Characteristics of the oil Formation in the Middle Jurassic Coa-Shale Strata in the Minhe Basin

Key words: 
• Minhe basin /
• oil shale /
• coal /
• depositional environment /
• reworked sedimentan organic matter

Abstract: Special petroleum geological and geochemical conditions lead to a special type of oils formed in theMiddle Jurassic coal-shale strata in the Minhe basin. The oils are characterized by a higher Pr/Ph ratio(2. 65-3. 15)，very low sterane/hopane ratio(0. 03)，higher C₂₇ /C₂₉ α α α strerane ratio(1. 07 )，higherTs /Tm value(1. 09)，higher abundance of C₂₉ Ts and rearranged hopane series, higher abundance ofbiphenyl series and alkyl tetrahydrogen naphthalenes, and high value of dibenzofuran/dibenzothiophene,etc. Many types of oil shales with very different oil potentials occur in the Middle Jurassic coal-sh alestrata. Most of them areformed in weakly oxidizing freshwater sedimentary environments, with higherPr/Ph ratios(averaging 1. 98) and very low values of sterane/hopane and dibenzofuran /dibenzothiophone as main evidence. Some oil shales show higher abundance of C₂₉Ts and rearranged hopanes, re-Electing that these oil shales are the predominant contributor to the Minhe oil. It‘s also proved that theoil shales contain reworked sedimentary organic matter by organic geochemistry, organic petrology andkerogen TGA and DTG analysis. Source rock maturation and oil}gas generation are also affected by ab-normal geothermal energy.