Ground drilling coal seam gas pressure measuring system and working method thereof

Abstract

The invention relates to the technical field of coal seam gas pressure measurement, in particular to a ground drilling coal seam gas pressure measurement system and a working method thereof. The invention aims to solve various problems occurring when the existing equipment is used for measuring the coal seam gas pressure during ground drilling. The measuring system is composed of a screen pipe, an expander, a packer and an oil pipe which are sequentially connected, a first pressure gauge is arranged at the bottom of the screen pipe, a second pressure gauge is arranged in the expander, a switch valve is arranged below a center pipe of the expander, and the oil pipe is connected with a high-pressure air pump through a pipeline. The device can meet the requirement for measuring the gas pressure of the ground drilling coal seam, is simple in structure and convenient to operate, and can be repeatedly used.

Description

Technical Field

[0001] The present invention relates to the technical field of coal seam gas pressure measurement, and in particular to a ground borehole coal seam gas pressure measurement system and a working method thereof, which can be applied to coal seam gas pressure measurement in the field of coal exploration, and can also be used for gas pressure measurement in the field of highway and railway tunnel exploration. Background Art

[0002] Measuring the gas pressure of the target coal seam is an effective technical means to obtain the gas pressure of the coal seam in the coal mining area. At present, the gas pressure measurement of the coal seam in the ground borehole is stipulated in the "Coal and Peat Geological Exploration Specification" (DZ / T 0215-2002). The device currently used is still the KZWY91-1000 borehole gas pressure measuring instrument developed by Hunan Coal Research Institute or its improved version and other traditional instruments. This type of measuring instrument generally includes a sealing mechanism, a pressure relief mechanism, and a pressure measuring mechanism.

[0003] The KZWY91-1000 borehole gas pressure measuring instrument or its improved version and other traditional instruments are generally operated through the following steps:

[0004] 1. After drilling to expose the coal seam, the measuring instrument is connected to the drill pipe and sent to the predetermined position in the hole through the drill pipe;

[0005] 2. When the support rod at the lower end of the measuring instrument reaches the bottom of the hole, the instrument expands the rubber cylinder of the sealing mechanism under the pressure of the drill pipe or external load, which plays the role of sealing the test layer;

[0006] 3. The borehole drill pipe is connected to the mud pump, and the mud pump is used to pressurize the mud or clean water to push the pressure relief mechanism; after the pressure relief structure is actuated, the pressure relief hole is opened to release the mud pressure at the bottom of the packer, and at the same time, the pressure measuring mechanism is connected to the test coal seam;

[0007] Fourth, the pressure gauge in the pressure measuring mechanism records the change of coal seam gas pressure over time;

[0008] 5. When the gas pressure in the coal seam reaches a relative balance, lift the drill bit and release the hole seal;

[0009] 6. Pull out the drill bit at a constant speed and complete the gas pressure measurement.

[0010] In actual operation, the following problems often occur in traditional instruments such as the KZWY91-1000 borehole gas pressure measuring instrument or its improved version:

[0011] 1) The support rod is too long, and the sealing mechanism does not open at the predetermined position, resulting in a too long coal seam test section; or the support rod is too short, and the sealing rubber tube expands in the coal seam, causing an accident in the hole;

[0012] 2) The pressure relief mechanism does not work, the pressure relief hole is not opened, and the pressure measuring mechanism is not connected to the test coal seam;

[0013] 3) The sealing structure fails after sealing;

[0014] 4) Improper operation during drilling may cause the pressure measuring mechanism to be impacted, resulting in loss of control of the recording device;

[0015] 5) When the pressure relief mechanism is completed, the pump pressure and speed are too high, causing the pressure gauge to be impacted by additional pressure before it can fully receive the gas pressure;

[0016] 6) The volume of mud in the annulus below the sealing mechanism is too large, and the annular mud pressure on the pressure gauge is much greater than the coal seam gas pressure. Summary of the invention

[0017] In view of this, the present invention provides a ground borehole coal seam gas pressure measurement system and a working method thereof to solve various problems that occur when existing equipment measures coal seam gas pressure in ground boreholes. The system has a simple structure, is easy to operate and has better effects.

