Progress of Carboniferous oil and gas survey in Qaidam Basin

Carboniferous in Qaidam Basin is a new field for marine oil and gas exploration. Based on the investigation of Carboniferous oil and gas geological conditions, the resource potential is evaluated to provide a scientific basis for seeking oil and gas strategic succession areas. With Carboniferous system in Qaidam Basin as the main target, based on investigation and research, the first carbonaceous oil flow in Qaidam Basin was obtained, and the important discovery of oil and gas in Paleozoic marine strata in Qaidam Basin was obtained. Through comprehensive regional survey, balanced profile inversion, vitrinite reflectance and other comprehensive analyses, the authors assertained the main tectonic movement periods in Qaidam Basin. Through basin simulation techniques, reconstruction of the burial history of Carboniferous system, and analyses of oil and gas geochemical index of Carboniferous source rocks in Delingha depression of Qaidam Basin, the authors studied the evolution history of hydrocarbon generation from source rocks. The results show that Carboniferous source rocks in Delingha depression of Qaidam Basin are widely developed, with high abundance of organic matter and great burial depth without metamorphism, and these rocks are in mature-high maturity stage. The burial history of Carboniferous in Delingha depression is mainly characterized by rapid burial period, stable period and strong uplifting and erosion period. The history of subsidence and uplift-erosion has been different since Cenozoic. The thermal evolution history of Carboniferous source rocks is mainly charactered by “secondary hydrocarbon generation and late hydrocarbon generation”, which is mainly controlled by the tectonic movements in this area. The overall thermal evolution of Qaidam Basin is slowly decreasing, mainly controlled by the magmatic thermal events and tectonic activities in Qaidam Basin. The investigation results show that the new layer of Carboniferous has good oil and gas conditions and broad resource prospects, which is the successive layer for following exploration in Qaidam Basin.