Shale Reservoir Heterogeneity Of The Second Member Of Funing Formation In Subei Basin

As an important unconventional resource,Shale oil has been paid more and more attention by scholars.The shale of second member of Funing formation in Subei Basin is an important palaeogene source rock with lake face,which has been evaluated to be a favorable reservoir of shale oil by the unconventional resources preliminary survey carried out by Jiangsu Oilfield.However this shale reservoir has shown strong heterogeneities of rock components,bedding structure,storage space,oil-bearing ability,mechanical properties,instead of being the homogeneous black organic-rich deposits.In this paper on the basis of lithofacies features and division,we have used techniques of thin section analysis,cathodoluminescence(CL),FE-SEM and X-ray diffraction to research on heterogeneities of lithofacies space distribution,pore space,organic geochemical indexes,oiliness and brittleness in shale reservoir from second member of Fu formation.A few results and achievements have been obtained below:According to the core bedding structure and mineral composition,we have used the method of three grade nomenclature to establish the criteria for classification of lithofacies of mudstone.Shale reservoir in second member of Fu formation includes 13 types of major facies;Lithofacies are unevenly distributed in horizon and in vertical.Reservoir space includes core structural fractures,nine types of micro-pores and four types of micro-fractures.Solution pores and structural fractures contribute more significantly to reservoir space.Uneven distribution of reservoir space is affected by lithofacies(bedding,mineralogy),diagenesis and tectonism.Combining organic geochemical indexes,well testing data and core observation,we have concluded that organic heterogeneity of shale mainly reflects in the abundance,type,maturity of organic matter and oiliness,which have obvious uneven distribution vertically and horizontally.By analyzing elastic parameters obtained in triaxial mechanics of rock experiment,we found that mechanical properties in different lithofacies and layers differ greatly.Rock brittleness is mainly controlled by the brittle fragmentation content of mineral grains,bedding structure,temperature,pressure and micro-fractures.All of those aspects of heterogeneity above are considered in shale reservoir evaluation in the study area.The most favorable lithofacies are carbonate shale,silty shale,laminated mud carbonate,and the most favorable layers are the third and the fourth layer.