Distribution Law And Main Controlling Factors Of Carbonate Reservoir In Member Ma 5 Of Majiagou Formation In Yanchang Exploration Area

Research purposes:This paper mainly study the reservoir characteristics,distribution law and main controlling factors of reservoirs and gas reservoirs of carbonate in the Majiagou 5th Formation in Yanchang exploration area.Research methods: Firstly,this paper makes clear the Pre-carboniferous paleokarst landform characteristics,petrologic characteristics in Member Ma 5 of carbonate,reservoir diagenesis,diagenetic facies and lithofacies paleogeography of the study area by stratigraphic correlation,core description,thin section identification and geochemical analysis.Then,the distribution characteristics and law of reservoirs and gas reservoirs in the study area are ascertained by the interpretation method of logging data.Finally,the main controlling factors of reservoir and gas reservoir are confirmed through combing the law of reservoir and gas reservoir with the karst landform,diagenesis,diagenetic facies and lithofacies paleogeography.Research results:The reservoirs and gas reservoirs of carbonate in the Majiagou 5th Formation in Yanchang exploration area mainly distribute in Sub-Member Ma 5₁,Ma 5₂,Ma 5₄,Ma 5₅,and partly in Ma 5_6¹0.The main distribution areas of reservoirs and gas reservoirs include the karst platform and karst terrace of paleokarst landform,diagenetic facies such as the penecontemporaneous dolomite diagenetic facies,gypsum-salt dissolved breccia dolomite diagenetic facies,dissolved breccia dolomite diagenetic facies,seepage reflux dolomite diagenetic facies,seepage concealed dolomite diagenetic facies and degypsumization-dedolomitization diagenetic facies,and the paleogeography such as the dolomitic flat,gypsum-bearing dolomitite flat and gypsum dolomitite flat of the evaporate platform,gypsum-bearing lake and partial gypsum-salt lake of restricted platform and intertidal shoal and undertidal shallowsea of the open sea platform.Paleokarst landform,diagenesis,diagenetic facies and paleogeography are the main controlling factors of the carbonate reservoirs and gas reservoirs.