Study and application of the combination technique of secondary oil recovery with tertiary oil recovery in low permeability reservoirs

The study found out that 1-5 zones of the midland third section of Shahejie in Pucheng oilfield is fracture type reservoir with low porosity and permeability.Be- cause of strong heterogeneity in interlayer and high per- meability contrast,the producing condition in interlayer is quite different:the waterflooded area in major layer is big with high recovery,while the situation in non-essential layer is on the opposite.Therefore,the development effi- ciency is poor.In order to solve the difficulties occurred in profile control,the combination technique of secondary recovery with tertiary recovery is studied and adopted, namely the combination technique of controlled NAL gel and ZY microbial flooding.The application proves that the technique not only improves water absorbing profile in vertical but also enhances displacement efficiency,and it has brought great economic benefits.