Coal bed gas flow condition rapid recognition method based on starting pressure gradient

Abstract

The invention relates to a coal bed gas flow condition rapid recognition method based on a starting pressure gradient. The method includes the steps that five kinds of coal samples are acquired on an underground coal mine and made into standard coal cores, the geological strength index value of each coal core is determined, then the starting pressure gradient value of the coal cores is measured and calculated, a series of starting pressure gradient tests are conducted on the various coal samples, the stating pressure gradient value of the various coal samples is acquired, regression analysis is conducted on the starting pressure gradient value of the various coal samples and the corresponding geological strength index values, and then the relation between the starting pressure gradient value and the corresponding geological strength index values is acquired; eventually a conclusion is drawn, the coal body structures of a coal bed are acquired by acquiring the coal samples on the underground coal mine or directly observing coal walls, after the GSI value of the coal bed is determined, the starting pressure gradient of coal bed gas can be acquired, the starting pressure gradient and a gas pressure gradient are compared, and then the flow condition of coal bed gas can be quickly judged. According to the method, the guidance is provided for extraction complexity evaluation and selection of extraction processes, and the reference is provided for further improving a gas extraction theory.

Description

technical field [0001] The invention relates to a coal seam gas flow state identification method, in particular to a coal seam gas flow state rapid identification method based on the starting pressure gradient. Background technique [0002] Efficient extraction of gas is one of the fundamental measures for disaster management and resource utilization, and its effect mainly depends on the link between coal seam and external space—permeability. The permeability of coal seams in my country is generally below 1 md, which has the characteristics of "low permeability". The long-term development practice of low-permeability oil and gas reservoirs shows that the fluid flow in low-permeability porous media no longer obeys Darcy's law, but low-speed nonlinear flow with threshold pressure gradient. The concept of starting pressure gradient was proposed by the former Soviet scholar B.A. Ferlaurin in 1951. He believed that flow can only occur when the actual pressure gradient is greater...

AI Technical Summary

Problems solved by technology

However, most of the current gas drainage technologies follow the linear seepage theory-Darcy's law, often ignoring the low-speed nonlinear seepage and diffusion phenomena in low-permeability coal seams, resulting in deviations in the evaluation of the difficulty of extraction and the selection of extraction techniques.

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