原油中硫代金刚烷的分析鉴定和地球化学应用

Identification and Geochemical Application of Thiadiamondoids in Crude Oil

硫代金刚烷在原油中普遍存在,其独特的分子结构和形成过程使其在石油工业中具有广泛应用。对目前在硫代金刚烷分析鉴别、成因机制、热稳定性和在油气领域应用等方面的研究进展及存在问题进行了系统总结。结果表明:目前原油中硫代金刚烷主要包括烃源岩生烃演化和热化学硫酸盐还原(TSR)作用两种成因机制,其中烃源岩生烃演化可形成原油中初始含量的硫代金刚烷,TSR作用可进一步生成大量的硫代金刚烷;硫代金刚烷的笼数越高热稳定性越高,在高成熟时可以发生热裂解作用;硫代金刚烷随TSR作用增强而不断富集,是TSR作用可靠的分子标志物;硫代金刚烷的δ^34S值通过TSR作用来改变,能够反映TSR作用的成因类型;在未遭受TSR作用的前提下,原油中硫代金刚烷的初始含量和δ^34S值代表着原始烃源岩的特征,可以应用于原油族群的划分。从目前的研究现状来看,硫代金刚烷的具体成因机制和详细的热稳定性界限还不甚明确;应用硫代金刚烷的含量来判识TSR作用时,要结合硫同位素和其他指标参数等结果才最为可靠;硫代金刚烷目前主要应用于TSR作用判识研究,在油-油对比和油-源对比方面的研究尚待进一步加强。

Thiadiamondoids are commonly found in crude oil.Because of their unique molecular structure and formation process,the thiadiamondoids are widely used in petroleum industry.The research progress and existing problems in identification,formation mechanism,thermal stability and application in oil and gas fields were summarized systematically.The results show that there are mainly two formation mechanisms of thiadiamondoids at present in crude oil,including hydrocarbon evolution of source rocks and thermochemical sulfate reduction(TSR)process,the first one can generate the initial small amount thiadiamondoids in crude oil,and TSR process can further form large amount thiadiamondoids;the higher the number of cages are,the higher the thermal stability of thiadiamondoids is,and the thermal cracking can occur in the high thermal maturity;thiadiamondoids are enriched with the enhancement of TSR process,thus can be regarded as reliable molecular markers of TSR process;δ^34S values of thiadiamondoids can be changed by TSR process,which can reflect the genetic type of TSR process;the initial content and δ^34S value of thiadiamondoids in crude oil without TSR process represent the characteristics of original source rocks,and can be applied to the division of crude oil group.According to the current research status,the specific formation mechanism and detailed thermal stability limit of thiadiamondoids are not clear;when the contents of thiadiamondoids are used to identify TSR process,it is necessary to combine sulfur isotope and other parameters;the study on thiadiamondoids is mainly focused on identification of TSR process,but the application on oil-oil and oil-source correlations needs to be further strengthened.