Hydraulic fracturing works by mixing available water [i] with ‘fracking fluid and injecting the mix, under high pressure, to make thousands of extremely small ‘micro-earthquakes’ in deep well holes. These induced seismic activities, [ii] with a few exceptions, are too small to be felt.
As a result seismic activity along dormant or previously unknown faults are sometimes caused by the deep-injection disposal of hydraulic fracturing flow-back into fractured wells.[iii], [iv]
Fluid injection must be done at sufficient distances from faults to reduce the risks of reactivating them and thus becoming conduits for fluids to flow to groundwater resources.[v]
There are a number of faults throughout Nevada’s Great Basin where oil and gas fracking seems inevitable. [vi], [vii]
In 1995 Michael Johnson then the hydrologist with the Virgin River Water District (VVWD) in Mesquite, NV., located high-yielding wells along fault zones Virgin River Valley Basin (222). That Basin is one of 14 identified by the Bureau of Land Management (BLM) for oil and gas lease auctions. [viii]
In 2002, Dixon and Katzer took an extended look at the Geology and Hydrology of the Lower Virgin River Valley in Nevada, Arizona, and Utah [ix] to better understand the ground-water flow through faults and fracture zones.
Dixon and Katzer pointed out that all ground water in the Virgin River Basin (Hydrographic Area 222) (part of the Muddy River Formation) flows from upper altitudes to lower altitudes in response to gravity. Undoubtedly, they note, ground water flows through the basins along fault/fracture zones of high permeability that extend downward to the carbonate rock faults trending northeast to east-northeast. [x]
These Paleozoic carbonate rocks are the same type of rocks that act as a conduit for ground-water flow for the White River ground-water flow system to the west and north of the lower Virgin River basin.
The White River regional groundwater flow system consists of a string of hydraulically connected hydrographic basins in Nevada spanning about 270 miles from north to south. The northernmost basin is Long Valley (HA 175) and the southernmost basin is the Black Mountain (HA 215) area, a valley bordering the Colorado River within the circle area.
As such the White River flow system likely touches or significantly involves aquifers included in the BLM oil and gas auctions.
Dixon and Katzer found that all major washes in the Virgin Valley area are fault controlled. These faults do not have large displacements (a maximum of 300 feet of vertical displacement), but they cut through the dense calcrete cap-rock exposing the soft silts, clays, and sands of the easily eroded underlying Virgin Valley-Muddy Creek Formation.
Toquop Wash is one of the largest washes North of the Virgin River. Just north of the Virgin River, the wash is a few hundred feet across. It contains more than 20 separate drainage channels that originate in the Tule Desert (HA 221), East Mormon Mountains, Mormon Mountains, and Tule Springs Hills.
Toquop Wash flows to the south, eventually emptying into the Virgin River, miles from its northern origin in the Tule Desert (Hydrographic area 221). The south fork of Toquop Wash veers to the northwest at the power lines and forms a gap as it passes through the East Mormon Mountain and becomes a series of washes originating out of the Mormon Mountains. Olmore (1971) [xi]stated that the entire length of Toquop Wash is structurally controlled by a complex series of normal faults.
If the faults continue to the north into the Tule Desert, they probably provide an additional potential linkage to ground-water flow from the north. Dixon and Katzer argue that the Gourd Springs fault and parallel faults in the Tule Springs Hills provide significant flow paths into the Virgin River (Muddy Creek formation) basin. As the wash continues to the south, the strike of the faults become more northerly.
Other faults in the area include minor faulting along the Pulsipher Wash controlling the width and length of Abbott Wash.
Town Wash, a north-south fault zone splits and forms two tributaries about 5 miles north of the Virgin River and continues northerly past the Lincoln County/Clark County border, east of the Mesquite Landfill site, and then on towards the southern boundary of the Tule Springs Hills.
Sand Hollow Wash located east of Town Wash and extends from the headwaters in the Tule Springs Hills southward to Terry Benches, and into Arizona and the Virgin River. In the upper part of the wash, one large fault in the bedrock affects the entire upper drainage area. Sand Hollow Wash is the eastern margin for faults that are downturn to the west and strike to the north and northeast.
Beaver Dam Wash is a major conduit for significant amounts of ground water and surface water moving into the basin from the north. Only the southernmost part of the Beaver Dam Wash drainage basin was included in the Dixon and Katzer study area. The total drainage area is about 820 mi (Holmes and others, 1997)[xii]. The upper drainage area is in the Beaver Dam and Bull Valley Mountains in Utah and the Clover Mountains in Nevada.
Dixon and Katzer argue that given the geology and structural geometry of the Virgin Valley basin, all ground-water flow appears to be toward the river. Undoubtedly, much of this water moves along fault/fracture zones because of greater permeability in those zones. This is not to say that the aquifer system bounded by fault/fracture zones would not yield water readily to wells, but in the long term, the system may not have the ability to replenish pumped water as fast as appears to occur along fault/fracture zones.
They point out that fault/fracture zones that are prime targets for ground-water development control the movement of ground water throughout the system. They also note that: Geologic mapping will be necessary to better define areas to the north that were not covered in this investigation.
In the final analysis, the careless fracking for oil and gas anywhere on or near faults in the Great Basin may create seismic activity that disrupts and contaminants underground and surface water along a high number of fault zones.
Endnotes:
[i] Water For Fracking in Nevada’s Great Basin Identified at: https://nevada-today.com/water-for-fracking-in-nevadas-great-basin-identified/
[ii] Induced seismicity refers to typically minor earthquakes and tremors that are caused by human activity that alters the stresses and strains on the Earth’s crust. Most induced seismicity is of a low magnitude.
[iii] Kim, Won-Young ‘Induced seismicity associated with fluid injection into a deep well in Youngstown, Ohio’, Journal of Geophysical Research-Solid Earth.
[iv] United States Geological Survey (USGS) Earthquake Hazards, Induced Earthquakes
[v] Wilson, M.P, Worrall, F., Davies, R.J., Almond, S. “Fracking:How far from faults? , Geomechanics and geophysics for Geo-Energy and geo-Resources, June 2018 at: https://link.springer.com/article/10.1007/s40948-018-0081-y
[vi] Beneficial Use of Fracking Water Considered at:
https://nevada-today.com/beneficial-use-of-fracking-water-considered/
[vii] Fracking in Nevada’s Great Basin Inevitable at: https://nevada-today.com/fracking-in-nevada/
[viii] Water For Fracking in Nevada’s Great Basin Identified at: https://nevada-today.com/water-for-fracking-in-nevadas-great-basin-identified/
[ix] Dixon, Gary and Katzer, Terry “Geology and Hydrology of the Lower Virgin River Valley in Nevada, Arizona, and Utah, Report Virgin Valley Water District (VVWD-01), 2002.
[x] Winograd, I.J., and Thordarson, William, 1975, Hydrogeologic and hydrochemical framework, south-central Great Basin, Nevada-California, with special reference to the Nevada Test Site: U.S. Geological Survey Professional Paper 712-C, 126 p.
[xi] Olmore, S.D., 1971, Style and evolution of thrusts in the region of Mormon Mountains, Nevada: Ph.D. thesis, University of Utah, Salt Lake City, Utah, 213 p.
[xii] Holmes, W. F., Pyper, G. E., Gates, J. S., Schaefer, D. H., and Waddell, K. M.
