Well Re-Entry for a Permanent Well P&A in Deepwater - Case Study

Abstract An appraisal well was drilled in 2008 in a field offshore and later abandoned by the operator. During the cement plug abandonment process at the selected depth, the cement volume pumped was higher than expected, indicating loss to the formation. No cement drill out or re-logging was performed afterward. The well was also drilled through a salt layer, raising concerns for the current operator that salt creep over 17 years may have collapsed the 10.3/4″ production casing. The extent of collapse couldn't be estimated without well access, so risk assessment addressed contingencies for none/light, medium, and severe collapse. A final concern was pressure buildup from hydrocarbons below the cement plug potentially permeating through the formation over time. This P&A project encompassed a comprehensive suite of technical solutions developed, qualified, and made available before execution. To manage potential pressure beneath the well cement plug, a modified Retrievable Bridge Plug (RBP) was engineered, allowing coiled tubing drilling through the RBP while containing sudden annular pressure release, with surface BOPs closed around the hydrill pipe. For casing integrity, various Bottom Hole Assemblies (BHAs) were prepared: drift BHAs to address light collapse by milling and polishing the casing to a 9″ ID; a collapsible blade milling tool for medium collapse scenarios; and Cut & Pull BHAs, including Perf, Wash & Cement systems, for severe collapse and casing retrieval. To ensure barrier integrity, 80 meters of high-quality cement were placed in the annular space between the 10 3/4″ and 14″ casings using the perf, wash and cement system. A pressure formation testing system was also prepared to qualify the salt layer as a potential abandonment barrier, depending on well conditions. To mitigate operational risks, support tools like circulation subs and magnetic retrieval systems were deployed. The project resulted in a successful permanent well abandonment, marked by several key achievements. A total of 13 Bottom Hole Assembly (BHA) runs were executed using P&A tools, alongside four successful fishing operations. Notably, 80 meters of the Perf, Wash, and Cement system were deployed in a single run, effectively placing cement both in the annulus and inside the 10-3/4″ casing. Following this, 80 meters of cement were drilled out inside the casing to allow for cement logging evaluation, which yielded excellent results. Over the course of the operation, approximately 1,350 tool hours were logged without any non-productive time or incidents, showcasing exceptional operational performance and safety. This campaign also set important milestones, including the deepest well abandonment in Latin America to date, and the world's first successful Perf, Wash, and Cement operation on a salt formation.