Design, Fabrication and Installation of the First Ever Reeled Pipe-In-Pipe System in Offshore Brazil

Abstract

The domestic demand of gas is increasing in Brazil. Petrobras is responding to this challenge by bringing several gas fields on stream offshore Brazil. Among them is the Canapu field, located east of the State of Espirito Santo, about 75 km off the coast, in a water depth of 1608 m. The produced gas is transported using a 20 km long pipe-in-pipe (PIP) system to the Cidade de Vitoria floating, production, storage and offloading system (FPSO) located in the Golfinho field to be processed and then exported onshore through an existing gas pipeline.Technip was awarded an engineering, procurement, construction and installation (EPCI) contract and was responsible for the detailed design and installation of the first ever reeled PIP system offshore Brazil. The project was awarded on a fasttrack basis, which required design, qualification, fabrication and installation of the PIP system in less than 18 months. The scope also included two pipeline end terminations (PLET) with seven gate valves, free span rectification, the crossing of three flexible flowlines, and, pre-commissioning activities (flooding, cleaning, gauging and hydrotesting). The PIP system was also prone to lateral buckling, which required definition of a robust mitigation strategy.The design requirements for the Canapu PIP system involved the design and qualification of several technically advanced components and novelties in PIP design including the application of the first ever reelable mechanically clamped waterstop system and the use of buoyancy modules for lateral buckling management on a PIP system. This paper presents the overview of the design, fabrication and installation of Canapu PIP system as well as a summary of the qualification test program performed for the different PIP system components.

A Discussion of Practical Aspects of Reeled Flowline Installation

“…During stalk fabrication, the inner pipe and outer pipe stalks are fabricated separately. As described in [16], inner pipe stalks are transferred to the firing line in the spoolbase where insulation materials (in the form of short panels) are wrapped around the inner pipe and centralizers are bolted in place at predetermined intervals. The prefabricated inner pipe stalk is then inserted into the prefabricated outer pipe stalk using the pushing machine to make a PIP stalk.…”

“…The prefabricated inner pipe stalk is then inserted into the prefabricated outer pipe stalk using the pushing machine to make a PIP stalk. Individual PIP stalks that are stored in the spoolbase are then spooled onto the reel, each connected by tie-in welds; see [16].…”

“…Waterstops are fitted in the annulus between the inner and outer pipe at approximately one stalk intervals in order to minimize the damage to the insulation system in case a wet buckle happens. The use of mechanically clamped waterstop systems are now common after its first time success in Petrobras Canapu project (see [16]) and design for annular gap of as low as 20 mm has been achieved in more recent projects. However, due to significant additional stiffness of the waterstop joint, it is to be ensured that the high spoolingtension is maintained and extra centralizers are fitted in the vicinity of the waterstop as shown in Fig.…”