Valve switching reverse circulation drilling air inlet position adjusting system and using method thereof

Abstract

The invention belongs to the technical field of geological drilling, and particularly relates to a valve switching reverse circulation drilling air inlet position adjusting system and a using method thereof. The air inlet position adjusting system comprises an air compressor, an air inlet pipeline, a valve switching assembly and at least two air inlet ends, the air inlet ends are arranged at different height positions in the depth direction of a drill hole, the top of the air inlet pipeline is communicated with the air compressor, the bottommost part of the air inlet pipeline is arranged at the position close to a drill bit, and the air inlet end on the lower portion is communicated with the interior of a drill rod. The middle of the air inlet pipeline communicates with the interior of the drill rod through the valve switching assembly and the upper air inlet end. According to the invention, the air inlet position change originally depending on structure adjustment is converted into valve control switching operation, so that the construction process is simplified, the labor intensity and the safety risk are reduced, and the stable reverse circulation gas lift working condition can be maintained under different drilling depth conditions.

Description

Technical Field

[0001] This invention belongs to the field of geological drilling technology, specifically relating to a valve-switching reverse circulation drilling air intake position adjustment system and its usage method. Background Technology

[0002] Reverse circulation drilling technology is a drilling method that relies on compressed air to form a gas-liquid mixture column inside the borehole, generating negative pressure inside the borehole or drill pipe to lift and remove drill cuttings in the reverse direction. Due to its advantages such as high cuttings removal efficiency, good hole quality, and applicability to complex formations, reverse circulation drilling technology is widely used in geological exploration, hydrogeological drilling, engineering pile foundation construction, and deep hole drilling.

[0003] In reverse circulation drilling, compressed air typically enters the borehole through an intake pipe, mixes with the fluid inside the borehole to form a gas-liquid mixture, and carries drill cuttings to the surface under the influence of buoyancy and pressure difference. Existing reverse circulation drilling systems often employ a fixed-height intake structure, where compressed air enters the borehole from the bottom or a specific location through a fixed intake end.

[0004] However, as drilling depth increases, the fixed air intake method gradually reveals its significant shortcomings. On the one hand, the increased length of the air intake pipeline leads to greater frictional and local resistance, reducing the effective air volume reaching deeper parts of the borehole and making air lift startup difficult. On the other hand, in deep hole conditions, a fixed air intake position cannot simultaneously meet the different air lift requirements of shallow and deep hole stages, easily resulting in unstable reverse circulation, reduced slag removal efficiency, or even reverse circulation interruption. To maintain the reverse circulation effect, it is usually necessary to increase the air compressor output pressure or frequently lift the drill bit to adjust the air intake structure, which not only consumes more energy but also has low construction efficiency, complex operation, and significant safety risks.

[0005] For deep-hole reverse circulation drilling, some technical solutions attempt to reduce air lift starting resistance by changing the position of the air intake device to allow compressed air to enter the borehole at a higher position. However, these solutions often require disassembly, relocation, or rearrangement of the air intake pipe or device during drilling, which is cumbersome, labor-intensive, and difficult to implement in the drilling environment, making it hard to achieve rapid and reliable switching of the air intake position.

[0006] Therefore, how to achieve flexible adjustment of the air intake position during reverse circulation drilling without changing the overall layout of the air intake pipeline or increasing the complexity of construction, so as to adapt to different drilling depths and working conditions and improve the stability and construction efficiency of deep hole reverse circulation drilling, remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the above problems, this invention provides a valve-switching reverse circulation drilling air intake position adjustment system, including an air compressor, an air intake pipe, a valve switching assembly, and at least two air intake ends. The air intake ends are positioned at different heights along the drilling depth direction. The top of the air intake pipe is connected to the air compressor, and the bottom of the air intake pipe is positioned near the drill bit. The lower air intake end is connected to the inside of the drill rod, and the middle of the air intake pipe is connected to the inside of the drill rod through the valve switching assembly and the upper air intake end.

