Downhole geophysical prospecting double-wall drill pipe gas drive replacement system and using method

Abstract

The invention relates to the technical field of mine exploration, in particular to an underground geophysical prospecting double-wall drill rod gas drive replacement system and a using method.The underground geophysical prospecting double-wall drill rod gas drive replacement system comprises a rod body arranged in an exploration drill hole, and the end of the rod body extends out of the exploration drill hole and communicates with an external cleaning assembly; the rod body comprises a double-wall drill rod end, and the double-wall drill rod end is connected with a plurality of double-wall drill rod standard knots which are sequentially connected end to end. The double-wall drill rod standard section comprises a standard section inner pipe and a standard section outer pipe which are coaxially arranged, and the standard section inner pipe and the standard section outer pipe are connected with the end of the double-wall drill rod. A coaxially-arranged cavity is formed among the standard knot inner pipe, the standard knot outer pipe and the exploration drill hole, and the cavity communicates with the cleaning assembly. According to the method, gas replacement is carried out on the media influencing electromagnetic waves or elastic waves around the exploration drill hole before detection, interface noise is reduced, a clear detection environment is created for a geophysical prospecting instrument, and therefore accurate recognition of the geological structure is achieved.

Description

Technical Field

[0001] This invention relates to the field of mine exploration technology, and in particular to a gas-driven replacement system for double-walled drill pipes in downhole geophysical exploration and its usage. Background Technology

[0002] In the process of mine construction and production, accurately identifying underground geological structures (such as faults, fracture zones, and collapse columns) is crucial for preventing water hazards, gas outbursts, and controlling the stability of the surrounding rock.

[0003] Currently, downhole geophysical exploration methods often suffer from significant “interface noise” due to the strong absorption, scattering, and reflection of electromagnetic waves or elastic waves by the surrounding drilling mud, mine water, and high-humidity gases. This noise masks the effective signal and severely reduces the accuracy of the exploration. Existing geophysical technologies mostly use direct-transmission instruments for data acquisition, lacking proactive optimization of the exploration environment. Although borehole cleaning is sometimes necessary, it is still difficult to eliminate the influence of residual mud or highly conductive media. Especially under complex hydrogeological conditions, the exploration results often have multiple interpretations and a high risk of misjudgment.

[0004] Therefore, there is an urgent need to design a downhole geophysical exploration double-wall drill pipe gas-driven replacement system and its usage method to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a downhole geophysical exploration double-wall drill pipe gas-driven replacement system and its usage method, which can effectively replace the medium around the borehole before detection, reduce interface interference, improve the data signal-to-noise ratio and detection accuracy, and solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: The present invention provides a downhole geophysical exploration double-wall drill pipe gas-driven replacement system, including a rod body, the rod body being embedded in the exploration borehole at the construction site, and the end of the rod body extending out of the exploration borehole and communicating with an external cleaning component;

[0007] The rod body includes a double-walled drill rod end located in the exploration borehole and communicating with the outside. The double-walled drill rod end is connected to a number of double-walled drill rod standard sections connected end to end. The end of the double-walled drill rod standard section extends out of the exploration borehole and communicates with the cleaning assembly.

[0008] The standard section of the double-walled drill pipe includes an inner tube and an outer tube arranged coaxially, and the inner tube and the outer tube are respectively connected to the end of the double-walled drill pipe; a coaxial chamber is formed between the inner tube, the outer tube, and the exploration borehole, and the chamber is connected to the cleaning assembly.

[0009] Preferably, the double-walled drill pipe end includes a coaxially arranged and independent end probe tube and an end protection tube. One end of the end protection tube is closed, and the end probe tube is fixed to the inner cavity of the end protection tube. The end probe tube is connected to the inner tube of the standard section, and the end protection tube is connected to the outer tube of the standard section.

[0010] Preferably, the chamber includes a detection chamber, an injection chamber, and a pressure replacement chamber arranged coaxially from the inside to the outside. The outer wall of the standard section is provided with a plurality of oblique outer tube pressure holes around its perimeter, and the side wall of the end protection tube is provided with a plurality of oblique end pressure holes around its perimeter. The outer tube pressure holes and the end pressure holes connect the injection chamber and the pressure replacement chamber.

[0011] Preferably, the air injection chamber is provided with a plurality of symmetrically arranged baffles. The baffles are of the same length as the outer tube of the standard section and are connected end to end in sequence. The baffles slide in contact with the inner wall of the outer tube of the standard section and the inner wall of the end protection tube. The baffles block the air pressure holes of the outer tube and the end air pressure holes, and the opening and closing of the air pressure holes of the outer tube and the end air pressure holes can be controlled by the sliding of the baffles.

[0012] Preferably, the cleaning assembly includes an air injection device and a waste recovery device. The air injection device is connected to the air injection chamber, and the waste recovery device is connected to the compressed air replacement chamber. The air injection device injects high-pressure gas into the air injection chamber, and the high-pressure gas enters the compressed air replacement chamber to discharge the impurities in the compressed air replacement chamber.

[0013] Preferably, the outlet of the exploration borehole is provided with a cavity-splitting device, which is sealed and fixedly connected to the outer tube and the inner tube of the standard section. The gas injection device is connected to the gas injection chamber through the cavity-splitting device, and the waste recovery device is connected to the compressed gas replacement chamber through the cavity-splitting device.

[0014] Preferably, the chamber-splitting device includes a steel casing embedded in the outlet of the exploration borehole, the steel casing being coaxially sleeved outside the outer tube of the standard section and sealing the end of the outer tube of the standard section; the gas injection device is connected to the gas injection chamber through the steel casing, and the waste recovery device is connected to the compressed gas replacement chamber through the steel casing.

