The above headline is not a typo, since there is no “k” in “hydraulic fracturing.” This correction was just one of many misconceptions addressed in a daylong session on hydraulic stimulation of petroleum at the Western Regional Meeting of the American Chemical Society, held October 4, 2013, in Santa Clara, CA. The audience was interested in learning about the science of fracing.* Prejudice was noticeably absent. One regulator commented that this was the least contentious meeting he had attended on this topic.
Some points from the lectures were:
- Leakage of gas and volatile organic compounds (VOCs) to the atmosphere is much smaller than anticipated. Even this can be reduced by engineering and good maintenance.
- Gas leakage to other formations is due to poor cementing.
- Groundwater pollution from fracking fluid is almost always traced to open ponds. Ponds have been replaced with water recovery/recycling systems using above-ground steel tanks.
- The appearance of fracking fluid in other formations is rare, and usually traceable to abandoned wells that were not recorded. One example: During WW2, steel casings were pulled from some wells to provide steel for the war. The remaining void was filled with any available material, including telephone poles.
- Flow-back of fracking fluids can approach 100%, but is much less in some formations.
- Responding to public pressure, drillers are reporting their fracking plans, such as composition (including CAS numbers) of the fracking fluid to regulators, where it becomes public record.
The morning scientific program of the meeting consisted of case histories, all with a focus on a particular location. The underlying message was that the geology is different, and hence the applicable technology is also. For example, gas wells in the Marcellus Shale (Pennsylvania, Ohio, and New York) produce lots of groundwater with the gas. The oil-producing formations in North Dakota and Texas produce very little water. This is easily collected and recycled. Also, the amount of liquid required for the fracking stimulation is double in the Marcellus than elsewhere. Still, the amount seems large, but it is comparable to one day’s consumption of a golf course.
Technical evaluation in fracking
Anders Sutherland of Soil/Water/Air Protection Enterprise (SWAPE) (www.swape.com) reported on emissions from a collection of fractured natural gas wells drilled in the Barnett Shale about 30 miles northwest of Dallas, TX. Natural gas is the main product, but significant amounts of VOCs exist in the well stream.
The sample site was in a small valley prone to forming thermal inversions during the night. This mechanism trapped volatile organics below the inversion layer. Residents complained of various symptoms often associated with air pollution from hydrocarbon vapor mixtures that included benzene, toluene, and hexane.
Fracking for natural gas in rural Texas accelerated significantly in the 21st century. Initial practices were sloppy, with open, unlined, waste pits; venting without flaring; and little attempt to control VOC emissions in efforts to maximize profitability and productivity. In a study evaluating air sampling conducted in 2010–2011 involving a patch of 56 wells, Sutherland divided the activity into Completion, Production, and Rework. VOC emissions were particularly high during well Completion and Rework stages.
Flaring could reduce the emissions, and is now generally used during all phases of the extraction and distribution for a majority of well sites. Condensate storage during production was determined to be a major source regionally due to poor design and management of the tank farm. Emissions from production are now greatly reduced, but not to zero.
The VOC load for the patch was estimated at 1–2 tons/day. Maximum concentrations of certain petroleum hydrocarbons measured in the rural, residential area surrounded by natural gas wells reached the following levels: benzene (120 ppb), toluene (290 ppb), and hexane (1700 ppb). By summing the upper confidence level (UCL) concentrations of petroleum hydrocarbons known to be associated with neurological symptoms—recorded in a total of 42 air samples—a neurological Hazard Index (HI) was calculated to be 7.39. The threshold value is 1.0, above which the U.S. EPA asserts that further investigation is warranted. The Texas Commission on Environmental Quality is required to implement nationally promulgated air quality controls on new natural gas wells beginning in 2015.
GC/isotope ratio mass spectrometry, accelerator MS, and radiometric assays
Methane is also a hot topic, particularly in the public press. Fracking is often cited as the obvious major emission source. However, ”stray” methane gas may be from leaks in natural gas production wells, pipelines, or underground storage caverns, or from decaying organic matter in swamps or landfills. Julie Sueker, Ph.D. (ARCADIS, www.arcadis-us.com), uses GC/IRMS (isotope ratio mass spectrometry), accelerator MS (AMS), and radiometric assays for methane forensics. For example, methane from “fossil fuels” such as coal and petroleum has no 14C or 3H content because these radioisotopes have decayed to concentrations well below detection, while “modern” methane from landfills and sewers has elevated 14C and 3H from atmospheric sources, including nuclear weapons testing. Sueker showed examples in which the isotopic composition was important in tracing the methane to surface and gas well leakage. Contamination of groundwater from a gas well was found. Remediation by recementing was successful.
Dr. Mark Zeko (Environmental Engineering and Contracting, www.eecworld.com) led off the lectures on groundwater contamination from hydraulic fracking. He focused on the flow-back water, which many fear contains toxic material. He found that flow-back was only 30–70% of the original charge. During the discussion, others reported values as low as 20% as being typical. For example, if the fracking zone is wet, the fracking water enters the formation and is rapidly diluted with the formation water. Tracer studies confirm that dilution is large.
Prof. Matthew Becker (California State University at Long Beach) had recently moved to California from New York. While at the State University of New York, he studied the permeability associated with faults in the Delaware water tunnels that supply water to New York City. The tunnels pass through many faults. Some are still porous. Becker described tomographic micro-seismic technology for the measurement of stress on the rock at the fault interfaces. Others described related technology for measuring the stress on rocks. Changes can be correlated with the fracking event, but for how far? Can these reach the groundwater aquifer?
