The Study And Application Of VSP Anisotropy Imaging

From vertical seismic profiling(VSP), geophysist can get accurate structure velocity,attenuation parameter caused by absorption, the seismic wavelet and parameters of anisotropy.During VSP acquisition, the source is placed on the surface and receiver system is located in borehole. VSP data can be widely used in seismic calibration, structure study, borehole lithology study, dynamic seismic wave estimating, fracture detection and pressure prediction.Compared with surface seismic, VSP has the advantage of high signal-to-noise ratio, high resolution, high-resolution information, directly reservoir observation and so on.Anisotropy research has become one of the frontier topics in the seismic field. Anisotropy parameters estimated from VSP data can be used to VSP processing and surface seismic anisotropy imaging processing, which can improve imaging precision of VSP and surface seismic. This technique has important practical influence for exploration and development of complex oil and gas reservoir.According with foundation theory of anisotropic medium, this paper analyzed seismic wave anisotropy formula, completed seismic wave ray tracing algorithm in anisotropy medium, and studied the VSP anisotropy imaging method. And finally this paper developed a set of VSP anisotropy processing software. This software copyright registration has been accepted.The main achievement is summarized as follows:1, A new method of VSP first break picking. In this section, this paper studed first break picking and quality control technique basis on amplitude ratio constrained by pilot first break.We first proposed that the wavelet energy center(around the peak) should be the first break picking position for VSP data. When picking the time in energy center, the velocity is equivalent to group velocity. When picking the first break time, the velocity is equal to phase velocity. Because seismic propagation velocity is group velocity, the corridor stack tied better with the surface seismic when picking the energy center. The new method for picking the first arrival of VSP can lead to accurate estimation of anisotropy parameters.2, Anisotropy parameters and imaging of VSP base on datas. In this section, this paper studied the VSP ray tracing forward and inversion algorithm, travel time computation of VSP anisotropy medium, VSP-CDP stack imaging, Kirchhoff migration imaging, wave equation migration imaging and reverse-time migration imaging. The anisotropy imaging method improves the VSP imaging.3, Software development of VSP anisotropy processing. With this software, many things can be done, such as inputting and outputting the three component VSP datas, first break picking,estimation of velocity and anisotropy parameters and VSP imaging. All the functions had been tested by field data.