Traditionally, over the decades majority of offshore oil and gas operating companies (OPCOs) have managed their electrical power demand independently using localized open cycle gas turbine generators.
With the declining reservoir plateau, adoption of new reservoir development techniques for sustained production, calls for increase in power demand (from few hundreds of megawatts to few thousands of megawatts).
Alternative means of safe, reliable, environmental friendly and economically viable solutions become inevitable.
The objective of this paper is to share our experience, key challenges and benefits in developing a strategic power supply master plan for all offshore OPCO's.
Approach, Methodology and Process
As a first step, feasibility studies were carried out to identify alternative means of sourcing the power which shall cater for the long term power needs of all offshore oil and gas facilities and facilitate phasing out of aged GTGs.
The following options of power supply were considered for evaluation:
Continue localized gas turbine generation (Business as usual)
Renewables (solar, wind, tidal)
Formation of power clusters by interlinking facilities and Centralized offshore generation
Power from onshore
Considering the order of power demand at each location, large infrastructure requirements at offshore where space is a premium and high cost localized, gas turbine generation and renewable energy resources were not considered as an optimal solution for long term offshore power supply for oil and gas facilities. Other alternative schemes of long term offshore power supply were evaluated.
Offshore facilities were interconnected by subsea cables to form power clusters based on geographical proximity. Each power cluster shall have a centralized power hub which could be located on a natural island or on a platform. One latest trend is to build artificial islands in shallow waters for this purpose.
Cluster power demand and distance from shore are drivers in techno-economic evaluation. Extensive feasibility studies followed by techno-economic screening shall be undertaken to develop a strategic master plan for phased implementation.
As the power demand approaches the order of gigawatts, HVDC systems become more attractive. While offshore HVDC network interconnecting onshore source and centralized power hubs serve as the backbone, the HVAC network facilitates power distribution up to individual facilities (rated in megawatts).
Considering the consequences of production loss due to power outage, stringent reliability requirements were adopted which calls for multiple interconnections. This necessitates forming HVDC grids offshore.
Use of redundant bipole converter stations at each power hub in order to effectively utilize the inherent reliability of bipole configuration is first of its kind for this order of magnitude.
Phased implementation of redundant bipole converter stations by installing monopole configuration initially and converting it to bipole configuration at a later stage, provides maximum flexibility and defers the investments, thereby making HVDC option more attractive.
Implementation of offshore HVDC grid for offshore oil and gas facilities mandates unique expertise of both offshore OPCOs and onshore utility power companies.
Observations and Conclusions.
Aggressive growth in power demand is imminent for Offshore Oil and Gas Companies to meet their business objectives and to implement state of art technologies.
Interlinked grid operation of HVDC system necessitates the enhancement of HVDC breaker technology
International standards are required to facilitate the seamless integration of HVDC systems by various original equipment manufacturers