Saturated Hydrocarbon Characteristics in Source Rocks and Palaeo-environment Significance in Dongling Block of Songliao Basin

The paper is aimed to research the character of saturated hydrocarbon and confirm paleosedimentary environment of source rocks, including Yingcheng Formation, Huoshiling Formation and Quantou Formation in Dongling Block of the Songliao Basin. Based on GC/MS analysis data of saturation hydrocarbon of core extracts and methods of molecular organic geochemistry. The results show that the carbon number of n-alkanes is mostly unimodal distribution, and the nC16～nC18 was main peaks, which indicates evolutionary level of hydrocarbon source rocks was upper. The C29 sterane's 20S/(20S+20R) and αββ/(αββ+ααα) showed positive correlation, and 20S/(20S+20R) and αββ/(αββ+ααα) was about 0.4. All these results indicate the source rock organic matter is at mature stage, the hydrocarbon source rocks of Huoshiling formation in 2154.78m of well SN183 is better than other samples. The hydrocarbon source rock's Pr/Ph is in the range of 0.706～2.179. The content of gammacerane is relatively higher. The distribution patterns of sterane are characterized by C29C27C28. All facts show that source rocks are formed under shallow water. The organic matter of these source rocks mainly come from terrestrial higher plants with lower contribution from the few aquatic organisms, deposite in the weak oxidation-desoxidation condition and slightly brackish-brackish lacustrine environments.