Passive ground drilling coal seam original gas pressure measuring device and working method thereof

Abstract

The invention relates to a passive ground drilling coal seam original gas pressure measuring device and a working method thereof. The method aims to measure the original gas pressure of a coal seam in ground drilling. The device is composed of a pipe string and a wellhead device, a pressure relief bin is arranged at the bottom of the pipe string, and a lower packer, a screen pipe, an upper packer and a drill rod are sequentially arranged on the upper portion of the pressure relief bin; a coal seam is arranged between the lower packer and the upper packer; a first switch valve and a second switch valve are respectively arranged between the screen pipe and the upper and lower packers; the wellhead device is arranged at the top of the drill rod and is provided with a pressure gauge and a gas flowmeter; sending the packer into a preset position in the hole by a drill rod or an oil pipe, and inducing gas to be output and flow by opening and closing a switch valve according to the test duration and the working system, and achieving a pressure balance state; and recording the pressure change conditions of different positions and different stages so as to obtain the original gas pressure of the coal seam. 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 gas pressure measurement in geological exploration, and in particular to a passive ground-drilled coal seam original gas pressure measurement device and a working method thereof, which is suitable for measuring the original gas pressure of coal seams during ground drilling (or well drilling) construction or after completion of drilling (or drilling). Background Art

[0002] The technology of measuring the original gas pressure of coal seams through ground drilling is an effective method to obtain the original gas pressure of coal seams through ground drilling during the geological exploration period or the supplementary exploration period of coal fields. The original gas pressure of coal seams obtained can move the gas prevention and control threshold forward, provide data support for coal mine disaster type evaluation, coal mine development design, and coal mine construction, and can also provide basic parameters and technical support for predicting the danger of gas outbursts and formulating reasonable gas prevention and control measures.

[0003] Under the guidance of the idea of ​​moving the gas prevention threshold forward, the Coal and Peat Geological Exploration Specification (DZ / T0215-2002) published in 2002 clearly stipulates that the general requirements for gas coal sample analysis and testing items include coal seam gas pressure (measured in boreholes); the Basic Requirements for Safety Approval of Coal Mine Construction Projects (AQ 1049-2008) in 2008 requires that the coal seam gas work in the field geological exploration report requires measurement parameters including: coal seam gas pressure (measured in boreholes); the F.4.3.5 of the Coal Geological Exploration Specification for Mineral Resources (DZ / T 0215-2020) revised in 2020 clearly requires that the following items should be added during the exploration stage, with no less than five points for each main mineable coal seam (for mines with an area of ​​less than 5km2); 2 The factors to be considered are: coal solidity coefficient f, gas emission initial velocity △P, coal adsorption isotherm test on biogas, coal porosity and permeability, and coal seam gas pressure (measured in drilling).

[0004] Although relevant standards and specifications have stipulated the measurement of coal seam gas pressure in ground boreholes, this technology has not been promoted due to the immaturity of the technology and equipment for measuring coal seam gas pressure in ground boreholes. Summary of the invention

[0005] In view of this, in order to solve the technical problem of measuring the original gas pressure of coal seams in ground boreholes, the present invention provides a passive ground borehole coal seam original gas pressure measuring device and a working method thereof, which has a simple structure, is easy to operate, and can be used repeatedly, thereby realizing the measurement of the original gas pressure of coal seams in ground boreholes.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a passive ground-drilled coal seam original gas pressure measuring device, the pressure measuring device is composed of a pipe string and a wellhead device, the bottom of the pipe string is a pressure relief chamber, and the upper part of the pressure relief chamber is a lower packer, a screen pipe, an upper packer and a drill pipe in sequence; there is a coal seam between the lower packer and the upper packer, and a first switch valve and a second switch valve are respectively arranged between the screen pipe and the lower packer and the upper packer, and the wellhead device is a pressure gauge and a gas flow meter, and the pressure gauge and the gas flow meter are connected to the top of the drill pipe.

