Forward modeling of fracture parameters in coal reservoir

Based on the three components of TTI coal seam by two-dimensional anisotropic elastic wave equation,the finite difference scheme of Lebedev grid was derived,and the numerical simulation of TTI medium on different fracture parameters were carried out,the impact of fracture parameters on the seismic wave field was analyzed,the three layer model was established,and the different theoretical models of crack density and crack filling were obtained. Also,the AVO records were obtained by forward modeling. The simulation results show that ① When the coal seam medium is a dry fracture,the velocity anisotropy of the compressional wave is sensitive to the fracture. When the coal seam medium is fluid fracture,the velocity anisotropy of the shear wave is sensitive to the fracture;② The reflection coefficient of coal seam roof is negative,the bottom plate is positive,and the reflection coefficient of coal seam is affected by many factors;③ When the coal seam fracture medium is dry,the change of fracture density to intercept the reflection coeffi- cient curve has a great influence and the effect on slope is small. When the fractured medium is saturated fluid,the fracture density has no influence on the reflection coefficient of coal seam;④ With the increase of the fracture density, the influence of the filling material on the reflection coefficient is relatively larger.