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optimum production, completion, and stimulation conditions.
Siimhole drilling
Application of slirr~ . drilling to both exploratory drilling and coring and to
prujuction has proved to bee ~;; economical ..ltemative. Because slimhole drilling uses
smaller rigs that can be transported with a helicopter, previously inaccessible locations
such as mountains and jungles can be reached. The technology of slimhole drilling
usually applies high rotational speed through top drives and often cores large sections
using 30 to 60 ft corebarrels on a sandline. The process is limited to about 15,000 ft
depth for safety reasons.
The problem with the slimhole exploratory drillmg is the narrow annulus that
during a "kick" might cause a blowout.':'Also the narrow annulus causes the.equivalent
circulating density to increase rapidly, which may fracture the fortnation.
Drilling rigs
Top Drive
DUal-speed top drives were introduced in the early 1980s. The demand'on this
type of rig has since increased worldwide. One of the new dual-speed top drives is rated
at 650 tons, which can handle larger bit sizes and drill-string dia::1eters and reach a
greater drilling depth and produce longer horizontal sections. ThIs type of rig meets
personnel-safety requirements much better than the old rigs. Safety is needed most around
the rotary table and on the rig floor; top-drive rigs eliminate the rotary table.
Instrumentation
The past decade has put a higher demand on quality data collection. The sensors
used to ce··: drilling data are relatively simple. There have been some improvements
using digr:...:1ata collection, but the sensors used are not alwavs accurate. Calibration of
sensors must be done for all temperature and pressure ranges as well as for the whole
spectrum of parameters. Better sensors, especially for WOB, torque, and return flow,
must be developed to complement the application of s.me new software tools, otherwise
simulation results will be poor.
Conclusions - Application toWIPP discussion
The WIPP area would be a good candidate for applications of the latest technology
in directional drilling. Extensive drilling to reach the shallow oil in the Delaware
Mountain Group, at about 7500-8000 ft, and the deeper gas in the Morrow and Atoka
Groups is to be expected (if permitted) during oil and gas development under WIPP and
potash resources.
Possible underbalanced drilling with foam, air, or aerated mud might be best for
the Morrow gas fortnation because of the decreased risk of fortnation. damage, less
drilling-fluid treatment, and increased rate of penetration (ROP). In this case it is
necessary to set casing below the Atoka Fortnation, which of course, is an economical
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