Page 126 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:56 PM Page 102

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1.4.24 Well Design

Table 1-4 Casing Design Criteria—Production Casing

Drilling Criteria Production Criteria
Burst 1. Casing test pressure at top of casing. 1. Assume leak at top of production
2. Casing test pressure plus mud tubing; calculate burst at the pro-
hydrostatic to shoe less external duction packer with completion
pressure at shoe exerted by the fluid in the hole minus pressure due
mud used to run casing. to the mud used when casing run.
2. Calculate loadings imposed by
Safety factor 1.1.
fracturing, injection, artificial lift,
or other production processes.
Safety factor 1.1.
Collapse 1. Calculate collapse pressure at 1. Assume losses when perforated.
shoe when cement is displaced. Expected external pressure at the
Use planned fluid heights and loss zone; planned mud in use
densities inside and out. drops to height supported by
2. If there are any plastic squeezing thief zone. Maximum collapse
formations, resist 1 psi/ft outside may be at the top of the mud col-
at the relevant depth(s). umn or at the shoe. External
pressure exerted by mud in hole
Safety factor 1.1.
when the casing was run.
2. Expected drawdown pressure
during production internally and
reservoir pore pressure externally,
up to production packer depth.
Safety factor 1.1.

Tension 1. Weight of casing in air plus over-
pull allowance of 100,000 lbs.

Safety factor 1.1.
2. Axial load at the top due to buoy-
ant weight after displacing cement
plus overpull, if extra tension
applied before setting hanger.
3. Axial loads due to buoyant weight
plus test pressure.
Safety factor 1.75 if deviated or
1.5 if vertical.

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