基于流线积分法的注水井网非稳态产量模型

Non-steady Water-flooding Production Model of Areal Well Pattern Based on Flow Line Integral Method

低渗透油藏注水开发通常表现为油水两相非达西渗流,基于达西定律推导的计算方法不再适用。根据流线积分法基本原理,考虑启动压力梯度的影响,推导了单根流管中油水前缘突破前后的产量计算公式,然后引入面积井网注水开发过程中启动角的计算方法,最终通过建立数值积分可以得到不同井网形式下的非稳态产量计算模型。对比了模型计算结果与油田实际生产数据,证实了模型的可靠性,能够满足油田现场产量预测的要求。运用该模型计算并探讨了启动压力梯度、井网形式及生产压差对油井生产动态的影响,发现启动压力梯度对油井生产影响大,在开发指标预测过程中不能忽略;五点井网产量高、递减慢,在条件允许的情况下应该尽量采用五点井网;合理提高生产压差能够提高采油速度,缩短油田开发周期,开发效果好。

The development of low-permeability reservoirs displays non-Darcy flow in the process of water-flooding,which makes the calculation methods based on Darcy′s law not applicable. Based on the flow line integral method and considering the threshold pressure gradient,the production calculation formulas of the flow tube before and after water break- through were derived,then the calculation method of startup angle in the water-flooding development of areal well pattern was introduced,and finally the non-steady water-flooding production model of low-permeability reservoirs was established through numerical integration. This model could be used to predict the production of oil wells,and the reliability of the model was approved by comparison between calculation and realproduction. Applying the model to a certain block,we analyzed the effect of threshold pressure gradient,areal well pattern and production pressure drop in oil production. The results show that the threshold pressure gradient had great influence on the production of oil well,so it could not be ignored when predicting the development index;the production of five-spot well pattern was larger than others while its decrease was slow,so the five-spot well pattern is suggested in the oilfield;and the increase in production pressure drop could enhance the rate of production and shorten the development cycle of oilfields.