This paper documents a job campaign encompassing seven operations that were performed over a 6-month period in the Kuparuk River Unit, Alaska. The subject wells had all been selected for workover due to subsidence issues and the production casings in each of the wells were in varying conditions, ranging from slight tension to severe compression.
Many previous subsidence workovers had utilized drill-pipe conveyed cutters which required the casing to be in tension to ensure a quality cut. In order to get the casing in tension, a multi-step process was required. First the blowout preventers (BOP) and tubing heads had to be removed. That was followed by a controlled growth of the compressed casing after which the casing was then stretched and re-landed in tension. The excess casing was then cut off, and, finally, the BOPs were re-installed and tested. This entire process could many times take over 24-36 hours.
In an effort to reduce rig time and ultimately workover cost, research was performed to find a cutter that could cut production casing in compression. The one chosen was an e-line conveyed cutter that could be run in conjunction with the cement bond log required on subsidence wells prior to the cut. This tool has a history of making cuts in casing that was under compression, but had yet to be vetted in the compression ranges associated with severe subsidence damage.
This innovative technology can be used in other wellbores where a quick, precise, and non-explosive casing cut is preferred, but most importantly, can be used with pipe in compression. This solution proved successful on six out of the seven cuts conducted in this campaign and is a cost-effective alternative to the aforementioned, conventional pipe cutting method. The campaign resulted in a rig time savings of approximately 18 hours per well.