Exploiting proven technology, improving functionality and adding intelligent completions, create an intelligent level 4 multilateral junction ideal for offering commingled, isolated, or deferred production. The junction offers re-entry access to the lateral and a low risk installation. This intelligent multilateral installation should pay for the completion and drilling of lateral to new target zone in estimated "saved" revenue from the mainbore, which is normally lost in a traditional sidetrack. The TAML level 4 junction was built around the proven concept of a hollow whipstock. The hollow whipstock technology has been significantly improved allowing for high-pressure capability before and after milling the window. An innovative concave geometry protects the concave face from milling process. After drilling the lateral, the liner is installed and cemented across the junction. The hollow whipstock and liner are perforated to regain production. Selective isolation is then achieved through an intelligent sliding sleeve completion system. The all-hydraulic intelligent completion system combines several new and existing technologies. A downhole hydraulic logic unit was run which minimized the number of surface control lines whilst allowing individual flow control devices to be addressed from surface. The logic unit also controlled the setting of the production packers. Hydraulic flow controls were included to allow selective isolation without intervention of the producing intervals. Shortly after the completion installation the flow control devices were activated resulting in the avoidance of a probable ESP workover. Results This is the case history of the first intelligent TAML Level 4 multilateral installation at Wytch Farm. It will highlight the drivers that led to selecting multilateral and completion configurations, illustrate the installation sequences, and comment on continuous improvement efforts to ensure future successful installations of this technology. Introduction The oil industry defines value by the acceleration and maximization of production from the reservoirs over the initial cost, deferred cost, and risk involved in reaching those reserves. Therefore, any increase in initial cost, deferred cost, or risk will reduce value of the project. Multilateral and intelligent completions both increase initial cost of the well. A standard sidetrack in today's industry may run $30K USD, and the equivalent with multilateral technology as a minimum will justify $150K USD. The intelligent completions also run as much as 300% versus the standard completion. In addition to the rise in initial cost, many of the multilateral and intelligent completion systems exist with no or poor field histories, thus increasing the risk, and decreasing the perceived value. Where can the value of these systems be identified? Perceived Value Several years ago, discussions began with the oil companies in the North Sea to develop multilateral systems that provide economic answers to enhance the oil recovery in that area. Several oil companies were carrying out a drilling program that involved re-entering mature wells to recover bypassed oil.

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.

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.

The installation of the first single-trip Technology Advancement for Multilaterals (TAML) Level 4 multilateral (ML) junction system was completed in a subsea, gas-injection well. It was drilled to support oil production from the Tilje and Ile formations in the Smørbukk Sør field in the Norwegian Sea, approximately 193 km offshore in 300 m water depth.After injecting for ten years, the well will be converted to a gas producer from the same formations. Because of the Norwegian Sea's environment, the multilateral system had to be low risk and simple to install, with the capacity to minimize pipe trips and withstand the heaving seas. The casing exit had to be long enough to accommodate running a rotary steerable system through the window to drill the lateral to TD. This window had to be milled in a single trip in 13%Cr 110 casing followed by milling into the Garn 4 hard-impermeable sandstone with possible quartz stringers.Hollow-whipstock technology has been employed for more than ten years in the North Sea, but a new system, designed to be installed in a single trip--a savings of two pipe trips--was selected for this project. The hollow whipstock was perforated through after the liner was installed in the lateral to regain hydraulic access to the main bore below the junction. The hollow whipstock was used for the milling and production/injection phases and was not retrieved, saving an additional pipe trip. The well completion used several cementing and completion products and services, including liners with screens and swell packers. Stage cementing was performed to isolate permeable formations between the junction and the reservoir.The well was successfully completed and gas injection began with increases in production being noted from the adjacent producing wells. Although it was unusual to use a multilateral well for gas injection, the technology proved that it can be applicable to any multilateral well requiring a Level 4 junction.

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