 48 have the function of transmitting radio signals. The signal receiver 43 has wireless and wired signal receiving functions.

As shown in Fig. 1～3, the automatic control method of described gas-lift reverse circulation drilling system, it comprises the following steps:

S1. Set the pressure relief thresholds of the automatic pressure relief valve I32 and the automatic pressure relief valve II34 on the parameter input module 44 of the automatic control system 39 according to the pressure bearing capacity of the wellhead equipment, gas injection pipeline, and drilling fluid injection pipeline. Data and prediction data are input into formation pore pressure, formation collapse pressure, formation leakage pressure and formation fracture pressure on the parameter input module 44;

S2. The specific steps of gas lift reverse circulation drilling are:

S21, start the air compressor 27 and the mud pump 46, and drive the upper single-wall drill pipe 16 to rotate through the top drive 5, the upper single-wall drill pipe 16 drives the double-wall drill pipe 14 to rotate, and the double-wall drill pipe 14 drives the lower single-wall drill Rod 12, drill collar 11, drill bit rotate 9, and drill bit 9 drills into the formation;

S22, the air compressor 27 outputs compressed gas, and the compressed gas enters the rotary blowout preventer 4 through the supercharger 28, the automatic throttle valve I29, the pressure gauge I30, the flow meter I31, and the bypass valve 47 in sequence, and the high-pressure gas Under air pressure, pass through the side hole A19, the annulus of the inner pipe 17 of the gas injection valve and the outer pipe 18 of the gas injection valve, the annulus of the double-walled drill pipe 14, the inner pipe 23 of the air-water mixer, and the outer pipe 25 of the air-water mixer. The annulus and the side hole B24 enter the inner pipe 23, as shown by the single arrow in Figure 3, it is the flow direction of the gas, and the high-pressure gas lifts the drilling fluid in the inner pipe 23 toward the wellhead;

S23. The mud pump 46 pumps out the drilling fluid in the mud tank 33. Under the action of the pump pressure, the drilling fluid enters into the In the drilling spool 1, the drilling fluid is blocked by the gas-water isolating pipe 45, and falls to the bottom of the well along the annulus between the well wall and the gas-water isolating pipe 45, and the annulus between the well wall and the outer pipe 22, and then the drilling fluid under pressure Enter the double-wall drill pipe inner tube 21 through the drill bit 9, drill collar 11, lower single-wall drill pipe 12, and through hole B in sequence. The double arrows in Figure 3 indicate the flow direction of drilling fluid, and the three arrows represent gas-liquid Mixed fluid flow direction;

S24. The lifted drilling fluid passes through the inner pipe 21 of the double-wall drill pipe, the through hole A, the upper single-wall drill pipe 16, the hose 6, the riser 7, and the sand discharge pipeline 49, and finally enters the vibrating screen 8, After separation, it enters the mud tank 33, and finally completes gas-lift reverse circulation drilling, thereby avoiding the injected drilling fluid from flowing into crevices or caves, thereby avoiding the waste of drilling fluid. Therefore, this reverse circulation drilling method is especially suitable for fractures, Lost strata developed in karst caves;

S3. During the drilling process in step S2, monitor gas injection parameters and drilling fluid injection parameters in real time through flowmeter I31, pressure gauge I30, flowmeter II37, and pressure gauge II36, and monitor the annular space in real time through the annular space liquid level monitoring echo instrument 48 Liquid level height, real-time monitoring of drilling parameters such as bottomhole pressure and drilling fluid flow through the bottomhole electromagnetic MWD10;

S4. During the drilling process in step S2, calculate the bottom hole safety pressure window by computer 41, and judge whether the bottom hole pressure monitored by PWD10 in real time is within the safety pressure window, if not, calculate new gas injection parameters, injection drilling fluid parameters, and transmit the signal to the PLC controller 42 to control the automatic throttle valve I29 and automatic throttle valve II35 to adjust, change the gas injection volume and drilling fluid displacement, and keep the bottom hole pressure within the safe pressure window range to prevent Overflow and leakage occur;

