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A program was formulated to help educate public opinion leaders on the fundamentals of unconventional natural gas and oil extraction, to convey the current state of research on the topic, and to disseminate and discuss prospective regulations that have been formulated over the past two to three years.
I am writing this blog installment on a return flight from Bogota, Colombia, back to Texas (and through Miami). Yesterday, I participated in a forum, “Questions and Answers on Fracking,” hosted jointly by the Colombian government, oil and gas industry, and national media. The goal was to further a national conversation regarding the plan for Colombia to proceed with extraction of unconventional natural resources. A program was formulated to help educate public opinion leaders on the fundamentals of unconventional natural gas and oil extraction, to convey the current state of research on the topic, and to disseminate and discuss prospective regulations that have been formulated over the past two to three years. I was asked to provide presentations over our work on groundwater quality in the Barnett Shale of north Texas (1). I was accompanied by other international researchers, all of whom who had visited Colombia previously to help them draft prospective regulations. I had not been to Colombia previously. Our group included Prof. Mark Zoback, a Standard University geophysicist and member of the National Academy of Engineering; Dr. Frederic Schneider, Exploration Project Director and Petroleum System Expert for BeicipFranlab in France; Mr. David Yoxtheimer, a Pennylvania State University hydrogeologist and Extension Associate of the Marcellus Center for Outreach and Research; and Mr. David Neslin, Partner for Davis, Graham & Stubbs, LLP and Expert in Environmental and Energy Law. Prof. Rob Jackson, another Stanford University geologist, joined us through video conference, and a couple of presenters from Colombia also shared their views.
As an analytical chemist, I was somewhat of a fish out of water in the forum. I discussed our development of new analytical methods and their application to a variety of groundwater projects in Texas. Beyond that, the forum focused more directly on the nuts and bolts of unconventional exploration operations. I found the forum to be extremely educational - I learned a great deal about some topics that I previously knew were important, but could not speak about in great detail. Given that I heard many of the presentations more than once (they were given as part of a larger initial forum and then later in condensed versions for media reporters), I feel much more comfortable discussing some of the broader issues associated with unconventional oil and gas extraction, and I thought it might be of interest to share some of them here with you.
I think the first point to make clear, because it is a large misconception, is that the process of hydraulic fracturing does not affect groundwater quality. The depths of aquifers may range 100–1000 ft below the surface. Hydraulic stimulation is carried out to fracture low permeability rocks approximately 7000–10,000 ft below the surface. Out of more than 1,000,000 instances of hydraulic stimulation, there has never been a case where fluids have migrated through the rock bed into the aquifer, as long as these relative distances were maintained. Hydraulic fracturing is needed to release natural gas and oil that has been stored in source rock for millions of years. Even when fractures are opened, which might in some instances extend vertically as much as 500 ft, there are no pathways for fluids to travel through the remaining several thousand feet of rock stratus to reach the aquifer.
The biggest risks are actually associated with other components of the process, specifically well casing and handling of wastewater. When a well is drilled, it is supposed to be cased using steel and cement to a sufficient depth, so that hydraulic fracturing fluids or oil/gases cannot escape into the surroundings. In fact, there can even be pockets of gases at intermediate depths - not associated with the target shale - that could leak into aquifers in proximity to poorly cased wells. This is potentially a problem that could be attributed for problems of methane-contaminated water in Parker County, Texas, but more work is needed to assess that particular case (2). If a well has been appropriately cased, then handling and containment of wastewater becomes the next major concern. During the hydraulic fracturing process, “flowback water” is generated. This is a mixture of the hydraulic fracturing fluid (~90% water, 9.5% sand, and 0.5% chemical additives) and natural brines present in the deep shale formation. After well stimulation, during production, “produced water” is generated. This liquid will have properties similar to the flowback water, but can also contain significant amounts of hydrocarbons. Of the approximately 3–5 million gallons of fluid that is pumped into the well for hydraulic stimulation, about 15–25% will return to the surface as waste water. Salinity in these mixtures can exceed that for ocean water, and total dissolved solids (TDS) can be as high as 100,000 ppm. This waste must be either carefully disposed (underground injection is the norm in Texas) or treated (recycling and treatment is the norm in Pennsylvania). As one might expect, the choice is driven by cost and regulation. Improper handling of flowback or produced water could result in spills that allow chemicals to enter into surface water and groundwater supplies. Thus, well casing and wastewater handling are two aspects of the unconventional gas and oil extraction process that are of far more concern with respect to environmental contamination than the process of hydraulic fracturing itself.
Seismic activity and earthquakes have been associated with unconventional oil and gas operations, but these phenomena too are unlikely to be connected to the hydraulic fracturing process. When a fracture is rendered in the deep shale formation, it creates a microseismic event that would not generally be felt at the surface. Earthquakes have been more readily associated with wastewater disposal through means of deep well injection. This wastewater disposal process may very well have a connection to localized increases in higher magnitude earthquakes in recent years in states like Oklahoma. Interestingly, whereas only one magnitude 4 earthquake has generally been recorded per year in Oklahoma over the last many years, more than 20 have been recorded in 2014 alone, and this number is expected to rise. A magnitude 4 earthquake can be felt for quite some distance and can knock down old brick chimneys. Importantly, most underground injection well activities operate with no problems. Similar concerns for well casing and waste handling still exist, but with regard to earthquakes, these are generally attributed to cases where waste is inadvertently injected into an active fault. The belief is that some of these faults would naturally result in a seismic event anyway, at some point in time, but that the added pressure from the injection of fluid reduces the force between the fault planes and induces slip sooner rather than later - the bigger the fault, the bigger the slip. Thus, seismic events associated with underground waste disposal can be avoided when appropriate surveying is performed to locate and avoid fault lines before injection.
The Colombian government has essentially placed a moratorium on unconventional exploration for the past couple of years, while they consulted with experts and drafted a set of regulations that would govern their operations. They are approaching the situation with care and caution: They are considering all angles and are making a strong effort to educate the public and gain public favor for the activity. The initial exploration would only be the drilling of a handful of wells over the next few years. In that time, the appropriateness of regulations related to proximity of operations to natural waters, well casing guidelines, and the distance between hydraulic fracturing operations at depth to aquifer levels would be evaluated. Learning more about the geology at the prospective drill sites seems to be an immediate need. The regulations were designed as a starting point and will likely be revised on an annual basis as more is learned. In most ways, the regulations set forward are more stringent than those present in many states in the United States. It is clear that the environment and geology in Colombia require unique consideration, as would operations initiated in any new area of the world. That said, I left the forum extremely impressed by the preparation, the program assembled, and the messages communicated. I also left with a much better understanding that, based on our present understanding, unconventional extraction of natural gas and oil can be performed in an environmentally responsible fashion, if appropriate protocols are followed (3). It is my personal opinion that where problems of environmental concern have emerged in the United States, they are likely due to someone not following best practices.
(1) B.E. Fontenot, L.R. Hunt, Z.L. Hildenbrand, D.D. Carlton Jr., H. Oka, J.L. Walton, D. Hopkins, A. Osorio, B. Bjorndal, Q. Hu, and K.A. Schug, Environ. Sci. Technol.47, 10032–10040 (2013),.
(2) R. Jackson, Dec. 1, 2014. http://tribtalk.org/2014/12/01/reopen-barnett-shale-water-probe/
(3) M.D. Zoback and D.J. Arent, Elements, August, 251–253 (2014) (http://www.elementsmagazine.org/archives/e10_4/e10_4_dep_perspective2.pdf).
Previous blog entries from Kevin Schug: