Optimized Well Plug & Abandonment Methodology Applied on a Brownfield towards Future Development Offshore Malaysia

Abstract

A Workover or sidetrack is often performed, in brownfields, to revitalize idle wells or to produce alternate zones. Recently, with a larger number of fields being redeveloped; the proper plug and abandonment (P&A) of donor wells gained relevance. This is a study of the evolution of the P&A methodology in a brownfield, offshore Malaysia, where engineering techniques and risk management strategies have been developed into a consistent approach to well P&A. The methodology has allowed economic access to reserves and has become a process that can be applied across the field based on well configuration, best practices and current technologies. The operations entail not only intervening wells for gravel pack removal, fishing of mechanical obstructions and retrieval of completions, but also isolation of completed reservoirs from surface whilst isolating cross flow between them, which is of paramount importance in a brownfield with plans for future enhanced oil recovery (EOR).Challenges, such as lack of information and the uncertain condition of ageing wells related to corrosion, leaking elements, zonal isolation, annulus pressure and well integrity; as well as inadequate maintenance, mechanical obstructions and failure of existing downhole equipment have been successfully managed in all cases.Key processes include extensive data gathering and upfront well investigation and preparation for contingency planning. The wells sequence has been optimized to minimize the impact of un-foreseen events; and the decision making process has been drafted to cover for a wide range of situations.Results show reserves that have been accessed at 40% the cost of a sidetrack, by retrieving old gravel pack assembly and workover the well; also, sidetrack wells have enabled reaching reserve opportunities in the field without the costly addition of slots to offshore platforms. This consolidates the methodology for its further application in the field with the potential to be implemented on other similar redevelopments.