[0015] Preferably, the outer tube of the standard section is provided with a protrusion arranged along the length direction. The top of the protrusion extends inward toward the hole wall of the outer tube of the standard section to form an arc-shaped bayonet. The top of the protrusion, i.e. the edge of the arc-shaped bayonet, is in sealing contact with the outer wall of the inner tube of the standard section. The partition is in movable contact with the protrusion and the arc-shaped bayonet.

[0016] This invention also discloses a method for using a downhole geophysical exploration double-wall drill pipe gas-driven replacement system, comprising the following steps:

[0017] The geological environment of the selected area is explored, and then exploration boreholes are drilled based on the exploration results;

[0018] The off-site assembly of the downhole geophysical exploration double-wall drill pipe gas-driven replacement system was placed into the exploration borehole as a whole after assembly.

[0019] Based on the geological exploration results, corresponding measures are formulated to treat the medium around the exploration borehole that affects electromagnetic waves and reduce the impact of interface noise.

[0020] A constant pressure gas is injected between the outer tube of the standard section and the exploration borehole, and then a geophysical instrument is inserted along the inner tube of the standard section to collect data.

[0021] Preferably, when dealing with the medium affecting electromagnetic waves around the exploration borehole, a corresponding replacement gas is selected according to the type of the original medium in the exploration borehole. After the replacement gas is injected into the gas injection chamber, it enters the gas replacement chamber through the outer pipe pressure port and the end pressure port to discharge the original medium, which is then recovered through the waste recovery device.

[0022] Compared with existing technologies, this invention has the following advantages and technical effects: This invention discloses a downhole geophysical exploration double-wall drill pipe gas-driven replacement system and its usage method. The rod body is composed of a double-wall drill pipe end and several standard double-wall drill pipe sections connected end to end. The number of standard sections can be flexibly adjusted according to the exploration borehole depth. The end standard section extends out of the borehole and connects with the cleaning component, breaking the limitations of traditional single-diameter, fixed-length drill tools, adapting to the detection needs of different depths, eliminating the need to customize special drill tools for different hole depths, reducing equipment costs and construction complexity, and allowing the rod body and borehole wall to form a stable coaxial structure, avoiding detection position deviation caused by drill tool shaking; at the same time, the inner tube serves as a dedicated detection channel, ensuring stable signal transmission during instrument lowering and reducing signal attenuation caused by channel irregularities; furthermore, the modular splicing structure facilitates on-site assembly and disassembly, reducing the time spent on equipment installation in the borehole and improving operational efficiency. The standard section of the double-walled drill pipe consists of a coaxial inner tube and an outer tube, which are connected to the ends of the double-walled drill pipe, forming a double-layered tubular structure. Compared with the traditional single-walled drill pipe design, the double-tube structure allows for functional zoning. The inner tube can be used specifically for lowering geophysical instruments, avoiding interference between the instruments and the channel. The outer tube serves as the main channel for gas injection and flushing, ensuring directional flow of gas and flushing fluid during subsequent gas-driven replacement, preventing backflow from damaging the instruments. Simultaneously, through directional replacement of the chambers, the surrounding medium is replaced with highly insulating, low-interference gas. The reflected waves, resistivity, and other data collected by the geophysical instruments more closely match the true geological structure, reducing errors caused by medium interference and lowering the ambiguity of detection results. This provides accurate data support for subsequent water hazard prevention and surrounding rock stability control. The modular structure adapts to different hole depths, and the closed-loop cleaning components enable medium recovery and reuse, balancing construction efficiency and cost control, providing core technical support for fine geophysical exploration under complex downhole geological conditions.

[0023] This invention reduces interface noise by replacing the medium around the exploration borehole with gas before detection, which affects electromagnetic or elastic waves, creating a clear detection environment for geophysical instruments and thus enabling accurate identification of geological structures. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0025] Figure 1 This is a schematic diagram illustrating the application scenario of the downhole geophysical exploration double-wall drill pipe gas-driven replacement system of the present invention;

[0026] Figure 2 This is a schematic diagram of the rod structure of the present invention;

[0027] Figure 3 This is a schematic diagram of a standard section of the double-walled drill pipe of the present invention;

[0028] Figure 4 This is a schematic diagram of the connecting components of the standard section of the double-walled drill pipe of the present invention;

[0029] Figure 5 This is a schematic diagram of the air-driven operation area of ​​the present invention;

[0030] Figure 6 This is a schematic diagram of the cavity-splitting device of the present invention;

[0031] In the diagram: 001, Air-driven operation area; 002, Double-walled drill pipe layout area; 003, Core detection area; 01, Compressed air replacement chamber; 02, Air injection chamber; 03, Detection chamber; 1, Double-walled drill pipe end; 2, Double-walled drill pipe standard section; 201, Standard section outer tube; 202, Standard section inner tube; 3, Chamber splitting device; 4, Partition plate; 5, Air injection equipment; 6, Waste recovery device; 11, End detection pipe; 12, End compressed air port; 21, Outer tube end side; 22 1. External tube air compression port; 23. External tube upper spiral interface; 24. External tube end tail side; 25. External tube lower spiral interface; 26. Protrusion groove; 27. Arc-shaped bayonet; 28. Inner tube end side; 29. ​​Inner tube end tail side; 31. Steel sleeve; 32. Fixed pipe support; 33. First plate removal groove; 34. Second plate removal groove; 51. First air injection port; 52. Second air injection port; 61. First waste recovery port; 62. Second waste recovery port; 63. Third waste recovery port. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Reference Figures 1 to 6 As shown, this embodiment provides a downhole geophysical exploration double-wall drill pipe gas-driven replacement system, including a rod body, which is embedded in the exploration borehole at the construction site, and the end of the rod body extends out of the exploration borehole and communicates with the external cleaning components;

[0035] The rod body includes a double-walled drill rod end 1 located in the exploration borehole and communicating with the outside. The double-walled drill rod end 1 is connected to several double-walled drill rod standard sections 2 connected end to end. The end of the double-walled drill rod standard section 2 extends out of the exploration borehole and communicates with the cleaning assembly.

