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A test method for gas diffusivity in coal under triaxial stress conditions

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: 2017-10-20
SHANDONG UNIV OF SCI & TECH
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  • Abstract
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Problems solved by technology

Therefore, there is a large error in the gas diffusion coefficient calculated by using pulverized coal (particles)

Method used

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  • A test method for gas diffusivity in coal under triaxial stress conditions
  • A test method for gas diffusivity in coal under triaxial stress conditions
  • A test method for gas diffusivity in coal under triaxial stress conditions

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Embodiment Construction

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

[0030] Such as Figure 1-3 As shown, in the method for testing gas diffusivity in coal under triaxial stress conditions of the present invention, the specific testing steps are as follows:

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

[0032] Process the whole coal block into a cylindrical shape, with its axial direction perpendicular to the direction of coal seam and parallel to the direction of coal seam; insert the coal sample 4 into the middle of the rubber sleeve 3, and then insert two uncovered cylinders into the rubber sleeve 3 To make the two ends of the coal sample 4 form a closed cavity respectively, one end is used as the gas injection cavity 2 and the other end is used as the gas outlet cavity 5...

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Abstract

The invention discloses a method for testing the gas diffusivity in coal under the condition of triaxial stress, which is to put the coal sample test specimen into a closed clamping cavity, so as to form a gas injection cavity and a gas injection cavity at the two ends of the coal sample respectively. Out of the gas chamber, helium is introduced into the gas injection chamber, the helium first seeps into the coal cracks, and then begins to diffuse into the coal matrix; draw the curve of the percentage of the gas quantity and the square root of the diffusion time, according to the effective diffusion rate and the diffusion gas The relational expression of the mass, the slope of the curve fitted by the least square method, and the gas diffusivity is calculated. The present invention adopts the whole coal block as the coal sample, retains the unique pore structure of the coal body, and can truly reflect the influence of the complex pore structure of the coal on the gas diffusion. The migration mechanism provides important technical support.

Description

Technical field [0001] The invention relates to a method for measuring coal bed gas migration parameters, in particular to a method for testing the diffusivity of coal gas. Background technique [0002] In the process of coalbed methane mining or coal mine gas drainage, the gas in the coal will first desorb from the micropore walls of the coal matrix, diffuse into the pore system driven by the concentration gradient, and then flow through the fissure system to enter the drill 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 methods. One is Fickian diffusion in which gas molecules collide with each other in a macroporous environment or under high pressure; the other is Knudsen collision in which molecules and pore walls collide with each other when the fr...

Claims

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Application Information

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Patent Type & Authority Patents(China)
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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