Characteristic Of Organic Reef Reservoir Heterogenity And Its Mechanism In Changxing Formation Of Upper Permian? Eastern Sichuan Basin

The reservoir heterogeneity study is essential to reservoir characterization and it is also hard to study.Its contents refer classification,evaluation,mechanism and the affection to development of oil and gas field.There are lots of methods in studying heterogeneity,such as geological genesis method,sequence stratigraphy method,various experimental method,geological statistic method,various mathematics calculation method,logging explanation method,geological modeling method,seismic forecast,numerical stimulation and production dynamic analysis.So far,geological genesis method which emphasis on sedimentology and diagenesis is widely used in heterogeneity study.And based on it,it usually takes use of fine logging interpretation and property parameter such as porosity and permeability to quantitatively character the heterogeneity from those parts which include interlayer,the inner layer,plane and microscope.However,there are few people work on it in studying area,so that the heterogeneity study is weak.Currently,with the increasing growth of carbonate reservoirs exploration in Sichuan basin,strong heterogeneity becomes practical problem which has seriously restrained the exploration and development of reef and bank gas reservoirs.As the research objective,the external features of typical reef and bank section of Changxing Formation has been carefully observed and combining with the analysis of thin sections and rock data,the reservoir heterogeneity features and formation mechanism of Panlongdong reef and bank profile in Changxing Formation of eastern Sichuan basin has been discussed.The results show that a strong cyclicity and reservoir heterogeneity can be observed in the vertical direction of Panlongdong reef and bank facies.In terms of reservoir rocks distribution,reservoir thickness,the degree of dolomitization and dissolution phenomenon,appears cyclic variation with the cyclical change of sea level.Reef and bank reservoir heterogeneity has been controlled by high-energy sedimentary facies,changes of sea level and constructive diagenesis.The high-energy sedimentary facies is the key controlling element of primary pore,which determined the sedimentary heterogeneity.Dolomitization and dissolution is advantageous to the reef reservoir formation.Atmospheric fresh water leaching transformation has a key role for optimization of reservoir.Sea-level fluctuation determines the cyclicity of reef and bank development,and selective reform of constructive diagenesis which deepens the reservoir heterogeneity.