An underpressure composite drilling device and process for deep high-temperature wells

Abstract

The present invention discloses an underpressure composite drilling device and process for deep high-temperature wells. The ground drilling part includes a drilling rig, a drilling fluid cooling system and a drilling fluid circulation system; the downhole drilling tool part includes a drill pipe, a drill collar, a power assembly, a near-drill-bit decompression short section and a drill bit; the near-drill-bit decompression short section has an annular passage; the annular passage is evenly provided with a plurality of suction channels; the outer wall of the near-drill-bit decompression short section is circumferentially provided with a sand mixing throat connected to the suction channel; the outer wall of the near-drill-bit decompression short section is also provided with a suction channel, and the suction channel is connected to the node of the suction channel and the sand mixing throat. The present invention aims to comprehensively utilize the three methods of impact, rotation and thermal rupture to jointly destroy the bottom hole rock. The near-drill-bit decompression short section generates a local negative pressure in the annular passage near the drill bit position, and sucks the drilling fluid that has just been ejected by the energy-gathering nozzle to impact the bottom hole and carries rock cuttings back to the ground, thereby reducing the positive pressure difference at the bottom hole and reducing the pressure holding effect.

Description

Technical Field

[0001] The present invention relates to the technical field of vertical wells, directional wells and horizontal wells, and more specifically to an underpressure composite drilling device and process for deep high-temperature wells. Background Art

[0002] In the process of deep earth resource exploration and development, drilling is the most effective means to obtain underground physical data and establish production channels, but deep high-temperature drilling faces difficulties such as high rock hardness, low rock breaking efficiency, adverse effects of high temperature on drilling fluid and drilling tools, and insufficient power at the bottom of the deep well, which seriously affects the progress of exploration and development. At present, the commonly used rock breaking methods are rotary drilling or screw drilling tools. However, as the hole depth increases, the support pressure of the drilling tools gradually increases, and the power transmitted from the rotary drive to the bottom of the well is insufficient. The use of screw or turbine drilling tools can only provide rotational power during rock breaking, and the effect of breaking hard rocks is not good.

[0003] Therefore, how to provide a drilling device and process that can reduce the holding effect, increase the mechanical drilling speed, extend the life of the drill bit, and increase the single-trip footage is an urgent problem that needs to be solved by technical personnel in this field. Summary of the invention

[0004] In view of this, the present invention provides an underpressure composite drilling device and process for deep high-temperature wells, aiming to solve the above technical problems.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] An underpressure composite drilling device for deep high-temperature wells, comprising:

[0007] A ground drilling unit; the ground drilling unit includes a drilling rig, a drilling fluid cooling system connected to the drilling rig through a circulation pipeline, and a drilling fluid circulation system located on both sides of the drilling fluid cooling system is also installed in series on the circulation pipeline;

[0008] Downhole drilling tool section; the downhole drilling tool section includes a drill pipe, which is connected to the drilling rig and communicated with the circulation pipeline; and a drill collar, a power assembly, a near-drill bit pressure relief nipple and a drill bit which are sequentially connected to the drill pipe; the power assembly is used to provide drilling power and measure drilling parameters at the same time; the near-drill bit pressure relief nipple has an annular passage axially connected to the drill pipe; the annular passage is circumferentially provided with a plurality of suction channels; the outer side wall of the near-drill bit pressure relief nipple is circumferentially provided with a sand mixing throat communicated with the suction channel; the outer side wall of the near-drill bit pressure relief nipple is also provided with a suction channel, which is communicated with the node of the suction channel and the sand mixing throat; the front end of the drill bit is provided with an energy focusing nozzle, which is communicated with the annular passage.

[0009] Through the above technical scheme, the drilling device provided by the present invention aims to comprehensively utilize the three methods of impact, rotation and thermal fracture to jointly destroy the bottom hole rock. The near-drill bit decompression short section utilizes the Venturi tube effect or the vortex suction principle to generate local negative pressure in the annulus channel near the drill bit position, and sucks the drilling fluid that has just been ejected from the energy-focusing nozzle to the bottom of the well and carries the rock cuttings back to the ground, thereby reducing the positive pressure difference at the bottom of the well, reducing the pressure holding effect, increasing the mechanical drilling speed, extending the life of the drill bit, and increasing the single-trip footage.

