The number of wells to be abandoned on the Norwegian Continental Shelf will increase inthe forthcoming years. As a consequence, significant expenditures will be required paid bythe individual companies, the state and the society. Despite many technological advancesin the oil and gas industry the recent years, traditional P&A of platform wells is stillparticularly performed by using expensive drilling rigs. In an industry characterized bytime-consuming, costly, and complex operations, it is especially interesting to investigatethe technological potential of P&A and possible cost-savings this may entail. This thesistherefore considers rigless P&A of platform wells, where the use of well interventionequipment is presented as an alternative approach to traditional rig-based P&A.
Three different case studies of P&A are explored and presented: a rig-based approach,a rigless approach, as well as a combination of rig-based and rigless approach. Wellintervention equipment such as wireline and a hydraulic jacking unit are involved in theemerging, rigless method. In order to suggest the most appropriate and cost-efficientabandonment approach, three models are built and used in a Monte Carlo simulation toforecast cost and duration of the different P&A operations. By using well interventionequipment, risk and uncertainties related to unpredictability in the rig marked is removed,which simplifies the time and cost forecasting. To achieve accurate estimation of cost andduration, data is collected with awareness. Historical data, particularly from Aker BP,as well as expert opinions and knowledge, are thus used as simulation input to producerealistic forecasts. The simulation output of the different models is compared, discussedand evaluated using the percentile output values. Findings from the case studies identifiesthat rigless P&A is much more time-consuming than rig-based P&A. However, partlyreducing and completely removing the rig scope leads to significant cost-savings. Sincethe chosen simulation models consider P&A of a single well, this opens an opportunity forfurther research within time and cost simulation for multiple wells on platforms.