A Triple-String Cement Approach in Redefining Well Plug and Abandonment Techniques

Abstract Well Plug and Abandonment (P&A) process stands as the primary phase in decommissioning activities. Compliance with country regulations and industry standards is imperative for P&A methods. With over 2,000 wells requiring abandonment post-concession by the Operator, costs extend beyond P&A to encompass waste handling, logistics, scrap disposal, and SSHE concerns. To enhance cost-effectiveness, a novel barrier placement technique, the triple-string cement balance plug, has been innovated, trialled, and assessed. This paper introduces a novel technique, the triple-string cement balance plug, enhancing well Plug and Abandonment (P&A) processes. The primary objective is to establish well barriers across necessary sections via Off Rig operation (Phase 1 using a slickline/electric line and a cementing unit) as much as possible. The procedures for the first and second barriers are similar to Operator's best practices. The additional procedure involves the placement of the third barrier across three annuli. It is achieved by limited penetration perforation and placing a cement plug simultaneously across tubing (2-7/8" or 3-1/2" × 7" casing) and the 9-5/8" casing annulus. Then a well barrier is verified through pressure testing to the required test pressure. The tubing is cut below the SSSV, followed by circulating the well with kill-weight fluid and suspension. Phase 2, by utilizing a Rig/Rigless unit to retrieve tubing, cut and retrieve remaining casing and conductor, if any, and finally the placementof environmental plug. With successful trials during the 2021-2023 campaign and subsequent adjustments, this technique proves successful in perforation, circulation, cement placement, and meeting pressure testing criteria. Implementing this technique anticipates substantial cost savings in the Operator's extensive well P&A operations. Considering the Operator's potential 2,000 wells for P&A post-concession and non-usable wells, this technique could yield total savings of up to 12% for P&A operations alone. Moreover, minimizing the extraction of tubing and casing reduces waste handling, particularly hazardous materials like Mercury, Arsenic, and radioactive substances. However, the potential cost savings from reduced tubing and casing extraction are not factored into the cement balance plug in 3 annulus technique's estimated savings.