Successful Use of Real Time Dynamic Flow Modelling to Control a Very Challenging Managed Pressure Drilling Operation in the North Sea
- Knut Steinar Bjorkevoll (SINTEF Petroleum Research) | Alfrid Elin Vollen (Statoil ASA) | Ingvill Barr Aas | Svein Hovland (SINTEF Petroleum Research)
- Document ID
- Society of Petroleum Engineers
- SPE/IADC Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition, 24-25 February, Kuala Lumpur, Malaysia
- Publication Date
- Document Type
- Conference Paper
- 2010. SPE/IADC Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition
- 1.12.6 Drilling Data Management and Standards, 1.14 Casing and Cementing, 5.1.1 Exploration, Development, Structural Geology, 2.7.1 Completion Fluids, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 5.8.9 HP/HT reservoirs, 1.13 Drilling Automation, 1.7.5 Well Control, 5.3.2 Multiphase Flow, 1.6.1 Drilling Operation Management, 4.1.2 Separation and Treating, 1.11 Drilling Fluids and Materials, 1.6 Drilling Operations, 1.12.1 Measurement While Drilling, 5.1.5 Geologic Modeling, 1.10 Drilling Equipment, 1.6.10 Running and Setting Casing, 1.7.2 Managed Pressure Drilling, 2 Well Completion
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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.
This paper describes the use of an advanced hydraulic model during the drilling of an 8 ½?? reservoir section in MPD mode. The MPD service that was provided to Statoil consisted of hardware, software and a hydraulic model. The combined system was tested and tuned before being sent offshore, as described by Godhavn and Knudsen (Ref. 1). In addition the system was tested and tuned on the rig before the operation, to ensure that a constant bottom hole pressure could be maintained during drilling, tripping and displacement operations.
The well was planned as a sidetrack from a previously drilled well. The sidetrack was drilled through a formation that was over-pressurized due to migration of injected water pressure from nearby injection wells. The well was located in an area where maximum pressures in the Shetland Group were close to the estimated fracture pressure. This meant that the drilling window through the overburden was very limited; approximately 7 bars. The entire MPD system, including the hydraulic model, was therefore designed to be able to keep the bottom hole pressure constant with a maximum deviation of ±2.5 bars. This was the main reasoning behind choosing advanced MPD technology to drill through the overburden and into the reservoir.
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