Time Estimation of Future Plug and Abandonment Operation at Brage Field

Abstract

Production of oil on the Norwegian continental shelf started in the early 70’s. Many of these fields are now reaching the end of their production time. The industry is now awaiting a “plug wave” in the not too distant future. Decommission is a time-consuming procedure, and the cost of P&A can end up being 25 % of the total cost of the well. The task given from Wintershall was to plan P&A operation by setting a dual barrier plug against the creeping clay in the Hordaland formation. The Hordaland green clay will creep in and seal around the casing and create a bonding with the casing. This method has saved operators on the Norwegian continental shelf for millions of NOK, by avoiding milling or squeeze cement job. All the wells at Brage require permanent P&A in order to control subsurface pressure and prevent the free flow of pore fluids to the seabed. The wells at Brage was categorized depending on the different casing design. The objective was to determine the time for P&A for every category. There were three different casing designs that stood out: pre-drilled wells, production liner with tie-back casing and simplified casing design. The most likely time for plugging the 40 wells at Brage is estimated to be around 3 years. The time estimate is done with the technology available today. In the future there might be new technology that will enable the operator to P&A the field in a more cost-effective way. Many service companies are working on developing tomorrows P&A solution. Some of the new technologies will be presented and discussed in this thesis, together with the use of formation as a barrier.