[0018] In order to overcome the problems existing in the prior art, the technical solution adopted by the present invention is: a ground drilled coal seam gas pressure measuring system, the measuring system is composed of a screen pipe, an expander, a packer and an oil pipe connected in series in sequence, a first pressure gauge is arranged at the bottom of the screen pipe, a second pressure gauge is arranged in the expander, a switch valve is arranged under the center pipe of the expander, and the oil pipe is connected to a high-pressure air pump through a pipeline.

[0019] Furthermore, a valve is provided on the pipeline between the oil pipe and the high-pressure air pump, and the valve adopts an air source high-pressure needle valve.

[0020] Furthermore, a pressure gauge is provided on the oil pipe, and the pressure gauge adopts a high-pressure shock-resistant pressure gauge.

[0021] Furthermore, the first pressure gauge and the second pressure gauge are electronic pressure gauges with high-precision storage; the first pressure gauge is used to monitor the sealing effect of the packer, the liquid column pressure in the hole, and the liquid column pressure in the test section after sealing; the second pressure gauge is used to record the changing trend of the target coal seam gas pressure over time.

[0022] Furthermore, the expander is a gas source pressure expander, and its outer diameter matches the borehole diameter of the pressure measuring chamber.

[0023] Furthermore, the outer diameter of the packer matches the test borehole diameter.

[0024] Furthermore, the high-pressure air pump is a high-pressure air source air pump.

[0025] The steps of a working method of a ground borehole coal seam gas pressure measurement system are as follows:

[0026] 1) Connect the screen, expander, packer and tubing in sequence and place them in the borehole. The bottom of the packer should be placed within 1.0m above the top of the coal seam roof. The smaller the distance, the better the test effect. The positions of the upper and lower limits of the expander should match the buried depth of the top and bottom plates of the coal seam.

[0027] 2) Keep the switch valve in the closed state, open the valve, and use a high-pressure air pump to expand the expander. After the expander is expanded, its rubber tube is fully in contact with the borehole wall to discharge the drilling fluid in the pressure measuring chamber to achieve the purpose of pressure relief and prepare for gas production and flow;

[0028] 3) After the expander is in full contact with the hole wall, keep the expanded state, close the valve, slowly return the high-pressure air pump to zero pressure, set the packer according to the packer model, and after the packer is set, slowly open the valve to release the expander. After the expansion, the pressure measuring chamber is in a near-vacuum environment; at this time, the pressure measuring chamber is completely isolated by the packer into an independent pressure system, and the pressure in the pressure measuring chamber is much lower than the coal seam gas pressure. The coal seam gas pressure flows from the inside of the coal seam to the hole under the action of the pressure difference.

[0029] 4) Open the switch valve. Under the action of pressure difference, the gas in the pressure measuring chamber passes through the screen pipe and the switch valve to the vicinity of the second pressure gauge. The coal seam gas pressure in the pressure measuring chamber reaches a new balance. The second pressure gauge and the first pressure gauge record the pressure changes during the entire test process.

[0030] 5) Coal seam gas pressure, obtained by analyzing the curve of coal seam gas pressure variation over time collected by the second pressure gauge;

[0031] 6) The hydrostatic pressure gradient of the formation at 100 meters is obtained by analyzing the pressure change curve of the monitoring pressure point collected by the monitoring pressure over time;

[0032] 7) Information such as the original coalbed methane gas composition, methane concentration, and formation liquid composition is obtained by analyzing and testing the collected original coalbed methane samples and formation liquid samples.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] 1) The present invention can meet the requirements for measuring the gas pressure of coal seams in ground boreholes, and has a simple structure, convenient operation, and can be used repeatedly.

