Sugiura_subbed.qxp 27/3/09 04:22 Page 76
While-drilling Calliper Images Enhance Rotary-steerable Performance
echnology
ell T
a report by
Junichi Sugiura
Research and Development Design Engineer, Pathfinder Energy Services, Inc.
Drilling & W
Poor hole quality causes tight borehole, packing off, high torque/drag, different drill-bit performances. The images are also used to improve
stick–slip, degraded logging-while-drilling (LWD)/wireline log quality, the rotary-steerable bottomhole assembly (BHA) design for superior
unpredictable directional performance and, consequently, problematic steerability, stability, drillability, controllability and borehole quality.
casing runs. There was initial recognition of the ‘crooked hole’ problem The results from extensive drill bit and BHA research using the
in the early 1950s. This crooked hole was repeatedly observed by calliper images are also applied internationally during commercial
drillers for decades in the form of ‘tight hole’ and very high torque/drag runs to troubleshoot bit/BHA problems. Currently, the realtime
even without the aid of modern LWD tools. Advances in LWD imaging calliper images are available only to qualified R&D personnel for
technology now allow engineers to identify 3D borehole oscillation research purposes.
issues and oscillation frequencies while drilling.
Integrated Calliper Imaging Sensors
Borehole Oscillation Integrating near-bit sensors with the RSS allows consistent
In 1951, MacDonald and Lubinski first provided a precise definition of the measurement of borehole conditions, along with the three principal
so-called crooked hole or ‘spiral hole’ and provided a crooked-hole types of downhole vibration: torsional, lateral and axial. Near-bit sensors
formula for the maximum drift size with a given bit and collar also have been used to make comparative analyses of drill bit and BHA
combination. Since their study 58 years ago, significant progress has been performance among different assemblies and wells.
made in understanding the oscillating or cyclical nature of persistent
borehole problems. Today it is known that the use of an extended-gauge The mechanical calliper image while drilling is now a standard,
polycrystalline diamond compact (PDC) bit can reduce borehole integrated component of all RSS and provides realtime and memory-
oscillations and improve borehole quality with specially designed steerable based calliper images on all runs. The integrated mechanical calliper
motors and particular point-the-bit rotary-steerable systems (RSS). imaging has the following advantages:
Mechanical callipers obtained from wireline logs and acoustic stand-off
callipers from LWD logs have accelerated this understanding of borehole • calliper images are taken at the same position in a BHA (either
oscillation problems. The use of such equipment is no longer the only way point-the-bit or push-the-bit RSS);
to detect 3D borehole problems, such as borehole oscillation. • realtime borehole images are available to R&D engineers for all of
the RSS runs;
Rotary-steerable Systems • the integrated sensor does not add extra complexity to the RSS,
An RSS with a built-in mechanical calliper has been developed which means the system delivers superior reliability;
(SPE90482). This integrated mechanical calliper provides realtime • integrated sensors are more economical and affordable than
and memory-based calliper images while drilling and has become a specialised subs;
novel methodology for creating borehole calliper images compared • sensor use is transparent to the RSS operator and requires no extra
with conventional LWD acoustic stand-off calliper images. With this sensor/battery set-up; and
RSS, calliper images are available in both point-the-bit and push-the- • unlike specialised subs, the sensors do not alter the BHA’s length
bit configurations. or behaviour.
These new 2D/3D near-bit calliper images are extensively used in Non-commercial Field Testing
research and development (R&D) departments and help to quantify In one case, realtime mechanical calliper images were used in
extensive drill-bit testing for the push-the-bit RSS. Confidential
drilling rig test facilities were used to conduct the controlled RSS
Junichi Sugiura is a Research and Development (R&D)
Design Engineer with PathFinder Energy Services, Inc.,
directional test programme: the GTI Catoosa Test Facility near Tulsa,
based in Houston, Texas. He began his career as an Oklahoma and the Rocky Mountain Oilfield Test Center (RMOTC)
electrical engineer in Japan. Since joining PathFinder in
near Casper, Wyoming. Both facilities provided adequate geological
2002, he has focused on developing sensor technology and
downhole software algorithms for rotary-steerable systems.
variations and rig/pump capabilities for the tests in 8.5-inch and
He is the author of several Society of Petroleum Engineers
12.25-inch hole sizes. With no directional constraints at either of
(SPE), Offshore Technology Conference (OTC), International
Association of Drilling Contractors (IADC), American
the facilities, they both offered a perfect test ground for controlled
Association of Drilling Engineers (AADE) and Society of Petrophysicists and Well Log Analysts RSS testing.
(SPWLA) technical papers, and holds several patents in downhole technology. Mr Sugiura
holds a BSc (Hons) in electrical engineering from the University of Texas at Austin.
Since 2007, the RSS in push-the-bit modes has been extensively tested
E:
jsugiura@smith.com
with different drill bits at these test sites (SPE115395). An
experimental 8-inch push-the-bit tool (for 12.25-inch hole size),
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© TOUCH BRIEFINGS 2009
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