考虑非达西渗流及毛管力的低渗油藏油水相对渗透率计算新方法

A Novel Method for Calculating Oil-water Relative Permeability of Low-permeability Reservoirs Considering Non-Darcy and Capillary Pressure

油水相对渗透率是描述储层多孔介质油水渗流的重要参数,而低渗油藏的油水相对渗透率不能用已有的公式计算获得。通过考虑低渗储层多孔介质中油水渗流特征,建立了考虑启动压力梯度及毛管力影响的低渗油藏非稳态油水相对渗透率计算方法。进行了非稳态油水相对渗透率实验。计算了不同影响因素下的油水相对渗透率曲线,并分析了各因素对油水相对渗透率的敏感性。研究表明,启动压力梯度作为油水渗流的阻力,对油水相对渗透率的影响更为显著。毛管力作为动力,仅对油相相对渗透率有影响,对水相相对渗透率无影响。当考虑启动压力梯度及毛管力作用时,计算的产油量及产水量最为准确,误差仅为2.41%和3.51%。

Oil and water relative perm abilities are main coefficients in describing the fluid flow in porous media. However, oil and water relative permeability for low permeability oil reservoir can not be obtained from present correlations. Based on the characteristics of oil and water flow in porous media, the method for calculating the oil and water relative permeability of low permeability oil reservoirs, which considering effects of threshold pressure gradient and capillary pressure, has been established. Through conducting the non-steady oil and water relative permeability experiments, oil and water relative permeability curves influenced by different factors have been calculated. Finally, sensitivities of threshold pressure gradient and capillary pressure on oil and water relative permeability are analyzed. Results show that： the threshold pressure gradient more prominently affects the oil and water relative permeability; capillary pressure cannot influence the water relative permeability but only the oil relative permeability. When considering threshold pressure gradient and capillary pressure, calculated values of oil production and water production are the most accurate, whose errors are only 2.41% and 3.51%.