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A B
1 pontoon a power unit with propellers that the builder mounts
fore and aft on, the drill ship's hull below the
waterline.
2 towboat b portable hole factories
3 barge c a small, powerful boat for towing or pushing
ships, barges, etc.
4 caisson d short for semisubmersibles
5 land rigs e a vessel, usually flat-bottomed and with or without
its own power, used for transporting freight, esp
on canals
6 thruster f a long, relatively narrow, and hollow steel float
with a rectangular or round cross section
7 drilling g machine which creates holes in the ground
rig
8 rotary h any vertical spar for supporting sails, rigging,
drilling flags, etc., above the deck of a vessel or any
components of such a composite spar
9 semi i in engineering, a type of foundation most
commonly used underwater for a bridge, but
sometimes used in building construction. It is a
large hollow structure that is sunk down through
the earth by workers excavating from inside it.
10 mast J the act or process of drilling a borehole by means
of a rotary-drill machine, such as in drilling an oil
well.

Pre-reading and while-reading tasks
3 Scan the text and answer the following questions.

 What are the two main categories of rigs?

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