Page 62 - Drilling Technology in Nontechnical Language

Chapter 3 – DRILLING A LAND EXPLORATION WELL 53

Location preparation and conductor driving

On a land location, a preparation crew will build a location in advance
of the rig arriving. The site must be cleared of obstructions. (In some areas,
like the Western Desert in Egypt, unexploded World War II ordnance and
mines must be cleared away!) The boundary is marked and access roads
are created. A square hole with 10 ft (3 m) sides will be dug about 10 ft
(3 m) into the ground and lined with reinforced concrete. Around this pit
(called the cellar) will be a concrete or wooden pad for the rig to sit on

(fig. 3–9).
Why is it necessary to dig a hole under the rig location? On top of the
casing is placed a large piece of equipment called a blowout preventer
(BOP). Without a cellar for the BOP, the rig substructure would have to

be much higher to accommodate the BOP. When the well is finished, the
wellhead will be partially below ground level, as can be seen in this photo
of a completed well near Lake Albert in Uganda.

Fig. 3–9. Wellhead inside cellar after rig departed

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