[0036] The standard section 2 of the double-walled drill pipe includes a standard section inner tube 202 and a standard section outer tube 201 arranged coaxially. The standard section inner tube 202 and the standard section outer tube 201 are respectively connected to the end 1 of the double-walled drill pipe. A coaxial chamber is formed between the standard section inner tube 202, the standard section outer tube 201 and the exploration borehole. The chamber is connected to the cleaning assembly.

[0037] This invention discloses a gas-driven replacement system for a double-walled drill pipe in downhole geophysical exploration and its usage method. The rod body consists of a double-walled drill pipe end 1 and several standard double-walled drill pipe sections 2 connected end-to-end. The number of standard sections can be flexibly adjusted according to the exploration borehole depth. The end standard sections extend out of the borehole and connect with the cleaning assembly, breaking the limitations of traditional single-diameter, fixed-length drill tools. It adapts to the detection needs of different depths, eliminating the need to customize special drill tools for different hole depths, reducing equipment costs and construction complexity. The rod body and the borehole wall form a stable coaxial structure, avoiding detection position deviation caused by drill tool swaying. At the same time, the inner tube serves as a dedicated detection channel, ensuring stable signal transmission during instrument lowering and reducing signal attenuation caused by channel irregularities. Furthermore, the modular splicing structure facilitates on-site assembly and disassembly, reducing the time spent installing equipment in the borehole and improving operational efficiency. The standard section 2 of the double-walled drill pipe consists of a coaxial inner tube and an outer tube, which are connected to the double-walled drill pipe end 1 respectively, forming a double-layered tubular structure. Compared with the traditional single-walled drill pipe design, the double-tube structure allows for functional zoning. The inner tube can be used specifically for lowering geophysical instruments, avoiding interference between the instruments and the channel. The outer tube can serve as the main channel for gas injection and flushing, ensuring the directional flow of gas and flushing fluid during subsequent gas-driven replacement, preventing backflow of the medium from damaging the instruments. At the same time, through directional replacement of the chamber, the medium around the borehole is replaced with a highly insulating, low-interference gas. The reflected waves, resistivity, and other data collected by the geophysical instruments are more consistent with the true characteristics of the geological structure, reducing errors caused by medium interference and lowering the ambiguity of the detection results. This provides accurate data support for subsequent water hazard prevention and surrounding rock stability control. The modular structure adapts to different hole depths, and the closed-loop cleaning components enable medium recycling and reuse, balancing construction efficiency and cost control, providing core technical support for fine geophysical exploration under complex geological conditions downhole. This invention reduces interface noise by replacing the medium around the exploration borehole with gas before detection, which affects electromagnetic or elastic waves, creating a clear detection environment for geophysical instruments and thus enabling accurate identification of geological structures.

[0038] The scheme is further optimized. The double-wall drill pipe end 1 includes an end probe tube 11 and an end protection tube that are coaxially arranged and independent of each other. One end of the end protection tube is closed, and the end probe tube 11 is fixed to the inner cavity of the end protection tube. The end probe tube 11 is connected to the inner tube 202 of the standard section, and the end protection tube is connected to the outer tube 201 of the standard section. The end probe tube 11 and the end protection tube are coaxially arranged to form a layered blind tube structure, which facilitates its advancement into the exploration borehole. This reduces the entry of native media such as mud and mine water from the bottom of the borehole into the tube body, and prevents the open double-walled drill pipe end 1 from being blocked by mud or residue, thus reducing initial interference for subsequent gas-driven replacement. At the same time, during exploration, the geophysical instrument is located in the end probe tube 11, avoiding direct contact with rock cuttings and impurities at the bottom of the borehole, reducing the risk of equipment damage. When laying the tube in the exploration borehole, the inner tube 202 of the standard section is connected to the end probe tube 11 in sequence, while the outer tube 201 of the standard section is connected to the end protection tube in sequence. This can be adjusted according to the depth of the exploration borehole to maintain the continuity of the double-walled structure and avoid media leakage or signal transmission interruption due to misalignment.

[0039] In one embodiment of the present invention, in order to ensure that the axis of the drill rod is coaxial with that of the exploration borehole, the outer wall of the double-wall drill rod end 1 may be provided with several rollers or other similar structures in the circumferential direction. When it is inserted into the exploration borehole, several rollers or other structures are supported on the inner wall of the exploration borehole, so that during the operation of the device, its axis is as flush as possible with the axis of the exploration borehole.

[0040] The scheme is further optimized. The chamber includes a detection chamber 03, an air injection chamber 02 and a compressed air replacement chamber 01 arranged coaxially from the inside to the outside. The outer tube 201 of the standard section has several oblique outer tube compressed air holes 22 arranged around its side wall, and the end protective tube has several oblique end compressed air holes 12 arranged around its side wall. The outer tube compressed air holes 22 and the end compressed air holes 12 connect the air injection chamber 02 and the compressed air replacement chamber 01. The coaxial standard section inner tube 202 and standard section outer tube 201, combined with the exploration borehole, form three relatively independent chambers: from the inside out, they are the detection chamber 03, the gas injection chamber 02, and the compressed gas replacement chamber 01. The outer tube compressed gas port 22 and the end compressed gas port 12 are inclinedly arranged to connect the gas injection chamber 02 and the compressed gas replacement chamber 01. In specific operation, the detection chamber 03 provides an independent channel for geophysical instruments, isolating external interference media and ensuring stable signal transmission. The gas injection chamber 02 is specifically used to deliver high-pressure replacement gas to avoid conflict between the gas and the detection signal. The compressed gas replacement chamber 01 serves as a channel for discharging interference media and centrally processing impurities. Before detection, high-pressure air is injected into the gas injection chamber 02. The obliquely arranged outer tube compressed gas port 22 and end compressed gas port 12 cause the high-pressure gas to be ejected obliquely, creating a piston effect in the compressed gas replacement chamber 01, pushing the interference media from top to bottom, avoiding media residue, and reducing the risk of borehole collapse caused by direct gas impact on the borehole wall.

