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

Under the guidance of new principles and methods of modern sedimentlogy, reservoir geology, integrated with core observation, the data of thin section identification (conventional and casting thin section), X diffraction, geochemistry methods of cathodoluminescencean, strontium isotope, carbon and oxygen isotope, trace element, inclusion, etc this thesis has carried out detailed study on Ma5section of reservoir, and the sedimentary facies, diageneses, diagenctic model, reservoir characterization in the Lower Paleozoic carbonate rocks Majiagou member reservoirs in the Daniudi gas filed, Ordos basin, as objects of study.Though the regional correlation and study of reservoirs and sedimentary facies, sedimentary facies can be compartmentalized to2facices, open-platform and evaporative carbonate platform; on the whole is evaporative carbonate platform; only a part of Ma4section distributing area is open-platform, sub-facies is mostly tidal flat.Reservoir diversified in diageneses, complicated during diagenesis, the diageneses which are constructive to the reservoirs are mainly dolomitization, gypsumization, degypsumization, dissolution.The main destructive diagenesis consist of compaction, de-dolomitization, meta-somatic-filling; and pressure solution has double effects. Meanwhile, based on the model of diagenesis and porosity evolution, four diagenetic phase can be divided in sequence of syndiagenesis, early diagenesis phase, epidiagenetic phase, and post diagenesis phase.The preserving spaces are mainly secondary pore feature; high quality of pore structure parameters include intragranular pore space, intergranular pore space, and dissolution hollows, dissolution pores, dissolution fissures. Little affectred by filling and had a good connection, interparticle dissolution pore, interparticle dissolution fissures and structural fissures, can format better reservoir. The reservoir belongs to low porosity and low permeability reservoir type, the main throat types is micro-fine throat. Meanwhile, due to the influence of different sedimentary environment, diversity and multiple phases of diagenesis, lithology and physical properties of reservoir show strong heterogeneity.On the basis of specific study of lithology and physical properties porosity, permeability of reservoir, integrated with volume of production, four reservoir types can be divided in the research area, that is classⅠ,Ⅱ,Ⅲ,Ⅳ, which all belongs to low porous, low permeable type. Class Ⅰ, porosity:more than4%; class Ⅱ, porosity:3%-4%; class Ⅲ, porosity2%-3%. Class Ⅰ, belongs to supratidal dolomite ground, high quality of reservoirs, has a very narrow distribution; class Ⅱ, has a smaller effective thickness than class Ⅰ, but a wider distribution; class Ⅲ, supra-tidal muddy dolomite ground mainly distributes in the edge of research area, characterized by muddy intercalation.