S5. During the drilling process in step S2, the gas injection pressure and the injection drilling fluid pressure are monitored in real time through the automatic control system 39, and the automatic pressure relief valve I32 and the automatic pressure relief valve II34 are controlled by the PLC controller 42 when the pressure exceeds the pressure relief threshold Perform pressure relief to prevent high-pressure pressure hazards caused by flow channel blockage and other reasons;

S6. During the drilling process in step S2, the bottom hole safety pressure window, annular liquid level height, bottom hole pressure, gas injection parameters, drilling fluid parameters, automatic throttle opening, automatic Drilling parameters such as pressure relief valve switch status, real-time control of gas lift reverse circulation drilling dynamics.

The above description does not limit the present invention in any form. Although the present invention has been disclosed by the above-mentioned embodiments, it is not intended to limit the present invention. When the technical content disclosed above can be used to make some changes or be modified into equivalent embodiments with equivalent changes, but if they do not deviate from the content of the technical solution of the present invention, any simple modifications made to the above embodiments according to the technical essence of the present invention, are equivalent to Changes and modifications all still belong to the scope of the technical solution of the present invention.

Claims (7)

1. A gas lift reverse circulation drilling system characterized in that: the system comprises a wellhead device, a return pipeline, an in-well drilling tool, an air injection pipeline, a drilling fluid injection pipeline and an automatic control system (39);

the wellhead device comprises a drilling cross joint (1) arranged at the top of a wellhead, the top of the drilling cross joint (1) is sequentially provided with a lifting nipple (2), a ram blowout preventer (3) and a rotary blowout preventer (4), an annular liquid level monitoring echometer (48) is arranged on a bypass valve on the right side of the rotary blowout preventer (4), a gas-water isolating pipe (45) is arranged in the lifting nipple (2), the upper end of the gas-water isolating pipe (45) is flanged outwards and fixedly arranged on the inner wall of the lifting nipple (2), and the lower end of the gas-water isolating pipe (45) penetrates through the drilling cross joint (1) and extends into a well (51);

the return pipeline comprises a top drive (5), a water hose (6), a vertical pipe (7), a sand discharge pipeline (49) and a vibrating screen (8), wherein the water hose (6), the vertical pipe (7) and the sand discharge pipeline (49) are sequentially connected between the liquid outlet of the top drive (5) and the inlet end of the vibrating screen (8);

the downhole drilling tool comprises a drill bit (9), a downhole electromagnetic PWD (10), a drill collar (11), a lower single-wall drill rod (12), a gas-water mixer (13), a double-wall drill rod (14), an air injection valve (15) and an upper single-wall drill rod (16), wherein the drill bit (9), the downhole electromagnetic PWD, the drill collar (11), the lower single-wall drill rod, the gas-water mixer (13), the double-wall drill rod (14), the air injection valve (15) and the upper single-wall drill rod (16) are arranged in;

the double-wall drill rod (14) comprises an outer pipe (22) and an inner pipe (21), and the inner pipe (21) is arranged in the outer pipe (22) along the axial direction;

the gas injection valve (15) comprises a gas injection valve inner tube (17), a gas injection valve outer tube (18) and a partition plate A (20), the partition plate A (20) is welded in the gas injection valve outer tube (18), the center of the partition plate A (20) is provided with a through hole A, the gas injection valve inner tube (17) is welded in the through hole A, the upper end of the gas injection valve inner tube (17) extends upwards and is in threaded connection with the lower end of an upper single-wall drill rod (16), the lower end of the gas injection valve inner tube (17) is in threaded connection with the upper end of an inner tube (21), the gas injection valve outer tube (18) is provided with a plurality of side holes A (19) positioned below the partition plate A (20), the gas injection valve outer tube (18) is in threaded connection with the upper end of the outer tube (22), and the gas injection valve (15) moves in the range of a gas;

