Advances and application of key techniques for enhanced recovery of the Puguang sour gas field

The Puguang gas field, the first sour gas field developed in China, has maintained efficient and stable production for 15 years. As it enters the mid-to-late stage of development, however, three major challenges threaten its long-term production stability. First, elemental sulfur deposition, unique to sour gas fields, combined with strong edge water incursion, makes it extremely difficult to maintain stable production over an extended period. Second, the effective and economic development of low-permeability gas reservoirs is critical to the stable production of the gas field. However, these reservoirs cannot be accurately identified using conventional methods. Third, wellbore pressure boosting is recognized as an important method to reduce the abandonment pressure of gas reservoirs and enhance the gas recovery of a gas field in the mid-to-late stage of development. However, there has been no precedent for the application of wet gas pressure boosting to a sour gas field, and the technical scheme for such wellbore pressure boosting remains unclear. To achieve long-term stable production and enhanced gas recovery of the Puguang gas field, we identify the patterns of water invasion, sulfur deposition, and differential seepage in the gas field through experiments on their mechanisms. Accordingly, four key techniques are developed: geological and engineering integrated synergistic water control, whole-process sulfur deposition prediction and treatment, fine-scale characterization and effective production of low-permeability reservoirs, and wet gas compression tailored for high-acid gas fields. The application of these techniques has yielded significant results in developing the Puguang gas field, enabling stable production for 15 years, five years longer than the original design. Furthermore, the gas recovery is projected to exceed 70% by 2025. These advances have reinforced the leading position of sour gas fields operated by SINOPEC among their global counterparts in terms of development indices.