This paper describes a Subsea Powered Autonomous Remote Control System (SPARCS) which is designed to control subsea wells without the use of electro-hydraulic control umbilicals.
With oil exploration moving towards marginal fields, and fields connected to the existing infrastructure, SPARCS will provide a low cost solution to justify subsea developments. The paper looks at each of the main system components and provides commercial justification for such a control system.
SPARCS is highly innovative in that it controls hydrocarbon wellheads without the use of control umbilicals. The systems electrical power subsea is produced by a Turbine Generator fitted to a water injection flowline or alternatively a Thermo-Electric Generator fitted to a production flowline. Hydraulic power for operating wellhead and downhole safety valves IS produced from a subsea unit, with communication signals for valve control and sensor monitoring using acoustic telemetry with seawater as the transfer medlum.
The aim of SPARCS is to reduce the cost of future subsea hydrocarbon production developments by utilising innovative technology which does not require electro-hydraulic umbilicals from the platform to perform subsea wellhead control.
Over a period of 10 years it is estimated the SPARCS system would reduce overall costs by £72.5 million and additionally produce hydrocarbon reserves of £87 million per annum, which would not be economically feasible with existing technology. This is based on 5 single well developments per year at an average distance of 7.5km. The SPARCS system is shown in section 3.0 to be a commercially viable project.
As part of a joint industry programme, see Figure 1, Enterprise 011, EE Caledonia and FSSL are completing a demonstration project to fully qualify the system.
EE Caledonia have made available the use of a water injection well no. 15117–222 in the Saltire North Sea Development to demonstrate the system over a period of 18 months.
The SPARCS system will comprise of two groups of components, the Surface Controller and the Subsea Control System. The Surface Controller forms the control station which provides the operator with the means of controlling and interrogating the subsea system. The Subsea Control System forms the outstation which provides all the control and data monitoring functions for the well.
Subsea power is produced with a Turbine Electric Generator fitted to a water injection well flowline or a Thermo-electric Generator fitted to a hydrocarbon production flowline depending on the type of well to be controlled.
A local Subsea Hydraulic Power Unit provides power to operate the full range of wellhead and downhole safety valves.
Acoustic telemetry is used to communicate with the platform up to a distance of 10Km, this distance is expected to increase up to 30Km with the development of other non umbilical communication techniques.
The SPARCS system becomes economically more attractive when compared with long lengths of umbilicals in the field development, but breaks even on capital outlay with existing technology when the total umbilical distances would be approximately 2.3Km.