Reservoir Sedimentology Study Of Feixianguan Formation In Huanglongchang-Tianchengsi Area,Northeast Sichuan Basin

Carbonate reservoir plays an indispensable role in oil and gas exploration.China's marine strata are widely distributed with abundant oil and gas resources and huge exploration potential.In recent years,with the deepening of oil and gas exploration,great breakthroughs have been made in oil and gas exploration of marine carbonate rocks of the Lower Triassic Feixianguan Formation in northeastern Sichuan Basin.According to the dynamic data analysis,Huanglongchang-Tianchengsi area has the potential to acquire a large amount of reserves.Therefore,it is necessary to strengthen the study of reservoir sedimentology and reservoir distribution prediction in this area.In this paper,Feixianguan Formation in Huanglongchang-Tianchengsi tectonic area,northeastern Sichuan Basin,is taken as the research object.Field stratigraphic observation,logging data,thin section identification,scanning electron microscopy and physical property analysis data are used comprehensively.Combining macro and micro research methods,the sedimentary system and oolitic beach reservoir of Feixianguan Formation in the study area are studied in depth.The main achievements are as follows:1.The boundary between the top and bottom of Feixianguan Formation in northeastern Sichuan is clear,and it integrates with the micrite limestone and reef limestone of the underlying Changxing Formation,and with the medium-thin limestone and micrite limestone of the bottom of the overlying Jialingjiang Formation.Feixianguan Formation strata have various rock types,mainly including micrite?cloud-bearing?limestone,powder-fine-grained?lime-bearing?dolomite,granular limestone and gravel clastic limestone.2.Through the field profile survey,the field samples and drilling cores were identified and analyzed by microscopic thin sections.According to the characteristics of petrology,Paleontology and logging facies,it is believed that carbonate platform model developed in the early stage of Feixianguan Formation sedimentation and carbonate edge platform model developed in the middle-late stage of Feixianguan Formation sedimentation.3.The most favorable reservoir rocks of Feixianguan Formation in Huanglongchang-Tianchengsi tectonic area are granular dolomite and oolitic limestone.The main reservoir space types are intergranular?dissolution?pore and intergranular pore.According to the analysis of physical property data,the average porosity and permeability of Feixianguan Formation reservoir are 3.35%and 0.002�10^-3um²,which are low porosity and ultra-low permeability reservoirs.4.According to the distribution law of sedimentary facies and reservoirs in the study area,the most favorable facies zone for reservoir development of Feixianguan Formation is the platform margin shoal subfacies of platform margin shoal.The reservoir development degree is controlled by rock type,distribution of sedimentary facies zones,sea level rise and fall,diagenesis and other factors.