Abstract
In July 2004 Statoil introduced underbalanced drilling technology to the Gullfaks Field offshore Norway. The main driver for this technology was to overcome existing pressure control problems experienced while drilling conventionally through the cap rock in order to reach the reservoir. The project represents the first application of underbalanced drilling offshore Norway. The focus of the process design was on being environmentally friendly; consequently, no hydrocarbons were released to atmosphere or flared during the operation.
This paper addresses the challenges in implementing the UBO technology in Norway. There were issues related to equipment, procedures, standards and personnel. Most of the existing Norwegian requirements and guidelines have been developed for conventional drilling. The UBO surface equipment used by the project had to go through a detailed review and extensive modifications to fulfill the Statoil internal requirements as well as the external Norwegian standards and demands. Special quantitative risk assessment methods and software were developed throughout the project to define risk associated with UBO compared to conventional methods. Procedures, emergency measures and contingencies were established to ensure a safe operational environment for personnel at any time. Interfaces with existing platform production facilities had to be made in order to process produced gas and liquid hydrocarbons thereby ensuring an environmentally friendly operation. Some of the major challenges were related to communication and teams that consisted of personnel with very different backgrounds working towards a common goal, i.e. the production philosophy with automated processes vs. the drilling philosophy with manual processes. High focus was kept on open communication throughout the project.
