Analysis of the velocity anisotropy and its affection factors in shale and mudstone
泥岩、页岩声速各向异性及其影响因素分析

The velocity anisotropy is examined in laminated shale and mudstone under the laboratory ultrasonic frequency. The variation patterns of wave velocity in different directions as a function of confining pressure are also presented for dry and oil-saturated situations. Using the X-ray diffraction technique and electron microprobe imaging, we make analysis and conclude that the clay minerals and microcracks are the intrinsic factors that result in such strong anisotropy in rock samples. With the increasing confining pressure, microcracks are gradually closed, which low the anisotropy. Pore fluid increases the pore rigidity thus decreases the tendency of anisotropy change with confining pressure.