The well, flowline, and midline hardpipe jumpers utilized for the Troika subsea production system represent a significant and challenging engineering and construction effort. The system was designed using a horizontal connection method, which is common to all three jumper types. Each of the two 10–3/4 in. OD flowline jumpers that connect the flowlines to the cluster manifold system incorporates a load-limiting joint. Additionally, the flowline and midline jumpers have to allow for significant thermal elongation of the flowlines. The 5-9/16 in. OD well jumpers used to connect the subsea trees to the manifold include not only a production conduit, but hydraulic and chemical injection lines. The production pipe is also insulated. The effect of vortex-induced vibration (VIV), insulation design, flexibility, and rig installation of the jumpers will also be discussed.
The Troika subsea production system is a cluster-type development in 2,700 ft of water in Green Canyon Block 200 in the Gulf of Mexico.1 The manifold is tied-back to and controlled from Shell's Bullwinkle platform, which is approximately 14 miles to the northwest. The two are tied together by means of two 10-3/4 in. OD flowlines and separate hydraulic and electrical umbilicals (Fig. 1). The two flowlines, were installed as a four-part towed bundle.2 Each section is approximately seven miles long. The four flowline sections were connected approximately at the midway point with the midline jumpers. The decision was made to utilize the GC-200 #1 delineation well previously drilled by Marathon, so the template/manifold would have to be located so as to allow completion and connection of that well to one of the system's eight slots. Since the GC-200 #1 well did not encounter any shallow water flow problems, it was felt that locating the remainder of the Troika wells in close proximity to that well would maximize the probability of the same results. Well spacing was driven primarily by the desire to eliminate gyroscopic surveys of the shallow portions of the wells, thus creating the need to separate the wells and template piles enough to prevent magnetic interference. A minimum separation of fifty-five feet was needed, so the proposed well locations were set at a separation of 60 ft ± 2.5 ft. Additionally, the well locations were chosen so as to provide a clear area adjacent to the flowline end of the template/manifold for jumper connections to the flowlines, and to minimize the possibility of impacting a well if a flowline were to be snagged and pulled loose. These same considerations were given to the area adjacent to the pigging loop end of the template/manifold due to the possibility that the Troika system would be expanded into another area. This possibility was, however, given less weight in that a more restricted access corridor was preserved for the pigging loop end than for the flowline end. Common components of all three jumper types are the hub termination assembly, the hub support alignment structure (HSAS) and the jumper pipe itself (Fig. 2). The hub termination assembly contains the hub used to seal the various conduits and is manufactured from a solid forging. The well jumpers were designed using stainless steel since they were on the upstream side of the manifold corrosion inhibitor injection points.