[0010] Preferably, in the above-mentioned underpressure composite drilling device for deep high-temperature wells, the suction channel and the sand mixing throat are connected as one, and extend obliquely from the inner wall of the annular channel away from the drill bit; the suction channel extends obliquely from the outer wall of the near-drill-bit pressure relief nipple away from the drill bit. The Venturi effect or vortex suction principle is used to generate local negative pressure in the annular channel near the drill bit, and the drilling fluid carrying cuttings just ejected from the energy-focusing nozzle is sucked, thereby reducing the positive pressure difference at the bottom of the hole and reducing the pressure holding effect.

[0011] Preferably, in the above-mentioned underpressure composite drilling device for deep high-temperature wells, the power components are combined in different ways according to different well sections, specifically:

[0012] When drilling a vertical well section, the bottom end of the drill pipe is connected to a drill collar and a high-temperature resistant composite power drilling tool in sequence, and the high-temperature resistant composite power drilling tool is connected to the near-drill-bit decompression nipple.

[0013] When directional drilling is performed, the bottom end of the drill pipe is sequentially connected to a drill collar or a weighted drill pipe, a high temperature resistant MWD, a high temperature resistant composite power drill and a near-bit measuring short section, and the near-bit measuring short section is connected to the near-bit decompression short section.

[0014] When drilling in a horizontal section, the bottom end of the drill pipe is sequentially connected to a drill collar or a weighted drill pipe, an additional drill pipe, a high-temperature resistant MWD, a high-temperature resistant composite power drilling tool and a near-bit measuring short section, and the near-bit measuring short section is connected to the near-bit decompression short section.

[0015] Preferably, in the above-mentioned underpressure composite drilling device for deep high-temperature wells, the drilling fluid cooling system is an air cooling mechanism that uses an axial flow fan to blow and cool the sprayed drilling fluid, or a liquid cooling mechanism that uses a coolant and drilling fluid to perform non-contact heat exchange and cooling in a convection heat exchanger. The temperature difference between the drilling fluid and the bottom rock of the hole is increased, thereby increasing the thermal stress inside the rock.

[0016] Preferably, in the above-mentioned underpressure composite drilling device for deep high-temperature wells, the drilling fluid circulation system includes a vibrating screen, a desander, a desilter, a centrifuge, a degasser and a mud pump, which are used to establish ground circulation of the drilling fluid and remove rock cuttings particles in the drilling fluid.

[0017] The present invention also provides an underpressure composite drilling process for a deep high-temperature well, which specifically comprises the following steps:

[0018] S1. After drilling to the bottom, the pump is turned on for cyclic drilling. The high-pressure drilling fluid drives the power component to produce torsion and impact. Under the combined effect of drilling pressure and periodic impact force, the drill bit gradually eats into the formation rock. Under the action of the torque of the power component, the drill bit rotates and cuts off the circumferential rock.

[0019] S2. After being cooled by the drilling fluid cooling system, the low-temperature drilling fluid flows downward through the pressure reducing nipple near the drill bit. Most of the drilling fluid continues to flow downward through the energy-focusing nozzle of the drill bit and impacts the rock in the form of a high-speed jet. The thermal stress and jet impact force generated in the rock mass by the temperature difference between the high-temperature rock and the low-temperature drilling fluid are used to generate microcracks inside the rock, reduce the rock strength, and break the rock under the action of torsion and impact loads. A small amount of drilling fluid generates negative pressure after flowing through the suction flow channel, and the drilling fluid returned in the annulus channel is sucked in through the suction flow channel, reducing the bottom hole pressure at the drill bit and weakening the pressure holding effect.

[0020] Through the above technical scheme, the drilling process provided by the present invention aims to comprehensively utilize the three methods of impact, rotation and thermal fracture to jointly destroy the bottom hole rock, while generating local negative pressure at the bottom of the well, reducing the pressure holding effect, increasing the mechanical drilling speed, extending the life of the drill bit, and increasing the single-trip footage.

