Study Of Porous Media Reconstruction And Fingering Simulation

EOR(enhanced oil recovery), such as CO2flooding and polymer flooding, have been widely used in the reservoir development in our country. Microscopic mechanism of these petroleum recovery techniques needs further studies. To improve the recovery efficiency, it is significant to deeply understand the physical and chemical process of oil displacement at pore scale. In this article, we use electronic microscope and CT imaging technology to image synthesized porous planar membranes and real cores, and finally get images with a resolution of microns. With the obtained data, we built membrane structure characterization and simulated performance of permeability, reconstructed porous media, and investigated viscous fingering in porous media. The main reaserch results and innovation in this article are as follows:1. Experiments and numerical simulation study on synthetized porous media. Alumina ceramic planar membranes are obtained with the method of tape-casting and phase inversion. Through the analysis of electron microscopy (SEM) and CT images, we find that along the cross section, the film is divided into micropores, finger-like voids, sponge-like voids layer. Micropores layer is at the side of the water bath, wherein a large number of micro pores whose diameter are less than10microns are found. In the finger-like voids layer, micro pores merges into larger voids along the thickness direction along with the decreasing of pores. Sponge-like voids layer is located in the bottom of the membrane. This layer contains less pores of which the aperture is also small, because this layer is far away from the water bath which is bad for pore formation. By utilizing CT data of cores as boundary condtions, we used LBM method to simulate the permeance of the film before and after wiping off the surface pores. The simulated results fit well with the measured data.2. A method to reconstruct pore network based on maximal inscribed sphere(MIS) and pore corrosion process is presented. First to generate MIS in the pore space, then determine pore bodies, after finding out all locally maximal spheres by comparision of radius of intersecting balls. We design a process of pore body outward expansion to obtain the connection relationship between pore bodies. After all the throats are found, we complete network reconstruction with throat body radius obtained by the corrosion of pore throat space. 3. We propose a DLA viscous fingering model based on pressure gradient. The model, which is called pressure-guided rule, combines geometric space and pressure gradient. We investigate the DLA walking problem of particles in pore space and simulate the viscous fingering development process. The numerical simulation results show that:the path of viscous fingering is always along a specific port; the bigger of fluid viscosity ratio is, the greater the fingering develops, the lower the displacement efficiency is. The displacement efficiency no longer falls but fluctuates between2-3%when viscosity ratio is very large; the displacement efficiency is higher when particles walks under the pressure-guided rules than that of equal probability rules.