Page 131 - Environmental Control in Petroleum Engineering

118 Environmental Control in Petroleum Engineering

number of studies in this area. Sublethal effects of ferrochrome
lignosulfonate were observed on corals at levels of 0.1 ml/1 of used
drilling fluid in sea water. Lobsters were observed to have an inhibited
response to food odors at drilling fluid concentrations as low as 0.01
mg/1, and lethality (96-hr LD 50) was observed for lobster larvae at
concentrations between 0.074 and 0.5 ml/1 for various drilling fluids.
Behavioral changes, including delays in feeding, molting, and shelter
construction, were observed at levels as low as 0.007 mg/1. Drilling
fluid concentrations between 1 and 10 mg/1 adversely effected fertiliza-
tion and subsequent embryo development of estuarine minnows; but
the concentration where an effect was observed varied significantly
with the particular drilling fluid tested. Sea urchins showed reduced
fertilization rates when exposed to 223 mg/1 barium sulfate. Behavioral
characteristics, such as foraging by fish, gaping by scallops, and
burrowing by shrimp, however, were unaffected by what was con-
sidered a realistic deposition rate on the sea floor within a 50-meter
radius of a drilling platform.
Some accumulation of barium and chromium from the solids portion
of used lignosulfonate drilling fluids has been observed in some
benthic (sea bottom dwelling) species following exposure (American
Petroleum Institute, 1985d). Some sublethal impacts were observed that
included alterations in biochemical composition, depletion of micro-
nutrients, and altered respiration and excretion rates. Once contaminated
animals were placed in a clean environment, however, the concentrations
in the animals was reduced to nominal levels. In other species, how-
ever, there were no observed bioaccumulation or effects.
The concentrations of drilling fluids that had no observable effect
on the development of embryos of estuarine minnows (Fundulus
heteroclitus), sand dollars (Echinarachnius parma) and sea urchins
(Strongylocentrotus purpuratus, Lytechinus pictus, and L. variegatus)
were measured by the U.S. Environmental Protection Agency (1983),
Fish embryos were placed in the liquid phase of drilling fluids one
minute after fertilization and maintained for the duration of their
development. Sand dollar and sea urchin embryos were placed in the
test medium 10-15 minutes after fertilization and kept there for 96
hours. The "safe" concentration—the concentration that is 10% of the
lowest concentration that had an observable effect—was measured and
is reported in Table 3-23. These safe concentrations were typically 1-
100 microliters per liter.