[0021] Preferably, in the above-mentioned underpressure composite drilling process for deep high-temperature wells, in step S1, the drilling pressure when drilling in hard rock formations is 100-120 kN and the displacement is 30 L / s.

[0022] Preferably, in the above-mentioned underpressure composite drilling process for deep high-temperature wells, when the measured drilling pressure of the drill bit is smaller than the surface apparent drilling pressure, the composite drilling torque is low, and the sliding drilling torque remains basically unchanged during the drilling process, a pressure-supporting situation may occur in the well, and a short start operation is performed to pull and scratch the well wall, destroy the cuttings bed, enhance the purification of the drilling fluid, and add a proper amount of lubricant to the drilling fluid; when the torque and pump pressure suddenly increase during drilling, the drill bit may have accidents such as falling teeth and breaking palms, and the drill is pulled out for inspection; when the drilling occurs The torque and pump pressure suddenly decrease, and the high-temperature resistant composite power drilling tool may fail and other abnormalities. Observe whether there are abnormal objects returned from the vibrating screen in the drilling fluid circulation system. If so, pull out the drill for inspection. When the torque remains unchanged during drilling and the pump pressure gradually decreases, the upper drill pipe or drill collar may be punctured and leaking, so pull out the drill for inspection. When the drill is stuck, start the pump circulation. When the torque at the drill bit is large, it is judged that the stuck point is near the drill bit. When the torque at the drill bit is low, the stuck point is at the sudden change position of the upper wellbore diameter. Unblock the jam according to the location of the stuck point.

[0023] It can be seen from the above technical scheme that compared with the prior art, the present invention discloses an underpressure composite drilling device and process for deep high-temperature wells, which aims to comprehensively utilize the three methods of impact, rotation and thermal fracture to jointly destroy the bottom hole rock. The near-drill bit decompression short section utilizes the Venturi tube effect or the vortex suction principle to generate local negative pressure in the annulus channel near the drill bit position, and sucks the drilling fluid that has just been ejected from the energy-focusing nozzle to the bottom of the well and carries the cuttings back to the ground, thereby reducing the positive pressure difference at the bottom of the well, reducing the pressure holding effect, increasing the mechanical drilling speed, extending the drill bit life, and increasing the single-trip footage. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0025] Figure 1 The accompanying drawing is a schematic structural diagram of an underpressure composite drilling device for deep high-temperature wells provided by the present invention;

[0026] Figure 2 The accompanying drawing is a cross-sectional view of the connection between the near-drill-bit decompression sub and the drill bit provided by the present invention;

[0027] Figure 3 The accompanying drawing is a schematic structural diagram of the bottom assembly drilling tool during vertical well section drilling provided by the present invention;

[0028] Figure 4 The accompanying drawing is a schematic structural diagram of the bottom combined drilling tool during directional segment drilling provided by the present invention;

[0029] Figure 5 The accompanying drawing is a schematic structural diagram of the bottom combined drilling tool during horizontal section drilling provided by the present invention.

[0030] in:

[0031] 1- Ground drilling department;

[0032] 11-drilling rig; 12-circulation pipeline; 13-drilling fluid cooling system; 14-drilling fluid circulation system;

[0033] 2- Downhole drilling tools department;

[0034] 21-drill pipe; 22-drill collar; 23-power assembly; 231-high temperature resistant composite power drilling tool; 232-high temperature resistant MWD; 233-near drill bit measurement short section; 234-additional drill pipe; 24-near drill bit decompression short section;

[0035] 241- annular passage; 242- suction flow channel; 243- sand mixing throat; 244- suction flow channel; 25- drill bit;

[0036] 251-Energy-focusing nozzle. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0038] See attached Figure 1 and attached Figure 2 The embodiment of the present invention discloses an underpressure composite drilling device for a deep high-temperature well, comprising:

[0039] The ground drilling section 1 comprises a drilling rig 11, a drilling fluid cooling system 13 connected to the drilling rig 11 through a circulation pipe 12, and a drilling fluid circulation system 14 located on both sides of the drilling fluid cooling system 13 is also installed in series on the circulation pipe 12;

