Accelerating Mature Well Decommissioning Through Data-Driven Rig-Less P&A Strategies in Mature Fields of Southern Pakistan: A Fit-For-Purpose Approach

Abstract

As the oil & gas industry transitions toward more sustainable operations, efficient, safe, and environmentally responsible well decommissioning has become an increasingly critical priority, particularly in mature assets. This paper presents lessons learned from an integrated rigless Plug & Abandonment (P&A) campaign executed across multiple wells in southern Pakistan. The campaign targeted aging wells with significant wellbore access limitations, scaling, and tubular/casing integrity challenges. By leveraging adaptive engineering, structured data analysis, multi-service integration, and real-time optimization, the campaign achieved up to an 80% cost reduction compared to conventional rig-based operations. The project successfully abandoned 57 wells in 326 days while reducing CO2 emissions by approximately 200 metric tons through optimized equipment utilization. The wells, aged up to 40+ years, presented complex downhole conditions including severe scaling, tubing leaks, and compromised casing integrity Non-Intervention pressure surveys were conducted to determine appropriate well killing methodologies targeting cost-effectiveness and efficient job planning. As most wells exhibited sub-normal pressure conditions due to depletion, accompanied by moderate to severe losses, fit-for-purpose Loss Circulation Material (LCM) designs were deployed to enable single-stage cement plug placement. Laboratory testing played a critical role in validating the performance of GasTIGHT slurry system, which was specifically optimized for wellbore temperatures ranging from 120°F and 350°F. All testing was conducted in accordance with API 10B standards to ensure mechanical integrity, zonal isolation reliability, and long-term barrier performance. Operationally, each well was executed under a unified framework integrating slickline, coiled tubing, cementing, and pumping services while simultaneously streamlining the associated logistical resources including lifting equipment, accommodations, fuel and optimization of the sequencing of the wells. Field execution demonstrated remarkable efficiency, with cement plugs up to 335 m placed in a single stage via coiled tubing, exceeding the conventional ~ 200 m limitation typically associated with rig-based drill pipe, pump-and-pull methods. State of the art cement simulators were employed to accurately model downhole hydraulics, ensuring that frictional pressures remained within safe limits for surface equipment, coiled tubing, and well tubulars. The integrated rigless team, comprising only 20-24 personnel, significantly reduced risk exposure compared to conventional rig-based campaigns. This campaign underscores the effectiveness of integrated planning, robust laboratory validation, and adaptive execution strategies in overcoming the inherent challenges of mature wells. The approach delivers a fit-for-purpose, sustainable, and economically optimized solution for well abandonment, setting a new regional benchmark for safe and efficient decommissioning operations in Pakistan's mature fields.