[0008] This invention utilizes at least two air inlets distributed along the drilling depth direction on the same air inlet pipe, and a valve switching assembly in the middle of the air inlet pipe. This allows compressed air to selectively enter the borehole through air inlets located at different heights without altering the overall layout of the air inlet pipe or disassembling or moving the pipe. This enables adjustment of the air inlet position during reverse circulation drilling. Compared to existing methods that require disassembly, relocation, or rearrangement of the air inlet pipe or device during construction, this invention achieves air inlet position switching via the valve switching assembly, avoiding frequent manual intervention and structural adjustments. This significantly simplifies the construction operation process, reduces the labor intensity and safety risks for construction personnel, and improves the continuity and efficiency of reverse circulation drilling under different drilling depths.

[0009] Furthermore, multiple valve switching components are arranged along the drilling depth direction, connecting the air intake pipe and the air intake end at different drilling depths. This allows compressed air to selectively enter the borehole at multiple different heights, achieving multi-stage adjustment of the air intake position during reverse circulation drilling. Compared to schemes that can only switch between two fixed heights, this structure allows for more precise and flexible adjustment of the air intake position. It can select the most advantageous air intake height in stages according to the gradual increase in drilling depth or changes in formation conditions, helping to maintain suitable air lift conditions at different drilling stages and avoiding a decrease in air lift efficiency or instability in reverse circulation due to mismatched air intake positions. Simultaneously, all multiple valve switching components are fixedly installed on the air intake pipe, eliminating the need for disassembly, relocation, or rearrangement of the air intake pipe during construction. This further reduces construction complexity and labor intensity, improving the continuity, reliability, and construction efficiency of deep-hole reverse circulation drilling.

[0010] Furthermore, the valve switching assembly includes a three-way valve, which selectively connects the air intake pipe to one of the air intake ends under different operating conditions. Using a three-way valve as the valve switching assembly allows for clear selection and rapid switching between different air intake ends structurally. In any operating state, compressed air is allowed to flow to only one air intake end, thus avoiding airflow interference and reverse circulation turbulence caused by simultaneous intake from multiple air intake ends. Simultaneously, the three-way valve has a compact structure and reliable switching, enabling the conversion of the air intake path during drilling through simple valve position switching, without requiring disassembly or rearrangement of the air intake pipe or air intake end. This simplifies operation, provides rapid response, reduces labor intensity and safety risks during construction, and ensures the stability and continuity of reverse circulation drilling during switching between different air intake positions.

[0011] Furthermore, the three-way valve is a two-position three-way valve. By employing a two-position three-way valve, the valve has only two stable positions under different operating conditions. In each position, the air intake pipe is connected to only one air intake end, while simultaneously cutting off the connection to the other air intake end. Structurally, this avoids the occurrence of simultaneous air intake from multiple air intake ends or cross-contamination, which is beneficial for maintaining the certainty of the airflow path and the stability of the gas lift operation during reverse circulation drilling. At the same time, the two-position three-way valve has simple control logic and clear valve position switching, enabling rapid and reliable air intake position switching during drilling operations, reducing misoperation and switching delays.

[0012] Furthermore, it also includes a bypass quick-supply branch, which is located between the intake pipe upstream of the valve switching assembly and the pipe downstream of the valve switching assembly and before the intake end. The bypass quick-supply branch is equipped with a controllable bypass valve, allowing compressed air to bypass the valve switching assembly and directly supply air to the intake end during intake position switching or reverse circulation. Because the valve switching assembly inevitably generates instantaneous flow channel changes and additional resistance during switching, it is easy to cause short-term fluctuations in supply pressure and flow rate, especially in deep hole conditions, which can easily lead to a weakening or even interruption of the gas-liquid mixing column. This invention provides a low-resistance, fast-response air supply path to the intake end by opening the bypass quick-supply branch during the switching phase, which can quickly compensate for the insufficient air supply caused by the transient valve switching, maintain the continuity and stability of the gas supply in the hole, and facilitate the rapid establishment and maintenance of the gas-liquid mixing column. After completing the intake position switching and restoring stable reverse circulation, the bypass valve is closed, allowing the air supply to resume through the valve switching assembly. This reduces pressure fluctuations and the risk of circulation interruption during the intake switching process without affecting normal operation control, thereby improving the stability and reliability of reverse circulation drilling under deep hole conditions.

