This paper describes a Diverless System for deepwater pipeline installation and repair called the "Statoil Installation System for Diverless Coupling". As an extension to the work Statoil has carried out with their Pipeline Repar System, it makes use of a remotely operated mechanical coupling. This paper covers the salient points of the coupling installation system including the overall scope of work, some of the engineering detals of the coupling itself, its deployment and control.
The paper then goes on to discuss associated ROV tooling and the final stages of trials and testing prior to the offshore programme.
Statoil awarded a contract to SSOL in January 1996 to project manage the installation system. It included the design and build of the Power and Control Module and, in conjunction with NEMO Engineering a.s. of Oslo, to design and build the Coupling Carrier Module. Further to this, the final assembly, commissioning, integration and testing were carried out at a location in Norway.
One of the initial challenges to the project was the actual time schedule. While contract award was in January, the proven system was needed offshore in July. This was in fact achieved. Statoil had already carried out some initial engineering on the project and were able to free issue at appropriate points, the installation frame, the electronic control system and the coupling itself.
The equipment was developed as a diverless repair system as a contingency for the Troll oil and Haltenpipe pipelines, and for diverless tie-in of a spool near shore on the 16 inch Haltenpipe pipeline. The Troll Oil pipeline is a 16 inch oil pipeline from the western part of the Troll B platform to the shore at Mongstad while the Haltenpipe is a 16 inch gas pipeline from the Heidrun field area through Ramsoyfjord and to shore at Tjeldbergodden.
The equipment was designed for operation in water depths down to 600 msw and was based on the use of the Morgnp mechanical coupling. The mechanical coupling was installed and activated via a Coupling Installation Frame (CIF) remotely controlled from the support vessel via an ROV interface. This new system was based on the same operation and design philosophy as the existing Dry Pipeline Repair System (DPRS). Standard PRS type components were adopted wherever possible
The overall design basis for the Diverless Coupling was to cover a range of pipelines from 10 to 20 inches, but outfitted and ready for operation of installation of the 16 inch Morgrip Coupling on to the 16 inch Haltenpipe pipeline. The system was also designed for use on seabed slopes up to 28 degrees along the pipeline axis. Pipellne repair systems consist of many sub systems including large H frames used to manoeuvre the pipeline. However the following sections concentrate on the CIF and its component parts.
With reference to figure 1, the main assemblies which comprise the System are
Coupling Installation Frame
Coupling Carrier Module
Power and Control Module
These are described in the following sections.