[0041] In a further optimized design, the air injection chamber 02 is equipped with several symmetrically arranged baffles 4. The baffles 4 are the same length as the standard section outer tube 201 and are connected end to end in sequence. The baffles 4 slide in contact with the inner wall of the standard section outer tube 201 and the inner wall of the end protection tube. The baffles 4 block the outer tube air pressure port 22 and the end air pressure port 12, and the opening and closing of the outer tube air pressure port 22 and the end air pressure port 12 can be controlled by the sliding of the baffles 4. Each standard section of the outer tube 201 is equipped with two semi-circular partitions 4. The partitions 4 are attached to the inner wall of the standard section of the outer tube 201, blocking the outer tube compression port 22 and the end compression port 12. The unopened compression ports are sealed by the partitions 4 to prevent high-pressure gas leakage in the injection chamber 02, maintain a constant injection pressure, and ensure the replacement effect. During the compression process, the compression ports can be opened in the designed sequence by moving the partitions 4, so as to achieve orderly introduction of compressed gas into the compression replacement chamber 01. The compression ports can be opened segment by segment by sliding the partitions 4, so that the gas-driven replacement can be carried out in an orderly manner from top to bottom or from bottom to top, avoiding gas blockage or medium disturbance caused by simultaneous gas injection of the whole hole, and improving the uniformity of replacement. At the same time, according to the geological conditions at different drilling depths, the target section can be replaced separately by opening and closing the partitions 4 to reduce gas waste.

[0042] In one embodiment of the present invention, a grooved partition is provided between two partitions at the same height for limiting and positioning.

[0043] The solution is further optimized, and the cleaning components include an injection device 5 and a waste recovery device 6. The injection device 5 is connected to the injection chamber 02, and the waste recovery device 6 is connected to the compressed air replacement chamber 01. The injection device 5 injects high-pressure gas into the injection chamber 02, and the high-pressure gas enters the compressed air replacement chamber 01, discharging the impurities in the chamber. The injection device 5 is connected to the injection chamber 02, and the waste recovery device 6 is connected to the compressed air replacement chamber 01. The injection device 5 injects high-pressure gas into the injection chamber 02, and the gas enters the compressed air replacement chamber 01, pushing out the interfering medium along the chamber. The waste recovery device 6 collects the impurities simultaneously, avoiding secondary pollution and wellhead accumulation caused by indiscriminate discharge of the medium. Compared with traditional passive well cleaning, this method can quickly eliminate interface noise sources such as mud and suspended solids, shortening the operation cycle. The waste recovery device 6 centrally processes the impurities, facilitating subsequent solid-liquid separation and gas recovery, reducing resource waste and environmental pollution.

[0044] To further optimize the design, a cavity-splitting device 3 is installed at the outlet of the exploration borehole. This device is sealed and fixedly connected to the outer tube 201 and inner tube 202 of the standard section. The gas injection device 5 is connected to the gas injection chamber 02 via the cavity-splitting device 3, and the waste recovery device 6 is connected to the compressed gas replacement chamber 01 via the cavity-splitting device 3. The cavity-splitting device 3 is positioned at the outlet of the exploration borehole and is in sealed contact with the outer tube 201 and inner tube 202 of the standard section at the end, preventing high-pressure gas in the gas injection chamber 02 from leaking out of the borehole outlet. This ensures that all gas is used for gas-driven replacement and prevents external impurities from entering the borehole. Simultaneously, the cavity-splitting device 3 serves as a transfer hub for gas injection and recovery, integrating the connection channels between the gas injection device 5 and the waste recovery device 6, simplifying on-site pipeline layout and reducing equipment operation complexity. During subsequent exploration, the cavity-splitting device 3 can also seal the outlet of the exploration borehole, maintaining constant pressure in the gas injection chamber 02 and the compressed gas replacement chamber 01, preventing pressure fluctuations due to leakage, ensuring consistent gas-driven replacement effects, and improving the accuracy of geophysical data.

[0045] In one embodiment of the present invention, the exploration borehole of the present invention is set on the inner wall of the gas drive operation area 001, and the end of the cavity device 3 extends into the gas drive operation area 001 and is fixed by a plurality of fixed pipe supports 32.

[0046] Further optimization of the scheme: the chamber device 3 includes a steel casing 31 embedded in the outlet of the exploration borehole. The steel casing 31 is coaxially sleeved on the outer tube 201 of the standard section and the end of the outer tube 201 of the standard section is sealed. The gas injection device 5 is connected to the gas injection chamber 02 through the steel casing 31, and the waste recovery device 6 is connected to the compressed air replacement chamber 01 through the steel casing 31. The main body of the chamber-splitting device 3 is made of a steel sleeve 31, which facilitates the quick connection and disassembly of the gas injection and recovery pipelines, reducing the difficulty of equipment maintenance. During installation, the steel sleeve 31 is inserted into the exploration borehole to reinforce the borehole opening and prevent the borehole opening from collapsing due to gas injection pressure or medium flow, ensuring the safety of subsequent operations. At the same time, the steel sleeve 31 has high strength and good sealing performance, and can withstand the high pressure of the gas injection equipment 5, preventing gas leakage due to pipe deformation, and preventing impurities in the compressed gas replacement chamber 01 from overflowing from the borehole opening. Its end is sealed and has a hole corresponding to the detection chamber 03, which facilitates the entry of subsequent detection equipment into the detection chamber 03.

