Page 119 - Environmental Control in Petroleum Engineering

106 Environmental Control in Petroleum Engineering

membranes, erosion of teeth, and aggravation of respiratory conditions
such as asthma. Little aquatic toxicity data are available for acids.
Pesticides vary in toxicity. Prolonged or repeated exposure may
cause various systemic effects, including damage to the nervous and
muscular systems. Some pesticides are carcinogenic. Exposure to some
pesticides can be fatal.
Glycol can be fatal if ingested in quantities of about 100 ml. Lower
doses may be irritating to the mouth, throat, and stomach and can
cause disorders of or damage to the digestive tract. Repeated exposure
can cause kidney, brain, or liver damage. Blood chemistry and blood
cells can also be affected.
Bioassays have been conducted for a variety of production chemi-
cals using different freshwater and saltwater organisms. Table 3-10
summarizes the typical concentrations of some chemicals used for
different types of applications. This information includes typical ranges
of chemical concentrations when used, concentrations when discharged
for disposal, and the LC 50 values (Hudgins, 1992). From this table, it
can be seen that the toxicities of production chemicals vary widely.
More detailed toxicity data are summarized for scale inhibitors in
Table 3-11, for biocides in Tables 3-12a and 3-12b, reverse emulsion
breakers in Table 3-13, emulsion breakers in Table 3-14, corrosion
inhibitors in Table 3-15, paraffin inhibitors in Table 3-16, surfactants
in Tables 3-17a through 3-17e, coagulants in Table 3-18, foam breakers
in Table 3-19, and gas treatment chemicals in Table 3-20. Because of
varying test protocols, a direct comparison of the toxicities of these
chemicals may not be valid.

3.6 DRILLING FLUIDS

Two methods have been used to evaluate the environmental impact
of drilling fluids. First are bioassays conducted using various organ-
isms placed in different concentrations of drilling fluids. Second are
direct measurements of environmental impact following disposal of
drilling fluids, either in reserves pits or by offshore dumping.

3.6.1 Bioassays of Drilling Fluids

Bioassays using mysid shrimp (Mysidopsis bahia) are currently
required for the offshore discharge of drilling fluids in the United