Inverting And Applications Of Crack Parameters Based On Tang's Cracked Porous Medium Elastic Wave Theory And Experimental Data

The rocks in the crust contain both pores and cracks.Unlike pores with an aspect ratio of approximately 1,narrow and flat cracks are easily deformed under pressure and are easily closed.In recent years,such pores and cracks coexist in rock media and have received extensive attention and research.Experts and scholars are dedicated to studying the propagation mechanism of elastic waves in rock media with pores and cracks,and apply the theory to the exploration and development of oil and gas resources.With the constant exploitation of conventional oil and gas resources,the amount of conventional oil and gas resources has gradually declined.Unconventional oil and gas resources have received extensive attention.Unconventional oil and gas resources such as shale oil,shale gas,tight oil and tight gas have a common feature.The reservoirs are very dense with very lowporosity.In this case,the fracture development conditions in the rock,namely the fracture density ? and the fracture aspect ratio ?,especially the fracture density ? of the rocks,are of crucial importance to the influence of unconventional oil and gas resources.Based on the classical Biot-Gassmman elastic wave theory,Tang Xiaoming analyzed the effect of cracks on the elastic properties,introduced the contribution of “squirt flow”(squirt flow),and finally obtained the “A unified theory for elastic wave propagation through porous media containing cracks".This article is based on this theory,using experimental data to simulate the Vp and Vs with the confining pressure curve under dry and fluid saturated conditions,and compare the simulated curve with the laboratory measured data to observe whether the two are consistent.In addition,based on the “Unified Theory of Pore Medium with Pores and Fractured Media”,this paper inverts the fracture parameters of the rock,namely the crack density ? and the crack aspect ratio ?,and the bulk modulus and shear modulus of the rock matrix.Through the simulation of velocity curves and inversion of crackparameters for different lithologies,different pore permeability,physical conditions,or core sample data of different structures in the same oil field block,we found that the theory has achieved good results and proved the theory.In addition,based on the published experimental data,the rock brittleness calculation formula was used to calculate the rock brittleness value,and the correlation analysis was performed with the inversion crack density.The results show that the brittleness of rock is in a “positive correlation” relationship with the development degree of fractures(ie,crack density).The more developed the fractures in rock,the greater the crack density and the higher the brittleness of rock.Based on the above findings,the conclusion we found can be helpful to our analysis of rock brittleness evaluation and evaluation of rock fractureability.