Since 2019, a 340K type of Hydraulic Workover Unit (HWU) has been contracted by the Operator for production protection in case of ESP failures, primarily for the offshore assets. Due to the nature of contract and scope, there were times when the HWU was in standby mode while waiting for the next ESP replacement scopes and/or for the offshore vessel to be made available. When there was a requirement to recomplete a land gas well ‘S’ to increase gas lift supplies, an opportunity was seized to utilize the HWU to execute the recompletion scope.

Well S was a 4,300m deep exploration well that was drilled and tested in 2019 with a 2,000HP land drilling rig. The well had two zones of open perforation and it was then suspended with a combination of inflatable cement retainer, cement and sand plugs, and another V0 hydraulic plug above it. The first operational scope was to prepare the wellbore by clearing the access for the perforations, and the second scope would be the recompletion operation.

The opportunity was clear, but the solution wasn’t as straightforward. Originally this recompletion was planned to be executed with a land rig, but scheduling conflicts meant that the land rig arrival was delayed by a few years. The team saw the opportunity to maximize the assets at their disposal but there were two main challenges in realizing this opportunity. First, the offshore setup HWU required significant modifications to operate on land environment. This included adding components in the peripheral e.g. a crane, tanks/temporary pipe works and accommodation cabins. The second challenge was to assess and equip the unit that was supposed to perform non-complex hoisting operation, to be able to execute the recompletion scope which included fishing and milling, wellbore clean-up, TCP operation, and installing completions. The other important element of the HWU utilization is that it has a lower carbon footprint as opposed to drilling rig. In average, the fuel consumption of the HWU is nearly half of 1,500HP drilling rig and even though drilling rig operational efficiency is generally higher, the overall emission of HWU would still be lower in this case.

This paper describes the requirements set at the planning stage, to ensure that the minimum technical requirement was defined and that the project was competitively scoped. It outlines the challenges encountered in the preparation stage as well as in the operation stage, and how they were addressed, resulting in a safe and successful campaign and "out-of-plan" gas to support the production. Furthermore, this paper examines the boundary of the Hydraulic Workover unit and illustrates how thorough planning and risk assessment were critical for the non-routine activities.

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