An advanced dynamic flow and temperature model was used to optimize and control MPD operations in real time on the Gullfaks field in the North Sea. The well to be drilled only had a 7 bar window between the pore and fracture pressure according to prognosis. However, drilling objectives were eventually fulfilled aided by very accurate downhole pressure control. This paper addresses the model specific challenges, analyzes the differences between model calculations and downhole pressure data, and discusses how to bring hydraulic modelling further in accordance with future operational needs. Challenges related to how to tune the system efficiently and accurately, data quality issues, displacement operations, etc., are described and enlightened by downhole memory data made available when the string was back on surface. Ideas on how to build a more robust and easy to use system without sacrificing the advantages of having a high fidelity model in the real time loop are discussed. The experience and ideas described contribute to the development of a very accurate and reliable MPD system, which is capable of automatic pressure control during the whole sequence of drilling, tripping, circulation, displacements etc. An important goal for the future will be to reduce the offshore crew dedicated to the modelling function to a minimum, with the provision of onshore support during operations.

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The managed pressure drilling (MPD) technique was chosen to drill a well on the Gullfaks A platform as a risk mitigating factor. In addition, the MPD technique gives accurate flow measurement, provides the potential to handle pressure variations quickly, and determines the drilling window. This paper presents the successful implementation of a sophisticated hydraulic model during planning and execution of a MPD operation in Gullfaks Well A-10B. MPD service was delivered by a major service company with equipment coupled to a third-party real-time advanced transient hydraulic model. This model was used to calculate upstream choke pressure during MPD. It was also used in the planning stage to ensure operation was feasible within the pressure window with the selected fluids and drilling parameters. The system was run in automatic mode. Initially, only one section was planned for drilling in MPD mode. However, because of the losses observed and bottomhole pressure (BHP) flexibility provided by the MPD system, it was decided to drill the next section in addition to running and cementing the liner. When the well was completed, three sections were drilled and two liners were run and cemented using MPD. The use of an automatic MPD system with a sophisticated hydraulic model helped ensure the well delivery was achieved according to plan without any major issues. The losses that occurred were detected and reduced significantly only by reducing the bottomhole target pressure. Dynamic drawdown tests in addition to a dynamic formation integrity test (FIT) confirmed the drilling window before drilling the second section. During the planning of cement job, a close working relationship between all parties was established in order to find the best possible solution for the well and achieve a delivery of a successful well. The planning tool used is a sophisticated hydraulic model that calculates a constant dynamic well pressure during the simulation of the cement job. The simulations were verified during the cementing job, with a good cement job as the result. Both liners were run and cemented with full returns and rotation. This paper presents the challenges involved during this well project, how these challenges were handled by thorough planning, and finally the operational phase itself with focus on the MPD system, including the advanced flow model.