Method for determining extracted gas quantity of adjacent layer based on ground drilling extracted gas
Technical Field
The invention relates to a method for determining gas extraction quantity of multiple coal seams, in particular to a method for determining gas extraction quantity of an adjacent layer based on gas extraction of ground drilling.
Background
The extraction of coal seam group gas by ground drilling is one of the most common methods for gas extraction in coal mines. For a protective layer mining mine, gas extracted by ground drilling is mainly formed by mixing two parts of gas in a goaf of the coal seam and pressure relief gas in an adjacent layer. And the source-dividing calculation of the multi-coal-seam gas extracted by the ground drilling has important significance for the investigation of the extraction effect of the coal seam, particularly the adjacent layer. At present, the source-dividing calculation of the ground borehole extraction mixed gas is mainly carried out by a carbon isotope test method, and the principle is that the carbon isotope difference of different coal seams is obvious (namely, the proportion of different carbon isotopes in the gas extracted by the extraction borehole is measured by utilizing the difference of the carbon isotopes of the coal seam and an adjacent layer), and a quantitative analysis source calculation model of each coal seam gas source is established on the basis of the calculation model, so that the extraction gas quantity of the adjacent layer extracted by the ground borehole can be obtained and used for the research of a subsequent adjacent layer; although the method can obtain the extracted gas quantity of the adjacent layer, the method has the defects of long time for testing data, expensive equipment for testing isotope analysis, high difficulty in popularization and the like.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the method for determining the extracted gas quantity of the adjacent layer based on the ground drilling extracted gas, and the carbon isotope test is not needed, so that the time for determining the extracted gas quantity of the adjacent layer is effectively shortened, the accuracy of the extracted gas quantity of the adjacent layer can be effectively ensured, meanwhile, the construction is simple, the required cost is low, and the method is convenient for using various different coal beds.
In order to achieve the purpose, the invention adopts the technical scheme that: a method for determining the extracted gas quantity of an adjacent layer based on the extracted gas of a ground borehole comprises the following specific steps:
A. constructing a ground borehole on the coal mine ground, and enabling the ground borehole to penetrate through an adjacent coal seam and extend into the top plate of the coal seam to extract gas; then constructing a high-position drill hole around the ground drill hole, so that the gas inlet end of the high-position drill hole and the gas inlet end of the ground drill hole are positioned at the same extraction layer; (because the two are positioned at the same extraction horizon, the extracted gas is all extracted fromThe goaf is diffused to the same height of the top plate, so that the goaf and the top plate are approximately equal) so as to determine the gas concentration c extracted by the high-position drill hole in the coal seam0Equal to the concentration c of gas extracted in the coal seam by drilling on the ground1;
B. Respectively extracting gas from the ground borehole and the high-position borehole, and respectively measuring the concentration c of the gas extracted from the high-position borehole0Concentration c of gas extracted from ground drilling3Standard gas flow Q extracted from ground drilling3;
C. Establishing a ground drilling extraction multi-coal-seam gas source-dividing calculation model, and c2The concentration of gas entering a ground borehole adjacent to a coal seam is percent; q1Standard condition flow of coal bed gas gushing into ground borehole, m3/min;Q2Standard condition flow m of gas flowing into ground hole near coal seam3Min; setting the gas entering the ground borehole adjacent to the coal seam as pure gas; (because the gas in the adjacent layer before pressure relief is original gas, is not disturbed by mining and has no other gas entering, even if the coal bed is mined, the pressure relief gas in the adjacent layer is gushed out but not the other gas entering, so the extracted pressure relief gas can be determined as pure gas)
Namely:
C2=100% (1)
according to the law of conservation of mass, the amount of pure gas in the gas flowing into the surface borehole is equal to the amount of pure gas in the gas flowing out of the surface borehole per unit time, i.e.:
Q1c1+Q2c2=Q3c3(2)
according to the law of conservation of mass, the amount of non-gas flowing into the surface borehole per unit time is equal to the amount of non-gas flowing out of the surface borehole, i.e.:
Q1(1-c1)=Q3(1-c3) (3)
the system of equations consisting of equations (1) to (3) yields:
Q2=Q3c3-Q1c1(5)
the formula (4) and the formula (5) are calculation models of the ground drilling extraction multi-coal-seam gas source distribution:
D. according to the gas concentration c extracted by the high-position drilling hole measured in the step B0Concentration c of gas extracted from ground drilling3Standard gas flow Q extracted from ground drilling3(ii) a And the concentration c of the gas extracted by the high-level drilling0Equal to the concentration c of gas extracted in the coal seam by drilling on the ground1And D, substituting the model into the ground borehole gas extraction multi-coal-seam gas source-dividing calculation model obtained in the step C to obtain the standard condition flow Q of the gas flowing into the ground borehole from the coal seam1And the standard condition flow Q of gas flowing into the ground borehole from the adjacent coal seam2;
E. D, obtaining the standard condition flow Q of the gas of the adjacent coal seam gas gushing into the ground borehole2Namely the gas extraction quantity of the adjacent coal seam in unit time.
