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The Other Hazard of Hydraulic Fracturing -- Silica in the Air

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In my early career in the oilfield, when I was working on cement and frac crews, I breathed plenty of dust from cement, frac sand, and powdered guar used to make frac gel. Throw in a little xylene and hydrochloric acid, and I think my lungs have experienced plenty of challenges. This week, NPR broadcast a very interesting report about Eric Esswein, a researcher for the National Institute of Occupation Health and Safety, who has been studying health effects on workers on frac crews. Not familiar with hydraulic fracturing, he expected to find the workers exposed to toxics in drilling fluids when he want on location. What he found was very different.

First, a little about hydraulic fracturing, a process that makes oil and gas wells productive, but little understood by people outside of the industry. One of the misconceptions about hydraulic fracturing is that most of the public believe it's something new; that is far from the case. Fracturing has been around for decades, and Halliburton and the old Western company started frac'ing in the 1940s. (BTW, no one in the industry spells it fracking, it's spelled fracing or frac'ing.) The public became aware of hydraulic fracturing when the shale boom hit about six years ago when pressure pumping trucks began showing up in Ohio, Pennsylvania, and New York. I've written quite a bit about frac'ing that you can read about here, here, and here, but essentially it is the process of pumping gelled water blended with frac sand or ceramic beads into hydrocarbon substrates. When the gel breaks, it is flowed back to the surface, leaving the sand behind. As the fracture in the rock closes, it is propped open by the sand, creating a pathway to the well for oil and gas to flow. If it were not for hydraulic fracturing, something like 90 percent of wells drilled in the U.S. would be unproductive. Hence the necessity and the controversy of frac'ing.

After that explanation, back to the NPR story. Esswein didn't find on location what he thought he would find. Rather than exposure to toxics in drilling fluids, he found excessive particulates in the air, primarily silica dust from the sand being moved from trucks to bins to the blender to be pumped downhole. As I mentioned above, frac jobs involve sand. A lot of sand. Moving that sand causes dust in the air. Of the air samples Esswein collected, over 79 percent of those samples showed dust in excess of safety standards set by his agency. In many cases, the particulate content in the air exceeded the amount that the respirators that workers wore could handle. Based on this study, OSHA issued a joint OSHA/NIOSH Hazard Alert, citing Esswein's findings and recommendations for reducing dust and workers' exposure to dust, including:
  • Mandate the capping of unused fill ports (e.g., cam lock caps) on sand movers
  • Reduce the drop height between the sand transfer belt and T-belts and blender hoppers
  • Limit the number of workers, and the time workers must spend in areas where dust and silica levels may be elevated
  • Apply fresh water to roads and around the well site to reduce the dust
The alert also recommended equipment changes such as enclosed cabs for workers, covering components where dust is generated, and others, including screw augers rather than conveyor belts. Improved respirators for workers are also part of the alert.

The industry is also making improvements to equipment to reduce handling, the associated dust, and other hazards. Up until a few years ago, most sand was stored and handled by huge truck pulled bins, called Mountain Movers. They were set on the ground, filled with frac sand, and using a self-contained conveyor, would move sand from the bin to another conveyor that then moved sand to the blender where it was mixed with gel, then pumped downhole. The new system is called a Sand Castle, powered by solar panels, that is brought on location, then raised to vertical, taking up much less space for the same amount of sand. Using sand castles reduces handling of sand and the associated dust.

The reason that hydraulic fracturing has become so controversial is proximity. In traditional oilfields in Texas, Louisiana, New Mexico, and Oklahoma, fracs have been performed for decades, usually far away from populated areas, so no one noticed. Now, in areas like Pennsylvania and Ohio, wells are being drilled and frac'ed in backyards. People in these areas have taken a shocking wake-up call from the industry. As a normal response, the industry first dismissed the concerns; now it is responding with new practices and technology. A real advantage of this shale boom is that we are now importing less than 50 percent of our oil from other countries, most of which hate us. The disadvantage is that our drilling and completion technology has outpaced our ability to safely apply it. It's critical for the public and the industry that we keep making strides to make these technologies safer, protecting people and the environment.