Study On Provenance And Reservoir Characteristics Of The Fourth Member Of The Xujiahe Formation In The Xinchang Tectonic Belt,Western Sichuan Depression

The reservoir characteristics of the fourth member of the Xujiahe Formation in the western Sichuan depression are closely related to the provenance.Based on the previous research results,this paper is guided by the theory of sedimentology and reservoir geology,and based on the field analysis,drilling core,rock fragments,reservoir physical properties and other test data,the new field structure in the western Sichuan depression.The provenance and reservoir characteristics of the fourth member of the Xujiahe Formation were analyzed in detail,and the effects of provenance on reservoir characteristics were discussed.The following points have been learned from the research:1.the content of quartz from west to east in the four sections of the study area is gradually increasing,bounded by the eastern part of the Xinchang area.The west is mainly lithic sandstone,and the eastern part is mainly lithic quartz sandstone.The main direction of the provenance is from the northwest to the southeast.Combined with the distribution characteristics of cuttings,conglomerate,quartz cathodoluminescence and heavy mineral combination,it can be seen that the source of the whole area is affected by Longmen Mountain.The southeast part of the Xinchang tectonic belt is affected by the Longmen Mountain and Micang-Daba Mountain in the north of the basin.,and the Micang-Daba Mountain's provenance is mostly.2.The main characteristics of the reservoir granules in the fourth member of the Xujiahe formation of the study area are “very rich cuttings and poor feldspars”.The lithology of the study area is dominated by lithic sandstones,and the cuttings are dominated by sedimentary rock cuttings.According to the characteristics of rock components and provenance,the reservoirs in the study area can be classified as three types that quartz-rich sandstone reservoirs,cuttings-rich sandstone reservoirs and calcium-rich sandstone reservoirs.The reservoir grain size is medium,the sorting is better,and the rounding is dominated by sub-angular shape.The average porosity of the reservoir is 5.73%,the permeability is 1.43(mD),and the permeability after thecrack is excluded is 0.27(mD),which is a typical low porosity and low permeability reservoir.The types of reservoir reservoirs are secondary pores,primary pores(including residual pores)and cracks.The main diagenesis processes include compaction and pressure dissolution,cementation,dissolution and rupture.3.The reservoir properties affected by Micang-Daba Mountain are generally better than Longmen Mountain provenance,including the quartz-rich sandstone reservoirs in the upper sub-segment and the cuttings-rich sandstone reservoirs in the lower sub-reservoir.The main reservoir space is secondary dissolved hole.In summary,the far-source sandstone reservoir is better than the near-source sandstone reservoir.Due to the extensive development of the calcarenaceous sandstone in the middle sub-segment,only the middle sub-segment's reservoir which controlled by Longmen Mountain has good physical properties,and its reservoir space is dominated by primary or residual pores,good pore structure makes it become relatively high quality reservoirs with low porosity but high permeability.