Method Research Of Weak-anisotropy's One-way Wave-equation Seismic Numerical Simulation

Seismic anisotropy refers to seismic wave propagation velocity changes with the propagation direction.Nowadays, the anisotropy of seismic becomes a key factor in seismic imaging. In recent years, as the lack of oil and gas resources has affected the development of China, a great concern to the exploration of unconventional oil and gas resources is given. The anisotropy become the inevitable problem in geophysical exploration of unconventional oil and gas resources. Many factors causing anisotropy include seismic data offset, sedimentary environment, and the relationship between seismic wavelength and the thickness, and etc. The accuracy of seismic imaging can be improved by the anisotropic wave field numerical simulation and analysis.One-way wave equation is one of the most important anisotropic seismic wave field simulation methods. Although the seismic wave field information based on the method is not rich, it possessed wave field with higher S/N ratio, higher calculating efficiency and applicability in the seismic reflection analysis.The paper has the following innovations:1. Fourier finite difference method for weakly anisotropic mathematical derivation and error analysisWhich analyze VTI, TTI media dispersion relationship, and approximates dispersion relation by using rational polynomial. The A-PSPI + SSF method and optimal Fourier finite difference method of qP wave was proposed in the paper. Finally, the numerical simulation of seismic wave field demonstrate its correctness and feasibility.2. The parameters preferences in the forward modelingThe model parameters in seismic anisotropy simulation usually contain three or more data volumes. With the number increasing of data volume, it will be encountered two problems. Firstly, because of the lateral variation of the parameters, we must choose a large number of background parameters in simulation, which will lead to exponential growth in computing complexity. Secondly, if the interface of the media is not smooth, the simulation will produce much weak diffraction wave in the wave field. In order to improve such problems, an parameters optimization based on K-means clustering, and parameters smooth and enhancement based on the structure tensor were proposed in the paper.3. Prestack forward modeling of seimsic fields in weak anisotropy media by using one-way wave equation from rough surfaceBased on the Huygens theory and principles of digital geophone, one-way wave anisotropic prestack forward modeling method was proposed. The results of model-based simulation show that the method has higher calculating efficiency and extensive suitability.