Study On The Carbonate Reservior Characteristics Of Majiagou Formation In Fuxian Area, Ordos Basin

Based on the study of petrologic character, physical characteristics, pore types and structure characteristics, reservoir classification, diagenesis ect, this paper has systematic studied the carbonate reservoir characteristucs of Majiagou formation in Fuxian area.Majiagou formation in Fuxian of Ordos basin has deposited mainly the sediments of evaporation and tidal-flat carbonate consisting of dolomites and gypsum-dolomite. The reservoir space often include three types, such as pores, dissolved pores and fractures. According to the pore description of thin section, the image analysis of casting thin section, capillary pressure curves ect, the pore structure of reservoir in studying area divided into pore types, dissolve holed, fractured and mixed.Based on the observation of cores, conventional thin section and casting thin section identification, X diffraction, cathodoluminescence, electeonic probe spectrum and carbon and oxygen isotope analysis etc., together with physical properties, systematic studied the diagenesis and the diagenetic environment of Majiagou formation in Fuxian area, and establish diagenetic evolution sequence and porosity evolution mode.Though statistical analysis of petrophysical parameters and mercury injection parameters, the carbonate reservoir of studying area is divided into class I, class II, classIII, classIV, Combined with seismic datas extracted, Comprehensive RMS and Instantaneous Frequency to prospect advantageous regions for the five unit of majiagou formation.Research results show that:the carbonate reservior of majiagou Formation is low porous and low permeable in Fuxian area, Ordos Basin, the favorable reservoirs areas are dissolve holed and mixed. The diagenesis is complex, which are constructive to the reservoirs pore are dissolution, metamorphism and seepage-reflux dolomitization; the mineral filling, compaction, pressure solution and dedolomitization have strong influences on the reservoirs pore. There are rarely see class I reservoir, classIVbelongs to extra low porous and permeable reservoir and has poor reservoir property, commen to see class Ⅱ and classⅢ. Northwest of FG3and FG4are the mainly advantageous regions, southeast of FG7, northwest of FT1well and south of FG6are the second advantageous regions.