the gas-water mixer (13) comprises a gas-water mixer inner tube (23), a gas-water mixer outer tube (25) and a partition plate B (26), the partition plate B (26) is welded in the gas-water mixer outer tube (25), a through hole B is formed in the center of the partition plate B (26), the gas-water mixer inner tube (23) is welded in the through hole B, a plurality of side holes B (24) located above the partition plate B (26) are formed in the gas-water mixer inner tube (23), the upper end of the gas-water mixer inner tube (23) extends upwards and is in threaded connection with the lower end of the inner tube (21), the lower end of the gas-water mixer inner tube (23) extends downwards and is in threaded connection with the upper end of the lower single-wall drill rod (12), the gas-water mixer outer tube (25) is in threaded connection with the lower end of the outer tube (22), and the gas-water;

the gas injection pipeline comprises an air compressor (27), a supercharger (28) and a rotary blowout preventer (4), and an automatic throttle valve I (29), a pressure gauge I (30), a flow meter I (31) and an automatic pressure relief valve I (32) are sequentially connected between a gas outlet of the supercharger (28) and a left side bypass valve of the rotary blowout preventer (4);

the drilling fluid injection pipeline comprises a mud tank (33), a mud pump (46), a kill manifold (38) and a drilling four-way joint (1), wherein an automatic pressure release valve II (34), an automatic throttle valve II (35), a pressure gauge II (36) and a flowmeter II (37) are sequentially connected between the mud pump (46) and the inlet end of the kill manifold (38), and the mud pump (46) is communicated with the mud tank (33) through a pipeline;

the automatic control system (39) comprises a signal receiver (43), a display (40), a parameter input module (44), a PLC (programmable logic controller) controller (42) and a computer (41), wherein the signal receiver (43), the display (40), the parameter input module (44) and the PLC controller (42) are respectively in wired connection with the computer (41);

the signal receiver (43) is connected with the downhole electromagnetic PWD (10) and the annular liquid level monitoring echometer (48) through radio signals, and the signal receiver (43) is connected with the pressure gauge I (30), the flow meter I (31), the pressure gauge II (36) and the flow meter II (37) through wired electric signals;

and the PLC (42) is connected with the automatic throttle valve I (29), the automatic pressure relief valve I (32), the automatic throttle valve II (35) and the automatic pressure relief valve II (34) through wired electric signals.

2. A gas lift reverse circulation drilling system according to claim 1 wherein: the upper end of the air injection valve (15) and the lower end of the air-water mixer (13) are equal in diameter to the single-wall drill rod, and the lower end of the air injection valve (15) and the upper end of the air-water mixer (13) are equal in diameter to the double-wall drill rod (14).

3. A gas lift reverse circulation drilling system according to claim 1 wherein: bypass valves are arranged on the left side and the right side of the rotary blowout preventer (4).

4. A gas lift reverse circulation drilling system according to claim 1 wherein: and the kill manifold (38) is connected with a flat valve on the left side of the drilling four-way valve (1).

5. A gas lift reverse circulation drilling system according to claim 1 wherein: the downhole electromagnetic PWD (10) and the annular liquid level monitoring echometer (48) have a radio signal transmitting function.

6. A gas lift reverse circulation drilling system according to claim 1 wherein: the signal receiver (43) has wireless and wired signal receiving functions.

