This paper will present planning and execution details for different mechanical plug types used to prevent fluid loss and formation damage during workover interventions on deepwater wells with extreme hydrostatic overbalance conditions, between 2,000-2,200 psi. Actual case history for four wells, using different mechanical formation plug methods, from one deepwater field in the Gulf of Mexico will be included. The information is applicable to oil producing wells, to be worked over with similar extreme hydrostatic overbalance to producing formations, where well control needs to be maintained during the intervention, fluid loss to the producing formation needs to be minimized and subsequent removal of the isolation barrier is required to restore well production. The results obtained with all four different isolation methods used, suggest that a detailed assessment to the well conditions, along with ”fit-for-purpose” shop tests simulating the specific well conditions, has to be completed prior to selecting the most convenient option to execute the workover. This paper will describe the specific planning and operational process of the workover activities, and present a number of lessons learned and useful recommendations for similar activities in extreme hydrostatic overbalance wells.
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