Expert: 95 percent of oil, gas wells are fractured
Glenwood Springs Post Independent
RIFLE, Colorado – As much as 95 percent of the oil and gas wells in the world are now dependent on the technique known as hydraulic fracturing, because the easily reached petroleum reserves have basically been used up, an expert told a local audience this week.
“By definition, the low-hanging fruit in the oil and gas industry is gone,” said Jennifer Miskimins, associate professor of the Petroleum Engineering Department at the Colorado School of Mines in Golden for the past eight years. Prior to that, she said, she worked in the oil and gas industry.
Her talk to the Garfield County Energy Advisory Board on Dec. 3 was part of the board’s ongoing education program, which brings speakers to address a selection of issues at the EAB’s monthly meetings.
Miskimins explained that most of the gas and oil that is left is deeper in the ground and “entrained,” or embedded in various types of rock formations. And once a fluid is so entrained, she said, it tends to stay put unless jarred loose and permitted to flow by industrial intervention.
Before hydraulic fracturing, or “frac’ing” was invented in the 1940s, Miskimins said, “Most of these reservoirs [meaning formations like those in Garfield County] we never dreamed we’d be producing from.”
The process begins with the injection of a fluid, often water with no solids in it, down into a well bore to make the first horizontal fissures in the rock formation.
This is followed, she said, with a “slurry” that is mostly water but also contains a “proppant,” usually sand, and certain chemicals, the identity of which she said are “fairly common knowledge” despite public concern that the chemicals are kept secret.
The slurry, she said, widens the fractures initiated by the water and, once the slurry is drawn back up to the surface, the “proppant” stays in place to hold the fractures open. This permits the oil or gas, under natural pressure from the weight of the rock overburden, to flow to the well bore and up to the surface.
According to Miskimins, the first “stimulation” of gas and oil reserves was in the 1880s, when industry used “acidizing” agents or “nitroglycerin” to fracture the rock formations and get the petroleum flowing.
But in 1947 the first frac’ing effort was undertaken in western Kansas, and by 1989 some 35-40 percent of wells were being frac’ed. As the petroleum reserves became harder to get, that percentage rose until it currently stands at 95 percent of wells everywhere.
Miskimins said that even with frac’ing, typically only about 30-40 percent of the buried oil is recoverable, and roughly 70-80 percent of the gas.
She said that because of the nature of the geology involved, and the fact that deeply buried rock is under enormous pressure, the fractures created by the process will not “travel” to the surface and release either the chemicals introduced by the frac’ing process, or the hydrocarbons unearthed by the drilling.
And, she said, the thing to worry about is not that the chemicals get released, but the hydrocarbons – the chemicals that make up oil and natural gas.
“There’s nothing in frac’ing fluids that’s any more dangerous than the hydrocarbons we’re producing,” she declared, adding that the chemicals added to the fluids are in “very small volumes” compared to the gas produced.
When pressed by some of those in the room about the possibility of well-bore failures, seepage of chemicals into the surrounding ground water and other possible ways that drilling operations could pose a hazard, along with questions about putting tracer chemicals into the wells for identification purposes if accidents do happen, Miskimins said those were questions best answered by the companies or the government overseeing the industry.
“Universities can’t do it,” she said of those issues, due to a lack of funding.
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