Time Migration Of Convented Wave And Theanalytic Technique Of Birefringence

PSTM (pre-stack time migration) and Birefringence analysis are two converted wave image-forming techniques which serve as effective ways for detection and description of the oil and gas reservoir internal structures. This literature, by introducing the characteristics of the converted wave, gives details of these two methods. On the basis of the speed and anisotropy parameters obtained in the converted wave dispersion travel equation, it puts forward a model update method based on the calculation of the converted wave offset speed at the CMP diffraction tracks. At the same time, 2D and 3D processing softwares for the converted wave diffraction pre-stack time migration are developed and ready for use.Converted transverse wave is a practical way of analyzing the position of anisotropy of the oil and gas reservoir, which helps us to know more about the internal structure. Through studying the way and the software specially made for 2D birefringence analysis of the converted wave and by analyzing the converted wave data of igneous rock gas reservoir, we have found that converted wave experiences fast and slow changes of shear wave splitting while it travels through the igneous rock gas reservoir. By rotation scanning, fast and slow horizontal wavelength division is made and the polar and time shift information is obtained. The final result coincides with and the data of the known gas reservoir. This approves the potential of the method in future exploration of igneous rock reservoir.With the help of the multi-dimension model of the physical properties of rock put forward by Chapman (2003), the phenomenon which the seismic reflection energy varies with the change of frequency is well analogized and interpreted. Through the quantitative analogue, we have further found that the low frequency shadow occurs only when the gas reservoir wave impedance is lower than the front layer wave impedance, while high frequency luminous spot will occur when the gas reservoir wave impedance is higher than that of the front layer. In the method of chromatographic analysis, this phenomenon can be used to explore oil and gas reservoir.These studies have brought about some new algorithm and software of pre-stack time migration (PSTM) for anisotropy medium, and they are used in the practical seismic data acquisition.