低渗非达西渗流相对渗透率计算方法及特征

现有的相对渗透率计算公式是基于达西定律的,而低渗油层渗流为非达西类型。建立了低渗非达西渗流相对渗透率计算方法,导出了计算公式,并进行了非稳态流动实验。结果表明:在低渗油藏相对渗透率曲线中,束缚水和残余油饱和度较高,两相渗流区范围较窄;随含水饱和度增大,油相对渗透率递减较快,水相对渗透率递增较慢;非达西渗流使油相相对渗透率增大,使水相相对渗透率减小,使产水率增大;油井见水后,产油量会迅速下降,水驱低渗油藏采收率不高。

CALCULATING RELATIVE PERMEABILITY OF NON-DARCY FLOW IN LOW PERMEABILITY MEDIA

Existing calculation method of relative permeability is based on Darcy’s law. However, studies have shown that flow in low permeability media does not follow Darcy’s law, and that a starting pressure gradient (SPG) occurs in the percolation. Therefore, formulas of relative permeability with SPG taken in-to account are derived. Additionally, an unsteady state flow wa-ter- oil relative permeability test is performed. The results show that: 1)the residual water and oil saturations are higher in the relative permeability curves of low permeability media; 2)the region of two phase flow is narrower; 3)relative permeabili-ty of oil decreases quickly and relative permeability of water in-creases slowly with water saturation increasing; 4)oil production declines quickly after water occurs in the wells, and 5)water drive recovery for low permeability reservoirs is lower.