CN113123785B - Method for measuring and calculating standard effective extraction radius of coal mine gas extraction - Google Patents
Method for measuring and calculating standard effective extraction radius of coal mine gas extraction Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
- E21B49/008—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells by injection test; by analysing pressure variations in an injection or production test, e.g. for estimating the skin factor
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/006—Production of coal-bed methane
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F7/00—Methods or devices for drawing- off gases with or without subsequent use of the gas for any purpose
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
- G06F17/10—Complex mathematical operations
Abstract
The invention relates to the field of coal bed gas development and clean utilization, in particular to a method for measuring and calculating the standard effective extraction radius of coal mine gas extraction. The method comprises the following steps of S100-constructing the No. 1 extraction drill hole in the coal seam vertical coal wall with the coal seam not affected by faults, complete rock mass protection and no crack development. S200, constructing a No. 2 pressure observation drill hole at 0.5m of the right side of the No. 1 extraction drill hole, constructing a No. 3 pressure observation drill hole at 1.0m of the left side of the No. 1 extraction drill hole, constructing a No. 4 pressure observation drill hole at 1.5m of the right side of the No. 1 extraction drill hole, constructing a No. 5 pressure observation drill hole at 2.0m of the left side of the No. 1 extraction drill hole, and constructing a No. 6 pressure observation drill hole at 2.5m of the right side of the No. 1 extraction drill hole. S300, installing a positive pressure gauge and a negative pressure gauge in each pressure observation drill hole, and installing a gas extraction device in an extraction hole to extract gas. S400, recording the reading of a positive pressure gauge and a negative pressure gauge on the pressure observation drill hole. S500, determining the coal seam gas extraction radius.
Description
Technical Field
The invention relates to the field of coal bed gas development and clean utilization, in particular to a method for measuring and calculating the standard effective extraction radius of coal mine gas extraction.
Background
The gas seriously restricts the high-efficiency development of coal mines in China, and the improvement of gas extraction is the most effective way for controlling the gas. The gas extraction is improved, so that the air permeability of a coal seam can be changed, the extraction strength can be increased, and the number of extraction drill holes is increased. Obviously, the former is not easy to practice, so the number of drilled holes should be increased to improve gas extraction, wherein the coal seam gas extraction radius is the core for improving the gas extraction. The distance between every two extraction drill holes is too large, extraction blind areas are easy to form, gas extraction cannot achieve the effect, the distance is too small, and the waste of manpower and material resources can be caused when the drill holes are arranged too much, so that the reasonable gas extraction radius has extremely important significance for the effective extraction of the coal mine gas.
For the measurement of the gas extraction radius of a coal seam of a coal mine, China has no clear rule and specification for the moment. The method for measuring the extraction radius at the present stage of China comprises the following steps: (1) the method is a comprehensive measurement method of field measurement and numerical simulation. The method can quickly and conveniently obtain the coal bed gas extraction radius, the obtained coal bed gas extraction radius is data in an ideal state, characteristics such as anisotropy exist in the occurrence condition of the underground coal bed on a mine site, the simulation result cannot reflect the site condition under the influence of external conditions, and therefore the method cannot accurately measure the gas extraction radius. (2) Gas pressure drop method, gas content reduction method, gas flow method, gas tracer method, etc. The former has obtained a good result by adopting a pressure drop method to measure the gas extraction radius, but has some problems, such as more complex arrangement of pressure measuring holes, smaller test range and the like. The gas content reduction method and the gas flow method have the advantages that the measurement process is direct, the real gas extraction condition can be reflected more truly, and the measurement method and the calculation steps are required to be perfect. The gas tracing method is simple and easy to operate, but the reliability of gas is not high, the manual influence of field construction is large, and the measured influence radius of gas extraction is the radius of the gas extraction. In a word, the methods cannot accurately and effectively measure the coal bed gas extraction radius.
Therefore, it is necessary to find an effective and reliable method for measuring the coal seam gas extraction radius.
