Waveform Disturbance by Transversely Isotropic Medium with a Tilted Axis of Symmetry around a Borehole

Abstract

Sonic logging is an essential tool to understand the properties of reservoirs in detail. In particular, the more accurate method for understanding the anisotropy in the vicinity of well is demanded to develop the unconventional resources such as shale oil and gas. We use 3D Hamiltonian Particle Method (HPM) to simulate a seismic wave propagation including a borehole and transmit from dipole source to make use of the shear wave. We apply the cross-dipole orientation as the system of source and receivers. We set the Transversely Isotropic medium with a Horizontal axis of symmetry (HTI) as an anisotropic layer around a borehole. It is known that the shear wave splits into two polarized waves, i.e., as shear wave splitting. This is the distinctive feature to detect the azimuthal anisotropy. In addition, we conduct numerical simulation for Transversely Isotropic medium with a Tilted axis of symmetry (TTI). We use the conventional Slowness Time Coherence (STC) to detect the slowness of formation for both HTI and TTI. Our results clearly show that obvious difference appears as received waveform. We conclude that the Full Waveform Inversion (FWI) could apply to estimate anisotropic properties around a borehole with high accuracy and resolution.