[0047] Further optimizing the design, the outer tube 201 of the standard section is provided with a protrusion 26 arranged along its length. The top of the protrusion 26 extends inward toward the borehole wall of the outer tube 201 of the standard section to form an arc-shaped bayonet 27. The top of the protrusion 26, i.e. the edge of the arc-shaped bayonet 27, is in sealed contact with the outer wall of the inner tube 202 of the standard section. The partition 4 is in movable contact with the protrusion 26 and the arc-shaped bayonet 27. The arc-shaped bayonet 27 is in sealed contact with the outer wall of the inner tube 202 of the standard section, fixing the position of the inner tube and preventing it from shaking during drilling operations. This ensures the stability of the axis of the detection chamber 03 and improves the accuracy of the geophysical instrument's lowering and signal acquisition. The protrusion 26 provides a sliding track for the partition 4, preventing the partition 4 from shifting or getting stuck during sliding, ensuring precise control of the opening and closing of the air vents, and ensuring orderly segmented replacement. The sealed contact between the arc-shaped bayonet 27 and the inner tube reduces gas leakage from the injection chamber 02 to the detection chamber 03, avoiding interference with the geophysical signal, and also preventing the instrument in the detection chamber 03 from being impacted by gas.

[0048] In one embodiment of the present invention, the inner tube end 28 of the standard section inner tube 202 is provided with an external thread, and the inner tube end tail 29 of the standard section inner tube 202 is provided with an internal thread that matches the inner tube end 28. The standard section inner tube 202 is connected by the inner tube end 28 and the inner tube end tail 29.

[0049] In one embodiment of the present invention, the outer tube end 21 of the standard section outer tube 201 is provided with an upper spiral interface 23, and the outer tube tail end 24 of the standard section outer tube 201 is provided with a lower spiral interface 25 adapted to the outer tube end 21. The standard section outer tube 201 is threadedly connected through the upper spiral interface 23 and the lower spiral interface 25.

[0050] This invention also discloses a method for using a downhole geophysical exploration double-wall drill pipe gas-driven replacement system, comprising the following steps:

[0051] The geological environment of the selected area is explored, and then exploratory boreholes are drilled based on the exploration results. Two-dimensional seismic wave detection or ground-based ground-penetrating radar is used to preliminarily determine the strike, dip, and depth of the target structure. Areas with fault fracture zones ≥5m wide are identified through seismic wave reflection characteristics and marked as core exploration area 003. Geological logging of the tunnel walls is carried out within a 30m radius of the target area, recording the strata attitude, fracture density, and lithological variations (such as the boundary between sandy mudstone and limestone), excluding areas with homogeneous lithology and no tectonic signs. Then, existing exploratory borehole data within the adjacent target area, such as borehole columnar sections, are retrieved, with a focus on analyzing the strata integrity within the 10-30m depth range of the geophysical target exploration area. If core fracture sections or abrupt water level changes exist, the area is designated as a priority borehole location area. In the core exploration area 003, a flat area free of floating debris and water accumulation was selected to mark the borehole positions. A total station with an accuracy of ±2mm was used to measure the coordinates of the borehole positions, and the downhole environmental parameters at the positions were recorded. The double-wall drill pipe layout area 002 was then selected. For the exploration borehole construction, a ZYJ-4000 drilling rig with a thrust ≥180kN and a rated speed of 80-150r / min was used, equipped with a TDS-3 directional drilling tool. After starting the drilling rig, a low speed of 50r / min and a low thrust of 50kN were used to drill 0.5m to form a guide section, preventing borehole collapse. After the drilling tool had fully entered the rock formation, the speed was adjusted to 120r / min and the thrust to 120kN, and drilling was carried out at a uniform speed of 0.8-1m / min. After the borehole construction was completed, a temporary casing was retained and left to stand for 24 hours. During this period, the borehole opening was sealed to allow the borehole wall stress to fully release, reducing the risk of borehole collapse during subsequent casing removal. The temporary casing was slowly removed using a hydraulic pipe puller. A Φ148mm steel casing was then inserted into the borehole, reaching a depth of 0.6m into the rock strata. The exposed section was secured with a pipe support 32. Finally, quick-setting cement grout was prepared to fill the gap between the steel casing 31 at the borehole opening and the borehole wall, thus initially constructing the geophysical exploration space.

