Advanced Thru-Tubing System Delivers Permanent Well Abandonment via Multi-Annular Cementing

Abstract

Well abandonment is an inevitable stage in the asset lifecycle, and current trends reflect a growing focus on subsurface resource protection. However, these operations do not generate return on investment, often leading to their postponement until they become unavoidable. Despite this, regulatory compliance and best practices demand more efficient, long-lasting, and cost-effective abandonment solutions. In this context, this paper presents a Thru Tubing permanent plug and abandonment (P&A) system that optimizes execution by eliminating the need for conventional rigs, which are commonly required in traditional abandonment methodologies.

To support this analysis, a case study is presented based on a recent intervention in South Texas, USA, where the need for permanent well abandonment in compliance with current regulations was identified. The abandonment operation was executed using a Thru-Tubing Perf, Wash & Seal technique, establishing a rock-to-rock barrier through the placement of a cement plug in both lateral and vertical directions.

This paper details the multi-annular and main borehole cementing process, utilizing Coiled Tubing to deploy a specialized bottomhole assembly (BHA). This BHA integrates key tools such as cup packers, flow diverters, and perforating guns with charges designed for selective perforation in single or double casing strings. Additionally, the methodology for interval cleaning using specialized chemicals and the application of dynamic cementing is analyzed.

The rigless intervention allowed the original drilling program to continue without the need to mobilize a rig for abandonment. This not only significantly reduced the environmental footprint by utilizing smaller equipment but also minimized exposure to operational risks by requiring fewer personnel on-site. Furthermore, it optimized operational times and substantially reduced the overall abandonment costs.

This paper will benefit well intervention engineers seeking alternative solutions to conventional techniques for optimizing permanent well abandonment operations.