Oil Shale—Conclusion: Technology may control adverse environmental effects

Feb. 9, 2009
Technology may help control the potential adverse environmental effects of oil shale development in accordance with current and future US environmental policy.

Technology may help control the potential adverse environmental effects of oil shale development in accordance with current and future US environmental policy.

It is critical that oil shale production not devastate the ecology of the region, atmosphere, or surrounding groundwater. This, however, may come at a high dollar value.

The environment and climate change have become topics on the global stage. Amid this movement, future demand for liquid fuels may out strip conventional world oil supply. Recent tight world oil supplies and record high prices have led industry and the federal government to look to US unconventional resources including oil shale as a means to augment domestic oil supply.

While there are many benefits associated with an increase in domestic production of oil, it is important to consider the potential adverse impacts that shale oil production activities may have on the environment including air quality, water use and quality, land disturbance, and wildlife.

Although the US has had no commercial development to date, analyses on technologies provide an approximation of the scale and scope of potential future development and associated impacts.

This concluding article of four, discusses environmental effects of shale oil development. Parts 1-3 covered the resource base (OGJ, Jan. 19, 2009, p. 56), production technologies (OGJ, Jan. 26, 2009, p. 44), and economics (OGJ, Feb. 2, 2009, p. 48).

Air quality

The extraction of oil from shale requires heat. When the carbonate rock reaches temperatures necessary to pyrolize the kerogen, it will release the shale oil and a slate of gases. The associated effects on air quality depend on the process temperatures and control technologies employed.

Depending on the process used, the released gases from retorting oil shale include oxides of sulfur and nitrogen, particulate matter, water vapor, carbon dioxide, and hydrocarbons. The potential also exists for the release of other hazardous trace materials into the atmosphere.

Click here to enlarge image

Fig. 1 displays the gases along with potential uses for captured gases.

Air pollutants

Federal regulations cover many emitted gases under the Clean Air Act of 1963 (which was amended, most substantially in 1990). As currently written, the act sets limits for emissions on particulate matter, ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead.1

The oil shale industry will have access to commercial stack-gas cleanup technologies for controlling emissions to within permitted quantities. Some beneficial uses for these captured hydrocarbon gases with these technologies include use in plant operations or sales for conventional energy use.

The industry can control nitrous oxides and sulfur oxides with commercially proven technologies developed for petroleum refining and coal-fired power generation.

CO2 emissions

According to the Department of Interior Bureau of Land Management (BLM) Programmatic Environmental Impact Statement (PEIS) of December 2007, an oil shale project that processes 1.5 million tons/year of oil shale with a surface retorting plant would emit 802,061 tons of carbon dioxide.2

The retorting process produces the majority of these emissions. Other processes emitting carbon are the start-up burner, electrical sources, hydrogen plant reformer, flue gas flaring, diesel combustion, and mine opening methane.

Much pressure is on the US Congress to enact legislation for limiting CO2 emissions. In light of the long lead times on oil shale development, producers likely will have to contend with CO2 regulations and possibly other greenhouse gases.

Several promising technologies, such as amine absorbers, may be able to capture a large portion of CO2 from the gas stream. If producers can capture CO2 successfully, they have several options for sequestering the CO2.

Click here to enlarge image

With much conventional oil production in close proximity to the oil shale regions of Utah, Colorado, and Wyoming, one potential beneficial use for the CO2 is improved oil recovery. Fig. 2 shows the location of reservoirs that are candidates for CO2 miscible flooding in the US.3

Opportunities also may exist to sequester CO2 from oil shale operations in depleted oil and gas reservoirs, and in the coal deposits in the region. Sequestering in coal beds could enhance coalbed methane production.

Water use, quality

The oil shale industry requires large amounts of water and the processing of the shale may greatly affect the quality of surface and groundwater. Water use in the Colorado, Utah, and Wyoming area will affect not only this three-state region, but also states that are downstream as well.

Development of oil shale resources will require large quantities of water for mine and plant operations, reclamation, supporting infrastructure, and associated economic growth. Current estimates based on oil shale industry water budgets suggest that water requirements for new retorting methods will be 1-3 bbl of water/bbl of oil.4 Some processes may eventually be net water producers.

Click here to enlarge image

An oil shale industry producing 2.5 million b/d will have a cumulative demand on water of between 105 and 315 million gpd. Municipal and other water requirements related to population growth associated with industry development will require an additional 58 million gpd. This amounts to 0.18 million to 0.42 million acre-ft/year of water (Table 1).5

In the West, water will be drawn from local and regional sources with the majority likely coming from the Colorado River basin, including the Colorado, Green, and White Rivers5 that have an annual flow of 12 million acre-ft/year.1

Western oil shale has high water content; some oil shale contains 30-40 gal/ton of shale. More typically, it holds 2-5 gal/ton of water. Much of this water can be recovered during processing and used to support operations.

Produced water will contain organic and inorganic substances that conventional filtering technologies can remove. Recycling and re-use of process water will help to reduce water requirements.

The operations will require protection of surface and groundwater contamination from mining and retorting operation runoff, treatment facility products, other wastewaters, and particularly the retorted shale waste piles that contain heavy metals in the leachate.

In addition, in situ heating and combustion of oil shale will require controls to prevent contamination. The varying processes for developing oil shale likely will lead to technology specific methods for ground and surface-water quality protection.

Click here to enlarge image

Groundwater protection is of critical importance and is of greater consideration for in situ processes. Currently emerging technologies create a barrier between the heated oil shale zone and any potential sources of groundwater (Fig. 3).

