Research On The Elastic Parameter Simulation And Application Based On The Finite Element Method Of Digital Core

The elastic properties of rocks are not only affected by the macroscopic elastic properties of the matrix and fluids,but also depend highly on the physical mechanism of microscale.Therefore,the traditional rock physics experiments and equivalent theory are facing with challenges in accurate calculation of elastic parameters and reliable prediction of physical parameters.Based on the high-resolution imaging of microstructure of the real core,3-D digital cores quantitatively characterize the relationship between elasticity and reservoir properties with numerical simulation method,thereby overcoming the weaknesses of conventional rock physics experiments and theories.Combining the advantages of digital cores and rock physics theory,this paper studies the elastic parameter calculation and reservoir parameter prediction of digital core by finite element method.The finite element simulation represents one of the essential methods for calculation of elastic parameters.In this paper,the elastic modulus of Fontainebleau sandstone and Berea sandstone digital core are calculated by FEM and the accuracy of the calculation method is evaluated.In conventional digital core research,most of the digital cores are only divided into two components(matrix and pore),which can not describe the real structure and material composition accurately.Based on the original digital core model with two components,this paper develops the 3-D digital core with multi-mineral components,so that the model is more consistent with the actual core.Using the finite element method of multi-mineral components digital core,this paper studies the influence of different microscopic factors such as shale distribution,fluid type,saturation and cement on the elastic properties of digital cores.In this paper,we compare the results of finite element simulation with theoretical rock physics models,systematically study the equivalence between the digital core model and various rock physics models,and carefully analyze the conditions of the equivalence relationships.Compared to previous studies,the influences of the pore aspect ratio and consolidation coefficient on the equivalence relationships are also further refined.Therefore,digital core technology can,to some extent,replace the theoretical rock physics models to simulate the elastic patameters more accurate.The relationship between reservoir parameters and elastic parameters simulated by finite element method is very complex.Therefore,it is difficult to calculate the reservoir parameters directly.This paper apply the inverse rock physics modeling method to the digital core to estimate the reservoir properties.Based on digital core basis function,we establish the digital core dataset in 3-D spatial domain to determine the link between the geophysical parameters and reservoir parameters,which constructs the finite element numerical solution of elastic modulus quickly.The digital core inverse modeling is to search the single value isosurface of the elastic parameters in 3-D database,intersect the isosurface and get the coordinates of the intersection point,which are the values of the reservoir parameters.Tests show that,the inverse digital rock physics modeling method for reservoir parameter prediction is feasible.Based on this theory,a new method of shear wave velocity estimation based on digital core inversion modeling is proposed.Under the control of digital core,the reservoir parameters are predicted by inverse modeling theory directly,and the shear wave velocity can be calculated according to the prediction results accurately.