Abstract: On the basis of core observations and systematic sampling in the Mandong area of Qaidam Basin, and using rock pyrolysis, casting thin sections, sub-ion polishing scanning electron microscopy and other techniques, this paper studies petroleum geological conditions of reservoir formation and prospecting in the Mandong area of Qaidam Basin through typical reservoir anatomy. The results show that well-developed mature source rocks occur in Lower Gangchaigou Formation, Upper Gangchaigou Formation, and Lower Youshashan Formation in the Huangguamao-Kaitemilike-Youdunzi, and are the favorable reservoir-forming areas. Due to the long-term shore-shallow lake environment and lack of terrestrial debris supply in the Mangdong area, the reservoir is mainly composed of beach-bar sand bodies and stucco flat of the shore-shallow lake. Overall, the reservoir property is poor and most are tight reservoirs. The oil and gas reservoir in the Mangdong area is mainly structural reservoir, which is characterized by“upper oil and lower gas”and near-source accumulation. Also, it is mainly transported and accumulated vertically through faults. Based on the analysis of petroleum geological conditions and drilling results in the Mangdong area, deep natural gas is considered one of the most important targets for oil and gas exploration in this area. In addition, lithologic lens traps such as beach dams and plaster flats are the types that have great exploration prospects in this area.

Key words: Qaidam Basin, Mangdong area, Upper Ganchaigou Formation, petroleum geological conditions, the exploration direction