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replacement of broken or damaged guidelines by diver or remote operation.

In actual operation, the TGB is set on the spider beams of the drilling vessel

for attaching the guidelines (usually %- or %-in. diameter wire rope). Weight

material (barite or cement) is added to the TGB to increase its weight to between

25,000 and 30,000 lb. A running tool is installed in the four J-slot preparations in

the TGB with left-hand rotation. The temporary guide base is then run to the ocean

floor on drill pipe. The running tool is released by slacking off the weight of the

drill pipe and turning the tool to the right Vs of a turn. (In the past, each guideline

was tensioned with a fixed weight over a sheave. Today, hydraulic or pneumatic

guideline tensioners, each with 16,000-lb capacity, keep the guidelines in tension.)

The next operation is to drill the 36-in. hole for the 30-in. conductor casing.

The 36-in. drilling assembly is made up and lowered through the rotary table and

down through the moonpool or spider deck area.
The next piece of equipment to be prepared is the four-post permanent guide

structure. The PGS is set on the spider beams and the four guidelines are inserted
and trapped in the guide post slots. The 30-in. casing is then run through the center

hole of the PGS.
The first joint of 30-in. conductor (called the shoe joint) has a nonreturn or

float valve included in the guide shoe that is usually welded to the bottom of the

shoe joint. Soft line rope is used often to guide the 30-in. casing shoe into the

predrilled hole. The individual 30-in. conductor joints are usually 40 to 50 ft long.

The joints of conductor pipe are connected by threadless mechanical connectors.

Each 30-in. casing joint may have pad eyes attached to support the

conductor joint in the rotary table during running and connection. After the next

conductor joint is stabbed and made up to the joint in the rotary table, the pad eyes

are cut off and the casing is lowered to the next set of pad eyes. Thirty-in. casing

elevators are sometimes used in lieu of the pad eyes as a means of handling the 30-

in. conductor.

After the casing string is made up to the 30-in. housing joint, the conductor
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