Page 227 - Practical Well Planning and Drilling Manual

Section 2 revised 11/00/bc 1/17/01 12:04 PM Page 203

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2.5

Drilling Fluids Program

(Most of this section contributed by Stuart Smith, drilling fluids consultant)

Mud has a great influence on the stability, safety, cost, and produc-
tion potential of the well. Mud properties must be engineered to mini-
mize potential hole problems (for instance, as seen on offset wells) and
meet the other objectives.
Casing points are often designed to separate pressure regimes.
Several potential problems can occur in the same hole interval, which
may call for conflicting mud properties. An example might be the ter-
tiary section of a northern North Sea well. The 17 /2 in interval may
1
comprise the complete tertiary sequence with a pressure transition
zone in the Paleocene, which requires the setting of a 13 /8 in casing.
3
1
The 17 /2 in section can comprise young, “gumbo” type, reactive shales
which overlie the mature, brittle shales of the lower tertiary. The opti-
mum water-based fluid to deal with the reactive shale may not stabilize
the lower shales.
A mud program should outline the concise approach for each hole
interval to address problems. It should define the range in which indi-
vidual relevant fluid parameters will be controlled and explain how the
fluid will be maintained within this range.

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