[0052] The off-site assembly of the downhole geophysical exploration double-wall drill pipe gas-driven replacement system is placed into the exploration borehole as a whole. The rod body consists of a double-wall drill pipe end section 1, fourteen standard double-wall drill pipe sections 2, and twenty-eight partition plates 4, with a total length of 30m. The specific layout length can be adjusted according to the actual borehole depth in the exploration area. The fourteen standard double-wall drill pipe sections 2 are divided into two layers: the outer tube 201 and the inner tube 202. Both the outer tube 201 and the inner tube 202 are made of high-strength polyethylene. The inner tube 202 has an outer diameter of 50mm, a wall thickness of 5mm, and a length of 2m; the outer tube 201 has an outer diameter of 90mm, a wall thickness of 5mm, and a length of 2m. The two tubes of the same diameter are connected by threads. The end protection tube of the double-walled drill pipe end 1 and the standard section outer tube 201 are respectively equipped with oblique end air pressure holes 12 and outer tube air pressure holes 22 around the perimeter of the tube wall, spaced 50mm apart vertically. The inner wall of the standard section outer tube 201 has symmetrical protrusions 26, the top of the protrusions 26 extending inward toward the outer tube wall to form an arc-shaped bayonet 27. The top of the protrusions 26 and the outer side of the arc-shaped bayonet 27 contact the standard section inner tube 202. The inner side of the symmetrical arc-shaped bayonet 27 is used to fix the partition plate 4. Each double-walled drill pipe standard section 2 is matched with two partition plates 4. The outer diameter of the partition plate 4 matches the inner diameter of the standard section outer tube 201, and the length matches the length of the standard section. It is used to temporarily block the air pressure holes. The upper and lower adjacent partition plates 4 are connected by snap-fit. Each partition plate 4 has two snap-fits at the bottom, and the extension of the snap-fits is embedded in the upper slot of the lower partition plate 4. During the compression process, partition plates 4 are sequentially extracted from the first plate extraction groove 33 and the second plate extraction groove 34 in the cavity device 3 at the bottom of the double-walled drill rod. Rubber sealing rings are designed along the groove openings to prevent gas from escaping during the compression process, realizing a segmented compression and replacement process from top to bottom, and preventing all channels from opening simultaneously and obstructing the discharge of the medium. The bottom of the double-walled drill rod is sealed by the cavity device 3, which is equipped with annular first and second air inlets, connected to the air injection equipment 5 via an air injection pipeline. The outermost ring of the cavity device 3 is provided with a first waste recovery hole 61, a second waste recovery hole 62, and a third waste recovery hole 63, connected to the waste recovery device 6 via a waste pipeline. The size matches the inner diameter of the steel casing 31, and the discharged waste is treated using the "liquid-gas" separation principle.

[0053] Specifically, during the downhole equipment assembly and initial sealing stage, the double-walled drill pipe end 1 is sequentially connected to the standard section inner tube 202 and the standard section outer tube 201, and the equipment is extended along the steel casing 31. After the double-walled drill pipe has entered a certain distance, the partitions 4 are connected in pairs and installed into the standard section until the entire double-walled drill pipe section is delivered into the exploration borehole. The bottom of the double-walled drill pipe is connected to the gas injection equipment 5 and the waste recovery equipment through the cavity-splitting device 3, forming a double-walled + three-cavity structure together with the borehole wall of the exploration borehole. The inner cavity is the detection cavity 03, the middle cavity is the gas injection cavity 02, and the outer cavity is the compressed gas replacement cavity 01. Before being withdrawn, the partitions 4 completely cover the end pressure holes 12 and 22 of each section of the outer tube. During the compression process, the symmetrically connected partitions 4 are slowly removed from the first plate removal slot 33 and the second plate removal slot 34 of the cavity-splitting device 3 at the bottom of the double-walled drill pipe until the compression process is completed. The first and second air inlets, arranged in a ring on the chamber-splitting device 3, are connected to the ground gas injection device 5 via Φ10mm high-pressure hoses with a pressure resistance ≥10MPa. KZD-10 quick connectors with a sealing pressure ≥8MPa are installed at both ends of the hoses. The waste recovery device 6 is connected to the first waste recovery hole 61, the second waste recovery hole 62, and the third waste recovery hole 63 at the bottom of the chamber-splitting device 3. The outer ring grid is used to separate rock fragments from the mixed medium. The filtered mixed medium is connected to the waste recovery device 6 through the outer ring pipeline of the chamber-splitting device. The mixed medium is separated by a water-gas separator with a separation efficiency ≥95%. The exhaust gas is purified and collected by a gas purification unit containing activated carbon with a filtration accuracy ≤1μm and an adsorption efficiency ≥95%. During operation, open the main control valve of the waste recovery device 6, select an ISG80-160 variable frequency clean water pump with a rated pressure ≥8MPa, and a matching Φ10mm high-pressure water pipe. Connect one end of the water pipe to the annular first air injection hole 51 and the second air injection hole 52 of the chamber-splitting device 3. Start the clean water pump and gradually increase the pressure to 6MPa at a rate of 0.5MPa / min, stabilizing the flow rate at 10L / min, ensuring a water flow velocity ≥0.3m / s, to fully flush out the rock cuttings. Continue water injection for 15-20 minutes. This stage can remove loose rock cuttings from the borehole and filter them onto the screen of the outermost cavity of the chamber-splitting device 3. Turn off the clean water pump, remove the chamber-splitting device 3, clean the rock cuttings near the borehole opening and the screen, and reinstall the chamber-splitting device 3. This step, while flushing out the rock cuttings in the borehole to prevent clogging of the channel, can dilute the original medium in the borehole fractures, enhance the fluidity of the original medium, and facilitate subsequent compressed air replacement operations.Then, select the appropriate gas ratio during the compressed gas replacement operation stage according to the type of the original medium: For mud with a density <1.3g / cm³, use "90% nitrogen + 8% sulfur hexafluoride + 2% polyether modified siloxane defoamer", and the gas density after mixing is ≤0.8g / cm³. Stir for 10 minutes in a 2m³ mixing tank with a stirring speed of 400r / min in the gas injection device to ensure uniform mixing ratio; For mine water with turbidity >50NTU, use "95% nitrogen + 5% helium", and the gas solubility is ≤0.5mg / L, so no defoamer needs to be added; For gas with humidity >60%, use "96% nitrogen + 4% sulfur hexafluoride", and fill a calcium chloride drying tank with 1-2mm granular desiccant to assist in dehumidification before gas injection.

