Call it unconventional oil, tight oil, shale oil, continuous oil, you name it, but the end result is the same: the bottom of the barrel. Recent technological developments are changing the oil extraction industry dramatically and opening up oil reserves to economically viable extraction. Unequivocally, this new development will have repercussions for the environment and the development of renewable energy and a sustainable energy economy.

Hydraulic fracturing of a shale. Source: Environmental Protection Agency

Unconventional oil sources are created by the same processes as conventional oil—that is, through the combination of organic material, heat, and pressure. The main difference between the two is their ability to move underground. Conventional oil migrates upward due to its buoyancy. This oil moves through pathways in the underground rock in its fluid state and becomes trapped between impermeable layers of rock.

Unconventional oil, meanwhile, is formed in sealed spaces of rock and is not able to move up; it therefore remains in the source rock, trapped in unconnected pores. The development of new technologies such as hydraulic fracturing(or “fracking”), which is used to break up the porous rock in order to connect these micropores, is making the extraction of unconventional oil technologically possible and economically viable.

To put such advances into perspective, the amount of recoverable oil from the Bakken Reserve in the U.S. states of North Dakota and Montana increased 25-fold (an additional 3 to 4.3 billion barrels of oil) from the 1995 estimate, becoming the largest oil accumulation in the lower 48 states and accounting for 7 percent of the total U.S. onshore oil production. Other technically accessible shale oil resources in the United States include the Eagle Ford formation in South Texas and the Avalon and Bone Springs formations in southeast New Mexico and West Texas.

These new developments are transforming the U.S. energy outlook. The United States has increased oil production in the last three years by more than 1 million barrels per day, and it seems that the days of U.S. peak oil are in the rear view mirror. Undoubtedly, this new boom in the oil industry will lead to increased greenhouse gas emissions and affect the environment.

Although the environmental effects of hydraulic fracturing are being downplayed by the oil industry, concerns about this extraction technology amount to more than the risk of spills. Among top concerns are water usage, chemical composition of the hydraulic fracturing fluids, water and soil contamination, waste disposal, air quality, and land development.

The U.S. Environmental Protection Agency estimates that the country requires between 70 and 140 billion gallons of water to drill 35,000 oil and gas wells each year, equivalent to the total amount of water withdrawn from drinking water resources each year in roughly 40 to 80 cities with a population of 50,000 or about one to two cities of 2.5 million people. In the Bakken formation in arid North Dakota, the projected 5.5 billion gallons of water needed per year to access oil and gas has prompted serious concerns. In other regions where water is more abundant, concerns have focused on the high rates of water withdrawal from small streams in the headwaters of watersheds that supply drinking water. This practice could result in negative impact to a stream’s best uses, including reduced stream flow, impacts to aquatic habitat and ecosystems, and aquifer depletions.

The transportation of water to oil well sites depends on the location of the site, and in many areas trucks are the required method of water transport. If we add to these transport emissions the construction equipment, power generation, gas leaks, and volatile organic compounds present in flow back fluids (fracturing fluids that return to the surface), oil extraction is a significant source of air pollution. In states such as Wyoming and Pennsylvania, oil and gas exploration, production, and transportation have resulted in deteriorating air quality.

Another important concern about hydraulic fracturing is the chemical composition of the fluid injected to fracture the rock. Although the chemical concentration of fracturing fluids ranges from 0.5 to 2 percent of the volume, the large amount of fluid used in the process makes this share an important total volume. Since hydraulic fracturing companies are not required to disclose the chemical composition of the fracturing fluid when it is justified as a “trade secret,” lack of information about these chemicals, concentrations, and frequency of use creates difficulty for understanding the fluid toxicology. These chemicals could pose a risk to groundwater aquifers used for drinking water and the surrounding environment in the case of spillage, which has already occurred in Colorado and Pennsylvania, among other places.

Waste is another major impact of hydraulic fracturing. Estimates of the amount of fracturing fluid recovered as flow back in shale operations vary from as low as 25 percent to as high as 70 to 75 percent, and the rate at which the flow back exits the well can be more 100,000 gallons per day for the first few days. The amount and chemical composition of flow back present waste management challenges, and the level of dissolved solids in this fluid creates difficulties for reusing it for further hydraulic fracturing.

As we experience the impacts of the rapid expansion of gas extraction in states such as New York and Pennsylvania, it is important to establish a regulatory framework that minimizes the environmental footprint and ensures responsible extraction (through performance standards and oversight) of unconventional oil. Some states are moving in this direction, and more than 100 bills relating to hydraulic fracturing have been introduced across 19 states aiming to improve chemical disclosure, water protection, waste disposal, and air quality. Development of new technology that will lower the environmental footprint for the extraction of unconventional oil is also needed.  As this industry grows, the impacts on water consumption, chemical usage, and waste disposal will be environmentally unsustainable without new technology advancements.

In general, the extraction of unconventional oil is more carbon-intense than for conventional oil since it requires more energy. Although emissions from unconventional oil production depend on the amount of energy used in the process and on the type of energy source used, greenhouse gas emissions from unconventional oil production are higher than conventional oil. Carbon composition also varies depending on the type of oil. Light oils are rich in hydrogen, while heavy oils are very rich in carbon—waste referred to as “petroleum coke.” Petroleum coke is burned elsewhere, releasing the remaining carbon into the atmosphere.  A transition from exploiting conventional to unconventional oil sources could result in significantly increased greenhouse gas emissions.

Due to these additional emissions, it is important to approach unconventional oil emissions from two perspectives: to study the potential impact in terms of the anticipated level of emissions, and to regulate these emissions. Since the extraction of unconventional oils is expected to increase exponentially, any variation in the carbon composition of oil extracted will have big effects in terms of greenhouse gas emissions. At the moment we do not have sufficient information on the impacts of unlocking all this carbon. Techniques such as Life Cycle Analysis (LCA), which aims at addressing the environmental aspects of a product and their potential environmental impacts throughout that product’s life cycle, is one tool for determining the true impact of emissions from unconventional oil sources (well-to-wheel). Policies such as the Fuel Quality Directive from the European Union designate some oil sources as excessively carbon-intense in comparison with other fuels. Likewise, California’s Low Carbon Fuel Standards seek to reduce carbon intensity in transportation fuels. Carbon taxes for byproducts such as coke can also reduce emissions by reflecting the environmental cost of this new type of fuel.

As this new oil revival continues, governments will need to respond to other critical issues such as infrastructure development, socioeconomic impacts, and access to new lands and leasing permits, since vast lands with unconventional oil resources are owned by the federal government. These areas are subject to federal rules related to environmental reviews, permitting, and oversight, which provide some relief from the rapid development of new shale oil fields. A comprehensive regulatory framework is necessary to mitigate the environmental impacts of the recent unconventional oil boom.


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Bakken, fracking, Fuel Quality Directive, greenhouse gas emissions, hydraulic fracturing, life-cycle analysis, Low Carbon Fuel Standards, shale oil, tight oil, Unconventional oil