[0013] Furthermore, the intake end is equipped with a first channel and a second channel, both of which are connected to the intake pipe. The first channel is lower than the second channel, meaning the first channel is positioned at a lower position in the borehole, and the second channel at a higher position. A constriction structure is provided between the first and second channels, allowing compressed air to enter the borehole in stages at different heights, spatially organizing the gas-liquid mixing process. During operation, the gas entering the borehole through the first channel first forms a preliminary gas-liquid mixture with the liquid inside the borehole at the lower part of the borehole and develops upward under the action of buoyancy. The constriction structure provides geometric constraint and flow integration for this rising gas-liquid mixture, keeping it relatively concentrated and orderly when passing through the transition zone, reducing flow turbulence caused by abrupt changes in the flow channel or excessive space. Subsequently, the gas entering through the second channel superimposes and mixes with the already formed gas-liquid mixture at a higher position, avoiding strong disturbances caused by gas concentrating at a single height when entering the borehole. Therefore, the synergistic effect of the dual channels and the narrowing structure enhances gas-liquid mixing step by step along the drilling depth direction, making the mixing process more continuous and uniform. This is beneficial for maintaining a stable reverse circulation gas lift state, especially in deep hole conditions, which can reduce fluctuations and circulation interruption risks, and improve the continuity and reliability of reverse circulation drilling.

[0014] Furthermore, the cross-sectional area of ​​the first channel is larger than that of the second channel. This allows the compressed air entering the borehole through the first channel to enter at a lower flow rate and with less local resistance, which is beneficial for forming a stable and uniform primary gas-liquid mixing zone at the bottom of the borehole and avoids strong disturbances to the flow pattern inside the borehole caused by high-speed jets. At the same time, the larger cross-section reduces the pressure drop of the lower intake, improving the start-up reliability of the reverse circulation airlift during the circulation phase. In contrast, the second channel uses a smaller cross-section, which can throttle and slow down the flow of the incoming gas while ensuring the necessary air supply. This allows the gas to be added to the already formed gas-liquid mixture at a higher position in a smoother manner, reducing the impact of the air supply process on the rising mixing column. Thus, by setting different cross-sectional areas between the upper and lower intake channels, differentiated control of the primary mixing and air supply superposition process is achieved, improving the stability and continuity of reverse circulation drilling under different depth conditions.

[0015] Furthermore, a wire mesh is installed on the cross-section of the first channel to disperse and rectify the compressed air entering the borehole before it enters the borehole, thus preventing the gas from directly entering the lower region of the borehole in a concentrated, high-speed jet form. Through the damping and diversion effect of the wire mesh, the gas can be more evenly distributed at the lower air inlet and enter the borehole liquid in a gentler manner. This is beneficial for the gas to form fine bubbles and for primary gas-liquid mixing in the borehole liquid, increasing the gas-liquid contact area and promoting the rapid establishment of a stable gas-liquid mixing column. Simultaneously, the wire mesh can weaken transient fluctuations and backflow disturbances in the lower region of the gas flow, reducing the risk of gas lift failure due to flow instability during the initial circulation phase, thereby improving the start-up reliability and operational stability of reverse circulation drilling in the initial stage and under shallow hole conditions.

[0016] On the other hand, the present invention provides a method for using a valve-switching reverse circulation drilling air intake position adjustment system, comprising the following steps: Step 1: In the initial stage of drilling, compressed air is introduced into the borehole through the lower air inlet using the valve switching assembly; Step 2: Use the lower air inlet to make compressed air mix with the liquid in the hole at the bottom of the borehole to form a gas-liquid mixture column, and establish a reverse circulation airlift slag removal system. Step 3: As the drilling depth increases, the air intake path is switched by the valve switching component, so that compressed air enters the borehole through the upper air intake end.

[0017] Furthermore, it also includes a bypass quick-supply branch, which is provided on the intake pipe. The bypass quick-supply branch connects the intake pipe upstream of the valve switching assembly with the pipeline downstream of the valve switching assembly and between the intake end. When switching the intake position, the bypass quick-supply branch is opened.

