Objective By the end of 2020, the domestic lithium resources supply depending on external is as high as 70%. According to statistics, the gas fields of PetroChina Southwest Oil & Gasfield Company(Hereinafter referred to as Southwest Oil and Gas Field) generally produce water during development. At present, Southwest Oil and Gas Field has more than 1 900 production wells, of which more than 80% produce water. In 2020, the cumulative water production of conventional gas fields had exceeded 12×10⁹ m³. According to previous research reported, the gas field water, together with hydrocarbons such as oil and gas, has gone through a long period of hydrocarbon accumulation, and often contains more trace elements, especially for lithium content in some gas fields water, which is higher than in salt lake brine. Further sampling found that the lithium ion content in gas fields water of 17 wells in Southwest Oil and Gas Field was as high as 131.6 mg/L, and about 50% of the gas fields water of sampling wells had a higher lithium ion content than the lowest industrial grade, and also contained relatively abundant bromine, potassium and other associated resources. The follow-up evaluation of gas fields water in key wells confirms that the long-term stability of lithium and bromine resources in gas fields is relatively good. In addition, the Southwest Oil and Gas Field is rich in formation water resources, with the reserves of formation water in the three key blocks reaching 1.33 billion cubic meters. It is preliminarily estimated that the total potential value of lithium resources (calculated as Li₂CO₃) in the three blocks exceeds 310 billion yuan, which has a great value of development and utilization.