The Study Of Anisotropic Media Based On Two Groups Of Obliquely Intersecting Cracks

A growing body of research have shown that the anisotropy of underground mediumis a very common phenomenon. The oil and gas exploration has been developing rapidlyin recent years, the emphasis and difficulty in exploration has turned to complexreservoirs, fractured reservoirs, lithologic reservoirs and so on. These explorationobjectives are very complicated, and the need of precision for analysis of seismic data hasincreased. If ignoring the effect of anisotropy in seismic media, erroneous conclusionswill be caused in seismic data processing and interpretation. This is a challenge totraditional researches and production which based on isotropy wave theory.Cracks can not only act as hydrocarbon migration channel and reservoir space, alsocould undermine the oil and gas gathering, therefore the study of fracture medium is ofgreat significance. Given crack reservoir has obvious anisotropic characteristics, so thelast two decades, the anisotropic medium research has become an important subject inseismic exploration.In this paper, we first introduces the basic theory of anisotropy, secondly introducesthe thought that how to research the characteristics of elastic wave propagation, and lastwe has carried on the simple introduction of coordinate transformation formula of Bondand equivalent medium theory. Then, based on the anisotropy medium theory and thetheory of Hudson in this paper, we calculate the equivalent elastic coefficient of obliquefracture medium containing two groups, and with that the wave equation is derived. Afterthat, on basis of Christoffel equation, it’s relatively easy to obtain the phase velocity ofplane wave in the medium with ShengJin formula. Next, we study the influence of thecrack density, angle between two cracks and filling material to the elastic wave fieldbased on high-order finite difference method. Finally, we set up horizontal layered medium model and sag model, and carry out numerical simulation on the model, analysethe effects in the wave field snapshots and records when the model contains cracks in acertain layer.