[0018] The beneficial effects of this invention are: (1) By setting a valve switching component, the present invention enables the air intake pipe to selectively connect with the air intake end at different heights without disassembly, relocation or rearrangement, thereby realizing the rapid switching and adjustment of the air intake position during reverse circulation drilling. This method transforms the original air intake position change that relied on structural adjustment into a valve-controlled switching operation, which simplifies the construction process, reduces labor intensity and safety risks, and is conducive to maintaining a stable reverse circulation gas lift working condition under different drilling depths.

[0019] (2) The present invention will set up a bypass fast air supply branch between the upstream and downstream of the valve switching component, and open the bypass valve during the air inlet position switching or circulation stage, so that compressed air can bypass the valve switching component to supply air quickly, which compensates for the pressure loss and flow fluctuation caused by the valve switching transient, maintains the continuity of air supply in the orifice, prevents the gas-liquid mixing column from weakening or interrupting, and improves the reverse circulation stability and construction reliability during the air inlet position switching process.

[0020] (3) The present invention sets up a first channel and a second channel at different heights inside the air inlet, and with the help of a constriction structure, so that compressed air can enter the borehole in stages and at different heights, thereby organizing the gas-liquid mixing process in a spatially orderly manner; the lower first channel is conducive to forming a stable primary gas-liquid mixture, and the upper second channel realizes smooth air replenishment and superimposed mixing, avoiding strong disturbances caused by single-point air intake, and improving the continuity and stability of reverse circulation drilling in deep hole conditions.

[0021] Based on the above beneficial effects, this invention has good application prospects in the field of geological drilling technology. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a valve-switching reverse circulation drilling air intake position adjustment system.

[0023] Figure 2 This is a schematic diagram of the drill pipe and the air inlet.

[0024] In the diagram: 1. Drill rod; 2. Air inlet pipe; 3. Valve switching assembly; 4. Air inlet end; 5. Flange; 11. Drill hole; 12. Narrowing structure; 41. First channel; 42. Second channel. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments.

[0026] Example 1 This embodiment provides a valve-switching reverse circulation drilling air intake position adjustment system, including an air compressor (not shown), an air intake pipe 2, a valve switching assembly 3, and at least two air intake ends 4. This system is applied in reverse circulation drilling operations to adjust the height position of compressed air entering the borehole 11 according to changes in borehole depth during drilling, thereby improving reverse circulation airlift conditions.

[0027] The top of the intake pipe 2 is connected to the air compressor to receive compressed air output from the air compressor. The intake pipe 2 is arranged downwards along the borehole 11, with its bottom point located near the drill bit, and communicates with the internal channel of the drill rod 1 via the intake end 4 located at that position. Figure 1 As shown, drill pipe 1 is composed of multiple drill pipe units connected axially. Adjacent drill pipe units are connected and fixed by flanges 5, thereby forming a continuous internal channel of drill pipe, allowing compressed air to flow along the inside of the drill pipe.

[0028] like Figure 1As shown, a valve switching assembly 3 is installed in the middle of the intake pipe 2. The valve switching assembly 3 is used to control the communication between the intake pipe 2 and the intake ends 4 at different heights. In this embodiment, the valve switching assembly 3 includes a three-way valve, which is connected to the intake pipe 2, the lower intake end 4, and the higher intake end 4, respectively. Through the different operating states of the three-way valve, the intake pipe 2 can selectively connect to one of the intake ends 4 while cutting off the connection with the other intake end 4.

[0029] Furthermore, in this embodiment, the three-way valve is preferably a two-position three-way valve. This two-position three-way valve has two stable valve positions. In the first position, the air inlet pipe 2 is connected to the air inlet end 4 located near the drill bit, allowing compressed air to enter the internal channel of the drill rod 1 or the liquid inside the drill hole 11 through the lower part of the borehole 11. In the second position, the air inlet pipe 2 is connected to the air inlet end 4 located at a higher position, allowing compressed air to enter the interior of the drill rod 1 or the borehole 11 at a higher position, thereby changing the air inlet height.

