Improve Drilling Performance by Controlling Risk and Reducing Non-Productive Time in a Challenging High-Temperature, High-Pressure Well

Abstract To complete a very challenging high-temperature, high-pressure (HTHP) well in the North Sea, several engineering issues needed to be resolved before commencing drilling. One of the requirements of the well was to drill without replacing the existing drill pipe on location. Changing the drillpipe specification would result in extra tripping time and a high increase in cost. As the hydraulic window was narrow, maintaining the configuration of the drill pipe limited the equivalent circulating density (ECD). At the same time, the temperature regime was high; a specific oil-based drilling fluid (OBM) with treated micronized barite (TMB) was chosen as the only solution to resolve these challenges. In combination with this specific drilling fluid, the operator decided to utilize simulation software that enabled real-time hydraulic values to be displayed during the entire HTHP operation. The drilling fluid with micronized barite provided several benefits compared to conventional OBMs. A more conventional drilling fluid meant a significantly higher viscosity to maintain the weight material in suspension, thereby increasing the circulating pressures and ECD. As the micronized barite viscosity profile is low, even at high densities, tripping speeds were dramatically increased as compared to offset wells. This includes tripping in and out with drilling assembly and during running of casing. Furthermore, the viscosity of such a fluid enables any flow checks to be completed much faster, thereby reducing time spent. Additional benefits such as zero barite sag, low maintenance of the system and the elimination of expected circulating time to condition the fluid after a 10-day long static period were all part of this successful well completion.