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Since the modern oil industry began in the 1850's, hundreds
of thousands of wells have been drilled. Gradually, the most easily
accessible onshore areas have been drilled up and most of the
easy-to-find fields have been found. The result is that it has now
become increasingly difficult to find new oil and gas fields in the
old familiar areas. This has lead to the search for new frontiers in
which to explore for oil and gas. These new frontiers include
offshore areas on the continental margins; areas like the Grand
Banks of Newfoundland and the Labrador coast. The drilling
industry is a major industry in its own right. This being the case,
the offshore drilling industry is a major industry within the drilling
industry. It is an extension of that industry into the unfamiliar and
often unfriendly setting of the open ocean.

A Hostile Environment
Offshore drilling came about gradually as explorers first
built jetties out from the land and later mounted entire rigs on
barges that could drill in quiet shallow waters (Figure 4.7). Today,
offshore drilling takes place on the open ocean and, in addition to
dealing with the usual difficulties associated with drilling onshore,
it must also contend with waves, currents, fog and deep water. In
some areas, as on the Grand Banks, there are the additional
complications of cold temperatures, icebergs, pack ice, storms that
bring winds of more than 160 kilometres per hour, and waves that
can be more than 30 metres high. In this cha pter, we will learn
how the drilling industry meets the challenges of drilling in such a
hostile environment.

The Technology of Offshore Drilling
Perhaps the most obvious difference between drilling
offshore and onshore is that an onshore rig sits directly on the
surface through which it is to drill. However an offshore rig can be
floating anywhere from a few tens of meters to a couple of
thousand metres above the sea bed, and must therefore be attached
to the sea floor by a large steel pipe called a marine riser (Figure
4.7). The riser then acts as a conduit for the drill string and the
drilling mud. In essence, it is an extension of the casing that allows

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