This is a nifty idea: an oil field which employs solar energy to generate steam for enhanced extraction technologies. This particular innovation is due to Brightsource Energy who are using a 29 MW solar thermal power plant at a Chevron oil field based in Coalinga, California. The method of CTSP (Concentrated Thermal Solar Power), sometimes abbreviated further to CSP, uses an array of mirrors to focus sunlight onto a central boiler and so generates steam which can be employed to drive a steam turbine and generate electricity in the usual manner. This is a more efficient process currently than photovoltaic technology, but in the present example, rather than the steam being fed into a turbine, it is to be pumped down the oil-wells to help fluidise the oil.
The oil is thick and sticky at normal temperatures but when heated it flows more easily and can be pumped-out more readily. Oil companies often use steam for this purpose of so called enhanced extraction, but normally it is produced using fossil fuels such as gas, for example in the Fresno and Kern counties of California where the oil is particularly "heavy and gooey" to quote from the article cited below. Since this region also collects some of the most intense sunlight in the state, a happy marriage is to use some of it to get the oil out. Indeed, there are a number of other CSPs planned to be built in this region.
Brightsource has investments from Chevron, BP and the Norwegian Statoil Hydro (from a merger of Statoil and Norsk Hydro) and it has signed contracts to provide some 2,610 MW of electricity generating capacity from the CSPs. The solar-powered oil scheme is more important in view of the fact that a significant part of the costs of oil extraction relies on the cost of the natural gas. Presently, gas prices are around $3 per million Btus (British Thermal Units) and it is thought that once the price reaches $8.5 per Btu the solar steam system will prove competitive with the gas-fired units. Gas prices will rise as indeed will the price of oil and so in the longer run this could be a lucrative investment. I suppose there is less carbon emissions too, although since oil is being produced which will be burned overall it is not so environmentally friendly.
The rider is that the solar steam plants only work when the sun is shining and hence back-up units will be needed, which still use gas; the perennial problem of most renewable energy sources - that the power supply is not constant, be it solar, wind or wave.
"A Solar-Powered Oil Field?" By Todd Woody. The New York Times, Green Inc. Energy, the Environment and the BottomLine. http://greeninc.blogs.nytimes.com/2009/08/24/a-solar-powered-oil-field/?hp