[0030] During actual drilling, when the borehole 11 is shallow or reverse circulation air lift is easily established, the valve switching assembly 3 is in its first working state. Compressed air enters the lower part of the borehole 11 through the air inlet 4 near the drill bit, forming a gas-liquid mixture column with the liquid in the hole, thus achieving reverse circulation slag removal. As the depth of the borehole 11 increases, when the lower air intake is difficult to maintain a stable air lift, the valve position of the switching assembly 3 is changed to allow compressed air to enter the borehole 11 through the higher air inlet 4, thereby reducing the air lift start-up resistance and maintaining the continuous operation of reverse circulation drilling.

[0031] In this invention, the driving method of the valve switching component 3 is not limited to manual operation. Preferably, the valve switching component 3 can be electrically adjusted to achieve valve position switching. For example, the valve switching component 3 can be configured with an electric actuator to selectively connect the air intake passage by driving the valve core or valve body with a motor, thereby remotely, automatically or semi-automatically completing the switching of the air intake position during drilling. Using an electric adjustment method avoids frequent manual operation at the drilling site, improves the response speed and control accuracy of air intake position switching, and is beneficial for maintaining a stable reverse circulation gas lift state in deep hole drilling or complex working conditions.

[0032] With the above-described structure, this embodiment does not require disassembly, relocation, or rearrangement of the air intake pipe 2 or drill rod 1 during drilling. The air intake position can be adjusted simply by switching the valve switching component 3, which simplifies the construction operation process, reduces the labor intensity and safety risks of construction personnel, and improves the stability and construction efficiency of reverse circulation drilling under different drilling depth conditions.

[0033] Example 2 Based on Embodiment 1, a bypass quick-supply branch is provided on the intake pipe 2. The bypass quick-supply branch is located between the intake pipe 2 upstream of the valve switching assembly 3 and the pipe downstream of the valve switching assembly 3 and before the intake end 4, so that the bypass quick-supply branch spans both sides of the valve switching assembly 3, forming a backup air supply path in the intake pipe 2 that bypasses the valve switching assembly 3.

[0034] A controllable bypass valve is installed on the bypass quick-supply branch to control the conduction state of the bypass quick-supply branch. During the intake position switching or reverse circulation initiation phase, the bypass valve is opened to allow compressed air to be supplied directly and quickly to the intake end 4 via the bypass quick-supply branch, thereby bypassing the instantaneous resistance and flow channel changes generated by the valve switching assembly 3 during the switching process. After the intake position switching is completed and a stable reverse circulation airlift is established, the bypass valve is closed, allowing compressed air to resume supplying air to the intake end 4 via the valve switching assembly 3, thus ensuring the air supply control accuracy and operational stability of the system during normal drilling. Through the above settings, this embodiment can effectively reduce the transient fluctuations in air supply pressure and flow rate during valve switching, prevent the weakening or interruption of the gas-liquid mixing column, and improve the stability of the intake position switching process and the construction reliability of reverse circulation drilling.

[0035] Example 3 Based on Example 2, such as Figure 2 As shown, in this embodiment, a first channel 41 and a second channel 42 are provided inside the air intake end 4. Both the first channel 41 and the second channel 42 are connected to the air intake pipe 2 and are used to introduce compressed air into the borehole 11. The first channel 41 is located at the lower part of the air intake end 4, corresponding to the lower position in the borehole 11; the second channel 42 is located at the upper part of the air intake end 4, corresponding to the higher position in the borehole 11.

[0036] In this embodiment, the first channel 41 and the second channel 42 are arranged vertically along the borehole axis and are spaced apart in the axial direction, forming a transition zone between the first channel 41 and the second channel 42. This transition zone is constructed as a constriction structure 12. The channel cross-section of the constriction structure 12 gradually decreases from bottom to top along the axial direction, making the first channel 41 and the second channel 42 geometrically distinct and forming a continuous and smooth transition flow channel between them.

[0037] Furthermore, the cross-sectional area of ​​the first channel 41 is set to be larger than that of the second channel 42. Specifically, the first channel 41 is preferably an approximately cylindrical or axially extending straight hole structure with a relatively large inner diameter to reduce the flow resistance of the lower air intake; the second channel 42 is preferably a straight hole or short tubular structure with a smaller inner diameter, used to moderately throttle the upper air supply. The constriction structure 12 can be formed by machining a tapered hole section, a stepped hole section, or a circular arc transition hole section inside the air intake end 4, so that the first channel 41 and the second channel 42 gradually transition in the axial direction, avoiding abrupt changes in cross-section.

