Coal rock brittleness evaluation method

Abstract

The invention relates to a coal rock brittleness evaluation method which concretely comprises the following steps of 1, performing testing to obtain stress and strain data and a complete stress-straincurve; 2, establishing a rock damage constitutive model with power function distribution; 3, according to the complete stress-strain curve, adopting the rock damage constitutive model with power function distribution to perform fitting; 4, according to energy evolution law derivation of the whole coal rock uniaxial compression rupture process, obtaining a novel brittleness index evaluation modelconsidering the coal rock mechanical property and principle and the fissure system distribution characteristics; 5, performing calculation to obtain a coal rock brittleness index numeral value of a target fractured well layer; and 6, in the whole coal bed gas development block, corresponding evaluation results to the fracturing effects for wells with different fracturing effects, performing evaluation grading on the coal rock brittleness of the whole coal bed gas development block, and comparing a coal rock brittleness index calculation result of the target fractured well layer with an evaluation grading standard. According to the coal rock brittleness grading and brittleness index evaluation results provided by the invention, the fracability evaluation of coal bed hydraulic fracturing ismore accurate.

Description

Technical field [0001] The invention relates to a coal rock fracturability evaluation technology, in particular to a coal rock brittleness evaluation method. Background technique [0002] Coalbed methane is an important unconventional oil and gas resource, and its development and utilization have attracted more and more attention and attention from all over the world. my country has abundant CBM reserves, up to 36.8×10 12 m 3 , Is the world’s third largest coal-bed methane reserve country after Russia and Canada. If coalbed methane resources can be efficiently developed, it is of great significance to my country's energy supply. The main component of coalbed methane is methane. When its air concentration reaches 5% to 16%, it will explode when exposed to an open fire. This is also the root cause of coal mine gas explosion accidents. In addition, if coalbed methane is directly discharged into the atmosphere, its greenhouse effect is about 21 times that of carbon dioxide, which i...

AI Technical Summary

Problems solved by technology

This method can reflect the influence of coal and rock mechanical properties on brittleness, and the evaluation results have certain accuracy, but it still does not consider the influence of structural weak surfaces such as cleat systems in coal and rock, which will cause certain deviations in the evaluation results

[0012] Therefore, the existing coal-rock brittleness evaluation methods have different degrees of inapplicability when evaluating coal-rock brittleness. It is necessary to propose a new method suitable for coal-rock brittleness evaluation based on the mechanical properties and rock structure characteristics of coal rock.

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