American Oil and Gas Reporter - August 2015 - 115

SpecialReport: Rockies Activity Profile
Two fleets of four vibrator trucks were
used on the survey using a "ping-pong"
scheme. The original plan required six,
eight-second sweeps. However, after several days of data monitoring and extrapolation, the sweep effort was adjusted to
nine, 12-second sweeps (for a total of
34,965 sweeps). As demonstrated in
Figure 4, the adjusted sweep effort greatly
improved the reflection quality of the
Niobrara on the gathered seismic records.
The cableless system used for the survey allowed for only limited and nonreal-time data gathering, and the source
effort adjustment had to be made based
on the scheduled versus actual seismic
data collection. With that said, the survey
required only four weeks to acquire,
which was one week less than the contract
timeline. Fortunately, the Niobrara structural geology of the area is characterized
by subhorizontal layering, which favors
the common depth point method for increased S/N ratio.
Processing was performed by an experienced processing contractor using
state-of-the-art static corrections and noisereduction seismic processing techniques.
This was performed to help maximize
the quality and frequency content of the
final image, and to accurately preserve
the fault information, which is important
for horizontal well planning and execution.
Several iterations of static calculations
were tested, and the best solution was
selected. The irregular nature of the acquisition geometry and subhorizontal geology allowed the contractor to forgo
multichannel filtering, yet maintain a favorable S/N ratio for seismic data acquired
within the highly populated urban environment. This high-end seismic processing
helped ensure that the data quality would
be excellent for interpretation purposes.
Drilling Results
The final processed results were interpreted for both Niobrara structure and
reservoir characteristics. The interpreted
products included accurate time-to-depth
conversion of the seismic horizons and
volumes, detailed structural analysis and
kinematic framework modeling of the
Niobrara and Codell formations, and
neural network inversion for rock properties throughout the entire survey area.
Accurate interpretation of structural
dips, normal faulting, fault density and
fault orientations are important for determining the exact well landings and
placement of Niobrara horizontal laterals.

Moreover, seismic reservoir analysis for
sweet spot identification within Niobrara
chalks and the Codell Sandstone is essential for fracturing staging and completion optimization. Understanding variations in thickness, porosity, and saturation
of the A, B and C chalk benches helps
determine the orientation of the laterals
and which chalks will be exploited at
any given pad location.
The interpretation process and final
products are helping determine the precise
well plans and strategy for locations in
which to land laterals within the Niobrara
chalk benches and procedures to drill
and complete the horizontal portions of
the wells (Figure 5).
As noted, 25 extended-reach laterals
have been drilled based on the 3-D survey
results. All the wells were planned to
target Niobrara B and C chalks and the
Codell Sandstone, always keeping in
mind the placement of faults along the
length of the lateral and maximizing exposure to the chalk benches. Results from
the drilling program have been excellent
in terms of accurate prediction of the
subsurface geology as well as exceeding
production expectations by 25-35 percent
of published Niobrara estimated ultimate
JACK WIENER is chief technical adviser for Halliburton in Denver. He
began his career at Texaco as a development geologist in South Texas. Wiener
then transferred to the company's Denver
office, where he worked for 19 years in
frontier exploration, asset management,
technology development and global earth
modeling. He joined Halliburton after
Texaco's merger with Chevron, focusing
on petrophysics and neural networks.
He later served at Samson Resources
as a senior geologist and Laramie Energy
II in new business development. Wiener
holds several patents in neural network
applications in petrophysics and geophysics, and invented a neural network
technique for simulating open-hole triple
combo logs from cased-hole pulsed neutron data (CHI modeling). He has a
B.S. in geology and an M.S. in geophysics
from the University of Florida.
COLLIN RICHARDSON is an equity
partner at Mineral Resources Inc., a
privately held oil and gas operating
company based in Greeley, Co. Specializing in drilling and producing lowrisk, proven reserves, the company has

recoveries.
In fact, as a result of the acquisition,
processing, and interpretation of this 3-D
survey, and the design of the horizontal
Niobrara and Codell wells, the companies
involved have the distinction of having
drilled the highest-producing Niobrara
pads in the entire D-J Basin.
In conclusion, the final interpretation
results from the 3-D survey were significant for accurately, economically and
safely executing a horizontal pad drilling
program beneath Greeley. The data are
allowing the operator to correctly target
Niobrara and Codell objectives and remain
within the hydrocarbon layer while drilling
the lateral, navigate around geologic faults
that could impact both drilling costs and
ultimate production, reduce drilling days
through more effective prewell planning,
and improve communications with the
city with regard to the nature of the subsurface geology.
The data acquired in this survey also
are providing a profound understanding
of the geologic complexity within the
Niobrara beneath Greeley, representing
a strategic planning tool for drilling an
extensive horizontal pad program and
managing the asset.
❒
developed specialized systems to safely
and efficiently acquire, develop, permit,
drill and produce oil and gas reserves
in urban areas. Last fall, MRI formed
a strategic alliance with Denver-based
Extraction Oil & Gas, a privately held
exploration and production company,
which includes the Niobrara and Codell
assets in the Greeley survey area.

TAGIR GALIKEEV is managing director for Unified Geosystems LLC in
Denver, providing expertise in seismic
acquisition and signal processing, including multicomponent data, advanced
imaging, geostatistical integrated reservoir studies and algorithm development.
He started his career in exploration
geophysics as a juggy on a field crew.
Galikeev then served as a geophysicist
with Amoco and Texaco, and later
joined ION Geophysical, where he was
a geophysical project manager and provided guidance on projects involving
3-C digital seismic acquisition. He holds
an M.S. in geophysics from Lomonosov
Moscow State University, and an M.S.
and a Ph.D. in geophysics from the
Colorado School of Mines.

AUGUST 2015 115

American Oil and Gas Reporter - August 2015

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