The sedimentary basins of Xinjiang Uygur Autonomous Region, China, are moderately to poorly explored for petroleum. Volumetric adequacy of petroleum source rocks is a critical exploration risk in these basins, particularly because source rock data are limited. This study provides new source rock data and speculatively assesses the source rock potential of Xinjiang basins.
The Junggar (Zhungaer) basin, the best explored of the Xinjiang basins and containing a giant oil field, is underlain in many areas by an Upper Permian lacustrine oil-shale sequence remarkable for its organic richness and oil source quality. Depending on its position in the basin, the Permian section ranges from immature to overmature and is inferred to be the principal source of oil in the basin. Upper Triassic–Middle Jurassic coal measures, including lacustrine rocks, constitute a secondary source rock sequence in the basin.
The smaller, intermontane Turpan (Tulufan) basin contains a very similar Upper Triassic–Middle Jurassic sequence, which, where sufficiently buried, probably comprises the only significant oil source sequence in the basin.
The vast Tarim (Talimu) basin offers the greatest variety of potential source rocks of all Xinjiang basins but remains the least well documented. From limited but geologically planned and focused sampling, Cambrian, Carboniferous, and Permian strata are not considered major oil contributors in the dominantly shallow marine Paleozoic section of the northern Tarim basin. Only Ordovician black shales appear to have significant potential. The Upper Triassic–Middle Jurassic sequence of the northern Tarim basin is similar to that of the Junggar and Turpan basins—a section rich in coal and lacustrine shale that constitutes another potentially significant oil source. Due to the size, stratigraphic packaging, and structural relief of the northern Tarim basin, Paleozoic and Mesozoic potential oil source beds range from immature to overmature.