Formation controlling factors and development patterns of large-scale reservoirs in Carboniferous Huanglong Formation of eastern Sichuan Basin
The Carboniferous Huanglong Formation in the eastern Sichuan Basin is one of the important natural gas producing layers in the Sichuan Basin.The Carboniferous reservoirs are the key factor controlling the development of gas reservoirs.In order to further evaluate the Carboniferous reservoirs in the eastern Sichuan Basin,expand new exploration fields and search for replacement areas,this paper systematically studies the main factors controlling the development of the Huanglong Formation reservoirs,summarizes the development models,and predicts the distribution of large-scale reservoirs,based on the previous studies,combined with the data of drilling,core,outcrop and assay.And the following research results are obtained.First,the Huanglong Formation reservoirs are mainly composed of granular dolomite,brecciate dolomite and crystalline dolomite.The reservoir space is dominated by intercrystalline pores/intercrystalline dissolved pores,intergranular pores/intergranular dissolved pores,karst caves and fractures.The grain shoal is the favorable reservoir,and the fractured-dissolution porous reservoir is of high quality.Second,reservoir development is mainly under the joint control of sedimentation and diagenesis of Leshan-Longnüsi Paleo-uplift and Kaijiang Paleo-uplift.The two paleo-uplifts control the distribution of grain shoals and the penecontemporaneous diagenesis,which is the basis of large-scale reservoir formation.The superposition of penecontemporaneous dolomitization,interlayer karstification and weathering crust karstification is the key to the formation of large-scale reservoirs.The Himalayan movement has generated a large number of structural fractures,improving the permeability and scale of reservoirs.Third,Type Ⅰ-Ⅲ reservoirs with a certain thickness and a large area can develop into large-scale reservoirs.Five development areas of large-scale reservoir are evaluated.It indicates that the discovered gas reservoirs are mostly distributed in the anticlinal structures of the five large-scale reservoir areas.In conclusion,the Carboniferous in the eastern Sichuan Basin still has greater potential in natural gas exploration and development,and the large-scale reservoirs which are developed extensively in synclinal areas are the important direction for increasing natural gas reserves and production in the following step.
Eastern Sichuan BasinHuanglong Formation of CarboniferousLarge-scale reservoirsMain controlling factorsReservoir distributionEvolutionary patternsNatural gas exploration
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