Simulation Of Elastic Parameters Of Fluid Containing Rock Based On Digital Core

Rock is a natural porous medium that is saturated with various fluids in the depths of the ground to form a coexisting body.Rocks in the formation usually consist of three types of elements: skeleton,pores and saturated fluid.The different components and composition of these three types of factors are mainly influenced by the sedimentary environment and preservation methods.The combined effects of all these factors affect the various macroscopic physical properties of the rocks.In the process of fossil energy mining,various methods are generally used to test the three key properties of rock porosity,permeability and saturation.The commonly used methods include physical experiments,measured resistivity,and sonic velocity.However,these methods can only reflect the macroscopic physical properties and fluid saturation of the rock,and cannot explain the internal pore structure of the rock from the microstructure.The analysis of digital rock model can make up for the shortcomings of traditional physics experiments.Reconstructing the complex microscopic skeleton and pore structure of rock through a large number of digital signals provides a new means for petrophysical research.This paper takes artificial sandstone as the research object.Using micron CT to scan the rock layer by layer at a certain differential scale,obtain the cross-section analog signal information of each differential unit,and improve the recognition resolution of the cross section.Combined with image processing technology,the microscopic unit structure of the core is extracted,and a three-dimensional digital core model with real pore structure is established,and the scanned analog signal model is converted into a digital signal.Finally,the finite element method proposed by Garboczi is used for the digital signal model to obtain the stress-strain relationship.Then the homogenous Hooke's law is used to calculate the propagation velocity of sound waves in the rock.In this paper,the rock physics model is constructed by LIGGGHTS software,and the different distribution modes of fluid inside the rock are simulated by mathematical morphology method.The finite element method is used to calculate the elastic parameters of fluid-containing rocks and compare a series of theoretical models.By comparison,the distribution of fluid affects the variation of longitudinal wave velocity with water saturation.In order to accurately predict the longitudinal wave velocity of fluid-bearing rocks,the corresponding empirical formulas for different models with the change of water saturation are given.