This presentation led to a discussion on whether geophysical methods could be useful for guiding fracking. Could this information be valuable in mitigating risks, particularly contamination of overlying strata? The consensus was “probably not.” There are too many layers between the Monterey Shale and groundwater. Mr. Mark Nechodom (Director of the California Dept. of Conservation, Sacramento) reports they have no evidence of long-range fissure transport.
Prof. Andrew R. Barron (Dept. of Chemistry, Rice University, Houston, TX) described the startling advance made by his group in improving the quality of production water from fractured wells prior to reinjection. A typical gas well produces a stream that is less than 5% hydrocarbon in water. However, production water is often a suspension of particulates and film-forming bacteria, plus other materials that quickly reduce permeability around the reinjection site. Barron’s lab has developed a series of super-hydrophilic filtration aids that are added upstream of the ceramic filters. The flow-through water is lightly colored but clear. He closed with the admonition that water management is a major issue in gas and petroleum production.
Dr. Carl Fisher (Thermo Fisher Scientific, www.thermofisher.com) discussed the ion chromatography of anions in production water. Often the salt content of the water is so high that the column capacity is exceeded, even for small samples. Conductivity and charged aerosol detectors are commonly used for assay of anions. However, the salt content of the brines exceeds the column capacity. Thermo Fisher Dionex has developed an automated dilution protcol for the WPS-3000SL autosampler. The conductivity of the sample is measured and then diluted to fall within the range of the column. Smart dilution means that highly skilled operators are not necessary.
The temperature in the producing formation can be much higher than the surface temperature. Thus, dissolved material may precipitate in the cooler spots. This causes scale buildup in pipes, which restricts flow. In the Marcellus Shale, the salt content is high, but so is the radon from the decay of uranium in the rock. The scale entraps radon and radium, producing tons per year of radioactive waste. Activity ranges from 480 pCi/g to 400,000 pCi/g. The federal allowable maximum is 5 pCi/g.
The geology of the producing zone determines the wetness of the product stream. Humidity can range from dry to over 95%. Before water reinjection was adopted, land subsidence was a problem in some oilfields. California’s Long Beach Harbor is one example. Today, the field operators inject at least 5% more water (total of 105%) than is taken out. This helps maintain high bottom hole pressure and reduce subsidence.
Regulatory aspects of hydraulic fracking
The meeting was located in California. Mark Nechodom pointed out that secondary recovery of petroleum includes well-accepted processes, including steam or CO2 injection, acid treatment, and hydraulic fracturing. The department has managed these successfully over the last 60 years. During this time, there has been no instance of groundwater contamination from a hydraulically stimulated well. When contamination has occurred, it has been traced to other oil-filled operations, such as storage pits or an above-ground accident.
California is the fourth largest producer of petroleum fuels in the U.S.A. The Department of Conservation is charged with protecting public health and safety. The Department has cataloged 217,000 wells of which 94,000 are still active; 77,400 of these are candidates for secondary recovery, which may involve hydraulic stimulation. However, most wells in California are essentially vertical. Lateral drilling has been used to expand the number of wells per drilling platform or site.
In 2013, Senate Bill 4 passed. This requires a regulatory review of oil production with a special emphasis on identifying and mitigating risks to secondary recovery technology, including fracking. Director Nechodom asked the audience for ideas on how to identify and evaluate. I pointed out that the FDA faced a similar challenge. The FDA’s solution has been to catalog risks from knowledge experts and then evaluate the risks with a scoring system that includes independently estimating severity and probability along with possible mediation steps.
Monterey Shale and related formations underlie much of California, at a depth of about 8000 feet. Other oil-bearing formations are often found above or below Monterey. Monterey Shale has low porosity. Plus, it is usually heavily fractured and severely warped. Thus, drilling horizontal wells for modern fracking has not been economically viable. So, can Monterey be produced and, if so, how?
Fracking is a public topic, especially in locations that might be affected. Earl Hagstrom, a lawyer with Sedgwick, LLP in San Francisco, CA, observed that most of the controversy boils down to land use. People have a way of life; change it rapidly at your peril. Regulation can be at the state level as in New York, Texas, and California. These states have different regulatory philosophies. New York is considering a moratorium for several years, while California is revisiting existing regulations, with a goal of an update by July 2015. Regulation can also be local. This relies on the police powers of states, cities, and counties to adminsister zoning and business. These powers are being used to preclude fracking on the basis of public opinion rather than science.**
Summary and credits
Despite the public perception that fracking is a new technology, it has been used for decades for secondary recovery. In some locations, fracking is effective. But is it really different? Compared to vertical, do horizontal drilling and fracturing present significant new technical risks? I heard none at this meeting.
Ms. Donna L. Drogos (Alameda Country Health Agency, CA) and Ean Warren (U.S. Geological Survey, Menlo Park, CA) deserve special recognition for organizing a stimulating meeting with speakers who covered the subtopics very well.
Robert L. Stevenson, Ph.D., is Editor, American Laboratory/Labcompare; e-mail: firstname.lastname@example.org.
* The term “fracking” is used throughout since it is common usage.
** In a recent article in The New York Times (http://www.nytimes.com/2013/10/10/world/europe/as-drilling-practice-takes-off-in-useurope-proves-hesitant.html), Steven Erlanger claimed that Gazprom, the Russian gas company, is attempting to reduce hydraulic stimulation of gas production in Europe to preserve its monopoly. This was effective in France, which banned fracking. If Gazprom would try this in Europe, could OPEC organize and fund similar programs to preserve its market position in petroleum?