Page 14 - Environmental Control in Petroleum Engineering

Introduction to Environmental Control in the Petroleum Industry 3

surfactants, friction reducers, and scale dissolvers that were initially
injected into the formation (Hudgins, 1992).
Drilling wastes include formation cuttings and drilling fluids. Water-
based drilling fluids may contain viscosity control agents (e.g., clays),
density control agents, (e.g., barium sulfate, or barite), deflocculants,
(e.g., chrome-lignosulfonate or lignite), caustic (sodium hydroxide),
corrosion inhibitors, biocides, lubricants, lost circulation materials, and
formation compatibility agents. Oil-based drilling fluids also contain
a base hydrocarbon and chemicals to maintain its water-in-oil emul-
sion. The most commonly used base hydrocarbon is diesel, followed
by less toxic mineral and synthetic oils. Drilling fluids typically
contain heavy metals like barium, chromium, cadmium, mercury, and
lead. These metals can enter the system from materials added to the
fluid or from naturally occurring minerals in the formations being
drilled through. These metals, however, are not typically bioavailable,
An extensive discussion of the environmental impacts of drilling
wastes has been presented by Bleier et al. (1993).
Associated wastes are those other than produced water and drilling
wastes. Associated wastes include the sludges and solids that collect
in surface equipment and tank bottoms, pit wastes, water softener
wastes, scrubber wastes, stimulation wastes from fracturing and acidiz-
ing, wastes from dehydration and sweetening of natural gas, transporta-
tion wastes, and contaminated soil from accidental spills and releases.
Another waste stream associated with the petroleum industry is air
emissions. These emissions arise primarily from the operation of
internal combustion engines. These engines are used to power drill-
ing rigs, pumps, compressors, and other oilfield equipment. Other
emissions arise from the operations of boilers, steam generators,
natural gas dehydrators, and separators. Fugitive emissions from
leaking valves and fittings can also release unacceptable quantities of
volatile pollutants.
One common, but incorrect, perception of the petroleum exploration
and production industry is that it is responsible for large-scale hydro-
carbon contamination of the sea. The total amount of hydrocarbons
that enter the sea is estimated to be 3.2 million metric tons per year,
The individual contributions from the different sources of hydrocarbons
is given in Table 1-1 (National Research Council, 1985). The primary
source of hydrocarbon releases into the ocean is from transportation