Connected Structure refers to the ability of a submerged pipeline or bundle to be connected to a seabed installations then through to a surface vessel or loading facility. With the advent of exploration in progressively deeper waters the need for automatic systems or at best minimum diver intervention on the seabed is becoming a significant requirement. This necessity was recognised by R. J. Brown and Associates a number of years ago and design developments initiated at an early stage. RJBA has a long history of bringing innovative and cost effective pipeline installation methods to the offshore field development arena. Both for oil and gas installations in all parts of the energy producing areas of the world. This type of connectable system although of significant application for installation of single pipelines has particular use for the automatic installation of pipeline bundles contained within a carrier pipe.
Such a bundle would consist of production flowlines typically 6″dia. with a test line 6″dia. methanol/chemical injection lines 2″/l″ dia., control/instrumentation umbilical and possibly heat tracing. In addition the internal production flowlines may be insulated with solid cellular foam or gel. A carrier pipe of typically 24″ /3611 would contain the internal lines and probably the umbilical. The complete bundle system is therefore complex and for diverless connection there will also be automatically operating collet type stab-in connectors. F2JBA1s experience in the design, specification, fabrication and construction/installation supervision of these pipeline bundle systems is extensive.
Although not in deep water, RJBA designed such a system for automatic and diverless installation under the ice cap in the Canadian Arctic in 1976. This installation required all the consideration and innovative engineering that could be applied with the level of subsea equipment capability at that time. The bundle design and installation requirements were in fact ahead of the available technology and several areas of the installation requirements were prototype systems/instrumentation and installation equipment. From this significant early project to install a fully integrated connectable system in a diverless mode F2JBA has been at the forefront of this type of installation with more advanced and sophisticated systems developed for installation in the Gulf of Mexico.
The connectable system is a significant part of the overall pipeline/bundle installation and its requirements have particular emphasis on the installation design/method. The pipeline installation method usually specified by RJBA for installation of the complete system is the beach make-up and bottom-tow method. It provides an effective method of pipeline/bundle fabrication without costly offshore work. Also a considerably reduced offshore installation period without the need for heavy column stabilised pipeline installation vessels with extensive saturation diving suites. This engineering approach is also followed to provide the maximum cost savings possible for the installation of complete subsea production systems. FUBA has designed and supervised fabrication and installation of a large number of bottom-tow installations which has generated considerable knowledge of applicable costs for materials, fabrication and installation. This data base being used to refine further cost effective bottom tow and the associated connectable systems.