Method for predicting extraction productivity of underground coal-seam gas

A production capacity prediction and coalbed methane technology, which is applied in mining equipment, earthwork drilling, gas discharge, etc., can solve problems such as production capacity prediction of drilling groups that cannot be extracted, and models that cannot meet actual production conditions.

Active Publication Date: 2010-08-18
CHINA COAL TECH ENG GRP CHONGQING RES INST
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Problems solved by technology

[0004] The current downhole coalbed methane productivity prediction method has many defects, such as the following aspects: only for the single-hole coalbed methane extraction volume, but cannot predict the productivity of the drainage drilling group (group); the coalbed methane drainage mode

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  • Method for predicting extraction productivity of underground coal-seam gas
  • Method for predicting extraction productivity of underground coal-seam gas
  • Method for predicting extraction productivity of underground coal-seam gas

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Embodiment Construction

[0061] Preferred embodiments of the present invention will be described in detail below.

[0062] The main factors affecting the change of permeability in the process of coalbed methane drainage are effective stress and shrinkage effect of coal matrix. But the impact of the two on the permeability of the coal seam is just opposite, one is positive and the other is negative. Therefore, how to measure the comprehensive effect of the two factors on the coal seam permeability has become a problem that must be solved.

[0063] In the process of coalbed methane extraction, as the pressure of coalbed methane decreases, the effective stress increases, so that the permeability of the coal seam tends to decrease. At this time, the coal matrix shrinks, and the permeability of the coal seam tends to increase. The degree of influence of the two factors on the permeability of the coal seam can be expressed by the following two formulas:

[0064] ΔK 1 ...

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Abstract

The invention provides a method for predicting extraction productivity of underground coal-seam gas, in which the actual change of permeability of a coal seam is considered and the extraction productivity of extraction drilling group can be predicted. The method comprises the following steps: 1) measuring original parameters of the coal seam to be measured; and 2) by calculating a model provided by the invention, acquiring the mean permeability after the extraction, the coal-seam gas pressure after the extraction, the coal-seam gas average content after the extraction and the coal-seam gas extraction quantity. In the method for predicting the extraction productivity of the underground coal-seam gas, based on Darcy's law of seepage, a mathematical model for predicting the extraction productivity of the underground coal-seam gas based on the permeability variation in the extraction process is established; and because the actual change of the permeability in the extraction process is considered in the mathematical model, the seepage situation of the coal-seam gas can be correctly reflected. In the further calculation step, the mathematical model is calculated by adopting a differencediscrete method, the convergence rate is high, the precision is high, the stability is high and the calculation accuracy and speed are improved.

Description

technical field [0001] The invention relates to the technical field of coal gas exploitation, in particular to a method for predicting production capacity of underground coalbed methane extraction. Background technique [0002] Coalbed methane, that is, coal mine gas exists in the coal seam in an adsorbed state or a free state. Usually, the amount of gas in the adsorbed state accounts for more than 90%, and the amount of gas in the free state accounts for about 10%. When the coal seam is mined, the gas existing in the coal seam is continuously released with the disturbance of the coal seam mining, resulting in gas explosion, coal and gas outburst, gas suffocation and other hazards. Drainage of underground coalbed methane is not only an effective method for controlling coal mine gas disasters, but also an indispensable way for the development of coalbed methane resources. [0003] The prediction of underground coalbed methane production capacity can guide the orderly develop...

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Application Information

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IPC IPC(8): E21F7/00
Inventor 张志刚文光才孙东玲杜子健龙伍见
Owner CHINA COAL TECH ENG GRP CHONGQING RES INST
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