Page 66 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:56 PM Page 42

[ ] Well Design
1.4.3

tor/team leader), exploration or production (operator), and key con-
tractors (i.e., rig, drilling fluids, mud and wireline logging, logging
while drilling (LWD), coring, directional, completion, and testing as
relevant). It would be worth considering whether an outside consultant
can be used who can import experience onto the team for the first well
or two. A good consultant should be able to improve the plan, reduce
the cost, and ensure that all necessary data is captured from the well to
improve future slimhole planning. For instance, expert advice on well-
bore stability, well control in slim high pressure/high temperature
(HPHT) horizontal situations as relevant, or drilling hydraulics may
help specific areas of the program. The team leader has to have the full
authority to manage the project and the responsibility to create the best
possible well design and drilling program.
Data capture is essential to make the learning curve as short as pos-
sible. A lot of data goes unreported or gets lost or ignored at evaluation
time. As requirements are specified from each area of expertise, ensure
that the data capture requirements are also addressed.

1.4.3. Hole and Casing Sizes: Selection
The first decision required is “what should be the final hole size at
TD?” This has to be decided first because casing sizes, kick tolerance
calculations for proposed setting depths, and directional work decisions
all depend on hole sizes.
The following considerations will apply when choosing the
planned final hole size, in order of importance:
1. The size of the desired production or test tubing (as defined in the
well proposal).
2. Whether a monobore or a conventional completion design is
anticipated.
3. Whether a contingency hole size is required (exploration well or
other reason; should be justified based on the risk of having to run
an unplanned casing string).
4. The requirements for gathering information from the well (e.g., log-
ging, coring, DST tools) and any restrictions these place on the
minimum hole size.
5. Possibly the rig available and whether equipment, crew capability,
or other considerations apply. For instance in true slim holes, well
control considerations will dictate the need for accurate kick detec-
tion and capable crews.

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