The Driverless Maintained Cluster (DMaC) system has progressed from initial concept to deepwater application in the harsh environment West of Shetland.
The paper provides a brief history of the development of DMaC, a description of the flow line and umbilical connection used on Foinaven and an explanation of some of the issues involved in applying the concept to a specific development
The sub sea Hook-Up for Foinaven is totally driverless with no provision for non-remote operation of any sort. Flow lines, well jumpers and umbilicals are connected utilizing a system developed as part of the Esso U.K Driverless Maintained Cluster (DMaC) sub sea system. This is known as the DMaC connection system'.
Hook-Up was planned as a summertime activity utilizing semi-sub or mono hull vessels. In the event initial flow line connection operations were conducted in winter from the semi sub, lair. The field Architecture also presented severe challenges for the flow line connection system, requiring performance significantly beyond the original design envelope.
This paper provides some background to the DMaC connection system, examines field architecture issues associated with its use at Foinaven and provides a brief description of the equipment involved.
DMaC development commenced in 1989 with a design program funded by Esso UK and supported by Exxon Production Research Company. DMaC, shown in figure 1, was conceived as a cluster of wells connected through a manifold to pipelines routed to a host surface facility. The original study identified that the configuration shown in figure 1 provided cost benefits over alternatives when assessed against a set of design parameters, for a typical sub sea development. These parameters are given in table 1.")
The flow line connection system is the key technology which enables the cost benefits associated with DMaC to be realized. The critical feature is the compact flow line connection porch which can be easily incorporated into sub sea trees and compact sub sea manifolds.
The importance of the flow line connection system to the overall DMaC concept was recognized by ESSO UK who funded a follow up hardware development program which had the objective of developing the DMaC flow line connection system to the point where it was judged to be ready for commercial application. This was achieved in 19912 when the first underwater trials were conducted at Fort William, Scotland. These trials proved that an ROV operating system could pull-in and connect a thirty meter long flexible spool piece jumper with an in-water weight of 4.5 tones with a 50 hp work class ROV. Peak line tension required to pull-in the jumper was 4 tones. The trials also demonstrated the DMaC umbilical connection system figure 2, in which an umbilical 40 meters long, weighing 5 kg/m in water, was successfully installed by the same work class ROV.
Throughout 1992 the DMaC program was maintained as an internal R&D program, with the emphasis on the mechanical design of the flow line connection system. This work resulted in a Joint Industry Program (JIP)3 funded by Exxon Production Research Company, BP Exploration, Statoil, and BHP.