American Oil and Gas Reporter - November 2017 - 39

SpecialReport: Industry In Motion
is within detectable range of the compressional measurements, it is chosen as
the representative arrival.
Figure 4 shows an example of the
workflow in the vicinity of nearby beds.
The white boxes show several intervals
with dual compressional arrivals, indicating
beds within one to one-and-a-half feet.
In these zones, monopole shear was used
where possible. Where no monopole shear
was evident, the dipole shear could not
be used since the compressional indicates
nearby beds. Therefore, a multilinear regression using data from a much longer
interval was used to fill the gaps.
While measured velocities always are
preferred to modeled velocities, the shear
is so susceptible to the tangled effects of
nearby beds and anisotropy that this technique provides more reliable results than
simply picking the XX and YY slownesses
from observed semblances since they are
likely subject to averaging effects of
nearby beds and could falsely impact estimates of elastic properties.
This method differs from previous
workflows in that, instead of choosing
the primary compressional arrival to be
the one representing the formation in
which the majority of the wellbore lies,
the shale is always chosen when there
are both shale and carbonate arrivals.
This refinement is because of subsequent
field testing, which shows that if only
one bed is considered in the geomechanics
model, the weaker (more fracable) formation is more representative of the behavior during completion.
Using the new workflow, the entire
lateral was analyzed to determine nearand far- compressional and shear velocities.
Figure 5 shows a top-level view of the
entire lateral broken into segments, while
Figures 6 and 7 show two example sections
along with their vertical logs.
Figure 6 shows the third segment
from middle part of the lateral. The
wellbore traversed upward, and the
acoustic velocities agree with the traverse.
The upward trajectory resulted in multiple
lithologic boundaries being crossed and
the eventual wellbore position riding
upward into a completely different lithologic assemblage than where the trajectory began. Figure 7 is the fifth segment
(toe of the lateral). The wellbore traversed
back downward through lithological sections. Velocities on the up/down receivers

FIGURE 7
Fifth Segment (Toe of Lateral)

demonstrate the variability per zone.
The receiver in the up position recorded
four distinct zones of velocity contrast
versus the down receiver, which recorded
a minimum of seven discrete/varying
velocities.
Using the geosteering model to constrain the picking of compressional and
shear arrivals, representative compressional
and shear velocities were determined
along the lateral. From heel to toe, moving
from segment one through five, one can

ANDREW PERRY is a petrophysicist
at Anadarko Petroleum Corp. and manages the company's acoustics processing.
With 12 years of experience, he joined
Anadarko in 2006 following its merger
with Kerr-McGee and has worked on
both on- and offshore projects around
the world. Perry holds an M.S. in geology
from the University of Nevada, Reno.
STEPHANIE PERRY is a petrophysi-

cist at Anadarko Petroleum Corp. She
has worked on both on- and offshore
projects in roles spanning geology, geophysics and specialized petrophysics
during her seven-year career. Perry
holds a dual B.S. in geology and psychology from Union College, an M.S.
in earth sciences from the State University of New York, Albany, and a Ph.D.
in geology from Syracuse University.
INGA MATTHEWS is a senior staff
geoscience technologist at Anadarko

see how the wellbore trajectory crossed
measured lithological variability. This
improved understanding of near-wellbore
mechanical properties can significantly
aid in optimizing completions for the
well.
r
Editor's Note: The preceding article
was adapted from a paper presented at
the Society of Petrophysicists & Well
Log Analysts 58th Annual Symposium,
held June 17-21 in Oklahoma City.

Petroleum Corp., processing waveform
sonic and borehole image data. She began her career in 1984 as a log data
processor for Schlumberger, and subsequently worked in various technical
roles at several service companies.
Mathews holds a B.S. in computer science from the University of Houston.
JENNIFER MARKET is the global
acoustics adviser for Weatherford. Her
role involves acoustic data processing
and interpretation, along with the development of new software and applications. She has 20 years of experience
in borehole acoustics. Market has been
a distinguished lecturer of both the Society of Petrophysicists & Well Log Analysts and the Society of Petroleum Engineers, and is SPWLA's 2016-17 vice
president of technology. She holds a
B.S. in physics from Edinburgh University/Texas A&M University.
NOVEMBER 2017 39

American Oil and Gas Reporter - November 2017

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