Hydraulic fracturing, commonly known as fracking, is a process that blasts bedrock to create fractures for natural gas to escape form the bedrock. Fracking is used in unconventional wells that are extended horizontally from an initial vertical borehole. The process is used in Pennsylvania to extract natural gas from the Marcellus Shale Formation, which is encountered as depths as great as 8,000 to 10,000 feet below ground in the northern and western parts of the state.
Hydraulic fracturing of an unconventional gas well.
I am not anti-fracking. As a geologist, I understand how fracking is supposed to work, and I think it’s a viable means of extracting natural gas from deep formations in which conventional drilling is not practicable. But I also think that Pennsylvania has done a horrendous job of overseeing how the energy companies operating in PA drill for natural gas and manage their drilling wastes.
The Pittsburgh Post-Gazette does a great job covering Marcellus Shale gas drilling issues in PA, including reporting on negative environmental aspects of bringing this natural resource to market. Last week the Post-Gazette ran a great editorial piece that cited data they obtained from the Pennsylvania Department of Environmental Protection (PADEP) about compromised water supplies related to oil and gas operations. The editorial also criticized PADEP for issues with public access to information related to water supplies contaminated by oil or gas drilling activities. Many of the chemicals used in the fracking process are claimed by drillers to be trade secrets. And PADEP will not release information about those chemicals. So the public and their advocates have no opportunity to evaluate the risks they may be facing from fracking fluid contamination.
When the reports about methane in residential water wells near Marcellus gas wells in northern PA first started hitting the media five or six years ago, the red flags should have been clear to anyone familiar with drilling. The drillers were swearing that there was no way methane from their target formation at 8,000 feet below ground could have contaminated the shallow aquifer only 100 to 150 feet bellow ground where most domestic wells are built. And, if the wells were constructed properly, that should be true. But the drilling boom came upon PADEP too quickly. The DEP had neither the field inspectors nor the funding to hire enough field inspectors to be able to ensure that gas wells were being constructed properly.
Steel casing is supposed to be cemented into the surrounding bedrock to a depth far below the drinking water aquifer. The cement slurry, a mixture of cement and bentonite clay, effectively seals the annular space around the outside of the steel casing to prevent any drilling fluids or gas from leaking around the casing and getting into the aquifer. And a good annular seal also prevents surface runoff water from seeping down along the outside of the casing and tainting the underlying drinking water aquifer. That is assuming the wells are being properly sealed.
In my job, I have overseen drillers installing hundreds of groundwater monitoring wells or remediation wells designed to delineate or treat petroleum, solvents or metals contamination in groundwater. There have been many times I have given the driller my construction specifications and, when they thought I wasn’t looking, caught them cutting corners. Most often the corner getting cut involved how they were grouting the well materials in the borehole. And that's exactly what I think happened in the majority of instances in which methane was documented in domestic wells in close proximity to an unconventional gas well.
If the cement used to seal the steel casing into the borehole is mixed with too much water, the cement will shrink as it cures and will pull away from the borehole walls. If not enough bentonite is mixed with the concrete, if it is not mixed uniformly or if it is pumped too quickly down the borehole, there may be pockets of concrete that do not seal completely to the borehole walls. These are the conditions that PADEP inspectors should have been on hand to look for during well drilling. Presumably, at this point in the drilling boom, something as basic as proper well grouting has been rectified between drillers and PADEP.
Fracking fluid impoundment in western PA.
(photo credit: Observer-Reporter.com)
Assuming that gas wells are now being properly constructed, spills of drilling fluid are probably the biggest on-going concern for public health. Spills of drilling fluids are a largely preventable threat to groundwater and surface water resources. A different Post-Gazette editorial published earlier this week cited the disturbing frequency of drilling companies failing to detect or report spills on their drilling sites. Half of the drilling fluid spills for which PADEP fined drillers through 2012 were not reported to PADEP by drillers as required by law. Instead, they were reported by drilling site land owners or neighboring property owners or observed by PADEP inspectors or other officials.
PADEP needs to be better funded to better police Marcellus drilling sites so that drillers will be less likely to carelessly allow preventable spills to happen and will be more diligent in policing their sites to promptly discover and act on truly accidental spills. PA’s groundwater and surface water resources depend on it.