基于流管法的面积波及效率计算方法研究

中国已开发的大多数油田,经过多年的加密调整和注水开发,目前已处于高含水或高采出程度阶段,开采和稳产难度越来越大。因此,对注水开发油田进行水驱面积波及系数的研究意义重大。根据注水油田的基本特点,基于流管法建模基本原理,建立了五点法流管模型,利用BeckleyLeverett方程,结合单元分析法和流线积分法,对注水油田五点法井网面积波及效率的计算公式进行了详细推导,绘制并分析了面积波及系数和采出程度随时间的变化曲线。结果表明:当无流管突破时,注水油田的面积波及系数随时间的增加而线性增大;当主流管突破见水后,波及系数增大程度越来越慢,最后趋于平缓。当油田被注入水完全波及后,继续利用注水提高采收效果的作用很小,水驱效率明显降低。研究结果对于注水油田面积波及系数的求解及水驱动态开发规律的研究具有借鉴意义。

Calculation methods of areal sweep efficiency based on stream-tube method

Most of the developed oilfields in China have been in high water cut stage or high recovery stage after many years of encryption adjustment and water injection development. The mining and stable yield become more and more difficult. Therefore, it is of great significance to study the area sweep coefficient. On the basis of the characteristics of water flooding oil fields, based on the basic theory of stream-tube model, a five-spot well pattern is constructed. The Beckley-Leverett equation combing with element analysis and flow line integral method is used to deduce the areal sweep efficiency equation of the five-spot well pattern, and the equation is given. The curves of area sweep coefficient and oil recovery versus time are plotted and analyzed. The results show that before water breakthrough, injected water evenly spreads, and oil recovery and sweep efficiency linearly increase; after water breakthrough in the main stream tube, the increase of sweep efficiency is slower and finally getting gentle. After all the stream tubes are broke through, the effect of water injection for enhancing recovery is very weak, and the water flooding efficiency will decrease obviously. The research result provides reference for the solution of areal sweep efficiency of low permeability reservoir and the study of water flooding dynamic development.