Life Cycle Assessment of Desalinated Water for Enhanced Oil Recovery
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- Institutt for elkraftteknikk 
Currently, fossil fuels supply 85% of the world?s energy demand. Nevertheless, we consume more than we are able to produce from new discoveries of fossil resources. As energy demand is predicted to grow rapidly over the next few decades, the need for new methods to sustain oil production emerges. By using new technology, known as enhanced oil recovery, it is possible to recover oil previously considered too tightly bound to the reservoir rock to be recovered in a profitable way. One such method is low-salinity waterflooding, where desalinated water is injected into the reservoir in order to increase the crude oil recovery. If implemented, this method could result in significant economic benefit, but little is known on the environmental impacts associated with it. In this thesis, a life cycle assessment of desalinated water for enhanced oil recovery was conducted. Reverse osmosis was chosen as desalination technology and a generic model located in the North Sea was developed based on existing literature. The results show that the operation phase is the largest contributor to environmental impacts due to the generation of power by natural gas-driven turbines on the platform. The chemical treatment process is also a significant contributor to environmental impacts, due to energy inputs and wastes from chemical manufacturing. The emissions of greenhouse gases from the system were calculated to be 151 kg of CO2 equivalents for each standard cubic meter of recovered crude oil. This is three times higher than greenhouse gas emissions from oil production without enhanced oil recovery methods, but substantially lower than emissions from oil sands production. It is recommended to implement enhanced oil recovery methods such as low-salinity waterflooding, rather than producing oil from unconventional fossil reserves such as oil sands. A sensitivity analysis was also conducted, presenting alternative scenarios for power supply, by means of electrification of the platform. The results show that electrification of a platform could offer substantial environmental benefits in terms of reduced emissions of greenhouse gases, depending on the composition of the electricity mix. However, several issues will need to be addressed before this should be implemented on a large scale, in order to ensure that it will indeed reduce global greenhouse gas emissions. The results from this thesis create a basis and a starting point for future research. The environmental impacts associated with desalination of water are deemed reliable; however, great uncertainty is linked to the required amount of water per standard cubic meter of recovered crude oil. In order to calculate the environmental impacts from one specific oil field or enhanced oil recovery project, it is necessary to quantify material and energy inputs, emissions and wastes, as well as the exact water-to-oil ratio by mapping and identifying key parameters and properties of the petroleum reservoir in question.