辽河盆地过渡带有机地球化学（Ⅱ）──甾萜烷及芳烃系列化合物成熟度参数在过渡带内的系统变化特征

Organic Geochemistry of Bio-Thermocatalytic Transition Zone in the Lisohe Basin (Ⅱ)── Systematic Variation of Maturity Parameters of Steranes,Terpanes and Aromatics within Bio-Thermocatalytic Transition Zone

所研究的辽河盆地东部凹陷沙一、沙二段烃源岩主要处于未成熟演化阶段，其可溶有机质中甾萜烷立体化学参数显示出“地质型”异构体的“异常”富集。各参数在普遍高于各自门限值的背景上，大致以２２００—２３００ｍ、２５００ｍ、２７００ｍ和２７７０ｍ为界线，呈现出系统的变化规律。同时发现萘、菲、氧芴和硫芴等系列化合物的成熟度参数与甾萜烷的成熟度参数的变化规律十分相似。本文对比进行了深入研究，结合原始可溶有机质红外特征吸收参数的变化特征，指出过渡带内甾萜烷及芳烃成熟度参数的变化规律受控于原始可溶有机质的演化特征，定性地提出了辽河盆地东部凹陷过渡带的地球化学判识标志，并认为本研究结果同样有助于不同地区过渡带气或未成熟油、低成熟油的判识。

Hydrocarbon source rocks in Section Sha-1 and Sha-2 of the eastern depression in Liaohe Basin, dealt with in the present paper, are mainly in an immature stage and of which stereochemical parameters of steranes and terpanes in the soluble organic matter show an abnormal abundance of "geopolymer" isomers. Each parameter is generally over its corresponding threshold value and shows a systematical variation with depth roughly bounded by 2200m to 2300 m, 2500 m, 2700 m and 2770 m, respectively. Meanwhile, maturity parameters of phenanthrene, naphthalene, dibenzofuran and dibenzothiophene series are found to be similar in variation to those of steranes and terpanes. On the basis of the contrast study in detail and the integration of variations of infrared absorption parameters in the original soluble organic matter,the paper points out that variations of maturity parameters of steranes, terpanes and aromatics within the bio- thermocatalytic transition zone are dependent on the evolutionary features of the original soluble organic matter. The paper also qualitatively raises some geochemical identification markers for the bio-thermocatalytic transition zone of the eastern depression in Liaohe Basin. The present results can be applied to the identification of biothermocatalytic transition zone gases or immature and low-mature oils in other different areas.