[0054] Based on the geological exploration results, corresponding measures were formulated to treat the medium affecting electromagnetic waves around the exploration borehole, reducing the impact of interface noise. After equipment assembly and initial flushing, the core compressed air-driven replacement stage began. By precisely matching the recovery rate of the waste recovery device 6 with the injection pressure of 2MPa, the injected gas gradually occupied the original medium space, achieving orderly replacement from top to bottom. The injection device 5 was started, and a preset ratio of replacement gas was constantly injected into the injection chamber 02. The injection pressure was maintained at 2MPa, and the injection flow rate Q... inj Based on the volume of the air injection chamber 02 and the expected replacement efficiency, the waste recovery device 6 is started synchronously. To match the air injection and maintain pressure balance within the orifice, and to prevent air blockage or media residue, the suction rate Q of the waste recovery device 6 is set. rec Dynamic adjustment is required. Its basic control formula is Q. _rec =Q _inj ×(ρ gas / ρ media )×K, where Q rec Q is the instantaneous suction flow rate of waste recycling device 6, in L / min; inj ρ is the instantaneous flow rate of gas injection, in L / min; gas Density of the injected replacement gas, g / cm³; ρ media Q is the estimated density of the original medium in the current replacement section, in g / cm³; K is an empirical coefficient, ranging from 1.1 to 1.3, used to compensate for factors such as medium mixing and viscous resistance, ensuring smooth discharge. In actual operation, Q is finely adjusted in real time based on feedback from the air injection flow rate and orifice pressure sensor via the variable frequency pump and regulating valve on the waste recovery device 6. rec This ensures that the injected gas can effectively displace and expel the original medium.

[0055] The segmented replacement process follows a top-down principle. Since the double-walled drill pipe end 1 is not equipped with a diaphragm 4, the replacement begins at the deepest point. The diaphragm 4 corresponding to the standard section is extracted at a constant speed of 0.5 m / min through the first and second extraction slots 33 and 34 of the chamber-splitting device 3. As the diaphragm 4 is slowly removed, the outer tube pressure port 22 is gradually exposed from top to bottom, connecting with the injection chamber 02. Under constant injection pressure, gas is ejected obliquely from the exposed pressure port, forming a high-pressure gas cloud at the bottom of the borehole, creating a piston effect that pushes the original medium within the borehole section from top to bottom. The mixture of the displaced medium and some gas enters the pressure replacement chamber 01 and is effectively recovered through the first waste recovery port 61, second waste recovery port 62, and third waste recovery port 63 of the chamber-splitting device 3 under the suction of the waste recovery device 6.

[0056] After extraction from baffle 4 during each replacement process, the composition of the discharged medium is monitored every 5 minutes via the "three-in-one" sensor at the borehole opening and the medium analyzer at the outlet of the waste recovery device 6. When the target gas percentage in the discharged medium is consistently ≥85% and the solid rock cuttings content is ≤5%, the replacement of the current segment is considered to have met the qualification standard. The above process of "extracting baffle 4 → constant gas injection → matching recovery → component monitoring" is repeated segment by segment from bottom to top. When all fourteen standard segments have been replaced, and the target gas percentage in the discharged medium remains consistently ≥90% for 10 consecutive minutes, the full borehole replacement operation is considered successfully completed. At this point, the interfering medium in the borehole detection chamber 03 and surrounding fractures has been effectively replaced into a low-interference, highly insulating gas environment.

[0057] A constant pressure of gas is injected between the outer tube 201 of the standard section and the exploration borehole. Then, a geophysical instrument is lowered into the inner tube 202 of the standard section for data collection. Once the replacement objective is achieved, geophysical data acquisition begins immediately. A constant injection pressure of 2 MPa is maintained within the outer tube 201 of the standard section to ensure the stability of the detection environment. Subsequently, a high-frequency ground-penetrating radar or seismic wave detector is slowly lowered to the bottom of the exploration borehole through the detection cavity 03 formed within the inner tube 202 of the standard section. A guide head at the instrument tip ensures smooth passage. Starting from the bottom of the borehole, data is collected in 5-10 m segments, from bottom to top. Each segment lasts ≥20 minutes, with a data sampling rate ≥1 MHz. During this process, the injection pressure and geophysical signal intensity are continuously monitored. Because interface noise has been significantly eliminated or reduced, the obtained reflected wave signals are clearer, and the location and morphological characteristics of anomalies are more clearly represented in the data.

[0058] To further optimize the solution, when dealing with the electromagnetic wave-affecting medium around the exploration borehole, a corresponding replacement gas is selected based on the type of the original medium within the borehole. After being injected into the injection chamber 02, the replacement gas enters the pressure replacement chamber 01 through the outer pipe pressure port 22 and the end pressure port 12, discharging the original medium and recovering it through the waste recovery device 6. If the original medium is mud with a density <1.3 g / cm³, a mixed gas of "90% nitrogen + 8% sulfur hexafluoride + 2% polyether-modified siloxane defoamer" with a gas density ≤0.8 g / cm³ is selected. After the gas is ejected along the end pressure port 12 and the outer pipe pressure port 22, a high-pressure gas cloud forms at the bottom of the exploration borehole, pushing the mud downwards. The mud mixture flows into the sedimentation tank through the discharge pipe of the waste recovery device 6. If the primary medium is mine water containing suspended solids (turbidity > 50 NTU), a mixture of 95% nitrogen and 5% helium is used, with a gas solubility ≤ 0.5 mg / L. The pumped water flows out of the borehole or is blocked, maintaining a constant injection pressure for subsequent detection. If the primary medium is high humidity or ordinary gas (humidity > 60%), a mixture of 96% nitrogen and 6% sulfur hexafluoride is used. During the replacement process, the borehole medium (gas + mud / water) is recovered and separated using waste recovery device 6. If it is mud replacement, the separated gas is processed by a drying filter and then fed into a high-pressure gas storage tank for recovery; if it is mine water / high humidity air replacement, the separated dried gas is directly reused for subsequent borehole replacement, reducing fresh gas consumption and preventing gas escape. During the injection process, the medium discharged from the borehole is recorded every 15 minutes to ensure the replacement rate until the target gas accounts for ≥ 90% of the discharged medium.

