Tar sands: a primer

Tar sands “are sedimentary rocks containing bitumen, a heavy hydrocarbon complex,” says the Bureau of Land Management.

That definition is included in its final environmental impact statement for its 2012 amendment to land use plans changing the allocations of land available for application for leasing for oil shale development in Colorado, Wyoming and Utah, and tar sands development in Utah.

“Because of the very viscous nature of the bitumen, tar sands cannot be processed by normal petroleum production techniques,” the EIS says.

Tar sands also are known as oil sands or bituminous sands.

Unlike an unconventional fuel source like oil shale, tar sands contain actual oil, said Cameron Todd, chief executive officer of U.S. Oil Sands. But it’s a heavy oil sometimes also described as asphalt. Todd said the difference between bitumen and other oil is that tar sands developers need to figure out how to make the bitumen flow more easily to recover it.

Oil shale, by contrast, is a kerogen that has not yet undergone enough of a geological process to become oil. The technologies and levels of business risk involved with developing oil shale and tar sands vary considerably, Todd said.

The BLM says tar sand deposits are found around the world, except in Australia and Antarctica. The largest deposits are in Alberta, Canada, and in Venezuela.

The BLM says U.S. tar sands resources are mostly concentrated in eastern Utah, where there is an estimated resource of 12 billion to 19 billion barrels of oil in place, mostly on public lands. California, New Mexico and Kentucky also have some sizable deposits.

Other estimates of Utah’s total resource are as high as 32 billion barrels. Jennifer Spinti, a research associate professor in chemical engineering at the University of Utah, said any number is highly speculative because of a minimal amount of at least publicly available drill core data.

More than 50 tar sands deposits are in Utah, but much of the estimated resource is concentrated in a few areas, including what are known as the Sunnyside and P.R. Spring areas in northeastern Utah and what’s called the Tar Sand Triangle between Natural Bridges National Monument and Capitol Reef National Park. The Tar Sand Triangle is mostly off-limits to tar sands leasing by the BLM under its newly adopted land allocation amendments.


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