特低渗油藏水驱开发效果评价方法研究

EVALUATING METHODS OF WATER-FLOODING DEVELOPMENT EFFECTIVENESS IN ULTRA-LOW PERMEABILITY RESERVOIR

针对特低渗油藏生产采用常规开发指标难以有效评价油藏生产动态的问题,引入有效驱动渗透率的概念,认为只有渗透率大于有效驱动渗透率的油层中的流体才参与流动。运用活塞驱替理论推导了含启动压力梯度两相流的有效驱动渗透率计算公式,可以确定油藏中参与流动的小层比例,并对各小层渗透率、有效厚度等参数加权平均计算后,运用产能公式得到各层流量,进而计算出油井产量,最终确定实际启动的地质储量,运用启动地质储量对采出程度等常规开发指标进行修正。结合长庆特低渗油藏开发动态研究表明,修正后的开发指标能准确有效地评价生产开发效果。

Practice in production of ultra-low permeability reservoirs indicate that it is difficult to evaluate the reservoir production performance with conventional development index effectively,so,the effective flooding permeability is introduced,and research shows the fluid can flow in the sublayers whose permeability is greater than the limit.Formula calculation of the effective flooding permeability in two-phase flow of threshold pressure gradient is derived by using the method of piston drive,and proportion of flowing sublayers is determined.With net thickness and permeability of each sublayer that is weighted on on average,each sublayer and oil well deliverability are calculated,then actual threshold geologic reserve is determined finally.Conventional development indexes,such as degree of reserve recovery etc,are amended by using threshold geologic reserve.Study on production performance in Changqing oilfield shows that the development indexes that are amended can be used to evaluate development effectiveness accurately and efficiently.