[0059] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0060] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A downhole geophysical exploration double-wall drill pipe gas-driven replacement system, characterized in that: Includes a rod body, which is embedded in an exploratory borehole at the construction site, with the end of the rod body extending out of the exploratory borehole and communicating with a cleaning assembly in the outside; The rod body includes a double-walled drill rod end (1) located in the exploration borehole and communicating with the outside. The double-walled drill rod end (1) is connected to a number of double-walled drill rod standard sections (2) connected end to end. The double-walled drill rod standard section (2) at the end extends out of the exploration borehole and communicates with the cleaning assembly. The double-wall drill pipe standard section (2) includes a standard section inner tube (202) and a standard section outer tube (201) arranged coaxially. The standard section inner tube (202) and the standard section outer tube (201) are respectively connected to the double-wall drill pipe end (1). A coaxial chamber is formed between the standard section inner tube (202), the standard section outer tube (201) and the exploration borehole. The chamber is connected to the cleaning assembly.

2. The downhole geophysical exploration double-wall drill pipe gas-driven replacement system according to claim 1, characterized in that: The double-walled drill pipe end (1) includes a coaxially arranged and independent end probe tube (11) and an end protection tube. One end of the end protection tube is closed, and the end probe tube (11) is fixed to the inner cavity of the end protection tube. The end probe tube (11) is connected to the inner tube (202) of the standard section, and the end protection tube is connected to the outer tube (201) of the standard section.

3. The downhole geophysical exploration double-wall drill pipe gas-driven replacement system according to claim 2, characterized in that: The chamber includes a detection chamber (03), an air injection chamber (02), and a compressed air replacement chamber (01) arranged coaxially from the inside to the outside. The outer tube of the standard section (201) has several oblique outer tube compressed air holes (22) arranged around its side wall, and the end protection tube has several oblique end compressed air holes (12) arranged around its side wall. The outer tube compressed air holes (22) and the end compressed air holes (12) connect the air injection chamber (02) and the compressed air replacement chamber (01).

4. The downhole geophysical exploration double-wall drill pipe gas-driven replacement system according to claim 3, characterized in that: The air injection chamber (02) is provided with several symmetrically arranged baffles (4). The baffles (4) are the same length as the standard section outer tube (201) and are connected end to end. The baffles (4) slide in contact with the inner wall of the standard section outer tube (201) and the inner wall of the end protection tube. The baffles (4) block the outer tube air pressure hole (22) and the end air pressure hole (12). The opening and closing of the outer tube air pressure hole (22) and the end air pressure hole (12) can be controlled by the sliding of the baffles (4).

5. The downhole geophysical exploration double-wall drill pipe gas-driven replacement system according to claim 3, characterized in that: The cleaning assembly includes an air injection device (5) and a waste recovery device (6). The air injection device (5) is connected to the air injection chamber (02), and the waste recovery device (6) is connected to the compressed air replacement chamber (01). The air injection device (5) injects high-pressure gas into the air injection chamber (02), and the high-pressure gas enters the compressed air replacement chamber (01) to discharge the debris in the compressed air replacement chamber (01).

6. The downhole geophysical exploration double-wall drill pipe gas-driven replacement system according to claim 5, characterized in that: The outlet of the exploration borehole is provided with a cavity-splitting device (3), which is sealed and fixed to the outer tube (201) and the inner tube (202) of the standard section. The gas injection device (5) is connected to the gas injection chamber (02) through the cavity-splitting device (3), and the waste recycling device (6) is connected to the compressed air replacement chamber (01) through the cavity-splitting device (3).

7. The downhole geophysical exploration double-wall drill pipe gas-driven replacement system according to claim 6, characterized in that: The chamber-splitting device (3) includes a steel casing (31) embedded in the outlet of the exploration borehole. The steel casing (31) is coaxially sleeved outside the standard section outer tube (201) and the end of the standard section outer tube (201) is closed. The gas injection device (5) is connected to the gas injection chamber (02) through the steel casing (31), and the waste recovery device (6) is connected to the compressed air replacement chamber (01) through the steel casing (31).

8. The downhole geophysical exploration double-wall drill pipe gas-driven replacement system according to claim 4, characterized in that: The outer tube (201) of the standard section is provided with a protrusion (26) arranged along the length direction. The top of the protrusion (26) extends inward toward the hole wall of the outer tube (201) of the standard section to form an arc-shaped bayonet (27). The top of the protrusion (26) and the edge of the arc-shaped bayonet (27) are in sealed contact with the outer wall of the inner tube (202) of the standard section. The partition (4) is in movable contact with the protrusion (26) and the arc-shaped bayonet (27).

9. A method for using a downhole geophysical exploration double-wall drill pipe gas-driven replacement system, comprising the downhole geophysical exploration double-wall drill pipe gas-driven replacement system as described in any one of claims 1-8, characterized in that, Includes the following steps: The geological environment of the selected area is explored, and then exploration boreholes are drilled based on the exploration results; The off-site assembly of the downhole geophysical exploration double-wall drill pipe gas-driven replacement system was placed into the exploration borehole as a whole after assembly. Based on the geological exploration results, corresponding measures are formulated to treat the medium around the exploration borehole that affects electromagnetic waves and reduce the impact of interface noise. A constant pressure gas is injected between the outer tube (201) of the standard section and the exploration borehole, and then a geophysical instrument is placed along the inner tube (202) of the standard section to collect data.

10. The method of using the downhole geophysical exploration double-wall drill pipe gas-driven replacement system according to claim 9, characterized in that: When dealing with the medium that affects electromagnetic waves around the exploration borehole, the corresponding replacement gas is selected according to the type of the original medium in the exploration borehole. After the replacement gas is injected into the injection chamber (02), it enters the compressed gas replacement chamber (01) through the outer pipe compressed air hole (22) and the end compressed air hole (12) to discharge the original medium and recover it through the waste recovery device (6).

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