Page 51 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:55 PM Page 27

1.3.2
Precompletion and Completion Design [ ]

intervention work could be done under pressure; not killing the
well will eliminate impairment due to killing for workovers.
10. May be useful for deeper wells where many casing strings are needed.
11. Reduction in required consumables and tangibles may ease logisti-
cal problems in remote areas. Offshore rigs need less resupply.
12. Exploration wells can be drilled as slim, cheap, throwaway wells
instead of as expensive potential producers. The target zones can be
drilled using wireline-retrievable continuous cores to give better
petrophysical and geological information. Platform location can
then be optimized and wells designed for production can be drilled
from the optimum location.
13. Where production is not a constraint (e.g., observation, injection
wells) then a slim well may fully meet the objectives at minimum cost.
14. Smaller, compact wellheads and blowout preventers (BOPs) can
be used.

Disadvantages of slimhole wells.

1. Lack of contingency hole sizes.
2. A monobore completion may be less suited than a conventional
completion to wells requiring the ability to select different zones.
3. Few dedicated slimhole rigs are presently available and there will be
a lack of incentive for drilling contractors to invest in them, unless
operators find ways to create incentives.
4. In true slimhole sizes, well control presents more challenges and
requires better training and equipment to detect and deal with small-
er kicks, low annular capacities, and higher annular pressure drops.
5. Commitment is required both from operator management and from
contractors and service companies, where many senior people find
it hard to commit to radical change. Effective and committed man-
agement of the project is a prerequisite to success.
6. Slimmer wells generally mean reduced contractor and supplier
profits. New contracting strategies are required to align contractor
and operator goals, which will include sharing risks and rewards of
field development.
7. Planning and executing slimhole wells require high levels of
drilling engineering expertise and the involvement of multidisci-
pline teams (including contractor and service company personnel).
8. Limited mud densities due to high equivalent circulating densities
(ECDs).

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