Pressure-Activated Sealant Economically Repairs Casing Leaks on Prudhoe Bay Wells

Abstract

Abstract Pressure activated sealant was used to repair casing leaks in two Prudhoe Bay, Alaska oil wells without the use of a rig workover. The significance of the treatments, development of job screening criteria, and job planning and execution are reviewed. Production casing leaks are a frequent problem in mature oil fields, particularly where there is corrosion. Wells with casing leaks usually do not meet well operating criteria so they must be shut-in, causing a loss in valuable production. Casing leaks normally require a rig workover to repair since the tubing often has to be removed. Rig workovers are very expensive in offshore locations, remote areas, and harsh climates. Special pressure activated sealants, diagnostic tools, and treatment techniques have been developed to find and repair casing leaks without removing the tubing. Case studies of three Prudhoe Bay production wells describe how pressure activated sealant successfully repaired the small casing leaks in two wells without removing the tubing. The third well was not treated because it did not meet the screening criteria. One case study was unusual because the sealant fixed four deep casing leaks with one treatment. The case studies show how refinements in diagnostic techniques, candidate screening, and treatment planning and execution have resulted in the successful application of pressure activated sealant to repairing casing leaks in producing wells and in one case repaired four leaks with one treatment. Using pressure activated sealant to repair casing leaks can result in significant cost savings and return wells to production sooner. The treatment can be particularly useful in mature fields with corrosion problems and in offshore, remote, and arctic fields where rig workovers are expensive and rig availability is limited. Introduction Repairing casing leaks is one of the more challenging issues facing operators of mature oil and gas fields. Casing leaks are a frequent problem in mature oil fields, particularly where there is corrosion. Wells with casing leaks usually do not meet well operating criteria so they must be shut-in, deferring and possibly causing a loss in valuable production. Casing leaks normally require a rig workover to repair since the tubing has to be removed. Rig workovers are very expensive and are often time consuming in offshore locations, remote areas, or harsh climates. Also, the repair usually requires cement or other solidifying material pumped into the "A" annulus. This can make future workovers and other well operations difficult and impractical.