Diffusivity testing method for gas in coal on triaxial stress condition

A technology of triaxial stress and gas diffusion, which is applied in the direction of measuring devices, permeability/surface area analysis, suspension and porous material analysis, etc., can solve the problems of gas diffusion coefficient errors, achieve significant progress and highlight the effect of substantive characteristics

Active Publication Date: 2015-12-23
SHANDONG UNIV OF SCI & TECH
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Problems solved by technology

Therefore, there is a large error in the gas diffusion co

Method used

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  • Diffusivity testing method for gas in coal on triaxial stress condition
  • Diffusivity testing method for gas in coal on triaxial stress condition
  • Diffusivity testing method for gas in coal on triaxial stress condition

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Embodiment Construction

[0029] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and an embodiment. The test conditions of the embodiment are a hoop pressure of 6MPa and a constant temperature of 293K.

[0030] Such as Figure 1-3 Shown, under the triaxial stress condition of the present invention, gas diffusivity test method in coal, concrete test steps are as follows:

[0031] The first step: processing and making coal sample test specimens

[0032] The whole coal block is processed into a cylindrical shape, the axial direction is perpendicular to the coal bedding direction, and the circumferential direction is parallel to the coal bedding direction; insert the coal sample 4 into the middle of the rubber sleeve 3, and then insert two coverless cylinders into the rubber sleeve 3 twice end, so that the two ends of the coal sample 4 form airtight cavities respectively, one end is used as the gas injection cavity 2, and the o...

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Abstract

The invention discloses a diffusivity testing method for gas in coal on a triaxial stress condition. The method comprises the steps that a coal sample testing specimen is put into a closed clamping cavity, and therefore a gas injection cavity and a gas outlet cavity are formed in the two ends of the coal sample respectively; helium gas is guided into the gas injection cavity, and the helium gas is firstly infiltrated into coal cracks and then diffused into coal matrixes; a curve chart of gas quantity percentages and square roots of the diffusion time is drawn, the curve slope is fit through a least square method according to a relational expression between the effective diffusivity and the diffusion gas quality, and then the gas diffusivity is calculated. According to the method, a whole coal block is adopted to serve as the coal sample, the special pore structure of a coal body is retained, the influence condition of the complex pore structure of the coal on gas diffusion can be really reflected, and the tested and calculated gas diffusivity can supply important technical support to deeply understanding and grasping of the coal bed gas migration mechanism.

Description

technical field [0001] The invention relates to a method for measuring coal seam gas migration parameters, in particular to a method for testing the diffusion rate of gas in coal. Background technique [0002] In the process of coalbed methane mining or coal mine gas extraction, the gas in the coal will first desorb from the micropore wall of the coal matrix, diffuse into the pore system driven by the concentration gradient, and then flow through the fracture system into the drill hole driven by the pressure gradient. hole. Therefore, the migration of coalbed methane is mainly controlled by two parameters: one is the gas diffusion in the coal matrix, and the other is the permeability of the fracture system. In porous media, there are three typical diffusion modes. One is the Fickian diffusion of gas molecules colliding with each other in a large pore environment or high pressure state; the other is the Knudsen collision between molecules and pore walls when the free path o...

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Application Information

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IPC IPC(8): G01N15/08G01N7/10
Inventor 王春光翟培城蒋宇静刘继山魏明尧
Owner SHANDONG UNIV OF SCI & TECH
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