Page 64 - Environmental Control in Petroleum Engineering

52 Environmental Control in Petroleum Engineering

removed by contact with sulfinol, iron sponges (finely divided iron
oxide in wood shaving carriers), and caustic solutions. Amines and
sulfinol can be restored for reuse by heat regeneration, but iron
sponges and caustic solutions are spent as the iron is converted to iron
sulfide and other sulfur compounds. Other wastes generated when
removing sweetening natural gas include spent amine, used filter
media, and flared acid gas wastes. Sodium hydroxide is often added
to the amine to prevent corrosion of equipment.
During sweetening, amine compounds are attacked by carbon
dioxide and can break down. The solutions are filtered to remove
the degradation products from the usable amine. The degradation
products form toxic amine sludges that require treatment and disposal
(Boyle, 1990).
During the production of natural gas, hydrates can form from
the gas and water vapor. Hydrates are a slushy, ice-like substance
that can plug the production tubing and equipment. Various chemi–
cals, primarily methanol and ethylene glycol, are sometimes added to
gas-producing wells to lower the freeze point of hydrates to inhibit
their formation.

2.2.6 Other Operations

A variety of other operations associated with the production of oil
and gas generate wastes that have the potential to impact the environ-
ment. These wastes include wastewater from cooling towers, water
softening wastes, contaminated sediments, scrubber wastes, used filter
media, various lubrication oils, and site construction wastes.
Cooling towers are used for a variety of processes during oil and
gas production. The cooling water used in these towers often contains
chrome-based corrosion inhibitors and pentachlorophenol biocides.
In many areas, produced water is reinjected into the reservoir to
assist hydrocarbon recovery. Unfortunately, the level of dissolved
solids, particularly hardness ions (calcium and magnesium), is often
too high to be used because they readily precipitate and can plug the
formation. Thus, before produced water can be reinjected, it must be
softened to exchange the hardness ions with softer ions, e.g., sodium.
The most common way to soften produced water is through ion
exchange. There are two major ion exchange resins (substrates) that
are commonly used: strong acid resins, using sulfonic acid, and weak