Numerical Simulation And Seismic Response Analysis Of Rock Physical Response In Porous Media With Fractures

Complex reservoirs containing fractures have expanded the scope of oil and gas exploration and development,but the formation process of fractures in reservoirs is complicated by the influence of depositional environment and tectonic action,and the seismic response law is not clear,which makes the actual seismic data interpretation difficult and exploration difficult.Since the reservoir physical characteristics and rock elastic characteristics are closely related,and the physical and elastic characteristics determine the seismic response,the seismic analysis of fractured pore media based on rock physics model is of guiding significance to explore the seismic response law of fractured reservoirs.In this study,a model closer to the actual underground medium is constructed based on COMSOL using the finite element method,and the effect of each parameter change on dispersion attenuation is analyzed through numerical simulation experiments of oscillatory compression and shear.Considering the effect of dispersion attenuation in complex oil and gas reservoirs,the reflection coefficient dependent on frequency change is solved to study the reflection of seismic waves at the interface between elastic and dispersive media,analyze the seismic response law,and summarize the sensitive factors of fractured reservoir frequency change AVO.Finally,based on logging data of the actual work area,a fluid saturated fracture rock physical model is established to analyze the rock physical response and seismic response of limestone reservoir.The results show that:（1）the presence of fractures and fluids in complex oil and gas reservoirs leads to wave dispersion and attenuation in rocks,and the dispersion and attenuation have azimuthal anisotropy due to the directional arrangement of fractures and different incidence angles,and the seismic wave dispersion attenuation has good sensitivity to fracture parameters and reservoir parameters^[1];（2）at the interface between the elastic medium and the dispersive medium,the frequency-dependent reflection coefficient is sensitive to the fracture parameters（density）and reservoir parameters（porosity,permeability）;（3）There are fractures in the limestone reservoirs in the northwest work area,and the P-wave and S-wave dispersion attenuation is the most significant at 60°and 15°incidence,respectively.The P-wave reflection coefficient is negative at zero offset,and the amplitude is positively related to the offset.