Disclosure of Invention
The invention provides a method for measuring and calculating the standard effective extraction radius of coal mine gas extraction, aiming at solving the problems of complex measurement process and lower accuracy of the existing method for measuring the extraction radius of a gas extraction borehole.
The invention adopts the following technical scheme: a method for measuring and calculating the standard-reaching effective extraction radius of coal mine gas extraction comprises the following steps,
s100, constructing a No. 1 extraction drill hole on the vertical coal wall of the coal seam with the coal seam not affected by the fault, relatively complete rock mass protection and no crack development, and then immediately sealing the hole by using a hole sealing device.
S200, constructing a 2# pressure observation drill hole at a position 0.5m on the right side of the 1# extraction drill hole, constructing a 3# pressure observation drill hole at a position 1.0m on the left side of the 1# extraction drill hole, constructing a 4# pressure observation drill hole at a position 1.5m on the right side of the 1# extraction drill hole, constructing a 5# pressure observation drill hole at a position 2.0m on the left side of the 1# extraction drill hole, constructing a 6# pressure observation drill hole at a position 2.5m on the right side of the 1# extraction drill hole, immediately sealing holes by using a hole sealing device after the construction of each pressure observation drill hole is completed, and ensuring the sealing holes to be tight.
S300, installing a positive pressure gauge and a negative pressure gauge in each pressure observation drill hole, and installing a gas extraction device in an extraction hole to extract gas after the pressure is stable.
S400-recording the reading of a positive pressure gauge and a negative pressure gauge on the pressure observation drill hole every 24h, and drawing a gas pressure-time change curve.
S500, determining the coal seam gas extraction radius according to the gas relative pressure index and the effective extraction radius formula.
The step S500 takes the following method,
s501, recording the gas pressure drop of each pressure observation drill hole.
S502-gas emission quantity Qm of working face3The method comprises the following steps that (1) min corresponds to a corresponding working face gas extraction rate eta according to the safety supervision total coal charge (2011) 163 of the temporary standard for coal mine gas extraction, a gas pressure drop corresponding to an effective gas extraction radius is calculated according to the corresponding working face gas extraction rate eta, the corresponding relation between a working face gas emission quantity Q and the gas pressure drop is obtained, and the gas pressure drop corresponding to the effective gas extraction radius is calculated as follows:
pc-residual gas pressure, MPa;
p-original gas pressure, MPa;
Δ𝑃sign boardEffectively extracting gas pressure drop percent corresponding to the radius;
eta-gas extraction rate,%.
S503, if the pressure drop of the nth pressure observation hole reaches the gas pressure drop corresponding to the gas emission quantity Q of the working face, and the pressure drop of the (n + 1) th pressure observation hole does not reach the gas pressure drop corresponding to the gas emission quantity Q of the working face, then the effective radius calculation formula of coal seam gas extraction is as follows:
in the formula, R is the effective extraction radius of coal bed gas, m;
Δ𝑃sign board-gas pressure drop,%, corresponding to the effective gas extraction radius;
Δ𝑃𝑛-the pressure drop,%, corresponding to the nth pressure observation hole;
Δ𝑃𝑛+1-pressure drop,%, corresponding to the n +1# pressure observation hole;
𝑟𝑛the distance m between the nth # pressure observation hole and the extraction hole;
𝑟𝑛+1the distance m between the n +1# pressure observation hole and the extraction hole.
Compared with the prior art, the invention has the advantages of moderate drilling height, simple construction, small engineering quantity and wide test range, is suitable for any coal seam needing gas extraction, can accurately measure the extraction radius of the coal seam gas through the gas pressure change of each pressure measuring hole, can avoid the formation of extraction blind areas due to overlarge drilling intervals, and can reasonably arrange the drill holes to save manpower, material resources and financial resources.
Drawings
FIG. 1 is a front view of a method for measuring and calculating a standard effective extraction radius of coal mine gas extraction;
FIG. 2 is a cross section of a method for measuring and calculating a standard effective extraction radius of coal mine gas extraction;
in the figure, 1 is a gas extraction borehole; 2. 3, 4, 5 and 6 are gas pressure observation drill holes; 7 is a negative pressure gauge, 8, 9, 10, 11 and 12 are positive and negative pressure gauges.
