Numerical Simulation Of Elastic Properties Of Rock Based On Digital Cores

The acoustic properties of the rock has been playing an important role in geophysical prospecting.Exploring the relationship between the reservoir parameters such as rock matrix,pore structure or pore fluid properties,and the elastic parameters helps to improve the geophysical measurement methods of interpretation,but also has practical significance for the exploration and development of the oilfield.Currently,the acoustic characteristics of the reservoir rock is studied mainly through petrophysical experimental measurements and differential effective medium model.Petrophysical experiment has the higher cost,and it takes the longer time.For some special lithology,the experiment is unable to be carried out.The rocks pore structure of differential effective medium model is simplified,and the pore characteristics is characterized inaccurately.Therefore,the investigation that the acoustic numerical simulation is carried out based on 3-D digital core has practical significance.The study builds 3-D digital core by X-ray CT scanning,combined with elastic mechanics theory,to explore the relationship between the reservoir microscopic factors and the elastic parameters calculated by the finite element method.Combining the extracted 3-D microscopic pore network model and simulating oil-water distribution in formation by mathematical morphology,the acoustic numerical simulation is carried out under varying degrees of water saturation.First of all,we carry out the X-ray CT scanning of sandstone samples to get the sample of 2-D slice grayscale through image filtering and image binarization processing.The 2-D grayscale image is digitized,and we carry out the representative elementary volume to get 3-D digital core,and reconstruct the 3-D image at the same time.Then,analyzing the connectivity of porous media in 3-D digital core,the maximum ball algorithm is utilized to extract the micro pore network model and calculate the associated pore network model parameters.Secondly,we use the finite element method to conduct the acoustic numerical simulation of the 3-D digital core based on the basic theory of elastic mechanics,carrying out the micro impact factor analysis of elastic mechanics parameters to explore the impact law of the main reservoir parameters on the elastic parameters.The thesis studies the effect of porosity,permeability and porosity(oil,water)on the elastic parameters in saturated rock.Finally,simulating the occurrence in the rock pore space of water-wet formation after oil displace water on the basis of mathematical morphology.Conducting the acoustics numerical simulation study on oil-water two-phase by finite element method to explore the relationship between water saturation and elasticity parameters.The study found that the rock structure compactness decline with porosity,permeability and shale content increasing,so that the elastic modulus decreases and Poisson’s ratio increases.Pore fluid has no effect on the shear modulus.Increasing of rock compactness makes the effect on pore fluid for the elastic parameters fall and decreasing of compactness makes the effect enhance.With the increase of water saturation,bulk modulus increase gradually,and the shear modulus basic no effect.When the lithology is not the same,the effect on water saturation for bulk modulus is also different.