Optimization of Well Diagnostics and Repair

Abstract

Abstract Well Integrity discipline is all about barriers. Double barrier envelope policy is a well integrity requirement well-known worldwide. This can be found in international standards: API RP90 (1 & 2), Norsok D10, ISO 16530 (1 & 2). This policy applies to wells with positive pressure at surface capable to flow naturally. Primary barrier envelope consists of well equipment which is in direct contact with produced or injected media. Secondary barrier envelope will be exposed to well media in case of primary barrier element failure. This paper focuses on such kind of wells that have a positive pressure at surface and fall under double barrier policy. Any failure in primary barrier envelope (means - completion) is easily repairable during workover by simply re-completing the well with new completion. This can be done almost unlimited number of times, as long as there is a place to set the packer. Failure in secondary barrier envelope (means - casing) can be done as well, but not that easy and limited amount of time. In some cases, especially for onshore wells it might be economically more reasonable to drill the new well rather than to deal with complicated workover. Depending on the Company policy, casing integrity can be restored in sections using casing patches or the entire length can renewed by running and cementing casings of smaller diameter. Obviously, in both cases it impacts the size of the completion and cannot be done multiple times. Once the primary barrier element fails, it will result in sustained annulus pressure (SAP) appearance. SAP wells create a risk of external leak to surface (or subsurface) in case of secondary barrier element, such as wellhead, casings, or different accessories failure.