Page 76 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:56 PM Page 52

[ ] Well Design
1.4.5

The next step is to note which formations may give problems relat-
ing to wellbore stability, losses, mobile formations, differential stick-
ing, etc. Examination of these may flag where separation of problem
areas is needed or where a hazard would be created by having two sets
of problems in the same section (e.g., a weak “loss” zone in the same
section as a hydrocarbon bearing zone). It might also show where deal-
ing with the problems would cause serious incompatibility in the
required solutions (e.g., different/conflicting mud properties required).
Offset well data as presented in “Hole section summaries” in Section
1.1.2 will be helpful here.

Start of Transition Zone

Fracture Gradient

Pore Pressure Gradient

Overburden Gradient

Normal Pressure Gradient

Fig. 1-7 Pressure-Depth Graph Illustrating a Transition Zone

If there are several target or reservoir zones to penetrate, it may be
necessary to drill through these in one hole section for efficient comple-
tion. In this case designing the casing points to set a casing shortly above
the top reservoir zone would minimize open-hole time in the reservoirs
and would offer the best chance to get through in one attempt.
With the possible casing points and problem areas in mind for a
directional well, draw up a rough directional plan. Formations giving

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