Page 167 - Introduction to Petroleum Engineering

154 DRILLING

Conductor pipe
Cement
(40–120ft)

Cement Deepest fresh water
Surface casing
(400–2000ft)

Cement
Intermediate casing

Cement
Production casing

Plug

FIGuRe 8.10 A wellbore diagram for a vertical well.
the smallest diameter. Production or injection tubing must be able to fit inside the
production casing.
Casing is set with cement to attach the casing to the formation and to prevent
fluid movement behind the casing. Cement leaks or fractures in the cement are pos-
sible. The cement must be tested to ensure it is functioning properly before the well
is completed. During the completion stage, perforations (holes) must be punched
through casing at the target formation to allow fluids to flow into the production
tubing.
Casing is tested by the manufacturer to determine its ability to withstand the
forces that will act on it. Tension forces pull at the top of the casing, collapse forces
push against the outside of the casing, and burst forces from fluids in the casing
push against the inside. The casing and casing joints must not split or separate
during high‐pressure fluid injection because the breach would lead to contamination
of formations.

example 8.5 Volume in the Annulus
Calculate the volume in the annulus between a section of pipe with outer diam-
eter OD = 45 in., length L = 1500 ft, and the casing with inner diameter = 7 in.
.
3
Express your answer in ft .