Abstract
The growing number of upcoming well abandonments has become an important driver to seek efficiencies in optimizing abandonment costs while establishing long term well integrity and complying with local regulatory requirements. With an increasing global inventory of Plug and Abandonment (P&A) candidates, Exxonmobil has been driven to look for the most reliable, safe, and cost-efficient P&A technologies. ExxonMobil's P&A guidelines are consistent with and often more stringent than the local regulatory requirements but are also achievable, at least in part, with rigless technologies, leading to a more cost-efficient approach while ensuring well integrity. The objective of this paper is to demonstrate the success of rigless abandonments and their benefits compared to rig-based solutions.
When developing a well abandonment plan, it is essential to consider a number of factors. These include local regulations, identification of zones to be isolated and suitable caprocks, and recognition of constraints including well history, conditions and uncertainties. Teams should begin with low cost operations without a rig if possible, estimate costs and effectiveness to achieve the barrier requirements, and evaluate batch operation opportunities for multi-well programs. ExxonMobil case studies are shown to help describe in detail how to make decisions about applicability of rigless abandonment options and how to properly execute such abandonments to achieve compliance with the barrier requirements.
It has been demonstrated that significant cost savings can be achieved by staging the abandonment program in a way that lower cost technologies are utilized during the early stages of well abandonment, starting with wireline where possible, followed by coiled tubing and finally by a pulling unit, as appropriate. P&A execution could be achieved without a rig in a majority of cases, including most offshore wells, with the need to use a rig only in special circumstances or phases of execution. It is important to note that the barrier placement and safety of rigless P&A execution will not be compromised, as compared to the rig-based P&As. Additional cost savings could be achieved by further optimizing P&A design at the well design stage, ensuring that there are no built-in limiters that would prevent rigless P&A execution at the end of well life.
Several case studies from ExxonMobil's global offshore experience demonstrate the feasibility and effectiveness of rigless P&A operations, with significant cost savings compared to rig-based P&As. It has been evident that rigless P&A choice is applicable to the variety of ExxonMobil's P&A projects of different complexities, with the same or superior quality of abandonment and safety record.