In conjunction with its in situ conversion process (ICP) currently being tested in Colorado, Shell Oil Co. has under test an environmental barrier system called a freeze wall. It creates the freeze wall by freezing groundwater occurring in natural fractures in the rock into a ring wall surrounding the area to be pyrolized.

The barrier protects groundwater from contamination with products liberated from the kerogen while at the same time keeping water out of the heated area. Once pyrolysis is completed, the area is sufficiently cleaned and the freeze wall is melted to allow groundwater to flow through this area once more.

Land disturbance

The estimated maximum cumulative land needed for a 1 million b/d oil shale industry is 80,000 acres during 40 years.6 Of this total, the industry needs about 50,000 acres for mine development, storage of overburden, storage of raw and processed shale, surface facilities, off-site land for access roads, power and transmission facilities, water lines, and natural gas and oil pipelines.

It will require up to 20,000 acres for urban development, and need the remaining 10,000 acres for utility rights-of-way.

Click here to enlarge image

The entire Green River formation covers about 11 million acres, so that the surface area impacted by development is about 1% of the total land area of the oil shale region (Fig. 4).

Spent shale disposal

Surface retorting operations produce leftover spent shale, composed of carbonate materials and other minerals, after extracting the shale oil. Depending on the location, ore characteristics, and the process, some spent shale can be contaminated with heavy metals or toxic organic compounds that may require special handling, treatments, or disposal methods.

In addition, the spent shale will have a 13-16% greater volume than its in-place volume.6 Void spaces in the spent shale that are not present in the compacted shale before it is mined cause this volume increase.

Because of the increased volume, operators cannot return all spent shale to the oil shale mine, but will need surface disposal or alternative uses.

Some beneficial uses of spent shale can include roadbed material, and aggregate for concrete production and building materials.

In situ recovery residuals

True in situ processes do not have the problem of spent shale disposal; however, other subsurface effects, including potential groundwater contamination, are possible and must be controlled.

While the surface requirements are relatively small, oil shale processing will affect the local and regional environment. The actual affect on the land will vary from process to process.

Mining and surface retorting processes create more land disturbance, but existing reclamation regulations require oil shale developers to restore the land once they have finished developing.

Wildlife

Oil shale development also affects wildlife. Before commercial oil shale development, site evaluations for individual projects will have to include project-specific environmental impact studies. Evaluating the specific flora and fauna for each project will help determine appropriate action needed for mitigating the effects on plants and animals.

Development will require wildlife management plans with federal and state wildlife authorities for monitoring and tracking wildlife dislocation and maintaining habitat quality.

The Endangered Species Act protects several species that live in areas with oil shale development potential (Fig. 5).
Click here to enlarge image

Of utmost importance in developing oil shale is considering the endangered species in the region and in habitats in close proximity to oil shale production sites. Fig. 5 shows some species listed as endangered and therefore protected by the Endangered Species Act.

Click here to enlarge image

In addition, several species are threatened that may potentially be upgraded to an endangered status (Table 2).

Four of 12 native fish species are listed and protected under the Endangered Species Act. Designated critical habitat for these species is within the Upper Colorado River basin. An additional 25 nonnative fish species also are in the basin.1 Oil shale activities could contaminate the water system and use water needed by these fish.

Both large and small mammals range across the oil shale region. Large game includes elk, mule deer, pronghorn, bighorn sheep, moose, American black bear, and mountain lion. Smaller mammals such as jackrabbit, American badger, bobcat, coyote, red fox, bats, and rodents also live in the region.

The PEIS cited water supply as a major restrictive factor for large game. The oil shale industry’s consumption of water in the region may affect greatly these species.1

Fragmentation of habitat is another important consideration. Fragmented habitats from oil shale projects may limit the species’ ability to maintain a minimum viable population.

Various strategies exist for minimizing the effect of development on wildlife including wildlife corridors.

The region contains one endangered mammal and two that are threatened. The industry will have to give special consideration to these species in the wildlife management plans.

Many migratory and permanent birds reside in the region. The habitat, water supply, and overall ecosystem are important for supporting the avian populations.

The California condor and the Mexican spotted owl are both listed as endangered species and protected by federal law.1

The oil shale region has 6 endangered and 10 threatened plant species. The BLM further classifies 41 species of plants as sensitive.1

Mining and other land disturbing activities could decimate many of these plants. Some are unique to the region; for example, the Barneby Ridge-Cress is thought to be found solely on the Uintah and Ouray reservations of the Ute Indians.1 The Endangered Species Act protects the range of these listed species.

References

  1. The Clean Air Act as Amended, PL 108-201, US Congress, Feb. 24, 2004.
  2. Programmatic Environmental Impact Statement, US Department of Interior, Bureau of Land Management, Washington, DC, December 2007.
  3. Hitesh Mohan, et al., “The Potential for Additional Carbon Dioxide Flooding Projects in the United States,” Paper No. SPE 113975, SPE/DOE Symposium on Improved Oil Recovery, Tulsa, Apr. 20-23, 2008.
  4. Cameron, C., et al., Energy Demands on Water Resources, Report to Congress on the Interdependency of Energy and Water, Draft, Sandia National Laboratories, July 2006.
  5. Wood, T., Water Resources for Oil Shale, Battelle, 2006.
  6. America’s Strategic Unconventional Fuels: Volume III—Resource and Technology Profiles, Task Force on Strategic Unconventional Fuels, Washington DC, September 2007.

The authors

James Killen’s biography and photo appeared in Part 1 of this series (OGJ, Jan. 19, 2009, p. 56), and Emily Knaus’s biography and photo appeared in Part 2 of this series (OGJ, Jan. 26, 2009, p. 44).