The Challenge to Minimise Emissions From Offshore Power Generation

There are many physical and financial factors that determine the optimum power generation solution on an Offshore installation - space requirements, weight, reliability, and maintenance requirements to name a few. On top of these factors, environmental impacts must be considered, such as emissions of Nitrous Oxides (NO_x) and Carbon Dioxide (CO₂), and visible pollution like flaring.

While on ‘conventional’ offshore oil and gas fields, there is usually plentiful gas available to provide the fuel for power generation, in some instances, such as Heavy Oilfields or Gas Condensate fields, using the preferred fuels available on the platform provides additional challenges: for instance Heavy Oilfields tend to be gas deficient, with insufficient associated gas over field life to fully fuel a power plant, and so either require the import of fuel, such as diesel or Heavy Fuel Oil, or the use of the produced crude oil itself; On Gas condensate fields with low condensate quantities that make export uneconomic, the condensates themselves maybe the preferred fuel. And increasingly process heat is required, potentially requiring the combustion of additional fuel to provide the energy required.

While CO₂ emissions are predominantly dependent on energy efficiency, both CO₂ and NO_x emissions are also fuel dependent. In addition to the ‘direct’ emissions caused by combustion of fuels to provide the energy required for Oil & Gas operations, there are also ‘indirect’ emissions, such as those involved in transportation of consumable items to the platforms, and wastes produced that must be disposed of in an environmentally safe manner.

This paper looks at the types of fuels that are most commonly used for offshore power generation, the most common technologies that are considered for power generation, and the potential advantages and disadvantages of these technologies in an offshore application. It also looks at ways of reducing combustion emissions such as NO_x, and using Cogeneration as a means of reducing CO₂ emissions by maximising overall energy efficiency.