Page 169 - Environmental Control in Petroleum Engineering

156 Environmental Control in Petroleum Engineering

and reduce the amount of water produced with the oil. The water
produced from the water zone must also be disposed of (reinjection),
but it should contain essentially no oil (Wojtanowicz, 1991). Polymers,
gels, or cement can be used to plug water production zones if they
are separate from oil producing zones.
Since many drilling and production operations are conducted by
contractors, they should be carefully reviewed and selected. Contrac-
tors should have a good environmental track record. When conducting
the bidding process for selecting equipment to be used, a visual
inspection of the equipment is advised to determine its general condi-
tion, particularly drilling rigs. Contractors should have properly func-
tioning equipment, with drip pans and splash guards.
Any contracts should specify activities that are prohibited while the
contractor is on site. Such activities can include unnecessary rig
washing, painting of the contractor's equipment, or changing lube oil
during downtime. This will minimize the probability that excess water,
painting wastes, or used oil gets dumped into reserves pits. An envi-
ronmental activity review should be conducted with all contractor
crews just prior to the start of activities. This review should include
waste handling and minimization procedures.

Materials Substitution

Another important method for minimizing the amount of potentially
toxic wastes generated is to use less toxic materials for the various
operational processes. A number of studies of material substitutions
have been presented (Derkics and Souders, 1993; Freidheim and
Shinnie, 1991; Peresich et al, 1991; Savage, 1993; Thurber, 1992;
Wojtanowicz, 1991).
Drilling muds represent a significant opportunity for toxic waste
reduction by materials substitution. When substituting materials,
however, it is important to ensure that the substituted materials yield
a drilling mud that still has acceptable properties.
One of the best opportunities for materials substitution is in wells
where oil-based muds are needed. Two alternatives to the use of diesel
oil as a base fluid are being studied: using a less toxic oil-based mud
and using a water-based mud with an improved additives package.
These alternative mud systems, however, are considerably more expen-
sive than traditional muds. Unfortunately, the use and discharge of