[0040] Downhole drilling tool section 2; the downhole drilling tool section 2 includes a drill pipe 21, which is connected to the drilling rig 11 and communicated with the circulation pipeline 12; and a drill collar 22, a power assembly 23, a near-drill-bit decompression short section 24 and a drill bit 25 connected to the drill pipe 21 in sequence; the power assembly 23 is used to provide drilling power or to measure drilling parameters at the same time; the near-drill-bit decompression short section 24 has an annulus channel 241 axially connected to the drill pipe 21; the annulus channel 241 is evenly provided with a plurality of suction flow channels 242 in the circumferential direction; the outer side wall of the near-drill-bit decompression short section 24 is circumferentially provided with a sand mixing throat 243 communicated with the suction flow channel 242; the outer side wall of the near-drill-bit decompression short section 24 is also provided with a suction flow channel 244, and the suction flow channel 244 is communicated with the node of the suction flow channel 242 and the sand mixing throat 243; the front end of the drill bit 25 is provided with an energy focusing nozzle 251, and the energy focusing nozzle 251 is communicated with the annulus channel 241.

[0041] In order to further optimize the above technical solution, the suction flow channel 242 and the sand mixing throat 243 are connected as a whole, and extend obliquely from the inner wall of the annulus channel 241 in the direction away from the drill bit 25; the suction flow channel 244 extends obliquely from the outer side wall of the near-drill-bit decompression short section 24 in the direction away from the drill bit 25.

[0042] See attached Figure 3 When drilling a vertical well section, the power assembly 23 includes a high temperature resistant composite power drilling tool 231 connected to the bottom end of the drill pipe 21, and the high temperature resistant composite power drilling tool 231 is connected to the near-drill bit decompression short section 24.

[0043] See attached Figure 4 When directional drilling is performed, the power assembly 23 includes a high-temperature resistant MWD 232, a high-temperature resistant composite power drilling tool 231 and a near-bit measuring short section 233 which are sequentially connected to the bottom end of the drill pipe 21, and the near-bit measuring short section 233 is connected to the near-bit decompression short section 24.

[0044] See attached Figure 5 When drilling in a horizontal section, the power assembly 23 includes an additional drill rod 234, a high-temperature resistant MWD 232, a high-temperature resistant composite power drilling tool 231 and a near-bit measuring short section 233 which are sequentially connected to the bottom end of the drill rod 21, and the near-bit measuring short section 233 is connected to the near-bit decompression short section 24.

[0045] In order to further optimize the above technical solution, the drilling fluid cooling system 13 is an air cooling mechanism that uses an axial flow fan to blow and cool the sprayed drilling fluid, or a liquid cooling mechanism that uses a coolant and drilling fluid to perform non-contact heat exchange and cooling in a convection heat exchanger.

[0046] In order to further optimize the above technical solution, the drilling fluid circulation system 14 includes a vibrating screen, a desander, a desilter, a centrifuge, a degasser and a mud pump, which are used to establish ground circulation of the drilling fluid and remove cuttings particles in the drilling fluid.

[0047] The underpressure composite drilling process for deep high-temperature wells provided by the present invention specifically comprises the following steps:

[0048] S1, after drilling to the bottom, the pump is turned on for cyclic drilling, and the high-pressure drilling fluid drives the power assembly 23 to produce torsion and impact. Under the combined effect of the drilling pressure and the periodic impact force, the drill bit 25 gradually eats into the formation rock, and under the torque of the power assembly 23, the drill bit 25 rotates and cuts off the circumferential rock;

[0049] S2. The low-temperature drilling fluid cooled by the drilling fluid cooling system 13 flows downward through the near-drill bit pressure relief nipple 24. Most of the drilling fluid continues to flow downward through the energy-focusing nozzle 251 of the drill bit 25 and impacts the rock in the form of a high-speed jet. The thermal stress and jet impact force generated in the rock mass by the temperature difference between the high-temperature rock and the low-temperature drilling fluid are used to generate microcracks inside the rock, reduce the rock strength, and break the rock under the action of torsion and impact loads. A small amount of drilling fluid generates negative pressure after flowing through the suction flow channel 244, and sucks the drilling fluid returned from the annulus channel 241 through the suction flow channel 242, thereby reducing the bottom hole pressure at the drill bit 25 and weakening the pressure holding effect.

