Study On Rock Physics Model For Cracked Porous Medium Containing Kerogen And Application

Rock physics model is physical basis of establishing forecasting tools and explaining inversion results.It relates the well logging data,seismic attributes and reservoir parameters together.For the geophysical response simulation of unconventional oil and gas reservoir,especially the shale reservoir,the existing work mostly focuses in the case of isotropic.The actual shale reservoir is different from conventional oil and gas reservoir.It has the characteristics of a high degree of anisotropy.Considering the shale's characteristics in rich organic matter,strong anisotropy,micro fracture,porous and anisotropic rock physical model containing cracks and kerogen is established.The acoustic characteristics of unconventional reservoir are also studied.It has great theoretical and practical values.The existing elastic wave unified theory of porous media containing cracks assumes that the rock medium is isotropic.So the multi-parameter inversion method is established for the core ultrasonic data of the laboratory.Then the measured core data is processed to obtain the fracture parameters and elastic modulus of rock matrix.Apply the multi-parameter inversion algorithm of experimental data to actual formation data processing and then obtain the fluid modulus and fracture density of tight sandstone gas reservoir and complex lithology reservoir.According the inversion results,fluid identification is conducted.Finally,establish the crossplot of P-wave-to-S-wave velocity ratio and P wave slowness.The oil and gas layer can be divided consequently.Using the cracked porous medium elastic wave theory,combining Ciz-Shapiro isotropic equation,introduce the influence of organic kerogen and establish a isotropic,rich organic matter and cracked porous medium model.Analysis the variation of compressional,shear wave velocities,their ratio and other acoustic parameters such as wave impedance.Shale formation owns the characteristic of anisotropy,therefore,rock background medium should be considered as anisotropic when forming model.Here rich organic,anisotropic shale rock physics model is constructed by combining with anisotropic self consistent theory,anisotropic effective medium theory and Kuster-Toks?z theory.It can be used to calculate the elastic parameters of kerogen-oil and gas mixture,and analysis the effect of kerogen and maturity on shale velocity and anisotropy.The theoretical simulation results of porous and isotropic medium containing cracks and rich organic matter can be used to predict the variation trend of actual data and verify the feasibility of the model.Anisotropic,rich organic shale rock physics model is used to simulate the rock compressional and shear wave velocity,which is parallel and perpendicular to the bedding and anisotropy.The simulated result is analyzed and compared with laboratory data.