Environmental Challenges of Heavy Crude Oils

The world is running out of crude oil! While this is certainly true for conventional crude oils that are easily and inexpensively processed into high-quality fuels, there are vast deposits of heavy crude oils in many parts of the world. In fact, these reserves are estimated at more than seven times the known remaining reserves of conventional crude oils. The largest heavy oil reserves are in the Orinoco oil belt of Venezuela, the Athabasca oil sands in Alberta, Canada, and the Olenik oil sands in Siberia, Russia.

These heavy crude oils are known as unconventional crude oils because they cannot be produced, transported, and refined by conventional methods. Heavy crude oils have a density (specific gravity) approaching or even exceeding that of water. They usually are extremely viscous, with a consistency ranging from that of heavy molasses to a solid at room temperature. Heavy crude oils usually contain high concentrations of sulfur and several metals, particularly nickel and vanadium. These are the properties that make them difficult to pump out of the ground or through a pipeline and interfere with refining. These properties also present serious environmental challenges to the growth of heavy oil production and use.

However, as proven reserves of conventional crude oil are depleted, there is a growing interest in developing the vast resources of these unconventional oils. To this end, the oil industry and government energy agencies are developing new, cost-effective methods for extracting the heavy oils from the reservoir, upgrading them either in situ or at the wellhead, transporting the heavy crude oils or synthetic crude (syncrudes) produced at the well to the refinery, and refining the heavy oils and syncrudes to obtain high yields of valuable light and middle distillate fuels.

Environmental concerns about heavy crude oils are of two types:

• Chemical wastes and byproducts of heavy crude oil production, upgrading, and refining may cause serious ecological injury if released to the environment.
• Spills of heavy crude oils and syncrudes are difficult to clean up and may cause long-term injury to the affected environment.

Many of the in situ and wellhead upgrading and refining technologies produce waste gases and solids that, if released to the environment, would cause serious ecological injury. Additionally, tanker or pipeline accidents involving heavy oils are difficult to clean up. The oil, particularly if it accumulates in upland soils, on the shore, or on the sea floor (some heavy crude and residual oils are denser than seawater and sink), may be extremely persistent and may cause chronic injury to the affected environment.

Battelle is actively involved in environmental studies to determine the environmental challenges of heavy crude oils.

For more information about heavy crude oils, contact Dr. Jerry Neff at (781) 952-5229, neffjm@battelle.org.