Research On Micro - Water Flooding Network Simulation

Water flooding is the most classical and widely-applied approach during secondary recovery. But the recovery of water flooding is not really high, due to some macroscopic factors (e.g. the heterogeneity of formation) and microscopic factors (e.g. porous structure and wettability). As the platform to study the flow in pore, network modelling of porous media provides the possibility to discover the influence of the microstructure of pore space on microscopic flow. Therefore, basing on pore-scale network modelling, this paper analyzed the properties of10samples from Section WD, and conducted the microscopic mechanism study of water flooding. The main achievements and conclusions are as follows:(1) Micro-CT scanning is conducted for10samples, and the obtained section images are processed. The3D pore space of samples is rebuilt and visualized, and REV analysis is also carried out based on the porosities.(2) Using the network model extraction program which is based on the maximal ball algorithm, the equivalent network models of10samples are built. By comparing the porosity, permeability and capillary pressure curve with the experimental data, these10network models extracted by maximal ball algorithm are proved to be valid.(3) The size of pores and throats, topological structure and shape character of the network model are statistically studied and analyzed. The statistical analysis of the different properties uncovers the reasons for the property differences among models.(4) Different wettabilities are assigned to these network models based on the wettabilities of the other samples from the same section, and water flooding simulation is conducted by two-phase flow simulator. The flowing characteristics of water-wet, oil-wet and mixed-wet models are in correspondence with the general flowing characteristics of the rocks with the same wettability respectively.(5) To study the microscopic mechanism of water flooding,4network models are selected to conduct water flooding simulation with strong wettabilities. Using the ratio of pores containing residual oil and the microscopic displacement efficiency as criteria, the factors such as pore size, pore shape, coordination number and ratios aspect are found to have influence on residual oil, and the influence differs for different wettabilities.The understanding of the pore-scale displacing mechanism is deepened through this study. This work also demonstrates a new approach to study the residual oil after water flooding, and provides theoretical evidence to develop fields appropriately and efficiently by water flooding.