The chances of rogue fractures due to shale gas fracking operations extending beyond 0.37 miles from the injection source is a fraction of one percent, according to new research led by Durham University.
analysis is based on data from thousands of fracking operations in the United States
and natural rock fractures in Europe and Africa.
believe it to be the first analysis of its type, something that could be used
across the world as a starting point for setting a minimum distance between the
depth of fracking and shallower aquifers used for drinking water.
study, published in the journalMarine and Petroleum Geology,
shows the probabilities of rogue fractures, induced in fracking operations for
shale gas extraction, extending beyond 0.6 kilometers, or 0.37 miles, from the
injection source is exceptionally low. The probability of fractures extending
beyond 382 yards was found to be one percent.
fracking operations, fractures are created by drilling and injecting fluid into
the rock strata underground to increase oil and gas production from
fine-grained, low-permeability rocks such as shale. These stimulated fractures
can significantly increase the rate of production of oil and gas from such
operations in the United States are growing in number, and many countries
across the world are looking at shale gas as a potential energy resource. The
process of fracking has come under increasing scrutiny. A recent test well in
the UK near Blackpool, Lancashire, was stopped after some minor earthquakes
were felt at the surface. The UK government is allowing the test fracking to
resume, but critics also have warned of other possible side-effects including
the contamination of ground water.
from Durham University, Cardiff University and the University of Tromsø looked
at thousands of natural and induced fractures from the United States, Europe
and Africa. Of the thousands artificially induced, none were found to exceed 656
yards, with the vast majority being much less than 273 yards in vertical
heights are important as fractures have been cited as possible underground
pathways for deep sources of methane to contaminate drinking water. But the
likelihood of contamination of drinking water in aquifers due to fractures when
there is a separation of more than a kilometer (or 0.6 miles) is negligible,
the scientists say.
Richard Davies, director of Durham Energy Institute, Durham University, says:
"Based on our observations, we believe that it may be prudent to adopt a
minimum vertical separation distance for stimulated fracturing in shale
reservoirs. 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 [0.37 miles].
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.
vertical separation distances for fracturing operations would help prevent
unintentional penetration of shallow rock strata."
team looked at published and unpublished datasets for both natural and
stimulated fracture systems in sediment of various ages, from eight different
locations in the United States, Europe and Africa.
"Sediments of different types and ages are potential future drilling
targets, and minimum separation depths are an important step towards safer
fracturing operations worldwide and tapping into what could be a valuable
need to keep collecting new data to monitor how far fractures grow in different
team accepts that predicting the height and behavior of fractures is difficult.
They now hope that the oil and gas industry will continue to provide data from
new sites across the globe as it becomes available to further refine the
of new sites should allow a safe separation distance between fracking
operations and sensitive rock layers to be further refined, the scientists say.
In the meantime, the researchers hope that governments and shale gas drilling
companies will use the analysis when planning new operations.