[0035] 2) The present invention adopts an instrument combination of a packer + expander + switch valve + pressure gauge + screen tube, and utilizes the action coordination of the expander and the packer to achieve the purpose of pressure relief in the pressure measuring chamber, and utilizes the pressure difference to produce gas and reach a balanced state. While obtaining the coal seam gas pressure, it can also obtain information such as the hydrostatic pressure gradient of the formation per 100 meters, the original coal seam gas composition and methane concentration, and the formation liquid composition.

[0036] 3) During the measurement process of the present invention, the borehole annular pressure and the packer setting effect can be monitored; the change trend of the target coal seam gas pressure over time can be recorded;

[0037] 4) This measuring system can obtain coal seam gas pressure, and can obtain information such as coal seam gas pressure, hydrostatic pressure gradient per 100 meters of the formation, original coal seam gas composition and methane concentration, and formation liquid composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the structure of the present invention.

[0039] Marking instructions: 1—screen; 2—first pressure gauge; 3—on-off valve; 4—expander; 5—second pressure gauge; 6—packer; 7—oil pipe; 8—pressure gauge; 9—valve; 10—high-pressure air pump, 11—borehole, 12—pressure measuring chamber. DETAILED DESCRIPTION

[0040] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] This embodiment is a ground borehole coal seam gas pressure measurement system, such as Figure 1 As shown, it includes a screen tube 1, a monitoring pressure gauge 2, a switch valve 3, an expander 4, a pressure gauge 5, a packer 6, an oil pipe 7, a pressure gauge 8, a valve 9, and a high-pressure air pump 10; the screen tube 1, the expander 4, the packer 6 and the oil pipe 7 are sequentially connected to form a pipe string, a first pressure gauge 2 is arranged at the bottom of the screen tube 1, the pressure gauge 5 is placed at the thread plug inside the center pipe of the expander 4, the switch valve 3 is placed at the lower boundary of the center pipe of the expander 4, and the oil pipe 7 is connected to the high-pressure air pump 10 through a pipeline.

[0043] As an implementation method in this embodiment, a valve 9 is provided on the pipeline between the oil pipe 7 and the high-pressure air pump 10 .

[0044] As an implementation method in this embodiment, a pressure gauge 8 is also provided on the oil pipe 7, and the pressure gauge 8 adopts a high-pressure anti-vibration pressure gauge; the valve 9 adopts an air source high-pressure needle valve, the bearing pressure is not less than 35.0MPa, and the size is not required;

[0045] As an implementation method in this embodiment, the first pressure gauge 2 and the second pressure gauge 5 are electronic pressure gauges with high-precision storage; the first pressure gauge 2 is used to monitor the sealing effect of the packer, the liquid column pressure in the hole, and the liquid column pressure in the test section after sealing; the second pressure gauge 5 is used to record the changing trend of the target coal seam gas pressure over time.

[0046] As an implementation method in this embodiment, the expander 4 is a gas source pressure expander, and its outer diameter matches the borehole diameter of the pressure measuring chamber 11; the working pressure difference is not less than 15MPa, the bearing pressure is not less than 25.0MPa, and the expansion coefficient is not less than 2.0. The length of the expander 4 should be close to the thickness of the target coal seam, and the positions of the upper and lower limits of the expander 4 match the buried depth of the top and bottom plates of the coal seam.

[0047] As an implementation method in this embodiment, the packer 6 is a common packer in the industry, and its outer diameter matches the test borehole diameter; the working pressure difference is not less than 20MPa, the bearing pressure is not less than 35.0MPa, and the expansion coefficient is not less than 1.4; the bottom of the packer 6 should be placed within 1.0m of the upper part of the coal seam roof, and the smaller the distance, the better the test effect.

[0048] As an implementation method in this embodiment, the high-pressure air pump 10 is a high-pressure air source air pump.

