Page 695 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

660 SECTION | IX Gases, Solvents and Other Industrial Toxicants

VetBooks.ir Air Emissions disposed by returning it to the formation or injection
underground using disposal wells. Tremors are being
Air emissions from the upstream oil and gas industry are
associated with disposal wells. Produced water can
from burning unwanted products, production testing of
damage soil. Coalbed methane can be a large source of
gas wells, controlled and uncontrolled releases of volatile
produced water (Moore, 2012).
substances, and emissions from internal combustion
engines and emissions from tank heaters. After gaswell
completion, production testing is done to estimate produc- Well Rework
tivity and remove corrosive fracking chemicals from the
Reworking a well can include dewaxing, descaling,
formation. During production testing the total production
replacement of downhole equipment, replacing location
from the well is generally burned in a flare or incinerator.
of downhole equipment and several other procedures.
Burned emissions contain various levels of products of
Reworking can include stimulation of the formation and
combustion, products of incomplete combustion (PICs)
fracking to increase flow to the well bore. Surfactants,
and may be a source of halogenated dibenzodioxins
acids, dewaxing solvents, biofilm inhibitors and numerous
(Martinez-Guijarro et al., 2017). Polyaromatic hydrocar-
other chemicals can be used during rework operations.
bons (PAHs) and particulates can also be formed. Sulfur
Some of these compounds are intrinsically toxic, and can
dioxide, reduced sulfur compounds (including carbon
enhance the toxicity of other substances in a mixture.
disulfide and carbonyl sulfide) PAHs and other com-
Chelating and descaling agents may increase the bioavail-
pounds are produced by burning sour well emissions
ability of chemicals that otherwise would be considered
by flaring (Strosher, 1996). Tank heaters are used in the
to have a low order of toxicity. Spillage of rework chemi-
production of heavy oil and bitumen. If the tanks are
cals can occur and livestock poisonings have been
vented to atmosphere, heating the petroleum in the tank
reported (Monlux et al., 1971). Down-hole equipment can
can drive off a variety of hydrocarbons and water into the
be laid out at unsecured sites and cattle will investigate
atmosphere.
and lick the petroleum and other substances from the
equipment.
Flowback and Produced Water
Sumps
Flowback fluid is the liquid that flows back during staged
drilling, fracking and completion operations. During the Earthen pits have been used for the disposal of upstream
flowback period, the fluids coming from the well are dril- oilfield waste by burning (flare pits). Many jurisdictions
ling and fracking liquids. Water from the formation have limited the use of sumps and do not allow sump con-
brought to the surface during production of crude oil and tents to be buried. Old buried sumps can be a hidden
natural gas is called produced water. It is estimated that source of surface and subsurface chemical contamination.
unconventional wells produce 1.7 14.3 million liters of Sumps also may be remote to oil and gas well sites
brine water/well over the first 5 10 years of production. (Heitman, 1986). Although environmental practices have
Produced water is the largest waste stream generated in changed, old sumps can be a cause of surface and subsur-
the oil and gas industry and contains inorganic and face issues because they may contain a variety of con-
organic compounds (Ahmaduna et al., 2009). Produced taminants inclusive of salts, acids, and heavy metals and
water is separated from crude petroleum and natural gas metalloids (Heitman, 1986; Gleason and Tangen, 2014).
and becomes a waste product and can be high in total dis- Extrusions from a drilling sump containing petroleum
solved solids. Ingestion of production water can induce hydrocarbons have been linked with maladies in cattle
poisoning. Produced water can contain heavy metals and and sheep (Mostrom et al., 1993; Adler et al., 1992).
metalloids. Both flowback water and produced water can Extrusions from an invert sump contaminated a pasture.
contain NORMs, predominantly radium ( 228 & 236 Ra) and Cows grazing this pasture had calves that were stunted.
with barium can form radioactive pipe scale. Production Necropsy findings were: abnormal epiphyseal plates in
water generally has a unique ratio of ions and this ratio is the long bones and myeloid-like bodies in the proximal
generally distinctly different from the ratio of ions found tubular cells of the kidney. The activities of hepatic poly-
in ground water. Leaks of produced water can contami- substrate mixed function oxidase enzymes were also ele-
nate ground and surface water and soil (Carpenter, 2016). vated. Sheep have been poisoned following extensive
Depending on the redox potential, produced water can be rains that caused extrusion of natural gas condensate from
very corrosive and corrosion of oilfield equipment can be the soil. Sumps and old oilfield equipment can contain
a cause of leaks. Produced water disposal is variable nonpesticide organophosphorus esters used to prevent
depending on its chemical and NORMs composition. foaming of lubricating oils. Reviews of the neurotoxicity
Produced water that is an environmental hazard is often and pathology of the tri-alkyl/aryl phosphate esters have