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operator tells a computer exactly where it should keep the rig positioned, the computer, using
information transmitted by the sensors, automatically controls the thrusters. The thrusters offset
wind, wave, and current forces that would move the rig away from the desired position.
Whether on land or offshore, and whether large, medium, or small, all rigs require personnel
to operate them. The people who drill wells usually work for a company whose business involves
drilling, either directly or indirectly. So, let's look next at companies involved in drilling and the
personnel who do the work.

4 Find synonyms in the text for the following words.
a swamp mild
to see a tool
a sobility primary
a team a stream
an appearance

5 Find antonyms in the text for the following words.
deep sea surface
an offshore rig tiny
light duty round
disassembled

6 Say whether the following statements are true or false.
1 Land rigs look differently, although they consist of similar details.
2 Classified by weight, land rigs are light duty, medium duty, heavy duty, and very heavy duty.
3 A rig can drill holes shallower than its maximum rated depth.
4 A rig cannot drill a hole at one site and be moved to another site to drill another hole.
5 Land rigs are sometimes defined as "portable hole factories."
6 MODU is an abbreviation for mobile offshore drilling unit.
7 MODUs are not portable; they drill a well only at one offshore site.
8 A submersible MODU floats on the water's surface when moved from one drilling site to
another.
9 The first MODU was not submersible.
10 A bottle-type rig has four tall steel cylinders (bottles) at each corner of the structure.

7 Fill in the gaps.
d) steel g) bottom
a) tow
b) deck e) swamps h) barge

c) waters f) inland i) drilling

A fourth submersible is an _____ (1) barge rig. It has a ____ (2) hull-a flat-bottomed, flat-
sided, rectangular ____ (3) box. The rig builder places a ____ (4) rig and other equipment on the
barge ____ (5). Inland barge rigs normally drill in marshes, bays, ____ (6), or other shallow inland
waters. By definition, barges are not self-propelled; they have no built-in power to move them from
one site to another. Therefore, boats ____ (7) them to the drilling location. When being moved, the
barge floats on the water's surface; then, when positioned at the drilling site, the barge is flooded so
that it rests on the ____(8) ooze. Since they often drill in swampy shallow ____(9) , drilling people
often call inland barges "swamp barges."

8 Scan the text and correct spelling and grammar mistakes.

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