Thru-Tubing Plug & Abandonment System Enables Rigless Setting of Cement Plugs Across Multiple Annuli

Abstract Plug and abandonment (P&A) regulations mandate permanent, cross-sectional wellbore barriers extending across all annuli. This typically requires recovering and disposing of production tubing, followed by section milling and, in some cases, casing recovery. Such operations demand heavy-duty workover units or drilling rigs, resulting in extended timelines, high costs, and significant emissions. In recent years, alternative techniques such as Perf, Wash and Seal (PWS) have demonstrated advantages over conventional methods like section milling. However, these techniques still require a rig or workover unit to pull the production tubing in order to deploy the equipment in the production casing. Conversely, existing rigless P&A solutions have been limited to single-annulus barriers, restricting their application and wider adoption. Thru-tubing P&A technologies capable of setting barriers across multiple annuli represent a step change for operators seeking to reduce expenditure, cut carbon emissions, accelerate decommissioning campaigns, and meet regulatory requirements. To the authors' knowledge, this paper presents the first successful installation of dual-annulus, rock-to-rock barriers using a thru-tubing PWS system conveyed on coiled tubing, making the operation fully rigless from start to finish. By eliminating the need to pull and dispose of fatigued or contaminated tubulars, the system reduces operational complexity and the likelihood of fishing operations, lowers costs, and minimises HSE exposure — all without impacting drilling activity. Furthermore, the thru-tubing PWS system also eliminates sustained casing pressure (SCP) and contaminants such as residual oil-based mud (OBM) trapped between casing strings. Finally, advancements are presented for optimising barrier placement in largely free-annulus scenarios, such as production tubing, through a one-trip straddle system that integrates limited-penetration perforating charges and can be deployed via coiled tubing.