Method for calculating the absolute permeability of orthogonal anisotropic coal seam cracks

An orthotropic, absolute permeability technology, applied in the field of calculating the absolute permeability of orthotropic coal seam fractures, can solve problems such as imperfections, and achieve the effect of improving accuracy

Active Publication Date: 2019-06-11
CHINA UNIV OF MINING & TECH (BEIJING)
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  • Abstract
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Problems solved by technology

However, the existing anisotropic absolute permeability evolution model of coal seams only considers some factors affecting absolute permeability anisotropy, which is not yet perfect.

Method used

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  • Method for calculating the absolute permeability of orthogonal anisotropic coal seam cracks
  • Method for calculating the absolute permeability of orthogonal anisotropic coal seam cracks
  • Method for calculating the absolute permeability of orthogonal anisotropic coal seam cracks

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Embodiment Construction

[0010] Coal Seam Fracture Structure

[0011] Coal is a fracture-porous medium composed of fractures and a coal matrix filled with tiny pores. Since the size of the pores in the coal matrix is ​​much smaller than that of the fractures, the absolute permeability of the coal seam usually refers to the absolute permeability of the fractures. According to the differences in connectivity and direction, fractures can be divided into nearly mutually orthogonal surface joints, end joints and bedding planes (such as figure 1 shown). Surface joints and end joints are the main channels for gas flow in coal seams: surface joints have large extension lengths, good connectivity, smooth surfaces, and are close to parallel to each other; end joints have smooth surfaces but poorer connectivity than surface joints, so end joints The absolute permeability of the bedding surface is usually lower than that of the surface joints; the absolute permeability of the bedding surface is usually much low...

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Abstract

According to the method, it is assumed that cracks in a coal seam are three groups of joints which are mutually orthogonal; By considering the anisotropy of fracture structure, joint mechanics parameters, coal matrix adsorption/desorption deformation and ground stress, evolution model of absolute permeability of orthotropic coal seam fissures under effective stress change and gas adsorption/desorption under the dual action is set up. The invention is closer to the real coal seam fissure structure than the previous coal seam absolute permeability model, so it can more accurately predict the evolution law of the absolute permeability in the coalbed methane mining and coal seam gas drainage process.

Description

technical field [0001] The invention relates to a method for calculating the absolute permeability of a coal seam, in particular to a method for calculating the absolute permeability of an orthotropic coal seam fissure. Background technique [0002] The quantitative relationship between coal seam absolute permeability and effective stress and adsorption / desorption is a research hotspot in the field of coal seam gas. The mathematical model describing this quantitative relationship is the coal seam absolute permeability evolution model. Existing models can be divided into three categories according to boundary conditions: absolute coal seam permeability evolution models under uniaxial strain boundary conditions, such models are mainly used for simulating and predicting the coal seam absolute permeability in the process of coalbed methane extraction and coal seam gas drainage. Evolution behavior; coal seam absolute permeability evolution model under constant confining pressure ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F17/10
Inventor 臧杰王凯
Owner CHINA UNIV OF MINING & TECH (BEIJING)
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