American Oil and Gas Reporter - July 2018 - 81

SpecialReport: New Tech & Geosciences
Figure 3 is a cross-section through
the static model, showing water saturation
on the left with warmer colors indicating
lower water saturation and lithologies on
the right-gray shale (gray), organic black
shale (green), marl (magenta), silt (yellow)
and carbonate (blue).
Lithological properties are distributed
in the 3-D grid from log data using sequential indicator simulation guided by
regional probability maps, vertical proportion curves, and variograms to control
the local horizontal and vertical property
population. Porosity is distributed within
the lithology bins and by stratigraphic
interval using matching probability maps,
variograms and histograms. A similar
approach was used for TOC. Water saturation was distributed using a transform
defined in log data between porosity and
saturation, specific for each lithology
and interval.
The major uncertainties to the model
inputs are lithology fractions (cutoffs),
porosity and saturation distributions. These
ranges were quantified using T-square
tests to estimate the range of the mean of
the data as well as by evaluating the bias
introduced by using differing data (e.g.,
lateral versus induction logs for saturation
calculation). The range from this analysis
was used to build an uncertainty model
with Monte Carlo sampling. Total uncertainty then was quantified as a function
of original oil in place.
Study Results
One of the products of this study is a
set of lithology fraction maps that provide
a regional to interwell estimate of the
fraction of each lithology. Figure 4 shows
lithology fraction maps of organic shale
for the Lower Spraberry (left) and the
Wolfcamp A (right). High fractions of
organic-rich shales indicate potentially
productive areas, often contrasted by the

carbonate fraction maps. All these maps
provide regional insight into the variability
of the Midland Basin.
The static model shows significant
vertical and lateral variability within
stratigraphic intervals. The clay content
is highest in the center of the basin,
where turbidite sheets are mapped, and
lowest at the slope margins. Quartz is
concentrated in a wedge in the southern
Midland Basin near the Ozona Arch in
all four main intervals. The volume of
quartz is low within the Wolfcamp in the
northern Midland Basin, but higher in
the Middle Spraberry and even more so
in the Lower Spraberry.
There are several clear northwest-tosoutheast trends in the Midland Basin.
Generally, the hydrocarbon saturation is
highest along the western slope margin,
south of the Horseshoe Atoll, and at the
mouth of the San Simon Channel. The
resource potential of the Middle Spraberry
decreases to the southeast; however, resource potential for the Lower Spraberry
increases to the southeast (with increasing
organic shale content and TOC) for the
Lower Spraberry.
The resource potential for the Wolfcamp is inversely proportional to the
presence of carbonates dominating the
western flank of the basin-as carbonate
content diminishes to the east and southeast, TOC increases. Our static model is
useful in evaluating regional trends as
well as providing specific resource potential in any area.
r
Editor's note: The preceding article
outlines the approach and limited data used
in the Midland Basin study. However, the
operator subsequently joined a consortium
with more than 100 core samples, and
after implementing model rebuilds, found
remarkable consistency in results based
on the approach detailed in this article.

Two PetroQuest Wells Produce 26,839 Mcfe/d
LAFAYETTE, LA.-PetroQuest Energy Inc. says its two latest wells in its
horizontal Cotton Valley drilling program
in East Texas have a cumulative maximum 24-hour gross daily production of
18,285 Mcf of natural gas, 1,354 barrels
of natural gas liquids and 55 barrels of
oil, for an equivalent rate of 26,839
Mcfe a day.
According to the company, PQ 29,
which had a lateral length of 6,250 feet,
recorded a 24-hour production rate of

15,371 Mcfe/d. PetroQuest says it has a
52 percent net revenue interest in the well.
PQ 30, with a 5,382 foot lateral, produced at 11,469 Mcfe/d over 24 hours.
The company adds it has a 59 percent
NRI in the well.
PetroQuest says it estimates the two
wells had an average drill and completion
cost of $887 a lateral foot. The company
adds it is evaluating joint ventures in
connection with planning its 2018 Cotton
Valley drilling program.
r

JAMES HARDT is a reservoir engineer at Piedra Resources LLC, an Encap
Company based in Midland, Tx. He has
17 years of reservoir engineering experience focused on reservoir modeling
and description. Before joining Piedra
Resources in 2015, Hardt served as a
reservoir engineer in Laredo Petroleum's
Permian Basin asset team, DeGolyer
and MacNaughton's Europe/Africa division, and BP's deepwater Gulf of Mexico and lower-48 business unit. He holds
a B.S. and an M.S. in petroleum engineering from Texas A&M University.
MATT HOUSTON is a senior geologist at Piedra Resources LLC. With
12 years of industry experience, he
began his career at Questar working
in the Anadarko Basin. Houston then
served as a geologist at Devon Energy
in the Cana Woodford and Barnett
shale plays, and as a project geologist
at Laredo Petroleum focused on the
Midland Basin Wolfcamp trend. He
joined Piedra Resources in 2015. Houston holds an M.S. in geology from The
University of Arkansas.
TAD GLADCZENKO is principal
geomodeler at Applied Geostats LLC
in Moraga, Ca. With 20 years of industry experience, Gladczenko previously served as a senior consultant at
International Reservoir Technologies,
senior geologist at Addax Petroleum,
reservoir modeler at Chevron, business
development manager at Schlumberger,
senior geoscientist at Technoguide,
and geophysicist at Dynamic Graphics.
He holds a B.S. in GIS and environmental science from University College
of Southeast Norway, and an M.S. in
geophysics and a Ph.D. in marine
geophysics from the University of Oslo.
RACHAEL MAYS is principal consultant at Bird Ridge Petrophysics LLC
in Golden, Co. She began her career in
1985 at BP as a petrophysicist, and
served at the company for 18 years. In
2003, Mays joined Canyon Investments
Inc. as a petrophysical consultant, and
subsequently served as a petrophysical
consultant for International Reservoir
Technologies and as petrophysical project
adviser at Anadarko Petroleum. Mays
holds a B.S. in geological engineering
from the Colorado School of Mines and
an M.S. in geological engineering from
the University of Alaska Fairbanks.
JULY 2018 81

American Oil and Gas Reporter - July 2018

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