Utilization of Purpose-Built Jack-Up Units for Plug and Abandonment Operations

The oil and gas industry working on the Norwegian continental shelf have the past years increased the focus on decommissioning of fields, after several years with attention to increase and enhance oil recovery. The topic plug and abandonment has been well-recognized by the Norwegian authorities, the oil and gas industry and the public media due to the expected cost which will affect both Norwegian taxpayers, licence partners and operators working on the shelf. There has been a large emphasis to cut these cost, where companies are currently developing new solutions to enhance the process to plug and abandon wells. The concept “rig-less” P&A have been expressed as a futuristic goal from “Norwegian Oil and Gas” in their roadmap for new P&A technologies [1]. This thesis investigates performance differences of a purpose-built P&A unit based on previous performed well abandonments with regular jack-up rigs. The unit is designed to be a cost-efficient rig alternative to regular jack-up rigs, which is designed to perform heavier well operations, such as drilling. The study focus on P&A operations of offshore platform wells, and includes estimates of cost differences between the chosen concept and a standard jack-up rig. Variables like tripping speed, pumping capacities, tubing retrieval efficiency and durations to mobilize equipment will determine the performance of the unit. A lot of the time spent during a P&A operation is related to tripping of pipe. Wireline and coiled tubing are equipment that reduce tripping time, but will the relationship between cost and performance improvements be satisfactory? The findings of the study indicate that employment of the chosen rig design concept provides better economics in the specific well abandonments used for the comparison. There are several factors which determines if the combination of coiled tubing and wireline yet are the preferred solution. With the “Norwegian Oil and Gas” ambitions to develop more technology to increase rig-less P&A scope, this combination may be the preferred solution, to cope with the future needs.