2011년 10월 3일 월요일

Solar and oil: New energy helps extract old in California


Think about the uses solar energy can be put to, and what comes to mind? Solar panels for making electricity, certainly. Solar thermal for heating water. Solar chargers for powering up cellphone and laptop batteries, maybe. But what about using solar energy to help pull more crude out of aging oil wells?
That’s what BrightSource Energy, a solar thermal technology company, is doing.  And not just for any oil drilling project, but for the largest enhanced oil recovery (EOR) project in the world.
The project got under way this week in Coalinga, California.  Built for Chevron Technology Ventures, the 29-megawatt-thermal “solar-to-steam” facility will use BrightSource’s proprietary technology to convert sun energy into high-temperature and high-pressure steam for EOR.
The BrightSource technology features 3,822 heliostats, each made of two 10×7-foot mirrors mounted to a six-foot steel pole. The mirrors are focused on a boiler on top of a 327-foot-tall solar tower. The boiler produces steam that is then pumped deep into the sub-surface oil reservoir to heat the area. That increases the pressure of the reservoir and reduces the viscosity of the oil, making it easier to bring to the surface. To conserve water use, the steam is then cooled and recirculated in a closed-loop system.
One of the oldest oil fields in the US, Chevron’s Coalinga site began operations in the 1890s. Because the field’s heavy crude does not flow readily, steam is injected into reservoirs to heat the crude, making it easier to bring to the surface. Steam at the field has traditionally been generated by burning natural gas.
“The energy intensity associated with extracting heavy-oil is extremely high,” said Paul Markwell, senior director of upstream research with IHS CERA. “Many of the known heavy-oil reserves around the world have limited access to cost-effective fuel sources and are located in areas with high solar resources. This provides an ideal environment for the use of solar thermal technologies for enhanced oil recovery.”

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