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ABSTRACT Due to the escalating number of ageing and depleted wells, the decommissioning of oil and gas wells has emerged as a critical aspect of the oil and gas industry. Nonetheless, decommissioning operations are known to be both time-consuming and expensive, requiring extensive workover operations that involve transporting heavy equipment, posing safety risks and environmental concerns. However, with the recent increase in the frequency of Plug and Abandonment (P&A), rig-less executions have become increasingly popular. They offer a cost-effective and time-efficient approach to decommissioning wells. However, it comes with unique challenges that vary from well to well and require sophisticated planning and utilization of specialized tools and procedures to ensure proper decommissioning of wells meets all regulatory requirements. The objective of this study is to analyze the challenges encountered during the execution of rig-less P&A and implement the lessons learnt to improve the overall efficiency of the operation. The paper encompasses the detailed study of unique challenges encountered during the P&A of more than 50 wells, both vertical and deviated wells and with different types of completion. The challenges encountered during execution include the inability to properly kill the well having tight formation (typically sandstone) with a very narrow pore /loss gradient resulting in a simultaneous loss and gain situation. This requires specialized formulation of loss circulation material that is pumpable through restricted IDs of coiled tubing while creating an ultra-low invasion layer across the perforations to withstand the differential pressure of kill fluid. There are certain challenges associated with establishing tubing-casing communication in deviated well, immensely scaled tubing restricting any intervention, old wells completed with mud as completion fluid and heavy-grade tubing. This paper provides insight for the selection tools and procedures considering well conditions to establish effective tubing-casing communication for cement plug placement. Moreover, this technical paper focusses on various remediation techniques and specialized chemical solutions that are at hand to address issues pertaining to sustained casing pressure (SCP) in a rig-less manner. This technical paper presents an incisive analysis of the unique challenges and optimal strategies of rig-less P&A operations that can be adopted in multi-array wells. The insights and recommendations outlined in this paper can be extrapolated to other comparable operations, yielding a significant contribution to make P&A cost-effective and time efficient.
Ahmad et al. (Mon,) studied this question.