Geochemistry characteristics of high-mature source rock extracts and using various approaches to discriminate the indigenity

摘要

A total of 11 core samples of Cambrian source rocks and 2 Cambrian-sourced crude oils (TD2, T904) were analyzed. High content of total organic matters indicates a good to excellent source rocks. However, high maturity was indicated by high T-max values and very low content of HI index and S-1+S-2. The relative intact alkanes can be detected in most samples with no odd/even predominance. A series of relatively high abundance of terpanes and steranes can be detected on m/z 191 and m/z 217 chromatograms, respectively. Ratios of C-21/C-23 tricyclic terpanes are greater than 1.0. All samples of Yuli 1 and Tadong 2 show high abundance of C-26 similar to C-28 triaromatic steroids and triaromatic dinosteroids, with ratios of (C-26+C-27) TAS/C-28 TAS and TDSI greater than 1.0 and 0.62, respectively. Oil source rocks correlation between sampled rock extracts and typical Cambrian oils reveals that high-postmature Cambrian source rock extracts are well consistent with those two typical Cambrian oils that are usually used as end members oils represented by Cambrian-sourced oils. Three approaches were proposed to discriminate indigenity of high-postmature source rocks.