Page 11 - 4925

may be 36 inches (91 centimetres) or more in diameter. It may be only tens of feet (or
metres) deep or it may be hundreds of feet (or metres) deep, depending on the surface
conditions.
The rathole crew lines the conductor hole in the cellar with conductor pipe.
Conductor pipe, or casing, keeps the hole from caving in. It also conducts drilling
mud back to the surface when regular drilling begins. The crew often secures the
conductor pipe in the hole with cement or concrete. With the conductor pipe, rathole,
and mousehole prepared, the drilling contractor can move in the rotary rig to drill the
rest of the hole.

Other Considerations

On drilling locations where the ground is soft, a rathole rig and crew may not
be needed. Instead, the contractor can usually move in the regular rig and its crews
right away. Once the drilling crew members get the regular rig ready, they rig up a
pile driver and drive the conductor casing into the ground, just as Colonel Drake did
at Oil Creek. Thus, people in the oil patch sometimes call conductor casing “drive
pipe.” After driving the casing, the rig crew begins drilling inside it.
If the ground is too hard for the conductor pipe to be driven, crew members can
use the regular rig to drill the conductor hole. What's more, they may also drill the
rathole and mousehole, using special equipment on the regular rig.

MOVING EQUIPMENT TO THE SITE
After the operator selects and prepares the drill site, the contractor moves the
rig to the site. Crew members move most land rigs by loading the rig components

onto trucks. The trucks then carry the components to the site where crew members
put the components back together and begin drilling. In remote areas, such as in
jungles and arctic regions, crew members may load rig components onto cargo
airplanes or helicopters. Boats often tow offshore rigs from one site to another. On
the other hand, some offshore rigs are self-propelled – that is, built-in units on the rig
provide the means to move it. Sometimes, especially where a rig has to be transported
a long distance, a special ship carries the rig.
Moving Land Rigs

Virtually all land drilling rigs are portable. If the rig is small enough to be built
on a truck, a person simply drives it from one place to another. Once at the site, the
rig stays on the truck and drilling commences. Rigs too big to fit onto one truck are
designed differently. Fabricators design medium and large rigs so that a contractor’s
crew can take it apart, load its components onto several trucks, helicopters, or cargo
planes, and move it to the drilling site. At the site, crew members put the rig together,
or rig up. After they drill the well, they dismantle the rig, or rig down.
As mentioned earlier, in deserts and other flat places, the contractor may skid
the rig. A rig suitable for skidding has enormous wheels attached to the substructure,
which, when engaged, allow the rig to be towed short distances without a crew's
having to dismantle it.

Moving and Setting Up Offshore Rigs

10