Quantitative Characterization Of Reservoir Space And Pore Throat Distribution Of Continental Organic-rich Shale

Nowadays,China has not systematically and effectively studied the physical properties and oil-bearing properties of Mesozoic-Cenozoic low maturity continental shale reservoirs.Aiming at organic-rich shales in different sedimentary environments,this article selectes organic-rich shale of Qianjiang Sag of Jianghan Basin the 10 th rhythm of Eq3 and Chang 7th of Yanchang Formation in Ordos Basin as the research object.The paper uses logging data,X-ray diffraction,rock conventional pyrolysis to study the mineralogical,organic geochemical and lithofacies characteristics of continental shale.The physical properties and oil-bearing properties of the target formation were characterized by nitrogen adsorption method,high pressure mercury injection method and multi-temperature pyrolysis method.The result shows that the 10 th rhythm of Qianjiang Formation in Jianghan Basin is mainly salt lake facies and composed of grey-black dolomitic mudstone,grey-black mudstone and grey-black mudstone.It is dominated by macropore,in which free oil accounts for a large proportion in the pore.The organic matter is mainly type II and in medium and low maturity.The organic carbon content is relatively high.The Chang 7th of Yanchang Formation in Ordos Basin is mainly freshwater deep lake-semi-deep Lake facies and composed of grey siltstone,grey tuff and grey-black mudstone.Mesopore is dominant in the Chang 7th of Yanchang Formation,and adsorbed oil accounts for the largest proportion in pore.The organic matter is mainly type I and in medium and low maturity.The organic carbon content is higher than that in the 10 th rhythm of Qianjiang Formation.Both target intervals have good reservoir physical property,oil-bearing property and hydrocarbon generation potential.The main geological factors controlling the physical properties and oil-bearing properties of continental organic shale reservoirs are diagenesis,sedimentary environment and lithology,mineral content and organic matter.Reservoir physical properties are negatively correlated with compaction,metasomatism,recrystallization and relative content of brittle minerals,and positively correlated with dissolution,relative content of clay minerals and organic carbon content.The physical properties of type II kerogen shale are better than that of type I kerogen shale.The main controlling factors of oil-bearing are the type of organic matter,abundance,maturity of evolution and closure of source rock system.The oil-bearing property of shale with type I organic matter is higher than that of type II shale,and the oil-bearing property is positively correlated with the organic carbon content.Different sealing conditions also lead to different oil-bearing property,and the thick salt roof and floor are favorable for shale oil reservoir.