Study On Microscopic Transport Characteristics Of Rock Based On Digital Rock Technology

Evaluation of reservoir medium is of great significance to the exploration and development of oil and gas.In recent years,in order to improve the rate of oil and gas recovery of the reservoir and geothermal energy development and other engineering application,the research on oil and gas reservoirs has gradually shifted from the macro to the micro scale.Digital rock technology can accurately characterize rock structure on microscopic scale,so it plays an increasingly important role in reservoir evaluation.In this paper,a new method for three-dimensional reconstruction of digital rock is introduced,and the transport characteristics of rock are studied on the micro scale,that is,the thermal conductivity of matrix and seepage characteristics of pore space are simulated and analyzed respectively.The main operations are as follows: Based on the high-resolution CT scan image of the Bentheimer rock,the binary image with rock matrix and pore characteristics is obtained through median filtering,noise reduction,threshold segmentation based on porosity,continuity processing based on Matlab,and REV selection.Then,the matrix and pore structure are reconstructed by using the software of reverse reconstruction and stl format used as the interface of data type.Finally,the three-dimensional model of the matrix and the pore space is meshed by CFD.Based on the Fluent software,the thermal conductivity,single-phase and two-phase displacement characteristics are numerically simulated by using the finite volume method to obtain the heat conduction and seepage characteristics at the microscopic scope.Meanwhile,the effective thermal conductivity and absolute permeability are also calculated.The simulation of thermal conduction characteristics shows that the internal structure and temperature distribution of the rock exhibit random and non-uniform characteristics,and the heat conduction process presents a variable characteristic attached to the complex structure of the matrix.At the same time,the comparison with the recognized empirical model verifies the reliability of the simulation results of the effective thermal conductivity of the rock;The results of single-phase seepage flow show that the complexity and variability of pore throat lead to unevenly flow and variability,the error between the calculated absolute permeability and the experimental measurement data is less than 10%.;The results of the three influencing factors of two-phase displacement show that the displacement pressure is the most direct factor affecting displacement efficiency,interfacial tension is an important element that hinders flow,and improvement of wettability can effectively increase displacement efficiency.All in all,these simulation results analyze the rock transport characteristics on the microscopic scale,calculate important effective physical parameters,and coincide with the experiment conclusions of rock physical,and provides an accurate and effective alternative method for more practical reservoir research and evaluation.