[0007] Furthermore, a first monitoring pressure gauge is provided on the top of the pressure relief chamber.

[0008] Furthermore, a second monitoring pressure gauge is provided in the drill pipe.

[0009] Furthermore, a pressure gauge is arranged inside the screen tube.

[0010] The working method of the passive ground-drilled coal seam original gas pressure measuring device includes the following steps:

[0011] 1) Connect the pressure relief chamber, lower packer, screen tube, upper packer and drill pipe in sequence to form a pipe string;

[0012] 2) Keep the first switch valve and the second switch valve in the closed state; send the pipe string into the borehole so that the screen pipe is at the coal seam; stop for 5 minutes every 100 meters when the pipe string enters the hole to detect the formation pressure gradient;

[0013] 3) After the pipe string reaches the predetermined position, the wellhead device is installed and left to stand for more than 1.0-2.0 hours to eliminate the pressure disturbance on the coal seam caused by the pipe string entering the hole;

[0014] 4) Set the upper and lower packers at the same time, so that they are close to the borehole wall. The internal and external pressure difference of the packer should not be less than 10MPa, and the pressure difference of the packer should be more than 1.2 times of the formation pressure. After the packer is set, let it stand for at least 0.5-1.0h to eliminate pressure disturbance;

[0015] 5) Open the first switch valve, and all the drilling fluid between the upper and lower packers (pressure measuring chamber) enters the pressure relief chamber through the first switch valve under the action of gravity and pressure difference, which serves the purpose of relieving the pressure of the pressure measuring chamber, unblocking the coal seam, eliminating pollution in the near-well area, opening up the seepage channel, and creating conditions for gas production;

[0016] 6) As the drilling fluid flows into the pressure relief chamber, the gas flows into the pressure measuring chamber under the action of the pressure difference; after reaching the designed opening time, close the first switch valve and wait for the gas to fill the pressure measuring chamber;

[0017] 7) Open the second on-off valve, and the coal seam gas enters the drill pipe through the pressure measuring chamber and the second on-off valve under the action of the pressure difference, so that the gas at the far end of the coal seam fully flows and enters the drill pipe; the surface pressure gauge and gas flow meter are used to record the changes in the gas pressure and flow in the pipe string;

[0018] 8) After reaching the designed second opening time, close the second on-off valve, so that the gas pressure in the pressure measuring chamber gradually tends to balance with the gas pressure in the remote coal seam, and the test is finished;

[0019] 9) Remove the wellhead equipment and unseal the upper and lower packers;

[0020] 10) The pipe string is pulled out and the pressure gauge data is read. During the test, the pressure gauge, the first monitoring pressure gauge and the second monitoring pressure gauge record the pressure changes at each stage of the test. The original gas pressure value of the coal seam is obtained by analyzing the data of the pressure gauge, the first monitoring pressure gauge and the second monitoring pressure gauge.

[0021] Compared with the prior art, the present invention has the following advantages and effects:

[0022] 1. The present invention adopts a double packer, so that the pressure measuring chamber is in an independent pressure system; and can effectively control the volume of the pressure measuring chamber, reducing the influence of the invalid pressure measuring chamber volume on the gas pressure measurement result.

[0023] 2. The present invention can unload the drilling mud in the pressure measuring chamber through the opening action of the first switch valve, unblock the coal seam, eliminate pollution in the near-wellbore area, open the seepage channel, and create conditions for gas production; the closing action aims to induce the gas in the near-hole area to be smoothly produced through the seepage channel.

[0024] 3. The present invention allows the gas at the far end of the coal seam to flow fully through the second opening action of the second switch valve; and the second closing action allows the gas pressure in the pressure measuring chamber to gradually balance with the gas pressure in the far end coal seam, thereby obtaining the original gas pressure of the coal seam.

