Deepwater Insulation System for the Steel and Flexible Flowlines of Roncador Field in Brazil

Abstract

Abstract The practical application and mechanical characteristics of steel and flexible pipes used in Campos Basin have been widely reported. However, the problem of subsea flowlines blockage by wax deposition and hydrate formation is one of the main concerns. The use of insulated pipes could prevent these problems. This paper outlines the various aspects involved in the design, qualification and installation of insulated flexible and steel flowlines in the Roncador field. The work discusses how an integrated design approach is able to select solutions for the insulation system required for the deepwater static flowlines laid in 1400 to 2000 metres water depths of the Roncador field. The static flowlines are composed of both steel and flexible pipes. Relevant factors are considered as material constraints in accordance with the insulation requirements and operation conditions. Qualification trials on full scale insulated pipes were performed to verify resistance to the loads imposed, by the reeling method and the hydrostatic pressure when the flowline is in operation. Important careful aspects are observed when reeling these pipes. Also, the resistance of the insulated layers to crushing loads when the flexible flowline is passing through the four 90 degree arranged pads using the vertical laying spread of the laying vessel is described. As a conclusion the thermal assessment of the flowlines when in operation is included. Introduction The Roncador Field located in the north area of the Campos Basin was discovered by the wildcat well RJS-436 in October of 1996. The field is entirely located in deep water varying from 1400 to 2000 metres. The preliminary investigation quickly showed considerable dimension for the field and also good quality (31 API) for the oil. Immediately a challenge to start production of the field was imposed to the design group of Petrobras. The strategy to start production of the field was defined as a FPU (Floating Production Unit) (P-36) anchored to receive the produced oil and export it to a FSO (Floating Storage and Offloading Tanker) (P-47). The subsea system defined to gather and transfer the oil to P-36 is composed of a single production line interconnecting each well to P-36. To maximize production each well receives a gas-lift line. A manifold distributes gas-lift service to six wells in the south area of the field. The others wells receive the gas by a single line from P-36. Figure 1 provides the location of the Roncador field in Campos Basin. Figure 2 shows the layout configuration for the three wells RO-12 (P-1-12), RO-14 (P-1-07) and RO-16 (P-1-11). Due to tight schedule and limitations of the Production Unit P-36, it wasS located in a water depth of 1360 metres. Thus, the average distance from the production wells to the floating production unit was around 8 kilometres. Such a distance imposed a challenge to the design group of Petrobras due to the high heat loss to the subsea environment. A solution had to be found to avoid hydrate formation and also to minimize wax deposition into the flowlines.