The Troll oil field has been drilled and completed with more than 100 geo-steered extended-reach multi-lateral (MLT) subsea wells having two, three or four branches each to maximize reservoir contact. The Troll team has drilled multilateral wells from semi-submersibles for more than 10 years. The wells are equipped with complex intelligent top completion (ITC) systems to optimize production.The oil column of the Troll oil field was initially between 11 and 26m thick, with an overlaying gas cap. The wells are 2-5,000-m-long horizontal multi-lateral branches; many completed with stand-alone sand screens and autonomous inflow control valves (AICD) for the lower completions, with up to 80-90% screen coverage per branch lateral.Production life of MLT wells on Troll is limited by gas break-through and/or high water cut. To increase production life and reservoir meters per well there is a need for flexibility through flow control from the surface.Until recently, the ITC system only allowed for individual control of two-branches by two dedicated inflow control valves (ICVs). For three or more branched wells, the upper-most branch would be individually controlled while flow for the other branches controlled together. If break-through occurs in one of the lower laterals, they would have to be choked/or shut-in together, resulting in lost production and reduced recovery from the other laterals. As a result, there was a need for greater flexibility and inflow control for wells with more than two branches.The operator requested contributions from a supplier for a system based on the existing multi-lateral system, the FlexRite® intelligent completion interface (ICI), which would allow for flow control of all branches. A development project began in 2010, and a new multi-lateral system, multibranch inflow control (MIC), was created in 2011. This system has an increased internal diameter (ID) for installation of the completion string with ICVs and swellable packers through the junction for enhanced well control.In October 2012, the Troll team installed the first multibranch MIC system on the Troll well N-24. This system is believed to be the first TAML Level-5, three-branched well with individual branch control worldwide. With this new and innovative junction and completion system, the operator now has the ability to optimize the oil production from new extended-reach multi-lateral wells.In the future, this innovative multi-lateral solution will enable the operator to increase oil recovery from Troll and other fields, which will help the operator to continue to push the functionality and economic viability of multi-lateral technology worldwide, especially in thin reservoirs.

Since 1996, more than 260 multilateral junctions have been installed in Norwegian Continental Shelf (NCS) fields; currently, 25 laterals are completed annually. This paper discusses a TAML Level-5 multi-branch multilateral system that was installed in Troll field in 2012. It is now the predominant system, with more than 200 junctions installed in subsea wells. This latest generation of sealed multilateral junctions combined with flow control equipment, including surface-controlled interval control valves (ICVs) and autonomous inflow control devices (AICDs), enables full production control of the main bore and each lateral. The production life of multilateral wells of the Norwegian Troll field is limited by gas breakthrough and/or water cut. Historically, this issue was mitigated by using intelligent completions to control the flow of a maximum of two laterals. If a breakthrough occurred in a lower lateral on wells with three or more laterals, all laterals would have to be choked or shut-in together. This process resulted in lost production and reduced recovery from the other laterals. As trilaterals and quadrilaterals became more common, however, it became necessary to provide flow control for all branches. In October 2012, the Troll team installed the first multibranch multilateral system on Troll N-24. This system is believed to have been the first TAML Level-5, three-branched well with individual branch control installed worldwide. With this new and innovative junction and completion system, the operator could optimize the oil production from new and extended-reach multilateral wells. In addition, the implementation of multilateral technology (MLT) early during 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. Multilateral junctions are typically constructed from the bottom up; the lower main bore is drilled, completed, and prepared for production before milling the window for junctions above. To help mitigate the risk with these operations, several technologies have been implemented, including premilled windows, extended length whipstocks, and lateral screen deployment. On multilateral operations, a dedicated coordinator focus and a proactive engineering team has helped eliminate and/or reduce installation risk to an acceptable level for operators using the technology. Presently, this innovative multilateral solution helps increase oil recovery from Troll and other fields. This increase should help expand the functionality and economic viability of MLT worldwide, particularly in thin reservoirs.