含煤地层各向异性介质有限差分数值模拟

煤储层是一种双重孔隙介质,其孔隙由基质孔隙和裂隙组成,并具有自身独特的割理系统。传统的煤田地震勘探将煤层假设为单一的各向同性介质,没有考虑其中裂隙对煤层的影响。利用交错网格高阶有限差分算法,分别对不同厚度VTI和HTI型煤层的弹性波传播特征进行数值模拟,获得波场快照和含煤层状介质的地震模拟记录。从波场快照中可以看出,弹性波在VTI和HTI型煤层中传播存在明显差异;煤层厚度变化对波场的敏感性要强于煤层类型的变化。

Anisotropic numerical simulation of coal-bearing strata with finite-difference

Coal reservoir is a dual porous rock composed of matrix porosity and fracture with its unique cleat system. However, coal is usually assumed to be an isotropic medium in the traditional coal seismic exploration, and the impacts of fractures on seam are not taken into account. Elastic wave propagation of VTI (transversely isotropic with a vertical symmetry axis) and HTI (transversely isotropic with a horizontal symmetry axis) coal with different thicknesses were simulated by high-order finite-difference of staggered-grid respectively to obtain wave snapshots of homogeneous coal and seismic records of coal-bearing layered strata. By comparative analysis, it was found that evident differences of elastic wave propagation exists between VTI and HTI homogeneous coal, that changes in coal thickness are more sensitive to wave field than the changes in coal type from the layered seismic simulation records.