[0025] 4. The present invention uses three pressure gauges to monitor the changes in the pressure in the hole at different positions and at different time periods.

[0026] 5. The first switch valve and the second switch valve of the present invention can set different working systems according to the requirements of the original gas pressure measurement of the ground drilled coal seam, for example: one open and one closed, two open and two closed, two open and one closed, three open and two closed, three open and three closed, four open and four closed, etc.

[0027] 6. The present invention has a simple structure, is easy to operate, can be used repeatedly, and can be used to measure the original gas pressure of the coal seam in a ground borehole. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1This is the structure diagram of the passive ground-drilled coal seam original gas pressure measuring device;

[0029] Marking instructions: 1—pressure relief chamber; 2—first monitoring pressure gauge; 3—lower packer; 4—first switch valve; 5—screen pipe; 6—pressure gauge; 7—second switch valve; 8—upper packer; 9—second monitoring pressure gauge; 10—drill pipe; 11—pressure gauge; 12—flow meter; 13—borehole; 14—pressure measuring chamber. DETAILED DESCRIPTION

[0030] 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.

[0031] 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.

[0032] The present invention is used to measure the original gas pressure of coal seams in ground drilling, and relates to a passive ground drilling coal seam original gas pressure measuring device and its working method, which is suitable for measuring the original gas pressure of coal seams during ground drilling (or drilling) construction or after completion of drilling (or drilling). Figure 1 As shown, it is composed of a pipe string and a wellhead device, wherein the pipe string includes, from bottom to top, a pressure relief chamber 1, a lower packer 3, a screen 5, an upper packer 8 and a drill pipe 10;

[0033] As an implementation method in this embodiment, a second monitoring pressure gauge 9 is arranged in the drill pipe 10; there is a coal seam between the lower packer 3 and the upper packer 8, and a first switch valve 4 and a second switch valve 7 are respectively arranged between the screen pipe 5 and the lower packer 3 and the upper packer 8, and a pressure gauge 6 is arranged inside the screen pipe 5; the wellhead device is a pressure gauge 11 and a gas flow meter 12, and the pressure gauge 11 and the gas flow meter 12 are connected to the top of the drill pipe 10.

[0034] As an implementation method in this embodiment, a first monitoring pressure gauge 2 is provided on the top of the pressure relief chamber 1, and its inlet is connected to the lower end of the lower seal 3. Its volume should be more than 1.2 times the volume of the pressure measuring chamber, and its pressure bearing capacity should be more than 1.5 times the formation pressure.

[0035] As an implementation method in this embodiment, the upper end of the lower packer 3 is connected to the lower end of the switch valve 4, and its setting pressure difference should be greater than 20.0 MPa; its working outer diameter matches the test aperture.

[0036] As an implementation method in this embodiment, the upper end of the switch valve 4 is connected to the lower end of the screen pipe 5, and its working pressure should be more than 1.5 times greater than the formation pressure.

[0037] As an implementation method in this embodiment, a pressure gauge 6 is built into the screen tube 5, and the upper end of the pressure gauge 6 is connected to the lower end of the switch valve 2 7.

[0038] As an implementation method in this embodiment, the upper end of the switch valve 2 7 is connected to the lower end of the upper packer 8, and its working pressure should be more than 1.5 times greater than the formation pressure.

[0039] As an implementation method in this embodiment, a second monitoring pressure gauge 9 is placed inside the upper end of the upper packer 8 and connected to the drill pipe 10. The setting pressure difference should be greater than 20.0 MPa; its working outer diameter matches the test aperture.

[0040] As an implementation method in this embodiment, a pressure gauge 11 and a flow meter 12 are installed at the orifice of the drill pipe 10 .

[0041] As an implementation method in this embodiment, the performance of the pressure gauge 11 and the flow meter 12 should meet the requirements of relevant standards and specifications.

[0042] The overall system pressure of the device of the present invention should be more than 1.5 times greater than the formation pressure.

