Effects of Coal Permeability Anisotropy on Gas Extraction Performance

To investigate gas flow characteristics in coal seams with strong anisotropy, a coupled anisotropic dual-porosity model was established. Effects of permeability anisotropy on variations pressure, extraction volume and effective areas were analyzed. Furthermore, mechanisms crustal stress, initial ultimate adsorption strain Langmuir constant amount studied. Results show that could result an elliptical pressure drop zone around production boreholes. Changes are divided into three stages: slow growth shape, rapid superposition effect steady funnel shape. Permeability isotropy enables faster reaching stage III than the case. As vertical stress increases, distribution boreholes gradually changes from ellipse horizontal direction as long axis to circle. Larger bring consistently higher middle stages, decrease late phase. When is 2.5 MPa, peak daily about times Ultimate positively correlated change. This relationship becomes more significant longer time. In contrast, variation inversely proportional stage. However, these factors directly The order significance each factor’s > constant. Moreover, has most volume, while least impact. provide theoretical reference for borehole design drainage parameter setting improve performance.