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Figure 1.4 – First true “off-shore” oil rig

In the early 1930s the Texas Co., later Texaco (now Chevron), proposed

augmenting fixed, wooden-piled drilling platforms with mobile steel barges that

could hold some of the machinery necessary for exploratory drilling. In fact,

Texaco’s drilling specialists went a bit farther by claiming they could explore the

shallow coastal areas more quickly with equipment that could move, relatively

intact, between well sites. To do so, they could transport a rig-equipped barge to

the well site, flood it to the shallow bottom and stabilize it with a minimum of

pilings. A superstructure erected over the top deck of the barge would raise the

drilling equipment 10 feet or more, with the derrick and drill string centered over a

slot notched into one end. Another barge moored alongside could hold the prime

mover engines, fuel, fresh water, racked tubulars, bulk and sacked drilling fluid

components. After drilling, crews could re-float and move both barges to the next

well location with relative ease. Texaco’s success spurred other operators to build

their own versions of the barge-mounted rig, which came to be regarded as the

industry’s very first mobile drilling unit.

In 1933 the process of locating oil (exploratory drilling) was revolutionized

when a barge-mounted rig was designed to be moved from one location to the next

with relative ease. This was the first mobile drilling unit (fig. 1.5).

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