Sedimentary evolution and reservoir-forming conditions of Taiyuan Formation in Jiaxian area,eastern margin of Ordos Basin
The Taiyuan Formation in Jiaxian area on the eastern edge of Ordos Basin has superior conditions for near-source reservoir formation,but the lithology combination is complex and diverse,the enrichment law is not clear,and the favorable target zone needs to be further implemented.Combined with drilling core,well log-ging and seismic data,the comprehensive research from lithology,sedimentary evolution,source rock distribu-tion,fault characteristics,reservoir characteristics and other aspects shows that:(1)The Taiyuan Formation in Jiaxian area is mainly composed of limestone type and interstratified type.(2)The paleogeomorphology of Tai-yuan Formation in Jiaxian area is generally high in southeast and low in northwest,and the paleogeomorphology controls the sedimentary facies belt in this area.(3)The sedimentary environment of the four submembers of Taiyuan Formation is obviously different in Jiaxian area.The southern part of Miaogou stage is carbonate plat-form gray flat phase,and the northern part is mud flat phase.The middle part of Maergou stage is the tide-con-trolled delta phase,the north and south ends are the carbonate platform gray flat phase,and local barrier sand bars are developed.Most areas of the ramp stage are carbonate platform gray flat facies and local barrier sand DAMS are developed.The whole Dongdayao stage entered the carbonate platform gray flat facies deposition.(4)The sandstone of the underwater distributional channel in the central tide-controlled delta of Jiaxian area is the preferred target of exploration and development,and the local rich and integrated reservoir of the sloping sec-tion limestone and Maergou limestone in the southeast is the replacement target of exploration and development.(5)The sedimentary evolution of the Taiyuan Formation in Jiaxian area provides favorable conditions for gas ac-cumulation in the area.Intergranular pores and debris dissolution pores are developed in the sandstone of the del-ta underwater distributary channel,and a large number of dissolution pores,biological pores and micro-fractures are formed in the limestone,providing sufficient storage space for gas rich and integrated reservoirs.The lower part is in contact with No.8 coal,and the upper part is close to No.5 coal,which has the congenital advantage of near-source accumulation.The tight rock inside the Taiyuan formation forms lateral sealing,and the multiple sets of mudstone in the overlying strata are good cap beds.These conditions lay a solid foundation for the rich ac-cumulation of the Taiyuan Formation,and the Taiyuan Formation in Jiaxian area has a good prospect of gas ex-ploration and development.
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