Large-scale plans for hydraulic fracturing and natural gas export in Maryland have recently been set in motion. From my vantage point as a scientist, let me point to clear dangers in hydrofracking.
A physical process occurs that is overlooked by methane gas developers. This overlooked process is the upward migration of fractures from depth. A breakthrough in understanding this physical process came with the publication of an award winning paper entitled "Hydraulic forces that play a role in generating fissures at depth" by D.C. Helm, published in the Bulletin of the Association of Engineering Geologists.
Over the decades, upward fracture growth that often intercepts the land surface has been observed in the American southwest, Mexico, and overseas, such as in Xi'an, China (home city of the terra cotta warriors). In less arid regions such as Maryland, these fractures morph near the land surface into upward migrating ribbons of enhanced porosity. This physical process is especially triggered by hydrofracking.
As a result of this subsurface process, the frequently asked question "will overlying freshwater aquifers become contaminated?" becomes "when and where will these aquifers first become contaminated?" The follow-up question becomes "does having about 30 years of an abundant supply of methane gas with its concomitant profits and revenue outweigh the eventual unavoidable loss of the freshwater aquifers of Garrett and Allegany Counties?"
It is important for the reader to picture these inevitable subsurface events. Hydrofracking is a decades-old technique for extracting methane gas from tight geological formations such as shale. In order for the trapped gas to be released to the land surface, highly pressurized water is introduced into a wellbore such that the target geological formation becomes fractured. When the water is subsequently depressurized to let the methane escape through the fractures into the borehole, solid particles, called "proppants" which were introduced along with the water, remain behind to keep the fractures propped open. Otherwise, the fractures might close upon depressurization and undo the very purpose of the effort.
Rock at the two opposite ends of a horizontal hydrofracking line will move apart, reflecting the cumulative expansion of the intervening fractures. From the point of view of these opposite ends, it makes no difference whether the initial fracking water pressure continues to be maintained with no proppants or whether this pressure is reduced with the new proppants in place.
In order to hydrofrack in the first place, the water pressure had to have been larger than the minimum in situ confining stress within the shale. With proppants in place, any such fracture within the shale will continue to expand in the local direction of minimum resistance. In order to accomplish this feat most easily and efficiently, the fracture is able to migrate upward, and it does.
It is worth noting that if the upward migration of a zone of fractures or enhanced porosity intersects the plane of an active fault zone and then follows this plane of weakness preferentially, it may essentially "lubricate" the opposing faces along the fault and thereby trigger the next earthquake.
When a producing well is capped or decommissioned after perhaps 30 years, water pressures at depth will rise. This causes the upward migration of any of the slower fractures to speed up.
For Congress to exclude gas companies from EPA regulations is inexcusable. It simply means that Maryland must step up and shoulder the responsibility to establish and enforce regulations that safeguard the health of citizens, our environment, and our natural resources. We can no longer ignore contamination through subsurface processes, especially when such contamination is unavoidable. Upward density flow of methane will follow the upward migration of fractures and porosity enhancement into and through aquifers on its way to the overlying atmosphere.
As an international authority, I believe that producers of gas through hydrofracking should continue to be held financially accountable for years after decommissioning a well for all subsequent consequences of their hydrofracking on the health of residents, the well-being of their lives, and on the sanctity of our environment and natural resources, including freshwater aquifers, lakes, wetlands, streams, and, of course, the atmosphere. Nor should the governor turn his back to science.
Donald Helm holds a U.S. Department of Energy Emeritus Professorship in Environmental Disciplines at Morgan State University.Copyright © 2014, The Baltimore Sun