[0038] The first channel 41, the second channel 42, and the constriction structure 12 can be formed by integral machining of the air intake end 4 body, for example, by drilling, boring, or milling in one step within the same air intake end body; or, the first channel 41, the second channel 42, and the constriction structure 12 can be formed by providing inner linings or sleeves with different inner diameters in the air intake end 4 and forming constriction sections between the inner linings.

[0039] With the above structural design, compressed air can enter the borehole 11 in stages and at different heights inside the air inlet 4: the gas entering through the first channel 41 forms a primary gas-liquid mixture at the lower part of the borehole 11, and after being constrained and rectified by the constriction structure 12, it develops upward. Meanwhile, the gas entering through the second channel 42 replenishes the already formed gas-liquid mixture at a higher position, thereby improving the stability and continuity of reverse circulation drilling under different depth conditions.

[0040] Example 4 Based on Example 3, a wire mesh is provided at the cross-sectional position of the first channel 41. The wire mesh is positioned near the air outlet end of the first channel 41, so that the compressed air entering the borehole 11 through the first channel 41 passes through the wire mesh before entering the borehole.

[0041] In this embodiment, the wire mesh is preferably a wear-resistant metal wire mesh, the shape of which matches the cross-sectional shape of the first channel 41. For example, when the first channel 41 has a circular cross-section, the wire mesh is set as a circular mesh sheet and fixedly installed on the inner wall of the first channel 41. Specifically, an annular step or limiting groove for installing the wire mesh can be machined on the inner wall of the first channel 41, and the wire mesh is embedded in the step or limiting groove; or, the wire mesh can be stably fixed at the cross-sectional position of the first channel 41 by setting a pressure ring, a retaining ring or other fixing structure to prevent displacement under the action of high-pressure airflow.

[0042] After the wire mesh is installed, the axial structure of the first channel 41 remains unchanged, and the constriction structure 12 is still located between the first channel 41 and the second channel 42 to geometrically constrain and rectify the gas-liquid mixture flow formed and rising through the first channel 41. When compressed air passes through the first channel 41, it is first dispersed and rectified by the wire mesh before entering the lower part of the borehole to form a gas-liquid mixture with the liquid inside the hole. This improves the flow state of the lower intake without changing the overall structural dimensions of the intake end. By setting the wire mesh at the cross-section of the first channel 41, the lower intake process is made more uniform and gentle, reducing the disturbance of the flow state of the lower part of the borehole by the high-speed airflow. At the same time, it is beneficial to promote the primary mixing of gas in the liquid inside the hole, improving the stability and reliability of reverse circulation drilling in the initial circulation stage and in shallow hole conditions.

[0043] Preferably, the wire mesh is elastic, such as stainless steel elastic wire mesh. When the wire mesh has an elastic structure, it can undergo elastic deformation during the passage of compressed air, buffering and damping the gas flow, thereby reducing gas supply pulsations and instantaneous impacts, and reducing the amplitude of airflow fluctuations entering the borehole. Simultaneously, the elastic wire mesh can absorb energy and generate micro-vibrations under vibration and multiphase flow, which helps to suppress structural fatigue and particle adhesion, reducing the risk of blockage. Therefore, the elastic wire mesh can adaptively adjust the gas passage state under different drilling conditions, improving the stability of the reverse circulation gas lift process and the reliability of system operation.

