Volumetric reconstruction experiments and multi-scale simulation of tight oil reservoir with considerations of imbibition and displacement

TField experiences show, before prompt blowout after fracturing, soaking process can proceed to sweep the crude oil in minor pores through displacement and imbibition to enhance oil recovery. Tests and simulation have been conducted to analyze the mechanism in these processes: First of all, pressurized imbibition tests were conducted to simulate imbibition of fracture sidewalls under joint effects of differential displacement pressures and capillary force by adding displacement (Δp) in the dimensionless time. Relevant test results were processed through normalization; Secondly, models on pore scale were constructed based on CT scanning. By fitting with oil recovery in tight cores, relative permeability and capillary pressure of displacement and imbibition can be determined; In the final step, matrix and fractures were given different relative permeability and capillary pressures on field scale to simulate actual oil/ water flows in formation. Test results show: oil recovery of pressurized imbibition is significantly higher than that of spontaneous imbibition approximately by 10%~15%; By adding the displacement term in dimensionless time, better normalization of test results can be obtained; By adjusting microscopic pore structures, such as pore/pore throat radius, pore throat ratio, coordination number and other parameters, satisfactory matching between imbibition and oil recovery can be performed; Partition of matrix/fracture and imbibition/ displacement on field scale may accurately reflect changes in watercut in early development stages.