[0043] The working method of the passive ground-drilled coal seam original gas pressure measuring device of the present invention comprises the following steps:

[0044] Preparation:

[0045] 1. Match equipment and instruments according to different purposes, test duration and working system (taking the two-on and two-off working system as an example) of the original gas pressure measurement of ground borehole coal seams;

[0046] 2. Calibrate equipment and instruments on the ground to ensure that they achieve optimal performance after entering the hole;

[0047] Specific working methods:

[0048] 1. Connect the pressure relief chamber 1, the lower packer 3, the screen tube 5, the upper packer 8 and the drill pipe 10 in sequence to form a pipe string;

[0049] 2. Keep the first switch valve 4 and the second switch valve 7 in the closed state; send the pipe string into the borehole 13 so that the screen pipe 5 is at the coal seam; stop for 5 minutes every 100 meters when the pipe string enters the hole to detect the formation pressure gradient;

[0050] 3. After the pipe string reaches the predetermined position, install the wellhead device and leave it to stand for more than 1.0-2.0 hours to eliminate the pressure disturbance on the coal seam caused by the pipe string entering the hole;

[0051] 4. Set the upper and lower packers at the same time, so that they are close to the wall of the borehole 13. The internal and external pressure difference of the packer is not less than 10MPa, and the pressure difference of the packer should be more than 1.2 times of the formation pressure. After the packer is set, let it stand for at least 0.5-1.0h to eliminate pressure disturbance;

[0052] 5. Open the first switch valve 4. All the drilling fluid between the upper and lower packers (pressure measuring chamber) enters the pressure relief chamber 1 through the first switch valve 4 under the action of gravity and pressure difference, which serves the purpose of relieving the pressure of the pressure measuring chamber, unblocking the coal seam, eliminating pollution in the near-well zone, opening up the seepage channel, and creating conditions for gas production;

[0053] 6. As the drilling fluid flows into the pressure relief chamber 4, the gas flows into the pressure measuring chamber under the action of the pressure difference; after reaching the designed opening time, close the first switch valve 4 and wait for the gas to fill the pressure measuring chamber 14;

[0054] The opening time is quantified according to the volume of drilling fluid in the coal seam pressure measuring chamber. During the opening time, it is necessary to ensure that all the drilling fluid in the pressure measuring chamber flows into the pressure relief chamber.

[0055] 7. Open the second switch valve 7. The coal seam gas enters the drill pipe 10 through the pressure measuring chamber 14 and the second switch valve 7 under the action of the pressure difference, so that the gas at the far end of the coal seam fully flows and enters the drill pipe 10; the surface pressure gauge 11 and the gas flow meter 12 are used to record the changes in the gas pressure and flow in the pipe string;

[0056] 8. After reaching the designed second opening time, close the second switch valve 7. After a period of time, the gas pressure in the pressure measuring chamber 14 gradually reaches equilibrium with the gas pressure in the remote coal seam, and the test is finished;

[0057] The second opening time is determined according to the gas pressure. The higher the gas pressure, the longer the time required.

[0058] 9. Remove the wellhead equipment and unseal the upper and lower packers;

[0059] 10. Remove the pipe string and read the data of the pressure gauge 6. During the test, the pressure gauge 6, the first monitoring pressure gauge 2, and the second monitoring pressure gauge 9 record the pressure changes at each stage of the test. The original gas pressure value of the coal seam is obtained by analyzing the data of the pressure gauge 6, the first monitoring pressure gauge 2, and the second monitoring pressure gauge 9.

[0060] The structure of the present invention can also be arranged in an oil pipe for use, and the oil pipe is used to replace the drill rod 10, and the packer is sent to a predetermined position in the hole by the drill rod or the oil pipe.

