Research On Oil Recovery Factor Prediction In Low Permeability Reservoir

The development of low permeability reservoir has becoming more and more important. The prediction of the oil recovery factor by waterflooding takes very important part during the development of the reservoir. Whether or not the best stimulation measures could be taken to improve the development result depends on the accuracy of the oil recovery factor prediction. The recovery factor prediction for medium-high permeability reservoir has been a mature technology. While the study on recovery factor prediction for the low-permeability reservoir is not sufficient because of the complex percolation mechanism.Based on the literature research, various kinds of existing percolation models are analyzed comprehensively in this paper, and the optimized model is selected, which could reflect the fundamental characteristics of low permeability reservoir. The three-dimensional and three-phase mathematical model considering the threshold pressure has been built and solved with finite difference method. Based on the above research, the numerical simulator for the low permeability reservoir has been programmed. We use the simulator to analyze the influence factors of recovery efficiency. The study shows that the recovery factor is affected by many factors such as the porosity, the permeability, the viscosity of the crude oil, the threshold pressure gradient, the well spacing density and the injection-production pressure difference. The result shows that, the recovery factor will increase with the porosity, the permeability of the reservoir, the well spacing density and injection-production pressure difference, and it will decrease when the viscosity of the crude oil or the threshold pressure gradient increases. At last, we get an empirical equation which could predict the waterflood recovery for low permeability reservoirs. We predicted the recovery factor of some block of Ordos basin using the empirical equation, and the result shows that, the equation could predict the recovery factor of the low permeability reservoirs accurately.