[0049] A working method of a ground borehole coal seam gas pressure measurement system, comprising the following steps:

[0050] 1) Connect the screen 1, expander 4, packer 6 and tubing 7 in sequence. Each component is connected by threaded connection. The connection method is not limited to that shown in the example figure. Put them into the borehole 11. The bottom of the packer 6 should be placed within 1.0m of the upper part of the coal seam roof. The smaller the distance, the better the test effect. The upper and lower limits of the expander 4 match the buried depth of the coal seam roof and bottom plates.

[0051] 2) Keep the switch valve 3 in the closed state, open the valve 9, and the expander 4 is provided with a high-pressure gas source by the high-pressure air pump 10. The high-pressure gas reaches the upper limit of the expander 4 through the high-pressure air pump 10, the valve 9, and the oil pipe 7, and enters the inside of the expander 4 through the guide hole on the upper limit of the central tube of the expander 4, so that the expander 4 expands slowly. After the expander 4 expands, its rubber tube is fully in contact with the wall of the borehole 11 to discharge the drilling fluid in the pressure measuring chamber 12, so as to achieve the purpose of pressure relief and prepare for the gas production flow;

[0052] The expander 4 is composed of a central tube, an upper connecting handle, a rubber tube, a connecting handle, a lower connecting handle, and an internal plug. Its outer diameter must match the aperture of the pressure measuring chamber. The length of each section of the rubber tube is not limited to 1.0m, and multiple sections can be used depending on the thickness of the pressure measuring chamber. A guide hole is provided on the upper boundary of the central tube, and the internal plug is located at the upper boundary of the central tube and below the guide hole. The pressure gauge 5 is placed on the lower disk of the internal plug. The switch valve 3 is placed at the lower boundary of the central tube. There is a certain independent space between the internal plug and the switch valve 3, and its volume should be approximately equal to the hollowed volume of the pressure measuring chamber after being expanded by the expander 4.

[0053] When the expander 4 is under pressure, the rubber tube expands, and when the pressure is released, the rubber tube naturally shrinks and recovers under the action of the rubber and spring steel belt;

[0054] The central tube of the expander 4 can be used as a closed container to collect coal seam gas and formation liquid.

[0055] 3) After the expander is in full contact with the hole wall, keep the expanded state, close the valve 9, slowly return the pump pressure of the high-pressure air pump 10 to zero, set the packer 6 according to the packer model, and after the packer 6 is set, slowly open the valve 9 to release the expansion of the expander 4, so that the pressure measuring chamber 12 is in a near-vacuum environment; at this time, the pressure measuring chamber 11 is completely isolated by the packer 6 into an independent pressure system, and the pressure in the pressure measuring chamber 12 is much lower than the coal seam gas pressure. The coal seam gas pressure flows from the inside of the coal seam to the hole under the action of the pressure difference.

[0056] 4) Open the switch valve 3. Under the action of the pressure difference, the gas in the pressure measuring chamber 12 reaches the vicinity of the second pressure gauge 5 through the screen pipe 1 and the switch valve 3. After a sufficiently long time (this time depends on the characteristics of the coal seam. The coal seam has a high permeability and takes a short time, while the coal seam has a low permeability and takes a long time), the coal seam gas pressure in the pressure measuring chamber 11 reaches a new balance. The second pressure gauge 5 and the first pressure gauge 2 record the pressure changes during the entire test process.

[0057] 5) Coal bed gas pressure, obtained by analyzing the curve of coal bed gas pressure variation over time collected by the second pressure gauge 5;

[0058] 6) The hydrostatic pressure gradient of the formation at 100 meters is obtained by analyzing the pressure variation curve of the monitoring pressure point collected by the first pressure gauge 2 over time;

[0059] 7) Information such as the original coalbed methane gas composition, methane concentration, and formation liquid composition is obtained by analyzing and testing the collected original coalbed methane samples and formation liquid samples.

