Page 128 - Drilling Technology in Nontechnical Language

Chapter 5 – RIG SELECTION AND RIG EQUIPMENT 119

Fig. 5–8. Drilling barge with derrick stowed for moving
Photo courtesy of Schlumberger.

Jackup

A jackup rig has a floating hull, usually triangular shaped but sometimes

square. At each corner is a large steel leg. The rig is towed to the wellsite

with tugs (fig. 5–9). Once in position, the legs are moved down until they
contact the seabed. By jacking the legs further down, the hull raises up out
of the water. This forms a temporary platform (fig. 5–10).

The derrick is located on a large cantilever beam that moves out from
the hull, placing the derrick over the side of the hull. This allows a jackup
rig to move next to a platform and position the derrick above a well within
the platform structure. Exploration wells are drilled by spudding directly
into the seabed. A platform is not installed until a decision is made to
develop any hydrocarbon discoveries.
A jackup rig might cost $50,000 to $250,000 a day.

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