Geology Reference
In-Depth Information
In Yukon Territory, Canada, similar exploration activity began in the mid-1960s. The
boreal forest was removed for seismic surveys, haul roads, and for exploratory drilling
sites. Similar disturbance resulted. A number of case studies of human-induced thermokarst
from Northern Canada are described in Chapter 8.
By the mid-1970s, environmental and regulatory measures had been put in place in
both Alaska and Northern Canada to minimize this sort of environmental damage. For
example, in Canada, the Federal Government passed the Territorial Arctic Land Use Act
and Regulations in 1971. These regulations largely restricted vehicle movement and drill-
ing activity to the winter months, and imposed numerous other drilling procedures and
management practices related to safety and environmental concerns. In both Alaska and
Canada, the use of gravel pads and other environmentally-friendly engineering practices
has now become standard for all operations, building, roads, and airstrips (Allmand, 1976;
Crory, 1991). Today, procedures such as these are accepted standard international practice
in the high latitudes (IUCN, 1993).
A similar history of exploration characterized northern Russia, where substantial oil
and gas reserves occur in the Yamal and Gydan regions of western Siberia. Exploratory
seismic and drilling activity commenced in the 1970s. There was little environmental
concern until the early 1990s, when awareness of North American operating techniques
and procedures became more widely available (Seligman, 2000).
In spite of modern environmental practice, terrain and environmental damage contin-
ues to occur in northern Siberia, where regulatory procedures are frequently avoided or
minimized. In Arctic North America, the absence of easily-accessible gravel aggregate
for pad construction in the Arctic islands remains a problem. A different set of problems
relates to the increasing number of exploratory wells that are drilled to greater depths as
deeper geological structures are tested. This increases the disposal problem of the much
larger volume of waste-drilling fl uids that is generated (see below).
14.7.2. Waste-Drilling-Fluid Disposal Problems
Some of the most diffi cult environmental problems associated with land-based drilling
now relate to the disposal of waste-drilling fl uids (French, 1980; Hardy BBT Ltd, 1988).
These usually consist of kaolinite slurry. Their function is to provide lubrication to the
drilling and, by varying the density of the mud, to counter any formation pressures
encountered at depth, thereby preventing “blow-outs.” To achieve these objectives, the
composition of the mud system requires continual modifi cation during drilling. Standard
regulatory procedure requires that waste mud is contained within below-ground sumps
that are subsequently buried upon abandonment of the hole. Problems arise because drill-
ing muds contain chlorides and other salts, do not necessarily freeze within the sump fol-
lowing burial, and are often highly toxic because they contain weighting agents such as
barites. In some instances, the sump is too small to contain the volume of waste mud that
is generated and the muds spill onto adjacent terrain, causing damage to vegetation and
pollution to adjacent water bodies. Efforts are continually being made to reduce the toxic
components of the mud systems used, reduce the volumes of waste mud produced by
recycling, and to experiment with other methods of containment or disposal of waste-
drilling mud. For example, the author supervised a drilling operation in the Canadian
High Arctic, sponsored jointly by the Federal Government of Canada and the Arctic
Petroleum Operators Association, in which drilling mud, claimed to be non-toxic by the
company concerned, was placed directly upon the tundra. The short-term effects were
monitored (French, 1984, 1985) and the longer-term effects of this experimental procedure
have yet to be determined. Other methods that are being tested include bioremediation
(Peck, 1998; Reynolds et al., 1998).