[0060] The specific working methods are:

[0061] 1. Match the models of packer 6 and expander 4 according to the aperture. The length of expander 4 should be close to the thickness of the target coal seam;

[0062] 2. Measure the sizes of screen tube 1, expander 4, adjusting handle, packer 6 and tubing 7; the bottom of packer 6 should be placed within 1.0m of the upper part of the coal seam roof. The smaller the distance, the better the test effect; the positions of the upper and lower limits of expander 4 should match the buried depth of the coal seam roof and floor;

[0063] 3. The second pressure gauge 5 and the first pressure gauge 2 are programmed to collect one data point every 1 second;

[0064] 4. The pressure gauge 5 is placed at the plug inside the center tube of the expander 4, and the plug is checked for tightness; the switch valve 3 is placed at the lower boundary of the center tube of the expander 4; the monitoring pressure gauge 2 is placed inside the screen tube 1;

[0065] 5. Connect the screen pipe 1, the switch valve 3, the expander 4, the regulating handle, the packer 6, the oil pipe 7 and other pipe strings in sequence;

[0066] 6. Keep the switch valve 3 in the closed state; slowly insert the test tube string into the hole, tighten each joint and keep it sealed;

[0067] 7. During the process of stringing the pipe into the hole, pause for 5 minutes every 100 meters; after the packer 6 reaches the predetermined position, let it stand for more than 30 minutes;

[0068] 8. Install the orifice device and connect it to the ground high-pressure air pump 10; keep the valve 9 in the closed state;

[0069] 9. Start the high-pressure air pump 10, open the valve 9, and slowly adjust the pump pressure to no less than 5.0 MPa; the high-pressure gas reaches the upper boundary of the expander 4 through the high-pressure air pump 10, the valve 9, and the oil pipe 7, and enters the inside of the expander 4 through the guide hole on the upper boundary of the center tube of the expander 4, so that the expander 4 slowly expands; after the expander 4 expands, its rubber tube is fully in contact with the hole wall to discharge the drilling fluid in the pressure measuring chamber, so as to prepare for the gas production flow;

[0070] 10. After the expander is in full contact with the hole wall, keep the expansion state, close the valve 9, and slowly return the pump pressure of the high-pressure air pump 10 to zero;

[0071] 11. Release the high-pressure manifold at the orifice and set the packer 6 according to the packer model;

[0072] 12. After the packer 6 is effectively sealed, connect the orifice high-pressure manifold; slowly open the valve 9, and the expander 4 slowly shrinks and recovers under the action of the rubber tube contraction force after losing the support of the high-pressure gas; under the action of the pressure difference, the gas is produced;

[0073] 13. Open the switch valve 3, and the gas in the pressure measuring room passes through the screen pipe 1 and the switch valve 3 to reach the vicinity of the pressure gauge 5;

[0074] 14. After a period of time, when the gas is fully flowing and balanced, close the switch valve 3 and the test is finished; the second pressure gauge 5 and the first pressure gauge 2 record the pressure changes during the entire test process;

[0075] 15. Disassemble the wellhead device and unseal the packer 6 according to the packer model;

[0076] 16. Lift up the test tube string;

[0077] 17. After the equipment reaches the ground, open the switch valve 3 to collect the original coal seam gas and formation liquid inside the central tube of the expander 10, and further obtain the gas gas component through the original coal seam gas; and further obtain the formation liquid component through the formation liquid;

[0078] 18. Replay the data stored in the second pressure gauge 5 and the first pressure gauge 2, and analyze the data to obtain the coal seam gas pressure.

[0079] In the above description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed above.

[0080] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A ground borehole coal seam gas pressure measurement system, characterized in that: The measuring system is composed of a screen tube (1), an expander (4), a packer (6) and an oil pipe (7) which are connected in series in sequence. A first pressure gauge (2) is arranged at the bottom of the screen tube (1), a second pressure gauge (5) is arranged in the expander (4), a switch valve (3) is arranged under the center pipe of the expander (4), and the oil pipe (7) is connected to a high-pressure air pump (10) through a pipeline.

