Use of PWC Technique for Abandonment in Deepwater Scenarios: Overview and Lessons Learned from Operations in Brazil

Plugging and abandonment of offshore wells are operations carried out at the end-of-life cycle of oil fields. With the increasing stringency of well abandonment regulations and the rise in decommissioning activities of offshore fields, the use of new technologies has been increasingly employed to enhance reliability, efficiency, and cost reduction. One of these technologies comprehends single operation well plugging by perforating, washing, and cementing, also known as PWC (Perforate, Wash and Cement). Improvements in cementing techniques for well abandonment in deepwater scenarios can lead to significant cost reductions and efficiency improvements. In this context, techniques such as PWC, when compared to conventional remedial cementing, cutting and removal, or milling of the casing, offer advantages in both operational time and the reliability of the established barriers. The PWC technique was developed to improve abandonment efficiency and enhance the quality of hydraulic isolation required to establish dependable barriers. In subsea scenarios, there are significant logistical challenges, such as the use of a large volume of spacers and the high operational times for complete circulations, which can prolong the operations prior to the actual cementing operation. The design phase is detailed to address these challenges, including cement slurry and spacer design, washing parameters, and operational procedure. Four successful PWC operations are described, comprehending a complete cement evaluation after job completion. The results demonstrate that excellent barrier quality can be obtained with this technique and the practices applied. As they were the first operations of this type in Brazil's deepwater basins, this knowledge provides valuable input for future abandonment projects. This article presents a summary and the evolution of the first four operations carried out in deepwater scenarios in Brazil, where particularities of Petrobras wells in relation to the history of scenarios already faced in other countries demanded the search for solutions to adapt the PWC for safe execution and high expectation of success.