Reservoir Heterogeneity In Chang 8 In Heshui Of Xifeng Oilfield

The Heshui District is located on the southwest of the central uplift in Ordos Basin. Its stucture is gentle.The sedimentary facies is braid delta front in Chang8 in the Upper Triassic of the study area.The underwater distributary channel deposit is dominating.The main type of the reservoir is arcose,syrosem arcose,and little lithic sandstone.The texture maturity is in middle.Matrix is less than 10%,including most clay and little carbonate.The cement is most composed of chlorite and calcite.The pore is mainly remaining primary pore,less secondary dissolution pore,least pore between crystals and micro-crack.The diameter of pore is mainly in middle and the radius of the throat is in small.Most of the reservoir is in very low porosity and in very low permeability.The type of the diagenesis is most included of compaction, cementation,denudation, cataclasis,replacement,and it is in the A stage of middle diagenetic grade.There are six types of diagenetic facies,i.e. the compaction facies of blackmica,fe-clay or calcite, the cementation facies of carbonate,the remaining pore facies with chlorite,the denudation facies of feldspar,the remaining pore facies with chlorite-denudation facies of feldspar,the cementation facies of cholinite,in which the remaining pore facies with chlorite-denudation facies of feldspar is the best one for oil ,and it is mainly in the north and the east.The heterogeneity of Chang8 is strong,the grade of which in Chang8₁ is stronger than in Chang8₂,and the most factor of it is sedimentation.Both the sand body and the impervious bed are controlled by sedimentary facies.The heterogeneity parameter is strong in permeability and weak in porosity.The distribution of cracks in Chang8 is probably popular,and it is stonger in Chang8₁.In the water displacing oil experiment of the micro-model from real sandstone.There are four types of displcing:the remaining pore between primary grains,the secondary dissolution pore,the micro-crack and the compaction. The heterogeneity is the primary reason for the irreducible oil or the remaining oil.The research on heterogeneity is a important part to reservior.So based on the above,hoping some research will play a positive effect for the oilfield.