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10) The guide shoe is made up on the bottom of the first joint of casing to
go into the hole.

7 Fill in the gaps.

a) centralizers d) casing g) fluid
b) springs e) diameter h) scratchers
c) tongs f) walls i) contamination

Surface casing is usually large in diameter — perhaps 20 inches (508
millimetres) or more. Casing is strong steel pipe. Running casing into the hole is
very similar to running drill pipe, except that the casing ________(1) is usually
much larger and thus requires special elevators, slips, and __________ (2) to fit it.
Also, the casing crew sometimes installs centralizers and scratchers on the
outside of the casing before they lower it into the hole. The crew attaches
_________(3) around the outside of the casing joints and, because the centralizers
have bowed ________ (4), they keep the casing centered in the hole after the crew
lowers it in. Ideally, casing should not come into contact with the ________ (5)
of the hole. If it does, cement may not be able to flow into the area between the wall

of the hole and the outside of the ___________(6). Consequently, a void in the
cement may occur, which could allow fluids to flow outside the casing. __________
(7) flow behind the casing is not desirable because _________(8) can occur.
For example, salt water from one formation could flow into another formation
containing fresh water and pollute it.
__________ (9) also come into play when the casing is cemented. The idea
is that if the driller moves the casing up and down or rotates it (depending on
scratcher design), the scratchers remove the wall cake formed by the drilling mud
and the cement will thus be able to bond better to the hole.

8 Scan the text and correct spelling and grammar mistakes.

Some wells, especially deep ones usually enconters formations that is easily
controled by using a suitable drilling fluid. Later however, as the borehole drills into a
deeper oil and gas formation, the drilling fluid used to control the uper zones is not
suitable for the productive formation. The drilling fluid could damages the producing
zone so badly that the operator could withdraw the hydrocarbons from the zone. To
avoid such a pitfall the operator plans the well to be drilled to an intermediate depth
above the pay zone (the productive formation). The drilling crew uses drilling fluid
formuleited to controll the formations to the intermediate depth. Than, they stop
drilling, come out of the hole (pull the bit and drill stem from the well), and run and cement
casing. The casing and cement seal off the intermadiate part of the hole so that the
formations neither affect nor are affected by subsequent drilling operations.

Translation section

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