7. The method of claim 1 ~ 6, wherein the method comprises the steps of:

s1, setting pressure relief thresholds of an automatic pressure relief valve I (32) and an automatic pressure relief valve II (34) on a parameter input module (44) of an automatic control system (39) according to the pressure bearing capacity of well head equipment, an air injection pipeline and a drilling fluid injection pipeline, and inputting formation pore pressure, formation collapse pressure, formation leakage pressure and formation fracture pressure on the parameter input module (44) according to adjacent well data and prediction data;

s2, the gas lift reverse circulation well drilling comprises the following specific steps:

s21, starting the air compressor (27) and the mud pump (46), driving the upper single-wall drill rod (16) to rotate through the top drive (5), driving the double-wall drill rod (14) to rotate through the upper single-wall drill rod (16), driving the lower single-wall drill rod (12), the drill collar (11) and the drill bit to rotate (9) through the double-wall drill rod (14), and drilling the drill bit (9) into the stratum;

s22, an air compressor (27) produces compressed gas, the compressed gas sequentially passes through a supercharger (28), an automatic throttle valve I (29), a pressure gauge I (30), a flow meter I (31) and a bypass valve (47) and enters a rotary blowout preventer (4), high-pressure gas sequentially passes through a side hole A (19), an annular space of an inner pipe (17) of an air injection valve and an outer pipe (18) of the air injection valve, an annular space of a double-wall drill rod (14), an annular space of an inner pipe (23) of an air-water mixer and an outer pipe (25) of the air-water mixer and a side hole B (24) and enters an inner pipe (23) under air pressure, and the high-pressure gas lifts drilling fluid in the inner pipe (23) towards the direction;

s23, a mud pump (46) pumps out drilling fluid in a mud tank (33), the drilling fluid enters a drilling four-way valve (1) through an automatic throttle valve II (35), a pressure gauge II (36), a flowmeter II (37), a kill manifold (38) and a flat valve (50) under the action of pumping pressure in sequence, the drilling fluid is isolated by a gas-water isolation pipe (45), falls to the bottom of a well along the annular space between the well wall and the gas-water isolation pipe (45) and the annular space between the well wall and an outer pipe (22), and then enters a double-wall drill pipe inner pipe (21) through a drill bit (9), a drill collar (11), a lower single-wall drill pipe (12) and a through hole B under pressure in sequence;

s24, enabling the lifted drilling fluid to sequentially pass through a double-wall drill pipe inner pipe (21), a through hole A, an upper single-wall drill pipe (16), a hose (6), a vertical pipe (7) and a sand discharge pipeline (49), finally entering a vibrating screen (8), separating and then entering a mud tank (33), and finally completing gas lift reverse circulation drilling;

s3, in the drilling process of the step S2, gas injection parameters and drilling fluid injection parameters are monitored in real time through a flowmeter I (31), a pressure gauge I (30), a flowmeter II (37) and a pressure gauge II (36), the height of the liquid level of the annulus is monitored in real time through an annulus liquid level monitoring echo meter (48), and the well bottom pressure and drilling fluid flow drilling parameters are monitored in real time through a bottom hole electromagnetic MWD (10);

s4, in the drilling process of the step S2, a bottom hole safety pressure window is calculated through a computer (41), whether bottom hole pressure monitored by a PWD (10) in real time is in the safety pressure window is judged, if not, new gas injection parameters and drilling fluid injection parameters are calculated, signals are transmitted to a PLC (42), an automatic throttling valve I (29) and an automatic throttling valve II (35) are controlled to adjust, gas injection quantity and drilling fluid discharge are changed, bottom hole pressure is kept in the range of the safety pressure window, and overflow and well leakage are prevented;

s5, in the drilling process of the step S2, gas injection pressure and drilling fluid injection pressure are monitored in real time through an automatic control system (39), and when the pressure exceeds a pressure relief threshold value, a PLC (42) controls an automatic pressure relief valve I (32) and an automatic pressure relief valve II (34) to relieve the pressure, so that high-pressure-relief hazard caused by channel blockage is prevented;

s6, synchronously displaying well drilling parameters such as a well bottom safety pressure window, annular space liquid level height, well bottom pressure, gas injection parameters, drilling fluid injection parameters, automatic throttle valve opening degree, automatic pressure relief valve switching state and the like through the display (40) in the well drilling process of the step S2, and controlling gas lift reverse circulation well drilling dynamics in real time.