[0061] 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. Passive ground-drilled coal seam original gas pressure measuring device, characterized by: The pressure measuring device is composed of a pipe string and a wellhead device. The bottom of the pipe string is a pressure relief chamber (1). The upper part of the pressure relief chamber (1) is composed of a lower packer (3), a screen tube (5), an upper packer (8) and a drill pipe (10) in sequence. A coal seam is located between the lower packer (3) and the upper packer (8). A first switch valve (4) and a second switch valve (7) are provided between the screen tube (5) and the lower packer (3) and the upper packer (8), respectively. The wellhead device is a pressure gauge (11) and a gas flow meter (12). The pressure gauge (11) and the gas flow meter (12) are connected to the top of the drill pipe (10).

2. The passive ground-drilled coal seam original gas pressure measuring device according to claim 1 is characterized by: A first monitoring pressure gauge (2) is provided on the top of the pressure relief chamber (1).

3. The passive ground-drilled coal seam original gas pressure measuring device according to claim 1 or 2, characterized in that: A second monitoring pressure gauge (9) is arranged inside the drill rod (10).

4. The passive ground-drilled coal seam original gas pressure measuring device according to claim 3 is characterized by: A pressure gauge (6) is arranged inside the screen tube (5).

5. The working method of the passive ground-drilled coal seam original gas pressure measuring device according to claim 1 is characterized by: The steps are: 1) connecting the pressure relief chamber (1), the lower packer (3), the screen tube (5), the upper packer (8) and the drill pipe (10) in sequence to form a pipe string; 2) Keep the first on-off valve (4) and the second on-off valve (7) in a closed state; send the pipe string into the borehole (13) so that the screen pipe (5) is located at the coal seam; stop for 5 minutes every 100 meters when the pipe string enters the borehole to detect the formation pressure gradient; 3) After the pipe string reaches the predetermined position, the wellhead device is installed and left to stand for more than 1.0-2.0 hours to eliminate the pressure disturbance on the coal seam caused by the pipe string entering the hole; 4) The upper and lower packers are set at the same time so that they are in close contact with the borehole wall (13). The internal and external pressure difference of the packer is not less than 10 MPa, and the pressure difference of the packer should be greater than 1.2 times of the formation pressure. After the packer is set, it is left to stand for at least 0.5-1.0 h to eliminate pressure disturbance. 5) Open the first on-off valve (4), and all the drilling fluid between the upper and lower packers (pressure measuring chamber) enters the pressure relief chamber (1) through the first on-off valve (4) under the action of gravity and pressure difference, thereby achieving the purpose of relieving the pressure of the pressure measuring chamber, unblocking the coal seam, eliminating pollution in the near-wellbore area, opening up the seepage channel, and creating conditions for gas production; 6) As the drilling fluid flows into the pressure relief chamber (4), the gas flows into the pressure measuring chamber under the action of the pressure difference; after reaching the designed opening time, the first switch valve (4) is closed, and the gas is allowed to fill the pressure measuring chamber (14); 7) Open the second on-off valve (7), and the coal seam gas enters the drill pipe (10) through the pressure measuring chamber (14) and the second on-off valve (7) under the action of the pressure difference, so that the gas at the far end of the coal seam fully flows and enters the drill pipe (10); the changes in the gas pressure and flow rate in the pipe string are recorded by the surface pressure gauge (11) and the gas flow meter (12); 8) After reaching the designed second opening time, the second on-off valve (7) is closed, so that the gas pressure in the pressure measuring chamber (14) gradually reaches equilibrium with the gas pressure in the remote coal seam, and the test is ended; 9) Dismantle the wellhead equipment and unseal the upper and lower packers; 10) The pipe string is pulled out and the data of the pressure gauge (6) is read. During the test, the pressure gauge (6), the first monitoring pressure gauge (2), and the second monitoring pressure gauge (9) record the pressure changes at each stage of the test. The original gas pressure value of the coal seam is obtained by analyzing the data of the pressure gauge (6), the first monitoring pressure gauge (2), and the second monitoring pressure gauge (9).

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