Study About Extra-low Permeability Reservoir Remaining Oil Distribution Based On Petrophysical Facies Flow Unit

For low,extra-low permeability reservoir,it is the influence of sedimentation,diagenesis,construction and a series of effects that result in the major difference in the reservoir property and percolation structure of the reservoir,the reservoir has strong heterogeneity and its remaining oil distribution is very complicated,whereas the heterogeneity controls the remaining oil distribution to some extent.Therefore,this article takes a extra-low permeability heterogeneity reservoir in the eastern part of Yanchang oilfield for example,making use of “petrophysical facies-flow unit” to study macroscopic remaining oil distribution of extra-low permeability reservoir and try to illuminate the remaining oil distribution law of this kind of reservoir.This can indicate the direction for digging the potential of the reservoir.By analyzing the internal relations between of petrophysical facies and flow unit in this article,illuminating that petrophysical facies and flow unit both can reflect storage-permeation characteristics from different angles,the same species of “petrophysical facies-flow unit” reservoir has the same rock physical properties and percolation characteristics.So taking the “petrophysical facies-flow unit” for key and fundamental unit of fine description of reservoir can turn these inhomogeneous problems to relatively homogeneous problems.Based on adequately studying geology and development situation in the research area,this article establishes “petrophysical facies-flow unit” ration comprehensive assessment target system,dividing the reservoir into several kind of “petrophysical facies-flow unit”.For each kind of “petrophysical facies-flow unit”,the article calculates single well reserves,demarcate technology recovery efficiency and study residue recoverable reserve distribution respectively.The research results show that “petrophysical facies-flow units” are elementary units that control the remaining oil distribution of this kind of reservoir.The same kind of “petrophysical facies-flow units” has the same remaining oil distribution law,thereby illuminating advantageous “petrophysical facies-flow units” remaining oil potential distribution characteristics and realizing from general research to elaborate research about macroscopic residual oil,it provides reliable geological basis for remaining oil potential tapping at the later period,meanwhile,it provides a neoteric research thought and method for remaining oil potential distribution research of the same type of extra-low permeability heterogeneous reservoir.