112
directly from rivers and streams, often below the outfall of a wastewater treatment
plant, or from brackish aquifers that contain groundwater too salty to drink. The
purchase of finished tap water for fracks has been curtailed, much to the disappointment of a number of water utility companies that had been doing quite well
with sales.
The issue of water availability is a concern, especially for fracking in areas that
may have limited water supplies. This is a worry in the Permian Basin that straddles
the Texas-New Mexico border area (Chapa 2019). Water supply and produced water
management have both become big issues here, and water is now big business in
this booming area. Because hydraulic fracturing can be done with lower quality
water, both recycled produced water and undrinkable, brackish groundwater are
being used to supplement freshwater supplies for fracking.
On other shale plays, water is generally being obtained from large sources like
the Ohio River for fracking in the Marcellus and Utica shales, and from the Missouri
River for the Bakken Shale. The multiagency investigation run by the U.S. government from 2012 to 2017 to assess the environmental impacts of unconventional oil
and gas development had “water availability” as one of the areas of concern
(USDOE 2015).
The multiagency study found that the water withdrawals for use on a shale play
are less than the water used by a small to medium-size city. Of course, a city returns
most of its water back to the watershed as runoff or wastewater effluent, while
fracking loses half to two thirds of the water downhole, where it remains forever.
This so-called “consumptive use” is a concern because it effectively removes water
permanently from a watershed, and it can affect a water supply. How this might
influence surface water and groundwater supplies is unclear, but some studies claim
to have documented consumptive water use by fracking that was detrimental to
ecosystems (Entrekin et al. 2018). However, given all of the competing demands for
water use in populated areas, the amounts required for fracking are comparatively small.
Most O&G wells do produce substantial amounts of formation water along with
hydrocarbons. The water cut ratio is generally about two to five barrels of saline
water for every barrel of oil and will often vary over the life of the well. O&G production sites typically have a tall, narrow, vertical tank called a separator located
near the wellhead that uses gravity to separate water, oil, and gas. The volume of
produced water that is economically tolerable from a well depends on the price of
oil and gas, because the water cut incurs handling and disposal costs. As the oil and
gas in a conventional reservoir are depleted, brines migrate up from below and the
remaining hydrocarbons often become isolated, non-mobile phases trapped in the
pore spaces. At this point, the well is producing almost nothing but brine, and is said
to have “watered-out.” Depending on what is left in the subsurface and the current
price of oil, it will either go into secondary or enhanced oil recovery, or it will be
abandoned. Mainstream operators often divest themselves of these watered-out
wells by selling them to small operators at very low prices. The wells would be run
for a few years as so-called “stripper wells” that produced only a few barrels of oil
6 Fracking and Water
directly from rivers and streams, often below the outfall of a wastewater treatment
plant, or from brackish aquifers that contain groundwater too salty to drink. The
purchase of finished tap water for fracks has been curtailed, much to the disappointment of a number of water utility companies that had been doing quite well
with sales.
The issue of water availability is a concern, especially for fracking in areas that
may have limited water supplies. This is a worry in the Permian Basin that straddles
the Texas-New Mexico border area (Chapa 2019). Water supply and produced water
management have both become big issues here, and water is now big business in
this booming area. Because hydraulic fracturing can be done with lower quality
water, both recycled produced water and undrinkable, brackish groundwater are
being used to supplement freshwater supplies for fracking.
On other shale plays, water is generally being obtained from large sources like
the Ohio River for fracking in the Marcellus and Utica shales, and from the Missouri
River for the Bakken Shale. The multiagency investigation run by the U.S. government from 2012 to 2017 to assess the environmental impacts of unconventional oil
and gas development had “water availability” as one of the areas of concern
(USDOE 2015).
The multiagency study found that the water withdrawals for use on a shale play
are less than the water used by a small to medium-size city. Of course, a city returns
most of its water back to the watershed as runoff or wastewater effluent, while
fracking loses half to two thirds of the water downhole, where it remains forever.
This so-called “consumptive use” is a concern because it effectively removes water
permanently from a watershed, and it can affect a water supply. How this might
influence surface water and groundwater supplies is unclear, but some studies claim
to have documented consumptive water use by fracking that was detrimental to
ecosystems (Entrekin et al. 2018). However, given all of the competing demands for
water use in populated areas, the amounts required for fracking are comparatively small.
Most O&G wells do produce substantial amounts of formation water along with
hydrocarbons. The water cut ratio is generally about two to five barrels of saline
water for every barrel of oil and will often vary over the life of the well. O&G production sites typically have a tall, narrow, vertical tank called a separator located
near the wellhead that uses gravity to separate water, oil, and gas. The volume of
produced water that is economically tolerable from a well depends on the price of
oil and gas, because the water cut incurs handling and disposal costs. As the oil and
gas in a conventional reservoir are depleted, brines migrate up from below and the
remaining hydrocarbons often become isolated, non-mobile phases trapped in the
pore spaces. At this point, the well is producing almost nothing but brine, and is said
to have “watered-out.” Depending on what is left in the subsurface and the current
price of oil, it will either go into secondary or enhanced oil recovery, or it will be
abandoned. Mainstream operators often divest themselves of these watered-out
wells by selling them to small operators at very low prices. The wells would be run
for a few years as so-called “stripper wells” that produced only a few barrels of oil
6 Fracking and Water