Oil shale process refined, but water sources vulnerable, researcher says

GOLDEN — Proposed methods of developing oil shale in place underground offer a lot of environmental benefits but pose more risk of groundwater contamination, a researcher working on behalf of the federal Department of Energy says.

“It’s important to know that this can happen, but you can mitigate it by proper operation,” James Covell of EG&G Technical Services said in an interview Tuesday after speaking at an oil shale symposium at the Colorado School of Mines.

Covell has been working on behalf of the DOE’s National Energy Technology Laboratory to review environmental risks of potential commercial oil shale technologies.

These include various “in situ” projects that Shell, Chevron and American Shale Oil (AMSO, formerly EGL Oil Shale) plan to pursue on federal research, demonstration and development leases in northwest Colorado.

The companies hope to free up kerogen from shale underground and then pump it to the surface. Shell and AMSO plan to heat the rock, and Chevron intends to inject carbon dioxide that would act like a solvent to draw out the kerogen.

Covell said one benefit of in situ processes is that they should result in less possibility of surface water contamination than in the case of the traditional method of mining and then retorting oil shale. However, the processes also could result in volatile organic compounds such as benzene and toluene tainting groundwater, he said.

Fortunately, such compounds are easy to remove by flushing them out, he said. He said Shell has been doing a good job of acknowledging the threat of benzene contamination and working on addressing that in its project.

Shell has been experimenting with using a subsurface freeze wall to surround its heating operations. The idea is to isolate the heated area from surrounding groundwater, and allow groundwater within the isolated area to be pumped out to protect it.

“I was a skeptic … and was converted by actually doing this,” Bill McKinzie, an engineer for Shell, said in a presentation Tuesday on Shell’s freeze wall tests.

In an earlier test involving a 25-foot-diameter freeze wall, Shell was able to create a sealed wall, produce kerogen without water getting in, and remove benzene left behind in the process before reintroducing groundwater, he said. Shell is now working on a test of a freeze wall that will be about an acre in size.

The DOE also is evaluating surface and air quality impacts and energy and water needs of various oil shale technologies.


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