Detailed Description
A method for measuring and calculating the standard-reaching effective extraction radius of coal mine gas extraction comprises the following steps.
S100-drawing I, drawing II is a structural schematic diagram of the construction, as shown in drawing I, an extraction drill hole 1# is constructed in a place which is not affected by faults, relatively complete in rock mass protection and incapable of developing cracks, the hole depth is 30m, the drill diameter is 94mm, and then a hole is immediately sealed by a 'two-plugging one-injecting' hole sealing machine.
S200-as shown in the figure I, constructing a pressure observation drill hole 2# at the position of 0.5m on the right side of the extraction hole, constructing a pressure observation drill hole 3# at the position of 1.0m on the left side of the extraction hole, constructing a pressure observation drill hole 4# at the position of 1.5m on the right side of the extraction hole, constructing a pressure observation drill hole 5# at the position of 2.0m on the left side of the extraction hole, constructing a pressure observation drill hole 6# at the position of 2.5m on the right side of the extraction hole, immediately sealing holes by using two plugs and one injection after the construction of each pressure observation drill hole is finished, and ensuring the sealing holes to be tight.
The depth of the drill hole is 80m, the hole sealing depth is 8m, the hole sealing mode is 'two-plug one-injection' and each drill hole is kept on the same horizontal line and cannot deflect, so that the drill hole is constructed in place according to design parameters.
S300, installing a positive pressure gauge and a negative pressure gauge of-0.1 MPa to the pressure observation drill hole, and after the pressure is stabilized for 24 hours, installing a gas extraction device in the extraction hole to extract gas.
S400, recording the reading of a positive pressure gauge and a negative pressure gauge on the pressure observation drill hole every 24 hours, accurately recording 180 days, and drawing a gas pressure-time change curve;
s500-assuming that the absolute gas emission amount of the working surface is 10-20 m3And/min, when the gas extraction rate reaches 30%, the gas extraction rate reaches the standard, according to the table 1, when the gas pressure drop corresponding to the effective extraction radius is more than or equal to 51%, the gas extraction rate is determined as the extraction standard effective extraction range, and then the accurate effective extraction radius is obtained according to an effective extraction radius calculation formula.
The step S500 takes the following method,
s501, recording the gas pressure drop of each pressure observation drill hole.
S502-gas emission quantity Qm of working face3Corresponding the gas extraction rate eta of the corresponding working face to the total coal charge (2011) 163 of safety supervision according to the temporary standard of coal mine gas extraction, calculating the gas pressure drop corresponding to the effective gas extraction radius according to the gas extraction rate eta of the corresponding working face, and obtaining the corresponding relation between the gas emission quantity Q of the working face and the gas pressure drop, wherein the effective gas emission quantity Q is the gas pressure dropThe method for calculating the gas pressure drop corresponding to the extraction radius comprises the following steps:
pc-residual gas pressure, MPa;
p-original gas pressure, MPa;
Δ𝑃sign boardEffectively extracting gas pressure drop percent corresponding to the radius;
eta-gas extraction rate,%.
S503, if the pressure drop of the nth pressure observation hole reaches the gas pressure drop corresponding to the gas emission quantity Q of the working face, and the pressure drop of the (n + 1) th pressure observation hole does not reach the gas pressure drop corresponding to the gas emission quantity Q of the working face, then the effective radius calculation formula of coal seam gas extraction is as follows:
in the formula, R is the effective extraction radius of coal bed gas, m;
Δ𝑃sign-gas pressure drop,%, corresponding to the effective gas extraction radius;
Δ𝑃𝑛-the pressure drop,%, corresponding to the nth pressure observation hole;
Δ𝑃𝑛+1the pressure drop corresponding to the n +1# pressure observation hole is percent;
𝑟𝑛the distance m between the nth # pressure observation hole and the extraction hole;
𝑟𝑛+1the distance m between the n +1# pressure observation hole and the extraction hole.
