American Oil and Gas Reporter - February 2016 - 36

SpecialReport: Unconventional Resource Science
digitized well log data. The 3-D data
were used first for horizontal well planning,
placement and geosteering. Once the data
were carefully merged and processed,
rock properties derived from well logs,
cores and samples allowed the creation
of seismic inversion volumes, coherency
cubes, and merged coherence/positive
curvature attribute volumes to guide
Olmos horizontal development as well
as drilling programs in the Eagle Ford
and the deeper Edwards formation.
Swift also has experimented with highfrequency seismic and inversion. This
rock property-based data interpretation
has allowed the limits of the field to be
extended considerably while facilitating
new insights into the best places to drill
and complete wells. To date, Swift estimates that advanced technology has extended the field by approximately 50 percent, adding more than 70 wells to its
drilling inventory, of which 35 have been
drilled with success.
Olmos Case Studies
Synthetic modeling showed that the
Olmos porosity zone could be detected
using acoustic impedance. After Swift
completed reprocessing the seismic data,
an acoustic impedance volume was created
in house. Well 1, drilled on seismic alone
before reprocessing and inversion, was
tight and yielded poor results. While the
responses were subtle on the seismic
data, the acoustic impedance response
was more obvious. Mapping suggested
that AWP could be extended to the west.

Well 2 was drilled and completed as a
producer, with estimated ultimate recovery
projected at 160,000 boe.
Both wells were logged with sonic
and density curves. Figure 1 shows the
excellent correspondence between the
acoustic impedance well log curves using
the same color bar as the acoustic impedance volume. The well 2 prediction
proved very accurate, with acoustic impedance successfully highlighting better
porosity in the Olmos Sand.
While the acoustic impedance data suggested less porosity to the south of the
AWP Field, a horizontal drilling program
was continued in this area, based on the
encouraging results of the 3,530-foot lateral
R Bracken 33H, which had been drilled
in the southern portion of the field. New
thinking was required. Our initial concept
was that the tighter rock actually might be
better for fracturing, and that other controls,
such as natural fractures, might contribute
to better production.
To test this hypothesis, coherence and
positive curvature attribute volumes were
created to see whether they could identify
fracture and fault trends. Each of these
data volumes contributed to our understanding of the area, so we decided to
merge the volumes by summing, affectionately naming the resulting attribute
volume "cFrac." Figure 2 shows the fracture trend, highlighted in yellow, on the
Olmos horizon extraction from the cFrac
attribute volume for a horizontal well
that encountered exceptional flow rates
in the stages near the highlighted trend.

FIGURE 3
Integrated Seismic and Geosteering Data
Using Automated Time-to-Depth Conversion

Another example of the technological
capabilities deployed in the AWP Field
is automated geosteering integrated with
3-D data. Swift had acquired a key lease
based on well control and a strong Olmos
seismic anomaly north of the acquired
lease area. The company initially drilled
six vertical wells with mixed results. But
after acquiring a seismic data license
covering the lease area, the company decided to put its considerable experience
in horizontal drilling to work in this part
of the field.
JOE SONNIER is the geoscience
technology supervisor at Swift Energy
in Houston. He has 35 years of experience in the seismic industry. Before
joining Swift Energy in 2007, Sonnier
served for 17 years in various positions
within the data processing division at
PGS. He holds a B.S. in mathematics
from Sam Houston State University.
SCOTT SCHOLZ is chief geophysicist at Houston Energy LP, and is former director of geoscience technology
at Swift Energy Company. Before joining Swift Energy in 2006, where he
served until May 2015, Scholz was
senior geophysicist at Spinnaker Exploration, manager of seismic processing quality control at TGS-Nopec,
a senior staff geophysicist at Western
Geophysical, and an explorationist at
Sohio Petroleum Company and Amoco
Production Company. He holds a B.S.
in applied physics from the Georgia
Institute of Technology.
BRUCE MORIARTY is chief geophysicist for Lumina Geophysical in
Houston. He previously served as geophysical adviser at Swift Energy Company, focusing on the company's assets
in the Eagle Ford and Olmos plays in
South Texas, along with the Lake Washington Field in Louisiana. Moriarty
has 35 years of experience, and began
his career working as an interpreter/independent and subsequently served as
project manager for Visos, principal
geophysicist at El Paso Production,
and chief geophysicist at Dominion
Exploration. He holds a B.A. in geology
from Colgate University.

36 THE AMERICAN OIL & GAS REPORTER

American Oil and Gas Reporter - February 2016

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