2. A ground borehole coal seam gas pressure measurement system according to claim 1, characterized in that: A valve (9) is provided on the pipeline between the oil pipe (7) and the high-pressure air pump (10), and the valve (9) is an air source high-pressure needle valve.

3. A ground borehole coal seam gas pressure measurement system according to claim 1 or 2, characterized in that: The oil pipe (7) is also provided with a pressure gauge (8), and the pressure gauge (8) is a high-pressure shock-resistant pressure gauge.

4. A ground borehole coal seam gas pressure measurement system according to claim 3, characterized in that: The first pressure gauge (2) and the second pressure gauge (5) are electronic pressure gauges with high-precision storage. The first pressure gauge (2) is used to monitor the sealing effect of the packer, the liquid column pressure in the hole, and the liquid column pressure in the test section after the packer. The second pressure gauge (5) is used to record the change trend of the target coal seam gas pressure over time.

5. A ground borehole coal seam gas pressure measurement system according to claim 4, characterized in that: The expander (4) is a gas source pressure expander, and its outer diameter matches the borehole diameter of the pressure measuring chamber (11).

6. A ground borehole coal seam gas pressure measurement system according to claim 5, characterized in that: The outer diameter of the packer (6) matches the diameter of the test borehole.

7. A ground borehole coal seam gas pressure measurement system according to claim 6, characterized in that: The high-pressure air pump (10) is a high-pressure air source air pump.

8. The working method of a ground borehole coal seam gas pressure measurement system according to claim 1, characterized in that: 1) Connect the screen (1), expander (4), packer (6) and tubing (7) in sequence and place them in the borehole (11). The bottom of the packer (6) should be placed within 1.0 m of the upper part of the coal seam roof. The smaller the distance, the better the test effect. The upper and lower limits of the expander (4) should match the buried depth of the coal seam roof and bottom plates. 2) Keep the switch valve (3) in the closed state, open the valve (9), and use the high-pressure air pump (10) to expand the expander (4). After the expander (4) is expanded, its rubber tube is fully in contact with the wall of the borehole (11) to discharge the drilling fluid in the pressure measuring chamber (12), thereby achieving the purpose of pressure relief and preparing for the flow of gas production; 3) After the expander is in full contact with the hole wall, the expanded state is maintained, the valve (9) is closed, and the pump pressure of the high-pressure air pump (10) is slowly reduced to zero. The packer (6) is set according to the packer model. After the packer (6) is set, the valve (9) is slowly opened to release the expansion of the expander (4). After that, the pressure measuring chamber (12) is in a near-vacuum environment. At this time, the pressure measuring chamber (11) is completely isolated by the packer (6) to form an independent pressure system, and the pressure in the pressure measuring chamber (12) is much lower than the coal seam gas pressure. The coal seam gas pressure flows from the coal seam to the hole under the action of the pressure difference. 4) Open the on-off valve (3), and under the action of the pressure difference, the gas in the pressure measuring chamber (12) passes through the screen pipe (1) and the on-off valve (3) to reach the vicinity of the second pressure gauge (5), and the coal seam gas pressure inside the pressure measuring chamber (11) reaches a new equilibrium. The second pressure gauge (5) and the first pressure gauge (2) record the pressure change during the entire test process; 5) Coal seam gas pressure, obtained by analyzing the curve of coal seam gas pressure variation over time collected by the second pressure gauge (5); 6) The hydrostatic pressure gradient of the formation per 100 meters is obtained by analyzing the pressure-time curve of the monitoring pressure point collected by monitoring pressure (2); 7) Information such as the original coalbed methane gas composition, methane concentration, and formation liquid composition is obtained by analyzing and testing the collected original coalbed methane samples and formation liquid samples.

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