[0050] In step S1, when drilling in hard rock formations, the drilling pressure is 100-120 kN and the displacement is 30 L / s.

[0051] During directional drilling and horizontal drilling, the near-bit measurement sub 233 transmits the measured engineering parameters and logging parameters to the high-temperature resistant MWD232 through the short transmission system, and the high-temperature resistant MWD232 packages the measured trajectory parameters together with the engineering parameters and logging parameters and uploads them to the ground.

[0052] The ground staff determines whether the target layer can be reached by continuing drilling according to the logging parameters and trajectory parameters. If the target layer cannot be reached by continuing drilling according to the current plan or the deviation from the original wellbore trajectory is too large, adjustment is made through sliding directional drilling or by sending commands to the rotary steering system.

[0053] When the measured drilling pressure of the drill bit is smaller than the surface drilling pressure, the composite drilling torque is low, and the sliding drilling torque remains basically unchanged during drilling, the downhole may have a pressure support situation, and a short pull-out operation is performed to pull the well wall, destroy the cuttings bed, enhance the purification of the drilling fluid, and add an appropriate amount of lubricant to the drilling fluid; when the torque and pump pressure suddenly increase during drilling, the drill bit may have accidents such as falling teeth and broken palms, and the drill bit should be pulled out for inspection; when the torque and pump pressure suddenly decrease during drilling, the high-temperature resistant composite power drilling tool may have abnormalities such as debonding of the drill tool, observe whether there are abnormal objects returned from the vibrating screen in the drilling fluid circulation system, and if so, pull out the drill for inspection; when the torque remains unchanged during drilling and the pump pressure gradually decreases, the upper drill pipe or drill collar may have puncture leakage, and the drill bit should be pulled out for inspection; when the drill bit is stuck, start the pump circulation, and when the torque at the drill bit is large, it is judged that the stuck point is near the drill bit, and when the torque at the drill bit is low, the stuck point is at the sudden change position of the upper wellbore diameter, and the jam is solved according to the stuck point position.

[0054] The underpressure composite drilling process for deep high-temperature wells provided by the present invention adopts a new method of downhole underpressure + impact rotary composite drilling to speed up drilling, and its working principle is:

[0055] 1) Impact and rotary composite rock breaking: The high temperature resistant composite power drill 231 is used to periodically apply vibration impact to the drill bit 25 to form crushing pits or continuous cracks, reduce the rock strength, and at the same time apply continuous rotary cutting torque to the drill bit 25 to shear and destroy the rock in the teeth, forming a three-dimensional planing and chiseling rock breaking.

[0056] 2) Hydraulic impact rock breaking: The energy-focusing nozzle 251 on the drill bit 25 uses the Bernoulli principle. After the drilling fluid flows through, the flow velocity increases, the kinetic energy increases, and a jet impact is formed to destroy the rock at the bottom of the well.

[0057] 3) Thermal stress rock breaking: The drilling fluid cooling system 13 is used to cool the drilling fluid and then transport it to the bottom of the hole through the drill pipe 21 to cool the exposed rock at the bottom of the hole. The thermal stress generated by the temperature difference is used to generate micro cracks in the hard rock at high temperature, thereby reducing the rock strength.

[0058] 4) Local negative pressure at the bottom of the hole: The near-drill-bit decompression sub 24 generates local negative pressure in the annulus near the drill bit by using the Venturi effect or the vortex suction principle, sucking the drilling fluid carrying cuttings just ejected from the energy-focusing nozzle 251, and reducing the positive pressure difference at the bottom of the hole.

[0059] The drill bit 25 in this embodiment can use a roller drill bit or a diamond-impregnated drill bit in high-hardness non-uniform formations, and can be a PDC drill bit in homogeneous formations; the drill bit 25 is equipped with a focused nozzle 251 that can impact the drilling fluid to the bottom of the well at high speed, and the bottom temperature and pressure can be quickly changed after the drilling fluid enters the bottom of the well.

