Well abandonment, although an activity as old as the art of well construction itself, undoubtedly is perceived as a high cost, revenue-eroding commitment for exploration and production companies. Nonetheless the fulfillment of this obligation is non-negotiable for an operator, and thus the application of an efficient methodology to prioritize the abandonment of inactive wells, and ultimately reduce risk exposure is fundamental for a cost effective abandonment campaign. This paper describes how an exploration and production company ("the Company"), working in conjunction with an asset risk management consultancy, successfully developed and applied a qualitative risk-based abandonment prioritization strategy for an inventory of inactive subsea wells.
The exercise entailed a preliminary identification of the inactive subsea well inventory, after which a qualitative assessment methodology was devised using twenty-five well integrity related criteria calibrated to allow for various well types, well function, condition, age, design, history etc. An aggregate of weighted scores was subsequently applied to the Company's corporate risk assessment matrix, for consistency, based on the escalation potential in the event of a loss of containment.
The results clearly highlighted the wells with the highest risks and thus formed one of the components (including abandonment phase and operational complexity) of an integrated abandonment campaign, ultimately incorporated into the drilling schedule.
An efficient prioritization strategy applied to legacy wells served as an improved risk management and proactive cost allocation tool in the hands of senior decision makers for managing medium to long term liabilities, ultimately leading to reduced risk exposure and long term capital savings.