Monday, May 16, 2011
As a follow-up to Blake's kind post regarding my brief sound bite, I'd like to offer a few thoughts that weren't reflected in the extremely short NPR statement. Natural gas has "exploded" in the United States, both figuratively and, in some cases, literally. In 2009, permits issued for natural gas drilling in the Marcellus Shale increased by about three-hundred percent. For specific permitting numbers visit the Pennsylvania Department of Environmental Protection's website, and click on the "Marcellus permits issued" maps. The Barnett Shale in Texas has seen a similar explosion in drilling permits. In 2010 alone, Texas's Railroad Commission issued 2,157 permits for natural gas drilling in the Barnett Shale. And these are not the only areas that are experiencing--or soon may experience--an explosion in natural gas development.
Most gas wells that are drilled (up to ninety percent of the wells, in fact), are now hydraulically fractured. Fracturing methods differ depending on where the drilling occurs, but in shales, hydraulic fracturing often requires "slickwater" fracturing, which uses millions of gallons of water and about 0.5 percent chemicals by weight. (See "sample fracture fluid composition by weight" in the previous link.) Some of these chemicals, such as benzene and toluene, are toxic; others are benign. For a slickwater fracture (a "frac" or "frack," as it is sometimes called), a company drills a well--often both a vertical and horizontal one--and then cases (lines) it. It perforates the well, injects an acid such as hydrochloric acid into the well to clean the formation surrounding the well, and injects several million gallons of water mixed with some chemicals into the well to induce or expand fractures in the formation around the well. It also injects proppant, such as sand, to prop open the fractures once they are formed, allowing gas to flow into and up the well. For a good summary of the process, see the New York Department of Environmental Conservation's Supplemental Generic Environmental Impact Statement starting at page 5-93.
The explosion in permits, drilling, and fracturing has been accompanied by explosions of gas wells, an intrastate gas pipeline, and water wells or homes near gas drilling and fracturing sites in Pennsylvania and Arkansas, among other states. Fracturing itself has not, in many cases, caused these incidents; they often are associated with the drilling and gas production activity that accompanies fracturing. The recent blowout in Pennsylvania, however, which spewed chemicals into a creek, occurred during a hydraulic fracturing operation. The growth of gas drilling and fracturing permits issued also has generated a number of potential environmental concerns, including, for example, the following:
1) Are chemicals that are transferred into water prior to fracturing stored and transferred in a safe manner? Some surface spills have highlighted the importance of this question.
2) What happens to the injected water and chemicals that do not come out of the formation after being injected?
2) How is the water/chemical solution that flows back up out of the well as "flowback water" after fracturing, along with the naturally produced water from drilling, stored on site and disposed of? Often, the flowback water--as described further below--is stored in a pit or tank at the well site and then either disposed of in an underground injection control well or through a wastewater treatment plant. Companies are improving flowback water recycling technologies, too.
3) Are onsite storage pits for flowback water properly constructed to ensure that chemicals do not seep into the soil and/or water? (Subtitle C (the hazardous waste disposal portion) of the Resource Conservation and Recovery Act does not apply to many oil and gas exploration and production wastes, as described in one of my previous posts. This might explain why many states allow gas companies to store flowback water, which sometimes contains toxic chemicals, in a pit on the surface while awaiting disposal. Some companies are moving toward storage in steel tanks on the surface. New York has proposed to require steel tanks.
4) When the flowback and produced water is disposed of in underground injection control (UIC) wells--as it often is in Oklahoma and Texas and other areas--are these wells properly constructed, as required by the Safe Drinking Water Act and the SDWA permits that accompany UIC wells?
5) When the flowback water is disposed of through wastewater treatment plants, are the plants able to handle the large quantities of wastes, the new chemicals, and the small quantities of natural radiation that the water sometimes picks up while sitting underground?
6) Is methane from fractured formations seeping into groundwater? A recent study in the Proceedings of the National Academy of Sciences begins to investigate this question. Have chemicals injected into perforated wells ever contaminated groundwater, and what is the risk of such contamination, if any? The Natural Resources Defense Council maintains a "list of incidents where drinking water has been contaminated and hydraulic fracturing is a suspected cause." The Interstate Oil & Gas Compact Commission--formerly headed by Governor Sarah Palin and now led by Governor Mary Fallin of Oklahoma--observes that "IOGCC member states have all stated that there have been no cases where hydraulic fracturing has been verified to have contaminated drinking water." Chesapeake Energy--a major gas extraction company--also states, "Based on reviews of state oil and gas agencies, there has not been a documented case of drinking water aquifer contamination related to the fracking of a deep shale natural gas or oil well."
7) A host of other questions relate to the drilling--not the fracturing--process, such as whether drilled wells are being properly cased to protect groundwater; whether companies are following proper stormwater control measures when constructing access roads and well pads; whether the naturally occurring radioactive materials (NORM) wastes that can come up out of a drilled well in the form of drill cuttings and other substances are being properly disposed of (land application often is allowed for certain types of drill cuttings); and whether substances such as used drilling muds are being properly disposed of.
Finally, authors of a recent draft Cornell study, also discussed on NPR, believe that natural gas may release more greenhouse gas emissions than assumed--so much so that considered over a certain time frame, the emissions could begin to rival emissions from coal.
My two cents? Natural gas seems important because it is abundant within U.S. borders and seems to release fewer greenhouse gases (on a CO2-equivalent basis) than do other fossil fuels, although the recent Cornell study suggests that scientists need to look at this more closely. But we should proceed cautiously and safely with natural gas extraction--just as we should with any other form of fuel extraction or energy production. We must carefully examine the risks of natural gas extraction and its alternatives. The EPA is beginning to do this with its "lifecycle" study of the effects of fracturing on water. Finally, we shouldn't forget that natural gas is, in the end, a bridge to something else--hopefully to an energy mix that will largely rely upon sustainable forms of energy such as renewables. A one-hundred year supply of natural gas looks like an "abundant" fuel source now, but from the perspective of future generations, it is a finite source. While relying on bridge fuels, we must start building the opposite shore to which the bridge will run. A bridge without a stable end point is a flimsy bridge, at best.