American Oil and Gas Reporter - July 2018 - 76

SpecialReport: New Tech & Geosciences

Model Yields Insights On Midland Basin
By James Hardt,
Matt Houston,
Tad Gladczenko
and Rachael Mays
MIDLAND, TX.-While unconventional resource evaluation at the basin
level primarily has been carried out using
two-dimensional mapping, Piedra Resources LLC has found these efforts inadequate to appropriately characterize
key smaller-scale variability within reservoir units in the Midland Basin. Based
on this premise, Piedra has successfully
identified and acquired more than 10,000

acres of multibench acreage in areas previously thought to be less prolific.
As the industry struggles to adapt
proven conventional evaluation methods
such as dynamic modeling and geochemical analysis to unconventional reservoirs,
our focus was developing a more accurate
assessment of a better defined, more well
understood quantity: Original hydrocarbon-in-place volumes.
We set out with the objective of building a 3-D static reservoir model to
provide a basinwide predictive dataset
that honors relationships of calculated
petrophysical properties, core measure-

FIGURE 1
Locations of Wells used in Petrophysical and Static Models

1,120,000

Depth (ft)
-3,500
-4,000
-4,500
-5,000

1,040,000

-5,500

560,000

640,000

720,000

800,000

880,000

960,000

-6,000
-6,500

1,360,000

1,440,000

1,520,000

76 THE AMERICAN OIL & GAS REPORTER

1,600,000

1,680,000

ments and appropriate property distributions between sampled wells. The
modeling efforts provide a tool to estimate
the most likely range of original hydrocarbon in place for more than 300,000
current and potential horizontal well locations in the Midland Basin. This solution provides a powerful predictive tool
for determining properties of the contacted reservoir being drained by producing horizontal wells to enable improved resource development planning
with the intrinsic capability of finetuning the model through history matching-type revisions.
Traditional methods previously have
identified major large-scale trends in
basin analysis, such as the northwest-tosoutheast trends in the Midland Basin,
including the decreasing reservoir potential
of the Middle Spraberry, the increase of
organic shales with increasing total organic
carbon in the Lower Spraberry, and the
decrease in carbonates with increasing
TOC in the Wolfcamp A formation.
Workflows integrating petrophysical
analysis of several hundred wells with
structural control from more than 1,000
wells create a basin-scale 3-D geocellular
static model of the Midland Basin. The
resulting model generates insights into
lateral and vertical variability not previously realized by traditional basin-level
analysis of resource plays.
The geostatistical approach in this
study honors relationships of calculated
petrophysical properties, core measurements and appropriate property distributions. The spatial detail provided by this
integrated model results in "well-level"
reservoir characterization that basin-scale
trends alone cannot quantify.
Study Area
The study area covers 105 miles from
north to south and 75 miles from east to
west, encompassing wells from 12 counties
within the Midland Basin. The petrophysical analysis includes 317 vertical wells
with modern triple-combo logging suites
with the intervals of interest including
the Middle Spraberry through the Wolfcamp B. The total thickness of the intervals
averages 1,700 feet, but varies significantly
within the basin-from more than 2,200
feet in the southeast to 1,200 feet in the
northwest part of the basin.
The map in Figure 1 shows the location
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