[0060] The near-bit decompression sub 24 in this embodiment includes but is not limited to a jet type and a vortex type. Taking the jet type as an example, Figure 2 As shown, the near-bit decompression sub 24 is installed above the drill bit 25. When the drilling fluid flows through the near-bit decompression sub 24, a part of the drilling fluid is transported to the drill bit 25 to cool the bottom of the well and carry the cuttings. At the same time, a part of the drilling fluid flows through the suction flow channel 244 to form a jet, generating negative pressure, driving the drilling fluid in the drill bit annulus to flow in through the suction flow channel 242 and mix in the sand mixing throat 243, reducing the positive pressure difference at the bottom of the well and weakening the pressure holding effect.

[0061] The near-drill-bit measurement subsection 233 in this embodiment includes but is not limited to engineering parameters and gamma imaging measurements. Its main function is to measure engineering parameters such as drilling pressure, torque, rotation speed, internal and external pressures and lithological characteristics at the position of the downhole drill bit 25, and to determine whether the pressure is supported and whether the drilling is normal.

[0062] The high temperature resistant composite power drilling tool 231 in this embodiment has a temperature resistance of over 180°C. The upper part adopts a high temperature resistant screw or turbine motor, the middle part adopts a valve-controlled or energy storage impactor, and the lower part is a main shaft section with a high-strength bearing installed inside to withstand the drilling pressure and the impact generated by the impactor.

[0063] The high temperature resistant MWD232 in this embodiment has a temperature resistance greater than 175°C. The lower part cooperates with the near-drill bit measurement short section 233 (engineering parameters, gamma imaging, etc.) to monitor and measure the wellbore trajectory, drilling parameters, and formation type, and upload the relevant parameters to the ground. The ground technicians can track and adjust the wellbore trajectory in time as needed to drill to the target layer.

[0064] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0065] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An underpressure composite drilling device for deep high-temperature wells, characterized in that: include: A ground drilling unit (1); the ground drilling unit (1) comprises a drilling rig (11), a drilling fluid cooling system (13) connected to the drilling rig (11) via a circulation pipeline (12), and a drilling fluid circulation system (14) located on both sides of the drilling fluid cooling system (13) is also installed in series on the circulation pipeline (12); A downhole drilling tool section (2); the downhole drilling tool section (2) comprises a drill pipe (21), the drill pipe (21) being connected to the drilling rig (11) and communicating with the circulation pipeline (12); and a drill collar (22), a power assembly (23), a near-drill-bit decompression sub (24) and a drill bit (25) connected in sequence to the drill pipe (21); the power assembly (23) is used to provide the drill bit with the power required for drilling and to measure drilling parameters at the same time; the near-drill-bit decompression sub (24) has an annular passage (241) axially communicating with the drill pipe (21); the annular passage (241) is provided with a plurality of suction channels (242) uniformly arranged in the circumferential direction; a sand mixing throat (243) connected to the suction channel (242) is arranged in the circumferential direction on the outer side wall of the near-drill-bit decompression nipple (24); a suction channel (244) is also arranged on the outer side wall of the near-drill-bit decompression nipple (24), and the suction channel (244) is connected to the node between the suction channel (242) and the sand mixing throat (243); the front end of the drill bit (25) is provided with an energy-gathering nozzle (251), and the energy-gathering nozzle (251) is connected to the annular channel (241); The specific steps include: S1, after drilling to the bottom, the pump is turned on for cyclic drilling, and the high-pressure drilling fluid drives the power component (23) to generate torsion and impact. Under the combined effect of the drilling pressure and the periodic impact force, the drill bit (25) gradually eats into the formation rock, and under the action of the torque of the power component (23), the drill bit (25) rotates and cuts off the circumferential rock; S2. The low-temperature drilling fluid cooled by the drilling fluid cooling system (13) flows downward through the near-drill bit pressure relief nipple (24). Most of the drilling fluid continues to flow downward through the energy-focusing nozzle (251) of the drill bit (25) and impacts the rock in the form of a high-speed jet. The thermal stress and jet impact force generated in the rock body by the temperature difference between the high-temperature rock and the low-temperature drilling fluid are used to generate microcracks inside the rock, reduce the rock strength, and break the rock under the action of torsion and impact loads. A small amount of drilling fluid flows through the suction flow channel (244) to generate negative pressure, and the drilling fluid returned in the annular channel (241) is sucked in through the suction flow channel (242), thereby reducing the bottom hole pressure at the drill bit (25) and weakening the pressure holding effect. When the measured drilling pressure on the drill bit is smaller than the surface apparent drilling pressure, the composite drilling torque is low, and the sliding drilling torque remains basically unchanged during drilling, short-start operations are performed to scratch the well wall, destroy the cuttings bed, enhance the purification of the drilling fluid, and add an appropriate amount of lubricant to the drilling fluid; when the torque and pump pressure suddenly increase during drilling, pull out the drill for inspection; when the torque and pump pressure suddenly decrease during drilling, observe whether there are abnormal objects returned from the vibrating screen in the drilling fluid circulation system. If so, pull out the drill for inspection; when the torque remains unchanged during drilling and the pump pressure gradually decreases, pull out the drill for inspection; when the drill is stuck, start the pump circulation. When the torque at the drill bit is large, it is judged that the stuck point is near the drill bit. When the torque at the drill bit is low, the stuck point is at the sudden change position of the upper wellbore diameter, and the jam is released according to the stuck point position.

