The Modeling Of Rock Physics In Tight Sandstones Considering The Effect Of Pore Structure

In recent years,the research on low porosity and low permeability tight oil and gas reservoirs has become a hot topic at home and abroad.Seismic rock physics is a bridge connecting reservoir physical parameters and elastic parameters.The correct construction of rock physics model is of great significance for the prediction of reservoir elastic parameters.This paper analysed the complex pore structure of the tight sandstone,the anisotropy caused by the crack and the dispersion caused by the fluid flow.The dispersion caused by fluid flow affects both the velocity of the P and S waves and the anisotropy of rock.On the basis of the anisotropy caused by the crack,the influence of the fluid is introduced based on the efficient solid modulus theory.The anisotropic attenuation rock physics model is established,which overcomes the limitation that the conventional dispersion theory requires the skeleton to be isotropic,and explains the mechanism of crack anisotropy and microscopic jet flow.Combined with the theory of isotropic efficient medium,there are defects in the fluid replacement of tight sandstone,and an anisotropic attenuation rock physics model of tight sandstone in saturated fluid is constructed.The paper discusses in depth the effects of fracture pore aspect ratio,fracture density and fracture porosity on the dispersion and anisotropy of elastic parameters.It is considered that the crack density is an important parameter affecting anisotropy and dispersion characteristics.If the crack density increases,the degree of anisotropy and dispersion will increase.The model is analysed based on the actual data measured by the laboratory,and the predicted results are in good agreement with the measured values.It is found that when the rock cracks are relatively developed,it indicates that the dispersion and attenuation have a great influence on predicting the anisotropic parameters of the rock,and should be considered when conducting seismic reservoir prediction.At the end of the paper,the model is used to predict the fracture density of the actual work area data,and the prediction result is more consistent with the fracture development zone of the actual geological understanding.