SERVICE SECTOR / Tesco Corporation Announces Two Successful Directional
Sidetracks on First Casing Drilling Well
CALGARY, Jan. 19 /CNW/ - Tesco Corporation today announced that it has
successfully completed two directional sidetracks on the previously announced
test well using the Company's proprietary casing drilling process. Casing
drilling represents Tesco's most important research and development project
and has the potential to dramatically change the way vertical, directional and
horizontal wells are drilled in the future.
With casing drilling, wells are drilled without drillpipe. Instead, the
well is drilled with standard oilfield casing, which remains in the hole at
all times. The drill bit and other downhole tools are retrieved and run by
wireline within the casing and latched to the last joint of casing. Since
casing drilling eliminates the use of drillpipe, the time required to trip, or
remove and reconnect the drillpipe, is also eliminated. In addition, because
the casing remains in the hole at all times, the integrity of the wellbore is
preserved and many of the problems associated with unscheduled drilling events
are eliminated. Tesco believes that casing drilling could have significant
worldwide commercial potential.
The well was originally plugged back from a total depth of 3040 feet and
suspended with cement plugs into the 7 5/8'' casing set at 577 feet. The
cement was drilled out to a depth of 633 feet. A directional drilling
assembly including bent housing mud motor, measurement while drilling (MWD)
system and isolation monel drill collar were deployed on wireline and latched
in the lowermost 5 1/2'' casing joint. The bottom hole assemblies were
successfully retrieved and re-run on wireline numerous times without having to
trip the casing. Hole angle was increased at a programmed 8 degree/100 feet
build-rate, to 85 degrees hole angle at 1775 feet measured depth (MD) and true
vertical depth (TVD) of 1385 feet. An additional 220 feet of hole was drilled
to a final depth of 1995 feet MD. Difficulties were encountered while sliding
(drilling ahead without casing rotation) due to the shallow nature of the well
(low available string weight) and true 90 degree horizontal was not achieved
(final angle was 84 degrees). This situation can also be inherent to the
conventional drilling process and is expected to be overcome with tool
modifications and well design considerations.
The lower open hole interval was plugged back to 1075 feet MD to enable a
second directional interval to be drilled. An open hole sidetrack was
initiated at 1010 feet MD with hole deviation of 30 degrees. Two attempts
were required to initiate the sidetrack and the second leg was drilled to a
final angle of 60.5 degrees at depth of 1517 feet MD and 1369 feet TVD. The
final wellbore was suspended with a cement plug to 968 feet MD. This suspended
wellbore will be used for continued testing of technical drilling and
completion services and products.
Upon completion of drilling operations, the casing was recovered and
inspected to determine any wear or damage. The lowermost 20 joints showed no
damage while two upper couplings exhibited some damage. Further examination
and testing of this type coupling is planned to ensure that full casing
integrity can be maintained throughout the drilling and subsequent production
operations.
To further evaluate the process for directional and horizontal drilling
with casing, Tesco is currently planning and applying for approvals to drill
another multi lateral well at its R&D test centre. The well will enable
testing of advanced tools and additional casing sizes.
Tesco is proceeding with the construction of a trailer mounted drilling
rig with top drive for casing drilling purposes. Commercial field trials are
scheduled to commence in Alberta in April 1999 on a series of shallow vertical
wells.
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