启动压力影响下确定油藏有效动用半径

低渗透稠油储层具有启动压力梯度,油藏储量的有效动用受到更多条件的限制。基于低渗储层基本渗流特征,文中分析了油藏弹性能量开发中的不稳定渗流过程,并采用稳定逐次逼近法求解包含启动压力梯度项的渗流方程;考虑启动压力梯度影响,建立了在低渗透油藏衰竭开发过程中满足油井开井日产油量要求的有效动用半径的求解方法;结合油田实际情况,分析了低渗透储层中压力和压力梯度分布规律,以及油藏储量极限动用、有效动用半径的变化规律。研究表明,对于此类油藏,要综合考虑技术和经济条件确定油藏储量有效动用的界限,才能合理部署油藏开发井网。

Determination of effective drainage radius for reservoirs considering threshold pressure gradient

Because of the existence of threshold pressure gradient in low permeability and heavy oil reservoirs,the effective drive of these reservoirs is restricted by more conditions.Based on characteristics of porous flow in low permeability reservoirs,the unsteady flow drive by natural elastic energy in low permeability reservoirs was studied,and the corresponding flow model in which threshold pressure gradient was taken into accounted was solved by using a method of steady-state successive approach to unsteady-state solution.A calculation method of drainage radius for low permeability reservoirs considering threshold pressure gradient was presented,which satisfied the daily oil production for well startup.Based on field cases,the characteristics of pressure distribution and pressure gradient distribution in low permeability reservoirs were analyzed,and the variations of limit drainage radius and effective drainage radius of low permeability reservoirs were studied.The analysis shows that the deployment of well pattern for low permeability and heavy oil reservoirs depends on limits of effective drive considering both engineering and economic factors.