Revised models for hydrocarbon generation, migration and accumulation in Jurassic coal measures of the Turpan basin, NW China

• Published in: Organic geochemistry 2001-01, Vol.32 (9), p.1127-1151
• Main Authors: Li, Maowen, Bao, Jianping, Lin, Renzi, Stasiuk, Lavern D., Yuan, Mingsheng
• Format: Article
• Language: English
• Subjects: Applied sciences; Chinese oils; Coal-derived oils; Crude oil, natural gas and petroleum products; Earth sciences; Earth, ocean, space; Energy; Exact sciences and technology; Fuels; Geology and geochemistry. Geological and geochemical prospecting. Petroliferous series; Hydrocarbons; Jursassic coal measures; Lacustrine source rocks; Prospecting and exploration; Prospecting and production of crude oil, natural gas, oil shales and tar sands; Sedimentary rocks; Stratigraphy; Turpan basin
• ISSN: 0146-6380; 1873-5290
• DOI: 10.1016/S0146-6380(01)00070-5

Whether or not the Lower-Middle Jurassic coal measures in the Turpan basin of NW China have generated commercial quantities of liquid petroleums is a problem of considerable importance that remains contentious as it has not yet been resolved unequivocally. This study provides evidence against the Jurassic humic coals as the only major source for the oils discovered in the Taibei depression of this basin and suggests additional significant contributions from the Upper Permian and Middle–Lower Jurassic lacustrine source rocks. The Carboniferous–Permian marine source rocks may have been important also in limited locations along the major basement faults. Molecular and petrographic data indicate that the majority of the Middle Jurassic strata are currently immature or marginally mature with respect to hydrocarbon generation. Within the major depocenters, the Middle–Lower Jurassic coal-bearing strata of the Baodaowan and Xishanyao formations has reached the conventional oil window (i.e. with vitrinite reflectance >0.7% Ro). Pre-Jurassic (Upper Permian in particular) derived hydrocarbons appear to be widespread in extracts of fractured Jurassic coal and fine-grained rocks. Large differences have been observed in the absolute concentrations of biomarker compounds in rock extracts of various source intervals. Thus, “coaly” biomarker signatures of the oils most likely resulted from mixing and migration contamination when hydrocarbons derived from mature source rocks migrated up through highly fractured coal seams along deep-seated faults. In addition to conventional exploration targets, revised petroleum generation and accumulation models predict that the focus in the Turpan basin should also include deep structures within the Carboniferous–Permian strata and subtle, low magnitude anticlines and stratigraphic traps within the Triassic–Jurassic sections. Crown copyright