Page 694 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

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VetBooks.ir Chapter 50

Petroleum

Robert W. Coppock and Ralph G. Christian

INTRODUCTION nonaqueous drilling fluids (invert drilling fluids) have
fresh or brine water emulsified in a hydrocarbon phase.
Intoxication of birds and animals with petroleum and che-
Hydrocarbons used include diesel oil, distillates. and
micals used by the petroleum industry does occur. This
hydrotreated mineral oil (low in polycyclics). Drilling
chapter essentially focuses on terrestrial animals and espe-
mud can also contain metals and metalloids and have a
cially livestock. Land used for agriculture and lands used
high alkaline pH. Biocides that can be added to drilling
by wildlife are used for oil and gas production. Land used
muds include glutaraldehyde and quaternary ammonium
by the upstream oil and gas industry include well sites,
salts. If naturally occurring radioactive materials
tank battery sites, sweet and sour gas plants, compressor
(NORMs) are encountered in the formations, radioactive
stations, and pipelines. Crude petroleum and chemicals
metals and gas can contaminate drilling fluids and drill
used in the oilfields can be spilled, and livestock and
cuttings.
other animals can be poisoned by dermal, inhalation, and
oral routes of exposure. Air emissions from oil and gas
facilities also occur. The production of sour gas, natural Fracking
gas containing hydrogen sulfide (H 2 S), and the removal
of sulfur (sour gas processing plants) present toxicology Oil and gas bearing formations are porous with oil, gas
issues when substances are released. and water filling the pores. Flow to the borehole is stimu-
lated by fracking. Hydraulic fracturing is performed by
pumping water containing chemicals and proppants down
OIL AND GAS WELL DRILLING the bore hole under high pressure and the formation is
AND COMPLETING fractured. Propping agents are used to reduce the closure
of the fractures. The United States Environmental
Drilling Protection Agency (USEPA, 2016) estimates that frack-
ing, a typical horizontal well for shale gas uses 15 million
Oil and gas wells are vertically and horizontally drilled
liters of water. Three are over 1000 different chemicals
into oil, gas and bitumen producing formations. During
used in fracking operations that have been listed by the
drilling operations, drilling fluids are used to cool and
USEPA. Toxicology issues associated with fracking che-
lubricate the drill bit, support the walls of the bore hole,
micals are known (Carpenter, 2016). Earthquakes are
control subsurface pressure in the drill stem, move the
associated with fracking and deep well disposal of
cuttings to surface and expose the borehole to various
unwanted oilfield liquids.
chemicals that assist in the drilling operation. Drilling
fluids generally are complex mixtures and the composi-
tion varies with the different geologic zones and target SOURCES OF TOXIC SUBSTANCES
formation. Water-based drilling fluid and the nonaqueous
drilling fluids are the two basic types of drilling fluids Toxicological issues are associated with chemicals used
used (Coppock and Christian, 2012). Water-based drilling in drilling, fracking and the crude petroleum. Crude
fluids generally consist of bentonite clay and barium sul- natural gas as it comes from the wellhead may have
fate for increasing density and other chemicals are added volatile liquids (condensate), produced water, NORMs,
to give desired properties such as lubrication, reduce and may contain H 2 S and other forms of sulfur. Sour
foaming. and bore wall stabilization. Brine or fresh water petroleum can have the H 2 S removed and disposed of by
can be used in water-based drilling fluids. The burning in a flare stack.

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