>>Dr. Robert Puls: Wastewater disposal of produced water options are: underground injection
control wells, on-site treatment, such as evaporation, recycling or reuse. A potential
emerging problem with underground injection control wells is that recent studies suggest
that UIC wells can cause earthquakes. This has been observed in Oklahoma, Texas, Arkansas,
Ohio, and Colorado. More on this later in the course. So what is produced water? It
is water that comes to the surface with oil and gas following completion operations and
during production. It contains many chemical constituents, high salt contents, high dissolved
solids, high electrical conductivity, oil and grease, compounds of many hydrocarbons
and other organic materials, toxicity from various natural organic or inorganic compounds
or chemical additives. Naturally occurring radioactive material also are possible in
produced water. Wastewater composition: the quality, the duration vary considerably between
shale plays and even vary geographically within the same play. In the Barnett for instance,
there are large volumes of produced water and TDS and chloride increase significantly
over time. In the Fayetteville, there is relatively low concentrations of chloride, magnesium,
and total dissolved solids. In the Haynesville there is high calcium concentrations, magnesium,
chloride, total dissolved solids, and total suspended solids. In the Marcellus, you have
high sodium, calcium, magnesium, chloride, total dissolved solids, and high specific
conductance, and often high barium and strontium as well. The salinity of produced water increases
over time as the percentage of formation water increases in the water that comes to the surface.
Produced water volumes from waste streams from oil and gas production, worldwide estimates
are 77 billion barrels per year. In the U.S., 21 billion barrels per year. 57 million barrels
per day, or 2.4 billion gallons per day. Resources related to these statistics are in the resource
section for the course. The main constituent of produced water that causes impacts is salt.
Other constituents can create problems in certain settings.
So what are the potential adverse affects of produced water? There are different impacts
at different locations. Depends on the level of key chemical constituents, and the nature
of the water, and other substrate into which the produced water is released. Salt can contaminate
soils near wellheads, pipelines, and other facilities. It can kill plants. It damages
the soil, and thus impacts future plant growth. In terms of spills and leaks, large spills
can move into surface water bodies. Toxic compounds and oil and grease can damage aquatic
life. Leakage from tanks or impoundments can soak into the ground and enter groundwater.
In addition to harming soils, large releases of produced water may soak deep into the ground
and enter sources of drinking water. Discharges of salty produced water into freshwater bodies
will cause damage to aquatic animals and plants. High total dissolved solid waters can result
in golden algae outbreaks and fish kills. Discharges of oil and grease and toxic chemicals
can cause damage in both fresh and salt water. Recycling of flowback and produced wastewater
is becoming more common in many plays. With up to 10 million gallons of water used per
well and water supplies scarce in some areas, several companies are now recycling their
wastewaters. This strategy can save money on water purchases and reduce environmental
impacts from disposal. Most simply use sedimentation and filtration of wastewater, and then mix
with freshwater. Some are looking at more complete treatment and reuse options. For
example, Chesapeake Energy has something called the "AquaRenew" program, which involves not
only filtration and dilution, but an evaporative reduction and solidification system. More
information on this technique is in the resource section. The recycling challenge is really
one of water quality. With freshwater there's no problems with frac jobs, no problems with
chemistry, it's all well understood. With produced water and flowback water, minerals
in that water can cause scale. Minerals can therefore interfere with the frac gel and
impact effective proppant delivery. Water quality varies widely from one play and even
within a play. We need more studies to determine water quality limits for recycling. Need results
that are specific to portions of the basin where the activities are greatest. These results
will point to the type of water treatment needed. Environmental regulations are becoming
more and more stringent. For instance, air emission rules now apply to recycling pits,
and many states now require baseline monitoring.