Reservoir Distribution Principles Of Lower Carboniferou Strata In Kokpansor Depression,CHU-SARYSU Basin

CHU-SARYSU basin is structurally stable as passive continental margin basin Early Carboniferous,about500 meters thick carbonate rocks deposit in Kokpansor depression.Drilling and logging data reveal that natural gas are widely distributed in the lower Carboniferous strata in the depression,but not yet obtains the significant breakthrough In this paper,the early Carboniferous geographical evolution,reservoir type,reservoir character,reservoir distribution,gas-water distribution has been systematic studied with the casting thin sectionscoring,logging and seismic data.Surveys show that terrain slopes gently in Kokpansor depression,thehydrodynamic conditions are weak,the tidal zone gradually converted into broad carbonate platform from the edge of basin toward the sea,The lithology is mainly marl and clay particles limestone dominated.The stratas are cemented strongly,filled with sparry calcite in the micro pores,poor petrophysical properties.Hypergene karstification occurs in local area,macroscopic karst caves didn’t develop overall.The cracks which formed later in Hercynian Period strengthen karstification to generate caves.According to the evolution relationship between Hydrocarbon source rock and reservoir,by the end of Permian the hydrocarbon were explused into the reservoir which had been compacted at the end of CarboniferousTherefore,the natural gas trips had been compacted before accumulated.The drilling gas test indicates that the pore-type reservoir cann’t create value for low production capacity.The distribution principles of fracture-type reservoir with high production capacity need further study.