April 25, 2012
Minimum Distance Urged To Protect Sensitive Rock Strata From Fracking
Brett Smith for RedOrbit.com
Artificial fissures in the earth´s crust caused by hydraulic fracturing, or fracking, typically extend less than 600 meters, according to a new Durham University study.These findings could be very important for government officials looking to regulate the fracking industry, which has come under scrutiny for allegedly contaminating drinking water and causing seismic events.
"Shale gas exploration is increasing across the world and sediments of different ages are now potential drilling targets. Constraining the maximum vertical extent of hydraulic fractures is important for the safe exploitation of unconventional hydrocarbons such as shale gas and oil, and the data from the USA helps us to understand how fracturing works in practice,” said Richard Davies, Director of Durham Energy Institute at Durham University.
"Minimum vertical separation distances for fracturing operations would help prevent unintentional penetration of shallow rock strata."
The new study, published in Marine and Petroleum Geology, shows the odds of so-called ℠rogue fractures´ reaching more than 600 meters from the injection source of a fracking operation is less than one percent. The probability of fractures achieving greater than 350 meters in length was found to be one percent.
"Based on our observations, we believe that it may be prudent to adopt a minimum vertical separation distance for stimulated fracturing in shale reservoirs,” Davies said.
“Such a distance should be set by regulators; our study shows that for new exploration areas where there is no existing data, it should be significantly in excess of 0.6 km.”
Researchers also said that horizontal fracking operations occurring at depths below one mile were not likely to contaminate the underground drinking water sources that are positioned above the natural gas in the rock strata.
During a fracking operation, existing fractures in a rock layer are widened by the high-pressure injection of fluid. This widening causes gas and petroleum to migrate from source rock formations to reservoir formations, where the fossil fuels can be more easily extracted.
The procedure has come under fire for its link to groundwater contamination. One of the first known incidents of contamination occurred in 1987, when the Environmental Protection Agency (EPA) published a report that said fracking fluid had leaked into a drinking water well in West Virginia. In 2006, a blown fracking well released over 7 million cubic feet of methane as well as contaminated groundwater.
Fracking probably came under the most high profile scrutiny with the release of the 2010 documentary “Gasland.” The critically-acclaimed film´s most visceral scenes show Pennsylvania families lighting their fracking -contaminated tap water on fire. Gasland was released nationwide and premiered on HBO in June 2010.
Fracking has also been linked to seismic activity in the UK. In 2011, a drilling operation near Blackpool was suspended after it was suspected to cause two small earthquakes.
The Durham University study is the first of its kind, and the research team admits that predicting the behavior of these artificial fractures is difficult. They have expressed hope that the oil and gas industry will continue to provide access and data from fracking sites that would help them more accurately predict how these fissures behave.