民和盆地中侏罗统煤-油页岩层系生油特征

本文简要论述了民和盆地中侏罗统含煤及油页岩层系的生油特征，探讨了盆地独特的石油地质和地球化学条件。原油主要地化特征为:Ｐｒ/Ｐｈ比值偏高（２.６５-３.１５）、甾烷/藿烷比值极低（０.０３）、Ｃ_２７甾烷较丰富、Ｔｓ/Ｔｍ＞１低硫芴/氧芴比值、较高含量的Ｃ_２９降新藿烷及重排藿烷类化合物及相对丰富的长链联苯及烷基四氢萘系列化合物。中侏罗统煤－泥页岩层系含生油潜力明显不同的多类型油页岩，多数油页岩属由藻类和陆生高等植物母质组成的混合型有机质，沉积环境为淡水－微咸水弱氧化条件，其地化特征也表现为高Ｐｒ/Ｐｈ比值（平均为１。９８），低甾烷/藿烷及低硫芴/氧芴比值等特征。某些油页岩富含Ｃ_２９降新藿烷及重排藿烷系列化合物，它们应为主力源岩。油页岩多含再沉积型或沉积改造型有机质。异常地热作用对源岩演化及原油地化特征有重要影响。

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

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.