Marcellus Shale

EWG Fractures the Truth on Hydraulic Fracturing

Last month the Environmental Working Group (EWG) released a missive with a stark headline -“Federal Scientists Warn NY of Fracking Risks.”  It conveyed the impression, yet again, that the sky was falling with respect to hydraulic fracturing and natural gas development in New York State, implying the United States Geological Service (USGS) itself had turned against the practice with severe warnings.  While a newcomer to this debate may have been mislead, we had a sense there was more to this story than was being conveyed. So we reached out to USGS ourselves in search of the truth. And lo and behold, we found it. Environmental Working Group Distorts USGS on Hydraulic Fracturing

The headline, and associated article, referred to comments a US Geological Survey official provided to NY DEC for its draft Supplemental Generic Environmental Impact Statement.  It turns out, not surprisingly, that USGS’s had a different interpretation of their views than was represented by EWG.  In a conversation with EID, a USGS official indicated the following:

I am aware of the article, and am not pleased. The EWG asked for our comments, which are appended below, and then wrapped their words around them to make it appear that we were “warning’ or otherwise, the NYS_DEC.  As you know, we are a neutral agency, who does not regulate……we do science.

The individual added:

The EWG did correctly quote from our comments but then ’embellished them’ to their needs.

Unsurprisingly, the EWG is one of those entities funded by the Park Foundation to generate negative headlines around natural gas, having received over $1 million from Park over the last seven years.  And at least in the context of that mandate — manufacturing headlines– EWG is good at its job. Not only when it comes to smearing natural gas development — but in attacking the safety of everything from lipstick, to sunscreen, to Diet Coke.

Of course, folks deserve to know whether the process of drilling and completing a natural gas well is safe. For answers, EID turned to someone who’s been studying what goes on at (and under) a wellsite his entire professional career. Below, Scott Cline, PhD, a noted expert in petroleum geology, takes a crack at explaining the basics of safe development:

Heights of Fractures in Natural Gas Operations

After developing, and hydraulically fracturing wells, for over fifty years, a tremendous amount of literature and knowledge have been developed in regards to fracture height emanating from these operations.  In fact, a review of micro-seismic field data of more than 15,000 applications in the Marcellus and Barnett Shale shows that induced fractures maintain significant separation from the groundwater aquifer.  This is evident in the graphs below.

Marcellus Shale Fracturing

Barnett Shale Fracturing

According to USGS data, most aquifers in New York like this one, and this one as just a few examples, are less than a few hundred feet below the surface of the earth making it highly unlikely that an induced fracture, at even the shallowest point in the Marcellus, has the potential to reach groundwater aquifers.  This point is proven by the development of the nearly 5,000 Marcellus wells sunk in Pennsylvania in recent years.

In fact, because of the physical laws of fracture propagation, as fracture stimulation occurs at shallower depths, the induced vertical fracture height diminishes and eventually rotates from vertical to horizontal along bedding planes at depths less than about 3,000 feet. This diminishing fracture height with decreasing depth of fracture stimulation is illustrated strikingly in the above graphs. Add this to the fact New York doesn’t even propose to allow fracture stimulations at depths less than 1,000 feet below the deepest groundwater sources.

How Does Fluid Move in Earth’s Subsurface?

Fictional images of pressurized fracturing fluids that could somehow migrate through underground faults or fractures to groundwater are neither scientifically supportable nor ever documented despite drilling and fracture stimulating over a million wells.

Hydraulic fracturing is simply the very short lived, few-hour application of localized hydraulic pressure on the target reservoir creating fractures of limited vertical height at depths thousands of feet below the surface. After the short lived stimulation, the localized induced pressure is then quickly released and the gas and un-trapped fluid is flowed back through the wellbore. The wellbore thus becomes a pressure sink with any available gas and fluids moving to that pressure sink and up to the surface through the wellbore that has triple or often quadruple redundant layers of steel casing and cement plus tubing that protect the shallow groundwater sources. Any fractures that have not been propped open with sand rapidly close under the tremendous pressures of the overburden and lateral tectonic stress. The only gradient and permeability path to move the un-trapped fluid is toward the wellbore as demonstrated from field experience, reservoir simulation and fracture architecture modeling.

Fluid flow dynamics, as exhibited in Darcy’s Law, require permeability and sustained pressure gradients to move whatever remaining water is left otherwise it will stay in place due to natural forces.   First the permeability and pressure gradient is to the wellbore and not vertically through the impermeable overburden. However in reality most of the fluid is also trapped for geologic time within the Marcellus Shale.

The Marcellus Shale traps fluids a number of ways, including:

  • Fluid “leak-off” into the large fracture surface area, a process where fluid is permanently trapped by capillary forces
  • Hydrophilic clay absorption and clay swelling which, in the shale, restricts water flow
  • The presence of narrow fracture branches which trap fluids that are subsequently imbibed and trapped by capillary forces in the undersaturated Marcellus Shale
  • The migration of fluids to the bottom of fracture proppant packs due to gravity and other forces

No Contamination Threat from Hydraulic Fracturing

Taken together, like the 1.2 million wells fractured previously without incident, it is clear that New York’s groundwater is not at risk from contamination emanating from hydraulic fracturing.

Any discussion on missing fault data, a key component of the USGS comments and the related EWG article which paraphrased their remarks, misses these key and fundamental scientific points of multi-phase fluid flow, fluid retention and fracture mechanics.  It is fine for a federal agency to urge for more data collection, such as the collection of additional seismic monitoring (which natural gas companies do extensively before developing a natural gas well), however it is quite another thing to use these pragmatic observations to forward a contrived unscientific narrative designed to block development of a resource that will help our people and communities flourish.

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