Catalytic hydropyrolysis for highly mature Carboniferous source rocks in the northern Xinjiang

The Carboniferous source rocks in the northern Xinjiang have the characteristics of high thermal evolution, which leads to the low level of biomarkers from conventional extraction. Catalytic hydropyrolysis was carried out in order to study the sedimentary background and organic matter biological sources. The results show that the n-alkanes and steranes from hydrogenolysis are representative of parent materials. The n-alkanes have a bimodal pattern with the main carbon peaks at n-C₁₈ and n-C_22-24 in shallow mudstones, indicating a contribution of pelagic aquatic zooplankton, and have a single-peak pattern with the main carbon peak at n-C₁₈-n-C₂₄ in deep mudstones, indicating a contribution of aquatic bacteria and algae. The contents of C₂₉ and C₂₇ steranes are comparable, which indicates a mixed source. In the pyrolysis products, the content of C₂₉ steranes is much higher, which clearly indicates a single parent material. Moreover, hydropyrolysis products contain more βα-moretanes and ββ-homohopanes. The Carboniferous source rocks were mainly developed in a reducing environment. High-quality marine source rocks of Carboniferous are mainly distributed in the lower segment with aquatic organisms such as bacteria and algae as a single source of organic matter. The experiments also confirmed that the hydrogen hydrolysis reaction could recover more information of biolo-gical markers, which is a useful supplement to conventional extraction methods.