During the 70's demand for subsea electrical cables for connection to subsea devices increased and introduced the industry to the offshore petroleum markets of drilling and production.
The massive economic risks taken on by a private industry were unprecedented in a field previously dominated by Government research funds. Accompanying the economic infusion to the market was an unrelenting demand by the petroleum customer for product reliability not known before that time.
Experiences with the various drilling and production projects has led to design philosophies structured for the solution of the observed operational problems encountered in these projects. Presented in this paper are design and fabrication techniques developed for those cable systems used in the critical drilling and production projects.
To maximize many offshore field recoveries, subsea wells for production and enhancement of the field are required. Ideally the subsea well hardware should have the capability to control the production (or injection) of the hydraulic production circuit to optimize the reservoir recovery and gather pertinent hydraulic data along the production circuit including downhole data.
Electrical devices for control, correction, and measurement would seem to satisfy the various requirements. Although these devices have proven service records in various applications, their subsea and downhole counterparts have had some problems. These problems have tended to discourage the expanded use of electrical systems so that industry development and improvements of these electrical systems are receiving less emphasis because of decreased commercial pressure and incentive.
Some electrical problems have resulted because the device was not designed within an integrated system approach. Devices are designed to preclude water access to susceptible electrical parts by packaging in subsea enclosures sometimes with little consideration given to the method of connection to preclude water access to the devices1 external terminals.
Fabrication and testing methods have been developed for subsea cable systems which may be useful in the systems design of electrical devices as well. Presented in this paper are design approaches and fabrication techniques used to process cable systems where each electrical and mechanical component of the system is attended to as a reflection of the ambient expected in service.
Subsea completions and Drillship BOP control cable systems using this systems approach are shown in Table 1.
Experience on the early deep water drilling vessels using electrical control of the BOP showed that the cable system would be flooded during the design life of the system. Water would pass through the jacket and flood the cable throughout its submerged length, and through capillary action, most of the full length. Subsequent experiences in drilling and subsea completions indicate that handling the cable at sea would often result in conditions that cause flooding of the full length. The immediate problem to be solved with this revelation was the retermination of flooded cables which had more than one hundred conductors.
Prior to the offshore drilling work Vector Cable's repair service was mostly limited to factory repair and retermination of logging and geophysical cables.