The gas extraction rate requirements are different according to different coal seam contents and emission amounts; according to temporary Standard regulations on gas extraction of coal mines (safety supervision general coal charge (2011) 163), when the gas extraction rate of the working face meets the regulations in the table 1, the gas extraction effect is judged to reach the standard, so that the gas extraction radius is calculated according to the corresponding standard;
the relation between the gas extraction rate of the working face and the content and pressure of the residual gas is as follows:
in the formula, eta represents gas extraction rate,%;
-residual gas content, m 3/t;
w is the original gas content, m 3/t;
-residual gas pressure, MPa;
-original gas pressure, MPa;
alpha is the coal bed gas content coefficient, m 3/(t.MPa 0.5).
According to the formula, the pressure indexes for measuring the coal seam gas extraction radius can be obtained as shown in Table 1
TABLE 1 gas extraction reach time corresponding measured borehole pressure drop limit
Claims (1)
1. A method for measuring and calculating the standard effective extraction radius of coal mine gas extraction is characterized by comprising the following steps: comprises the following steps of (a) carrying out,
s100, constructing a No. 1 extraction drill hole on a vertical coal wall of a coal seam which is not influenced by faults, relatively complete in rock mass protection and incapable of developing cracks, and then immediately sealing the hole by using a hole sealing device;
s200, constructing a 2# pressure observation drill hole at a position 0.5m on the right side of the 1# extraction drill hole, constructing a 3# pressure observation drill hole at a position 1.0m on the left side of the 1# extraction drill hole, constructing a 4# pressure observation drill hole at a position 1.5m on the right side of the 1# extraction drill hole, constructing a 5# pressure observation drill hole at a position 2.0m on the left side of the 1# extraction drill hole, constructing a 6# pressure observation drill hole at a position 2.5m on the right side of the 1# extraction drill hole, immediately sealing holes by using a hole sealing device after the construction of each pressure observation drill hole is finished, and ensuring tight sealing holes;
s300, installing a positive pressure gauge and a negative pressure gauge in each pressure observation drill hole, and installing a gas extraction device in an extraction hole to extract gas after the pressure is stable;
s400-recording the reading of a positive pressure gauge and a negative pressure gauge on the pressure observation drill hole every 24h, and drawing a gas pressure-time change curve;
s500, determining the coal seam gas extraction radius according to the gas relative pressure index and an effective extraction radius formula;
the step S500 described takes the following method,
s501, recording the gas pressure drop of each pressure observation drill hole;
s502-gas emission quantity Qm of working face3The method comprises the following steps that (1) min corresponds to a corresponding working face gas extraction rate eta according to the safety supervision total coal charge (2011) 163 of the temporary standard for coal mine gas extraction, a gas pressure drop corresponding to an effective gas extraction radius is calculated according to the corresponding working face gas extraction rate eta, the corresponding relation between a working face gas emission quantity Q and the gas pressure drop is obtained, and the gas pressure drop corresponding to the effective gas extraction radius is calculated as follows:
pc-residual gas pressure, MPa;
p-original gas pressure, MPa;
Δ𝑃sign boardEffectively extracting gas pressure drop percent corresponding to the radius;
eta-gas extraction rate,%;
s503, if the pressure drop of the nth pressure observation hole reaches the gas pressure drop corresponding to the gas emission quantity Q of the working face, and the pressure drop of the (n + 1) th pressure observation hole does not reach the gas pressure drop corresponding to the gas emission quantity Q of the working face, then the effective radius calculation formula of coal seam gas extraction is as follows:
in the formula, R is the effective extraction radius of coal bed gas, m;
Δ𝑃sign board-gas pressure drop,%, corresponding to the effective gas extraction radius;
Δ𝑃𝑛-the pressure drop,%, corresponding to the nth pressure observation hole;
Δ𝑃𝑛+1the pressure drop corresponding to the n +1# pressure observation hole is percent;
𝑟𝑛the distance m between the nth # pressure observation hole and the extraction hole;
𝑟𝑛+1the distance m between the n +1# pressure observation hole and the extraction hole.
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