Compared with the prior art, because the gas concentration of the ground drilled hole extraction goaf cannot be directly measured, the high-position drilled hole is constructed around the ground drilled hole, so that the gas inlet end of the high-position drilled hole is close to the gas inlet end of the ground drilled hole, and the gas concentration extracted by the high-position drilled hole in the coal seam can be determined to be equivalent to the gas concentration extracted by the ground drilled hole in the coal seam; then respectively extracting gas from the ground drill hole and the high-position drill hole, and then measuring the concentration of the gas extracted from the high-position drill hole, the concentration of the gas extracted from the ground drill hole and the flow of the gas extracted from the ground drill hole; and then constructing a ground drilling extraction multi-coal-seam gas source-dividing calculation model according to a mass conservation law, namely, the pure gas quantity flowing into the ground hole in unit time is equal to the pure gas quantity flowing out of the ground hole, and the non-gas quantity flowing into the ground hole in unit time is equal to the non-gas quantity flowing out of the ground hole. And substituting the measured data and the known data into the source-dividing calculation model to obtain the flow of the gas of the adjacent coal seam flowing into the ground borehole. Therefore, the method does not need to carry out carbon isotope test, thereby not only effectively shortening the time for determining the gas extraction quantity of the adjacent layer, but also effectively ensuring the accuracy of the obtained gas extraction quantity of the adjacent layer, and meanwhile, the method has the advantages of simple construction, lower required cost and convenience for use and popularization of various coal seams.
Drawings
FIG. 1 is a schematic view of the construction layout of the present invention.
Detailed Description
The present invention will be further explained below.
As shown in fig. 1, the method comprises the following specific steps:
A. constructing a ground borehole on the coal mine ground, and enabling the ground borehole to penetrate through an adjacent coal seam and extend into the top plate of the coal seam to extract gas; then constructing a high-position drill hole around the ground drill hole, so that the gas inlet end of the high-position drill hole and the gas inlet end of the ground drill hole are positioned at the same extraction layer; (because the two are positioned at the same extraction layer position, the extracted gas is diffused to the same height of the top plate from the goaf, so that the extracted gas and the goaf are approximately equal) so as to determine the gas concentration c extracted by the high-position drill hole in the coal seam0Equal to the concentration c of gas extracted in the coal seam by drilling on the ground1;
B. Respectively extracting gas from the ground borehole and the high-position borehole, and respectively measuring the concentration c of the gas extracted from the high-position borehole0Concentration c of gas extracted from ground drilling3Standard gas flow Q extracted from ground drilling3;
C. Establishing a ground drilling extraction multi-coal-seam gas source-dividing calculation model, and c2The concentration of gas entering a ground borehole adjacent to a coal seam is percent; q1Standard condition flow of coal bed gas gushing into ground borehole, m3/min;Q2Standard condition flow m of gas flowing into ground hole near coal seam3Min; setting the gas entering the ground borehole adjacent to the coal seam as pure gas; (because the gas in the adjacent layer before pressure relief is original gas, is not disturbed by mining and has no other gas entering, even if the coal bed is mined, the pressure relief gas in the adjacent layer is gushed out but not the other gas entering, so the extracted pressure relief gas can be determined as pure gas)
Namely:
C2=100% (1)
according to the law of conservation of mass, the amount of pure gas in the gas flowing into the surface borehole is equal to the amount of pure gas in the gas flowing out of the surface borehole per unit time, i.e.:
Q1c1+Q2c2=Q3c3(2)
according to the law of conservation of mass, the amount of non-gas flowing into the surface borehole per unit time is equal to the amount of non-gas flowing out of the surface borehole, i.e.:
Q1(1-c1)=Q3(1-c3) (3)
the system of equations consisting of equations (1) to (3) yields:
Q2=Q3c3-Q1c1(5)
the formula (4) and the formula (5) are calculation models of the ground drilling extraction multi-coal-seam gas source distribution:
D. according to the gas concentration c extracted by the high-position drilling hole measured in the step B0Concentration c of gas extracted from ground drilling3Standard gas flow Q extracted from ground drilling3(ii) a And the concentration c of the gas extracted by the high-level drilling0Equal to the concentration c of gas extracted in the coal seam by drilling on the ground1And D, substituting the model into the ground borehole gas extraction multi-coal-seam gas source-dividing calculation model obtained in the step C to obtain the standard condition flow Q of the gas flowing into the ground borehole from the coal seam1And the standard condition flow Q of gas flowing into the ground borehole from the adjacent coal seam2;
E. D, obtaining the standard condition flow Q of the gas of the adjacent coal seam gas gushing into the ground borehole2Namely the gas extraction quantity of the adjacent coal seam in unit time.