Innovative Wave Energy Converter for Oil and Gas Developments
Authors: Anres Stephane Jean , Colmard Christophe , Hallot Raymond , Lirola Francois , Ruer Jacques , Martin Eric 
Published: April 2012

Local energy generation (from a few kW for subsea control up to several MW forsubsea boosting) is an interesting option for future Oil & Gasdevelopments, especially for long subsea deepwater tie backs (30 to more than100 km) where it can avoid additional equipment on the existing productionfacilities and a long power umbilical.

One main challenge of power generation for the Oil & Gas industry is to beable to rely at any time on a defined power whereas the power generated frommost renewable sources is intermittent which leads to the definition ofsuitable power storage systems. This trend has already started with limitedpower supplied to control systems with small wind turbines and solar panels. Itwill grow up progressively in the near future with larger power for biggerconsumers.

This paper first gives an overview of the renewable energy sources availablefor offshore Oil &Gas developments (wind, wave, currents, solar, oceanthermal energy, geothermal…) and will present the main technical challengesassociated to the capture and the conversion of the energy.

The second part of the paper presents the Swell Barge, a large scale bargeequipped with several underwater resonators whose number and locations areoptimized according to the site conditions. This innovative wave energyconverter has been invented and specifically developed for deepwaterapplications in order to generate several MWs depending on the wave conditions. The system is passive with a large response spectrum. It is simple, robust andeasy to maintain with conventional offshore means. The dimensions of the bargecan be adapted to both directional and non-directional wave conditions.

Introduction

During the lifetime of a given offshore Oil & Gas field, additionalsatellite fields are progressively exploited and linked to the main productionsystem.

Sometimes, these satellites are located quite far from the hub. They all needsome electrical energy which must be provided from somewhere. Satellites needsmall power (few kW) for XMT control and chemical injection and larger power(few MW) when water injection is required. Remote satellite field will alsorequire large power for production boosting at mudline.

If the energy consumer is located in the reasonable vicinity from the shore orfrom the hub, the obvious solution is to transport the electrical power via asubmarine cable. The maximum distance which can be considered for a cable linkdepends on the power requirement. The higher the demand, the longer a cable maybe justified. However, it may prove not economical to install a long cable fora limited power requirement.

The alternative is to produce the electricity locally.

A conventional solution could be to use a diesel driven generator installed onboard of a nearby floater. The unit can be remotely operated, with no operatorpermanently on board. However, it is worth to note that the production of 1MWon a continuous basis consumes 6 tons of diesel fuel per day. If a large poweris required, it becomes necessary to refuel the generating floaterperiodically. If the refueling is planned every 3 months, a quantity of 540tons of fuel must be loaded.

Another factor to take into consideration is that the same unit releases 19tons of CO2 per day.

For these reasons, it is interesting to consider the production of electricalpower from local renewable resources.

Potential renewable energy sources offshore

Solar energy

The most convenient converters are photovoltaic panels. Nowadays, this is avery common method of offshore energy production for small distributedconsumers, like monitoring devices and control systems. Needless to say, theenergy is only accessible above the water surface and during daytime.