Study Of Fluid Discrimination Based On Rock Physics

With the increase of petroleum prospecting difficulty and cost, people are having higher demand in geophysics which is an important means of petroleum prospecting, from the early simple structure interpretation to the present lithology and fluid prediction. This thesis, on the basis of theoretical analysis of rock physics, mainly analyses the features of rock containing different fluids, performs two-phase media forward modeling by the method of reflectivity, and studies the impact of fluids on seismic corresponding and reflection coefficient. This thesis then gives an introduction and discussion about different fluid identification methods, on the basis of fluid factor of AVO analysis being different angle parameters obtained through the wells data analysis. Finally, the author studies fluid identification methods based on elastic impedance inversion: the effective fluid identification properties can be obtained through wells data analysis, and cross plot attributes can be used for effective fluid identification.Rock physics is the connection between reservoir characteristic parameters and seismic data, and is also necessary for forward and inverse calculation and comprehensive interpretation, which not only provides knowledge base and necessary data for forward and inversion modeling, but also reduces the uncertainty of inversion problem. This thesis introduces basic knowledge of rock physics theory, and influencing factors of elastic parameters, respectively discusses three commonly used two-phase media theory, studies the rule of density and P-wave and S-wave velocities varying along with the change of fluid saturation, and makes comparisons of different theories in the forecasting of media nature under different fluid, saturation and porosity.Forward modeling is an effective means to fully understand the propagation feature of seismic wave in complex media, and to help to explain the observational data and make clear the geological structure. Reflectivity method, a numerical transformation method, is an effective way of realizing full-wave field modeling with higher accuracy and lower cost calculation in layered half-space media. This thesis discusses seismic forward modeling method of two-phase media reflectivity and carry out forward modeling of two-phase media of different fluid saturation.The study of fluid factor method, among fluid identification methods is of great significance in fluid identification. Compared with pre-stack inversion, fluid factor angle and crossplot angle possess the characteristics of simple and fast calculation. Elastic impedance inversion has good fidelity and much information. Then lithological parameters reflecting lithology and fluids, such as P-wave and S-wave impedance, and P-wave and S-wave velocity ratio and Poisson ratio and so on can be figured out so as to effectively predict reservoir fluids. Poisson impedance method and fluid identification method based on Gassmann method, can effectively distinguish different fluids by selecting reasonable parameters. Various methods stated in this thesis have been tested and used in the actual data of a certain area. The application results show that the methods stated in the thesis is feasible and effective.