低渗透油藏水驱采收率计算新方法

分析了影响井网系数、驱油效率和波及系数的因素,结合非达西渗流理论,对低渗透油藏水驱采收率计算方法进行了研究.结果表明,对于低渗透储层,由于启动压力梯度的存在,不能全部有效动用井网控制储量,在井网系数中引入了有效驱动程度.水驱油效率是驱替压力梯度的函数,随井网密度的增大而增大;平面波及系数是注水方式、裂缝走向夹角及裂缝相对长度的函数.用该方法计算的水驱采收率与低渗透油藏动态比较吻合.该方法适合于测算低渗透油藏水驱采收率.

A new method for calculating recovery factor of water drive in low-permeability reservoir

The factors affecting coefficient of well pattern,oil-water displacement efficiency and sweep efficiency were analyzed. The methods for calculating recovery factor of water drive in low-permeability reservoirs were investigated with the theory of non-Darcy fluid flow. Because there is a kickoff pressure gradient in low-permeability reservoirs, reserves controlled by well-pattern can not be fully efficiently developed. The degree of efficient flooding is introduced into the coefficient of well pattern. The oil-water displacement efficiency is the function of displacement pressure gradient and furthermore increases with the rise of well spacing density. Lateral sweep efficiency is the function of injection-and-production system, angles between direction of injection and fractures, and the relative length of fractures. The recovery factor of water drive calculated by this method coincides with the data of reservoir performance. This method is reliable for the calculation of water drive recovery factor of tow-permeability reservoirs.