Study On Reservoir Heterogeneity Of 15th Sand Group Of Es₂ In Tuo142 Block Of Shengtuo Oilfield

Shengtuo Oilfield is the main oil exploration and development zone in Shengli Oilfield,the reservoir of the second member of Shahejie Formation is one of the main oil-bearing strata.After nearly 50 years of development,it has entered the high water-bearing stage,the problem of unclear understanding of reservoir heterogeneity has become increasingly prominent.Therefore,a detailed study on the heterogeneity of the reservoirs in the target reservoirs of the study area was carried out in order to provide effective guidance for optimizing the effects of injection and production of reservoir and improving the recoverable reserves.This paper took 15th Sand Group of Es₂ in Tuo142 Block of Shengtuo Oilfield as the research object.The cycle comparison,grading control and lithology-thickness comparison method were used for layer division.Various sedimentary microfacies were determined according to the sedimentary facies marking,the characteristics of the distribution of sedimentary micro-facies of each rhythmic layer were studied according to the order of single well-section-plane.The in-layer,inter-layer and planar heterogeneity of the reservoir were analyzed by means of rhythmic patterns,heterogeneity of permeability,characteristics of the distribution of interlayer and physical parameters.Based on the above various geological factors affecting reservoir heterogeneity,the reservoir heterogeneous synthetic index was calculated by entropy weight method to further characterize the heterogeneity of reservoirs quantitatively.The study showed that 15th Sand Group of Es₂ in the study area mainly developed delta front subfacies,in which the sedimentary microfacies of the debouch bar was widely developed,the sedimentary microfacies of the underwater distributary channel was less developed.A certain scale of interbed was developed in the layer,mainly composed of physical interbed and calcareous interbed,permeability of intra-layer exhibited medium-strong heterogeneity.The development of the interlayer was relatively stable,the development degree of the sand body of each rhythmic layer exhibited medium-strong heterogeneity,the permeability of the rhythmic layer exhibited the characteristics of the composite inverse cycle from the bottom to the top.The sand body connectivity of each rhythmic layer was medium-poor on the plane,the planar distribution of the porosity of each rhythmic layer was relatively homogeneous,exhibited medium-strong heterogeneity,the permeability difference was large,exhibited strong heterogeneity,planar heterogeneity was mainly controlled by sedimentation.The entropy weight method was used to calculate the heterogeneous synthetic index,which avoided the limitations of single parameter in characterization,the degree of reservoir heterogeneity was divided into four levels according to the distribution of heterogeneous synthetic index,the heterogeneous synthetic index of the reservoir in the study area was mainly distributed between0.2 and 0.5,the reservoir exhibited medium-strong heterogeneity.