Quantitative Analysis And Distribution Prediction Of Natural Fractures In The Tight Reservoirs From Jimusar Sag

The Lucaogou Formation in Jimusar Sag contains a typical tight reservoir,which has great exploration prospects.Natural fractures play an important role for improving the seepage structure of tight reservoir.Therefore,quantitative characterization and exact prediction of fracture parameters and distribution have great significance to tight oil exploration and development in Jimusar Sag.In this paper,by taking tight reservoir fractures in the Lucaogou Formation of Jimusar Sag as the research object,the parameters,development periods and distribution of tight reservoir fractures in this area are studied based on outcrop observation,core description,thin section analysis,experiment test and seismic simulation.The results show that: The major types of study area are tectonic fractures,diagenetic fractures(bedding fractures)and abnormal high pressure fractures.The opening degree and dip of fractures are small,and the filling resistance(38.1%)is poor.The lower reservoir interval density(3.42 strip/m)and porosity(4.16%~7.97%)of fractures are better than upper reservoir interval density(2.58 strip/m)and porosity(2.29%~6.98%).The study area is mainly developed with three periods of fractures,which belong to middle Triassic,middle Jurassic and early Cretaceous,and wherein the second and third periods of fractures are more conducive to the accumulation of tight oil in study area.The seismic coherence cube aims at the recognition of fault,while ant tracer technique can identify fracture clearly.The azimuth of fractures shows NW,NNE and NS trending in northern,middle and southern area separately.And the NNE trending fractures may contribute to the migration and accumulation of tight oil in study area.The fracture prediction by multi-attribute superposition shows that the central-southern part of Jimusar sag may be the favorable fracture-developed area.