[0044] Preferably, a spiral protrusion extending circumferentially is provided at the edge of the constriction structure 12. This allows the gas-liquid mixture entering and rising through the first channel 41 to acquire a tangential velocity component when passing through the constriction transition zone, thereby forming a controlled rotating flow state while rising axially. This rotation enhances the radial mixing of the gas and liquid phases, inhibits the rapid coalescence of large bubbles, and promotes the uniform distribution of gas in the liquid phase. On the other hand, the swirling flow creates a centrifugal stabilizing effect in the constriction region, ensuring that the mixed flow remains in a wall-attached and orderly flow state when passing through the cross-sectional contraction, reducing separation, backflow, and pulsation caused by abrupt changes in cross-section. Thus, the spiral protrusion ensures that the primary gas-liquid mixture formed in the first channel 41 is fully shaped and stabilized before entering the gas replenishment zone of the second channel 42, creating favorable flow conditions for subsequent superimposed mixing. This is beneficial for reducing the risk of reverse circulation fluctuations and circulation interruption, and is particularly suitable for deep holes and high gas volume conditions.

[0045] Example 5 Based on Example 1, the air inlet 4 is configured with a circumferential guiding function, so that compressed air preferentially distributes along the periphery of the borehole 11 when entering the borehole 11. Specifically, the air inlet 4 can be provided with circumferentially distributed air outlets, annular air outlet slots, or circumferential flow guide channels on its outer periphery, or a flow-dividing structure can be provided inside the air inlet to guide the gas from the central channel to the circumferential direction, so that the gas is radially deflected before entering the borehole 11, thereby entering the liquid in the borehole in a near-wall manner. In this way, the compressed air first contacts the liquid phase around the borehole 11 and forms an initial gas-liquid mixture, avoiding the gas from concentrating at the center of the borehole to form a high-speed jet or large-scale bubbles, which is beneficial for the gas to be covered and dispersed by the liquid. At the same time, when the gas entering along the periphery of the borehole moves upward under the action of buoyancy, it can form a relatively stable near-wall rising channel near the borehole wall, and gradually develop towards the center of the borehole through shearing, diffusion, and radial migration, so that the gas-liquid mixing process unfolds continuously from the circumferential to the radial direction, thereby improving the uniformity of gas holdup distribution. Therefore, adopting the air intake structure around borehole 11 helps to reduce the disturbance to the flow state inside the borehole in the initial stage of air intake, suppress rapid bubble coalescence and flow instability, enhance the continuity and stability of the gas-liquid mixing column, and thus reduce the fluctuation risk in the reverse circulation gas lift process. It is particularly suitable for the need for stable reverse circulation in deep hole drilling conditions.

[0046] Example 6 This embodiment provides a method for using a valve-switching reverse circulation drilling air intake position adjustment system, which is applicable to the working condition of adjusting the air intake position according to the change of drilling depth during reverse circulation drilling.

[0047] In the initial stage of drilling, the borehole 11 is relatively shallow, making it easier to establish reverse circulation airlift conditions. At this time, the compressed air in the intake pipe 2 is introduced into the borehole 11 through the lower intake end 4 located at the lower position of the borehole 11 by the control valve switching component 3. The compressed air fully contacts the liquid in the borehole at the lower part of the borehole 11 and forms a gas-liquid mixture. Under the action of buoyancy, it moves upward, thereby forming a gas-liquid mixture column inside the borehole 11 or inside the drill rod 1, establishing a stable reverse circulation airlift slag removal process, so that the drill cuttings are continuously carried out of the borehole with the mixture.

[0048] As drilling continues and the borehole depth gradually increases, the lower air intake method may encounter difficulties in starting the air lift or a decrease in slag removal efficiency under deep hole conditions. At this point, the air intake path is switched using the operating valve switching assembly 3, allowing compressed air in the air intake pipe 2 to enter the borehole 11 via the upper air intake end 4, located at a higher position within the borehole. By increasing the air intake height and shortening the air lift height, the energy requirements for starting and maintaining reverse circulation under deep hole conditions are reduced, thereby ensuring the continuous operation of reverse circulation drilling.

[0049] Furthermore, during the intake position switching process, the bypass quick-supply branch installed on the intake pipe 2 is opened, allowing compressed air to bypass the valve switching assembly 3 and be directly and rapidly supplied to the intake end 4. Through the bypass quick-supply branch, a continuous and sufficient gas supply can be provided to the borehole during the transient phase of valve position switching and flow channel changes in the valve switching assembly 3, preventing the weakening or even destruction of the gas-liquid mixing column due to supply interruption or sudden pressure drop. After the intake position switching is completed and a stable reverse circulation airlift state is re-established, the bypass quick-supply branch is closed, allowing compressed air to resume supplying air to the intake end 4 via the valve switching assembly 3. This ensures normal intake control while reducing system energy consumption and ineffective gas bypass during steady-state operation.

