Integrity Assurance Technologies for Plugged Wells in Wen 23 Gas Storage

As Wen 23 Gas Storage is a depleted sandstone gas reservoir, old wells that can no longer be reused need to be plugged before its construction. To guarantee the effectiveness of plugging old wells and assure the integrity of the gas storage, the design concept of wellbore integrity of the technical standard formulated by the Norwegian Oil Industry Association was adopted, and risks of channeling and leakage before and after plugging of the old wells in Wen 23 Gas Storage were identified. Furthermore, a well barrier system was drawn, a heat-resistant swelling-delayed gas-tight plugging system suitable for high-temperature gas layers was developed, and process designed to ensure the wellbore integrity of plugged old wells was created. Assurance technologies for wellbore integrity based on the design, construction, and monitoring of the well barrier were thus obtained and then applied to plug the old wells in Wen 23 Gas Storage. In addition to achieving a 100% success rate of field construction and favorable wellbore integrity after plugging, these wells also survived the long-standing action of alternating stresses during multiple rounds of injection and production. The research results and field application show that conducting wellbore integrity-oriented design and construction according to wellbore integrity can not only ensure the long-term wellbore integrity of old wells after they are plugged but also provide a reference for the design of similar gas storages.