by Gerry Calhoun
With each new discovery of astounding amounts of natural gas or petroleum derived from shale comes renewed concern for the environmental impact of hydro-fracking (HF).
U.S. Energy Secretary Stephen Chu commissioned a committee of state regulators, industry experts and environmentalists to study ways HF can be improved. A subcommittee reported in August that HF itself does not pollute drinking water. Rather, the group blamed faulty pipe or the cement surrounding it.
To understand this finding better, we need to review the drilling, cementing and fracking sequence. For at least the last 75 years, whenever wells are drilled through the fresh-water column, steel pipe, called surface casing, is cemented from ground level to a point well below the drinking-water level. After the cement hardens, drilling resumes down into the oil or gas zone. The bit is then turned horizontally, and drilling proceeds within the shale to the planned target.
Then steel casing is lowered into the borehole, through both the vertical and horizontal portions. The pipe, cemented from farthest penetration to several thousand feet above the shale, isolates the shale from shallower strata. When this cement has hardened, tools containing metal-piercing “bullets” are positioned opposite the formation and fired through the casing, through the cement, and for several feet through the formation at regular intervals to gain access to the oil or gas trapped there.
The fracking process begins with positioning tanks filled with a million gallons of water and 20-30 pump trucks to pressurize a combination of water, sand and surfactants like soap, which is pumped down the casing into the shale. This high-pressure mixture cracks the shale, and the sand props the fractures open.
I operated a frack truck for Halliburton, so I remember the narrow limits on pumping pressure and volume rates my supervisor used to control the fractures. By opening up these fractures in the shale, natural pressure, created by the sheer weight of the overlying rocks, makes the fracking fluids flow back to the surface along with newly released oil or natural gas. When possible, the used water is trucked to the next job. Otherwise, it is stored in plastic-lined ponds or in deep reservoirs.
Recent earthquakes have been attributed to fracking or disposal of the waste water. I lived for 35 years in a town of 100,000 people surrounded by fracked wells and never saw or felt such problems. In The End of Country, Seamus McGraw describes his native Pennsylvania soil emitting smelly gases (later identified as methane) long before any fracking occurred. These natural seeps “pollute” the atmosphere and fresh water far more than drilling. Obviously, neither such natural emissions nor natural earth tremors should indict hydro-fracking.
Factual information, not fearful ignorance, must direct our energy policies. My maps of prospective or producing shale fields indicate that at least 21 states have sizable natural gas or petroleum deposits. They will stimulate our sluggish economy and move us toward energy independence. This is the future — a good one, for a change.
Gerry Calhoun of Nashville is an energy consultant and a petroleum geologist. Email gercalhoun@aol.com.
Related articles
- No link between fracking, contamination: Study (energyindependenceforstates.com)
- Gas industry anxious for fracking regulations (cbc.ca)
- Fracking Isn’t Harming the Planet. Everything Else Is (ecocentric.blogs.time.com)
“I operated a frack truck for Halliburton …”
Hardly objective then, are you?
Posted by Fred Browne | March 11, 2012, 11:11 pm