American Oil and Gas Reporter - December 2016 - 52

SpecialReport: Well Stimulation & Completion Technology
Production results from a growing
population of wells demonstrate improvements in cumulative 90-day oil production
in line with forecast earth model expectations. This continues to assist Laredo
in ranking development areas and prioritizing exploration acreage. The earth
model workflow represents an "evergreen"
process that can be iterated and updated
on an ongoing basis with new data, including new complexities and changes
to development designs, to provide an
improved platform that may further improve individual well estimated ultimate
recoveries and economic returns.
Laredo recognized early in the evaluation of its Garden City acreage, which
is positioned on the eastern side of the
Midland Basin (Figure 1), that developing
multiple zones required a holistic and
rigorous technical workflow that integrated

all available data types to fully exploit
the total resource package. With resource
potential aggregating into the billions of
barrels, this represents a development
that requires careful consideration and
oversight.
Moreover, the multistacked nature of
the Midland Basin tight, unconventional
oil play presents additional challenges in
terms of vertical and horizontal spacing
when designing the overall development
and building the appropriate scale of facilities necessary to exploit these resources.
A key starting point to building any
type of high-quality, 3-D geocellular earth
model is acquiring the right data at the
right time in order to initiate the process.
A cornerstone principle in Laredo's operating philosophy is that a better understanding of the subsurface through inte-

FIGURE 1
Gamma Ray and Stock Tank OOIP
Cross-Section across Garden City Acreage
1

2

3

4

5

6

7

8

9

10

Upper
Spraberry
Middle
Spraberry

UWC
MWC
LWC
Canyon
Cline

GAMMA RAY
Stock Tank Original
Oil in Place (OIP)

Strawn
ABW

Laredo Leasehold

Flattened on the Middle Wolfcamp
ABW - Atoka, Barnett & Woodford
North
STOIP
TOTALS

South

292 MMBO 254 MMBO

305 MMBO

302 MMBO

320 MMBO

322 MMBO

272 MMBO

352 MMBO

354 MMBO

279 MMBO

FIGURE 2
Multivariate Model Example

Brittleness

Storage

Earth Model Predicted 90-day Oil Cumulative
(% of Type Curve)

36 Wells - 0.81 Correlation Coefficient
Fluid/Stress

200%

Fracturing
175%
150%
125%

Lithology
100%
75%
50%
25%
25%

50%

75% 100% 125% 150% 175%
Actual 90-day Oil Cumulative
(% of Type Curve)

52 THE AMERICAN OIL & GAS REPORTER

200%

grating data, science and technology leads
to improved value creation for the company's stakeholders.
Accordingly, Laredo has acquired
more than 400 square miles of high-fold
3-D data over its Garden City assets. Between 2012 and 2015, Laredo also acquired 100 dipole sonic logs.
High-quality 3-D seismic, in combination with an excellent population of
dipole sonic logs distributed relatively
evenly across the survey area, allows for
the development of a very high-quality
series of acoustic impedance inversion
products and associated derivative attributes. Laredo has been developing inversion
attributes relating to reservoir, lithology,
stress, natural fractures and geomechanical
properties since 2013.
Underlying Relationships
During early appraisal of the Wolfcamp
play, after a reliable and standardized
slickwater frac design had been established, operators favored "leading theories"
of underpinning production-driving mechanisms, including original oil in-place.
While an important factor in any tight
oil play, early bivariate analysis revealed
a limited correlation between OOIP and
production over the area of interest.
In fact, bivariate analysis of an extensive list of log properties and seismic attributes-including seismic inversion properties such as bulk modulus, Poisson's
ratio, Young's modulus, and brittleness-
versus oil production demonstrated poor
correlation in most instances. This is
clearly problematic, as it stringently impedes the ability to be predictive during
any development program and results in
a much higher degree of variance in anticipated well results.
A breakthrough occurred when nonlinear, multivariate statistical methods
were applied simultaneously to multiple
attributes. Developing nonparametric,
nonlinear multivariate models that incorporated attributes representative of reservoir quality, mechanical properties and
natural fracturing evaluated holistically
with valid sample sizes transformed the
historical bivariate approach. Combining
these effects revealed underlying relationships to production with correlation
coefficients commonly seen at 0.70-0.85.
Figure 2 shows an example of a multi-
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