Characteristics of Chang-6 Extra-low Permeability Reservoir in Ansai Oil Field

Chang 6 reservoir is a depositional sandbody of delta front facies. The sandbody is the superposition of forward and reverse cyclothems. It distributes widely and has homogeneous thickness. It is a extra low permeability reservoir. According to a large quantity of laboratory data, the authors analyze the characteristics of sedimentation, pore microstructure and physical property distribution of the reservoir, and analyze also the difference of the physical property distribution in longitudinal and horizontal directions. The permeability profile of the reservoir is divided into three types. It is held that the different type of the permeability profile has different effect on the output of oil wells and the result of waterflood development. The results of the study in the paper supply geological basis for controlling water and stabilizing oil output in the oilfield.