Simulations Demonstrate the Benefits of Continuous Improvement in Multilateral Wells in the Norwegian Sea
Authors: Mark Glaser , Clifford Allen , Bona Prakasa 
Published: October 2020

More than 350 multilateral junctions have been installed in the Norwegian continental shelf fields since 1996; currently around 25 junctions are completed annually. The current predominant junction is a TAML (Technology Advancement of Multi-Laterals) Level 5 multi-branch system. This paper discusses the evolution of TAML Level 5 junctions during this period and uses simulations to screen different junction technologies for value determination. This latest generation of sealed multilateral junctions when combined with flow control equipment, including surface-controlled interval control valves (ICV) and autonomous inflow control devices (AICD), enables full production control of the main bore and each lateral independently.

The production life of wells in the Norwegian Troll field is limited by early gas and water breakthrough owing to the thin reservoir. Historically, this issue has been mitigated by using multilateral wells to increase the reservoir contact. Intelligent completions were originally adopted to control the flow from a maximum of two laterals. The latest innovation is the multi-branch version, which provides individual control of each lateral in tri- and quad-lateral wells. Using published and estimated well data, this paper provides simulations to demonstrate the incremental benefits of each new multilateral junction configuration. The objective of screening with simulations is to show how evolving junction technology with integrated flow control, improves hydrocarbon recovery, minimises effluents and accelerates production akin to the performance observed in the Troll field over the past 20 years.

The multilateral technologies installed over that time period have demonstrated the benefits of having close collaboration between the operator and the service provider. This has enabled the technical advances described in this paper. Analysing well performance with simulations validates specific flux performances associated with each technical improvement and reinforces the benefits of collaboration. Each new junction innovation will be described, and the associated simulation of flux performance will be provided for comparison with prior junction technology. With the current innovative junction and integrated flow control, the operator can optimize the oil production from new and extended-reach multilateral wells. Also, in multilateral operations, dedicated coordinators along with a proactive engineering team have eliminated, or reduced, installation risk to an acceptable level for operators using the technology. In addition, the implementation of multilateral technology (MLT) early in the planning stage enables the addition of production intervals at a cost of 20% or less of the initial well cost, which makes many marginal field developments viable projects.

Simulations aid decision making by distinguishing the performance enhancements associated with technology evolutions that optimize well completion. As demonstrated for multilateral technology, this well completion technique can reduce construction costs vs. individual wells to access the same footage of reservoir contact, but the real benefit is the increase in oil production with reduced water production to lower the barrel-of-oil equivalent cost of production or injection.