Page 65 - Environmental Control in Petroleum Engineering

Drilling and Production Operations 83

acid resins, using carboxylic acid. Strong acid resins can be regener-
ated simply by flushing with a concentrated solution of sodium chlor-
ide. Weak acid resins, however, must be regenerated by flushing with
a strong acid-like hydrochloric or sulfuric and then neutralizing it with
sodium hydroxide.
During oil production, sand and shale sediments are often produced
with the oil. These sediments are separated out in the surface equip-
ment. They normally collect in tank bottoms and must be periodically
removed. These solids are normally mixed with oil, forming a sludge.
Sediments can also be contaminated with oil and other materials from
spills and leaks from equipment.
The hydrocarbon content of oil-contaminated sediments can exceed
4% by weight (Deuel, 1990). These sediments may also contain heavy
metals or hydrogen sulfide (Brommelsiek and Wiggin, 1990). Total
heavy metal concentrations in produced solids are generally low, as
indicated in Table 2-8 (Cornwell, 1993). It is not known whether the
differences in heavy metal concentrations for native soils in Alaska,
shown in Table 2-2, and for produced solids, shown in Table 2-8, are
from production activities or just natural variations in geology.
To remove the suspended solids that are not removed by settling,
produced fluids are often passed through filters. The filter media must
be frequently replaced or backwashed. The filled filters or filter
backwash must be disposed.
The operations of much of the oilfield equipment, including stuffing
boxes, compressors, and pumps, requires lubrication oil. As this oil
is used, it changes its composition, making it potentially unsuitable
for future use. The used lube oil must be replaced with fresh oil, and
the used oil must be disposed of.
In areas where lease crude is burned, e.g., where steam is injected
to recover oil, the combustion gases may need to be scrubbed to
remove pollutants like sulfur dioxide. One way to remove sulfur
dioxide from combustion gases is to bubble it through aqueous solu-
tions containing caustic chemicals like sodium hydroxide or sodium
carbonate. Sulfur dioxide dissolves into water, forming sulfuric acid,
which is neutralized by the caustic. Another form of scrubber uses
various amines. Typical wastewaters can have very high levels of
dissolved solids, as indicated in Table 2-9 (Sarathi, 1991).
In cold climates, like Alaska's North Slope, methanol is used for
freeze protection of equipment. It is used to protect pipelines, shut-in