Study On Water Displacement Efficiency And Sweep Efficiency For Sandstone Reservoir With Medium Or High Permeability

Waterflooding is not only a dominant producing method in the world oil industry, but also the most economical and efficient method to enhance oil recovery so far. Waterflooding sweep factor and displacement efficiency are indispensable parameters and final determinative factors in field development process. In recent years, sealed coring well data has demonstrated that there are great differences between vertical displacement efficiency and sweep factor in the reservoir. Because such differences can't be described by current method computing displacement efficiency, it is necessary to make in depth study.By means of statistical and analysis method for extensive test data companied with demonstration testing, using laboratory experiment as main study means , the correlations between different single factor including permeability , viscosity ratio of oil and water, rock surface properties, pore structure , total injection volume and displacement efficiency were developed respectively based on experiment data. Considering comprehensively the effect of single factor, the forecasting model for displacement efficiency was developed. Using large scale physical model, dynamic conformance factor was also studied.The studying results show that the positive correlation exists between permeability or porosity and displacement efficiency for varied oil/water viscosity ratio, the displacement efficiency of intermediately wet core is 1.63% higher than of water wet core and the displacement efficiency of water wet core is 2.47% higher than of oil wet core, the positive correlation presents between pore character parameters and displacement efficiency, the positive correlation exists between total injection volume and displacement efficiency or total injection volume for varied oil/water viscosity ratio. Trial calculation of developed mathematical model for displacement efficiency indicates that the error value between calculated result and tested results is 1.8% to 5.1%, and the relative error is 2% to 9%. By means of large scale physical model with well parameter controllability and physicochemical stability, sweep feature was studied and a method used to describing dynamic sweep factor for homogeneous and nonhomogeneous model was developed.With gradually increasing development intensities and difficulties in high water cut stage sandstone reservoir with medium or high permeability, determining the residual oil distribution is becoming more and more urgent , so all the research results can supply theoretical references for re-evaluating waterflooding reservoir's potential reserves and producing more residual oil.