Study On The Distribution Law And Main Controlling Factors Of Paleokarst Reservoirs In Majiagou Formation In Fuxian Area

Fuxian area is located in the southeast of the Shanbei slope.Majiagou Formation in the study area developed a set of karst reservoirs.Because the formation process of carbonate reservoir is complex,different layers have great differences in reservoir characteristics,and the main controlling factors of reservoir distribution and development are not clear,which greatly restricts the next step of exploration and development.Combined with the analysis of laboratory data and logging data,the reservoir petrological characteristics,physical properties and reservoir distribution law of Majiagou formation in Fuxian area are analyzed.The types of sedimentary microfacies,the characteristics of karst paleogeomorphology and the main types of diagenesis in the study area are clarified.The main factors controlling reservoir distribution are analyzed from three aspects:sedimentary facies,karst paleogeomorphology and diagenetic facies.The Ma₅¹～Ma₅⁴ layers in the study area is mainly developing evaporative tidal flat facies and the reservoir space is mainly composed of intercrystalline pores,intercrystalline solution pores and dissolution pores.The reservoirs are mainly developed in the central and western parts of the study area.Among them,M5₁³,M5₂² and M5₄¹ reservoirs have the best physical properties.The sedimentary microfacies are mainly dolomite flat,and see a small area of gypsiferous dolostone flat.The palaeogeomorphic units can be divided into karst monadnock,karst trench,karst terrace and karst platform,among which karst monadnock has the best reservoir development,followed by karst terrace.Dolomization and dissolution play a positive role in the development of reservoir space.Filling,pressure solution and dedolomitization are the main reasons for the deterioration of reservoir physical properties.The good rock assemblage types are developed in the favorable sedimentary facies,which provides a good basis for the later diagenesis to transform the reservoir,and the karst paleogeomorphology determines the diagenesis type to a certain extent.