2. The underpressure composite drilling device for deep high-temperature wells according to claim 1, characterized in that: The suction flow channel (242) and the sand mixing throat (243) are connected as one body, and extend obliquely from the inner wall of the annular passage (241) in a direction away from the drill bit (25); the suction flow channel (244) extends obliquely from the outer wall of the near-drill-bit decompression nipple (24) in a direction away from the drill bit (25).

3. An underpressure composite drilling device for deep high-temperature wells according to claim 1 or 2, characterized in that: When drilling a vertical well section, the power assembly (23) comprises a high temperature resistant composite power drilling tool (231) connected to the bottom end of the drill pipe (21), and the high temperature resistant composite power drilling tool (231) is connected to the near-drill bit decompression nipple (24).

4. The underpressure composite drilling device for deep high-temperature wells according to claim 1 or 2, characterized in that: When directional drilling is performed, the power assembly (23) comprises a high temperature resistant MWD (232), a high temperature resistant composite power drilling tool (231) and a near-drill bit measuring short section (233) which are sequentially connected to the bottom end of the drill pipe (21); the near-drill bit measuring short section (233) is connected to the near-drill bit decompression short section (24).

5. The underpressure composite drilling device for deep high-temperature wells according to claim 1 or 2, characterized in that: When horizontal section drilling is performed, the power assembly (23) comprises an additional drill rod (234), a high temperature resistant MWD (232), a high temperature resistant composite power drilling tool (231) and a near-drill bit measuring short section (233) which are sequentially connected to the bottom end of the drill rod (21); the near-drill bit measuring short section (233) is connected to the near-drill bit decompression short section (24).

6. The underpressure composite drilling device for deep high-temperature wells according to claim 1, characterized in that: The drilling fluid cooling system (13) is an air cooling mechanism that uses an axial flow fan to blow and cool the sprayed drilling fluid, or a liquid cooling mechanism that uses a coolant and the drilling fluid to perform non-contact heat exchange and cooling in a countercurrent heat exchanger.

7. The underpressure composite drilling device for deep high-temperature wells according to claim 1, characterized in that: The drilling fluid circulation system (14) comprises a vibrating screen, a desander, a desilter, a centrifuge, a degasser and a mud pump, and is used to establish a surface circulation of the drilling fluid and remove rock cuttings particles in the drilling fluid.

8. The underpressure composite drilling device for deep high-temperature wells according to claim 1, characterized in that: In step S1, when drilling in hard rock formations, the drilling pressure is 100-120 kN and the displacement is 30 L / s.

Images