The Study On Reservoir Characteristics And Storage Capacity Dominant Factors On Shale Of Lower Palaeozoic Erathem In Southeastern Chongqing Area

The marine organic-rich shales of Niutitang and Longmaxi formation in southeastern Chongqing area became the key horizons for shale gas exploration.Therefore,it was great significant for evaluation of gas resource condition potential in two shale reservoirs to clear the reservoir geological characteristics and reservoir capacity.Through the TOC analysis,thin section analysis,X-ray diffraction,field-emission environmental scanning electron microscope(FEI-SEM),high-pressure mercury injection,low-temperature gas(N2 and CO2)adsorption experiments and CH4 isothermal adsorption experiment,the results revealed that the total organic carbon of Niutitang and Longmaxi formation shale was 2.9% and 2.76% respectively,staying high to over mature stage;Mineral component mainly comprised quartz and clay minerals with over 30% quartz content;The pore volume of two sets shales were 0.0288 ml/g and 0.0300 ml/g respectively,with the largest proportion of mesoporous in two sets shale pore volume;The specific surface area of two sets shales were 29.09 m2/g and 24.07 m2/g respectively,with micropores and mesopores amounting to almost all of the specific surface area in shale.Micropores in the Niutitang formations were more well-developed compared with Longmaxi formation.The Langmuir volume of Niutitang formation was higher than Longmaxi formation,while the Langmuir pressure of two sets shales had little difference,which illustrated that the reservoir capacity of Niutitang formation was better than Longmaxi formation.