[0050] Through the above-described method, this embodiment achieves dynamic adjustment of the air intake position during reverse circulation drilling without disassembling or moving the air intake pipe, effectively improving the stability, slag removal continuity, and construction reliability of reverse circulation airlift under deep hole drilling conditions.

[0051] In summary, this invention proposes a valve-switching reverse circulation drilling air intake position adjustment system and its usage method. Addressing the problems of fixed air intake position, difficulty in starting the gas lift in deep hole conditions, and the complexity and high labor intensity caused by frequent disassembly or relocation of the air intake pipeline in existing reverse circulation drilling processes, this invention proposes a valve-switching-based air intake position adjustment scheme. This invention features a simple structure and flexible adjustment, improving the construction efficiency, stability, and safety of deep hole reverse circulation drilling, and has significant engineering application value.

[0052] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A valve-switching reverse circulation drilling air intake position adjustment system, characterized in that: It includes an air compressor, an air intake pipe, a valve switching assembly, and at least two air intake ends. The air intake ends are set at different heights along the drilling depth direction. The top of the air intake pipe is connected to the air compressor. The bottom of the air intake pipe is set near the drill bit and is connected to the inside of the drill rod through the lower air intake end. The middle part of the air intake pipe is connected to the inside of the drill rod through the valve switching assembly and the upper air intake end.

2. The valve-switching reverse circulation drilling air intake position adjustment system as described in claim 1, characterized in that: The valve switching assembly comprises multiple valve switching assemblies arranged along the drilling depth direction, and the multiple valve switching assemblies connect the air intake pipe and the air intake end at different depths of the drilling.

3. The valve-switching reverse circulation drilling air intake position adjustment system as described in claim 1, characterized in that: The valve switching assembly includes a three-way valve, which selectively connects the intake pipe to one of the intake ends under different operating conditions.

4. The valve-switching reverse circulation drilling air intake position adjustment system as described in claim 3, characterized in that: The three-way valve is a two-position three-way valve.

5. The valve-switching reverse circulation drilling air intake position adjustment system as described in claim 1, characterized in that: It also includes a bypass quick gas supply branch, which is located between the intake pipe upstream of the valve switching assembly and the pipe downstream of the valve switching assembly and before the intake end. The bypass quick gas supply branch is equipped with a bypass valve that can be controlled to open and close.

6. The valve-switching reverse circulation drilling air intake position adjustment system as described in any one of claims 1-5, characterized in that: The air intake end is provided with a first channel and a second channel. Both the first channel and the second channel are connected to the air intake pipe. The first channel is lower than the second channel, and a narrowing structure is provided between the first channel and the second channel.

7. The valve-switching reverse circulation drilling air intake position adjustment system as described in claim 6, characterized in that: The cross-sectional area of ​​the first channel is greater than that of the second channel.

8. The valve-switching reverse circulation drilling air intake position adjustment system as described in claim 7, characterized in that: The first channel has a wire mesh on its cross-section.

9. A method of using the valve-switching reverse circulation drilling air intake position adjustment system as described in claim 1, characterized in that, Includes the following steps: Step 1: In the initial stage of drilling, compressed air is introduced into the borehole through the lower air inlet using the valve switching assembly; Step 2: Use the lower air inlet to make compressed air mix with the liquid in the hole at the bottom of the borehole to form a gas-liquid mixture column, and establish a reverse circulation airlift slag removal system. Step 3: As the drilling depth increases, the air intake passage is switched by the valve switching assembly, so that compressed air enters the borehole through the upper air intake end.

10. The method of using the valve-switching reverse circulation drilling air intake position adjustment system as described in claim 9, characterized in that: It also includes a bypass quick-supply branch, which is provided on the intake pipe. The bypass quick-supply branch connects the intake pipe upstream of the valve switching assembly with the pipeline downstream of the valve switching assembly and between the intake end. When switching the intake position, the bypass quick-supply branch is opened.

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