Geochemical Characteristics Of Shale Oil And Gas Retention In The Shulu Depression And Prediction Of Movable Oil

The thick shale formations in the lower third member of the Shahejie Formation in the Shulu Depression are rich in shale oil resources.The dissertation studied the shale in the lower third member of the Shahejie Formation and the aim of this research is to discuss the composition of retained oil and gas in the shale interval,the pattern of its evolution and main controlling factors,from the perspective of organic geochemical characteristics and retained oil and gas characteristics by the thermal pressure simulation experiments,mass spectrometry chromatography and rock pyrolysis and analyzed the mobility of retained oil and gas in shale.The analysis showed that the shale organic matter types in the lower third member of the Shahejie Formation of Shulu Depression were mainly Type I kerogen,and some Type ?₁ and Type ?₂ kerogens.The organic carbon content was mostly distributed between 1.0%and 3.0%.the average content of Chloroform asphalt"A"is0.2464%,which is almost greater than 0.1%.S₁+S₂ is mainly distributed in the range of 5mg/g-20mg/g.In addition,the organic matter maturity of the shale in the plane goes up with the increase of burial depth,and reaches the maximum near the center of the depression.It has strong potential for oil and gas generation and provides superior material conditions for the shale oil formation.The results of rock pyrolysis and separation of group components indicate that the total hydrocarbon content of retained oil and gas in shale is between 20%and 75%,with an average ratio of 49.11%.The saturation ratio is from 0.8 to 3.58 and the value is 1.57 respectively.At the same time,the characteristics of hydrocarbon production and expulsion in shale were studied in combination with hot-pressing simulation experiments.The characteristics of oil-gas biomarker compound parameters that remained with changes in maturity were analyzed,indicating that Pr/n-C₁₇,Ph/n-C₁₈,and Pr/Ph which can be used as accurate indexes to estimate the thermal maturity of shale.Even if the hydrocarbons are homologously generated,the thermal maturity of shale oil and bitumen are also different.The lower of thermal evolution level,the more visible difference between the oil and bitumen,the higher the degree of thermal evolution,the smaller the difference between the two,and as the maturity increases,the amount of retained hydrocarbons increases first and then decreases.At a certain stage of evolution,the total amount of retained hydrocarbons is gradually stable.The retained oil and gas in the source rock is mainly affected by the total organic carbon content,the thermal maturity,and petrophysical properties of the rock,combined with the composition of the Shahejie shale-retained oil and gas in the Shulu Depression,the recovery coefficient of the chloroform asphalt“A”light hydrocarbon,and the calculation method of rock oil resources and the results of heating and pressing simulation experiments,the shale oil mobility model of the lower third member of the Shahejie Formation in the Shulu Depression was obtained,and the movable rate of the shale oil in Shulu Depression was calculated to be 5%-15%,which means a greater mining value.