American Oil and Gas Reporter - September 2017 - 46

ness data collected from regional correlations, seven wells were used to calculate
original oil in place. The higher average
OOIP values corresponded to Wolfcamp
B (4.5 million barrels per 160 acres),
followed by Wolfcamp A (2.5 MMbbls/160 acres) and the Wolfcamp Middle
B (1.4 MMbbls/160 acres).
These results highlighted that higher
amounts of oil may be accumulated in
the Wolfcamp B, and more so in the
northeastern area (OOIP = 7.8 MMbbls/160 acres, the highest value in a well)
with the lowest accumulations to the west
(OOIP = 0.9 MMbbls/160 acres, the
lowest value in a well) of the study area.
Figure 5 highlights the OOIP maps
for the Wolfcamp A, B and Middle B
across the study area. These maps help
support the evaluation of hydrocarbon
accumulation within the study area and
potentially the hypothesis of lateral hydrocarbon migration from the Midland
Basin axis to the basin's eastern flanks.
By utilizing compressional velocity,
shear velocity and density logs, the elastic
properties of Young's modulus and Poisson's ratio were derived to calculate brittleness. It was found that as brittleness
increases, the bulk volume of water decreases and carbonate volume increases.

FIGURE 4
Petrophysical Evaluation of Wolfcamp Formation

46 THE AMERICAN OIL & GAS REPORTER

in the northern study wells.
Figure 4 highlights the petrophysical
outputs from one of the study wells, including edited well logs, calibrated TOC
with measured TOC, calculated mineral
volumes, porosity, Sw and pay throughout
the Wolfcamp formation.
On the basis of the petrophysical calculations, specifically PHIE and Sw, and
the incorporation of net Wolfcamp thick-

FIGURE 5
OOIP Maps by Formation Based on Calculated Volumes
From Six Study Area Wells

Greater than 2,040,000

1,920,000 to 2,040,000

1,800,000 to 1,920,000

1,680,000 to 1,800,000

1,560,000 to 1,680,000

1,440,000 to 1,560,000

1,320,000 to 1,440,000

1,200,000 to 1,320,000

1,080,000 to 1,200,000

960,000 to 1,080,000

840,000 to 960,000

720,0000 to 840,000

600,000 to 720,000

480,000 to 600,000

360,000 to 480,000

240,000 to 360,000

Less than 240,000

Greater than 7,650,000

7,200,000 to 7,650,000

6,750,000 to 7,200,000

6,300,000 to 6,750,000

Middle Wolfcamp B

5,850,000 to 6,300,000

5,400,000 to 5,850,000

4,950,000 to 5,400,000

4,500,000 to 4,950,000

4,050,000 to 4,500,000

3,600,000 to 4,050,000

3,150,000 to 3,600,000

2,700,000 to 3,150,000

2,250,000 to 2,700,000

1,800,000 to 2,250,000

1,350,000 to 1,800,000

900,000 to 1,350,000

Less than 900,000

Greater than 6,500,000

6,100,000 to 6,500,000

5,700,000 to 6,100,000

5,300,000 to 5,700,000

4,900,000 to 5,300,000

Wolfcamp B

4,500,000 to 4,900,000

4,100,000 to 4,500,000

3,700,000 to 4,100,000

3,300,000 to 3,700,000

2,900,000 to 3,300,000

2,500,000 to 2,900,000

2,100,000 to 2,500,000

1,700,000 to 2,100,000

500,000 to 900,000

900,000 to 1,300,000

1,300,000 to 1,700,000

Wolfcamp A

Less than 500,00

and pay.
Before commencing with any petrophysical calculations and interpretations,
the well logs were edited and normalized
to remove any logging and/or wellbore
artifacts such as differing calibration
methods and poor wellbore conditions to
ensure sound petrophysical calculations.
Elemental capture spectroscopy (ECS)
and measured TOC data from the cuttings
analyses were utilized to provide "real
rock" constraints to the final petrophysical
lithology model.
The petrophysical results highlighted
that the Wolfcamp A and B host higher
carbonate content, compared with the
Wolfcamp Middle B, C and D, which
host increased clay and quartz volumes
replacing carbonate volumes. The recorded
kerogen volume is reasonably constant
throughout the entire Wolfcamp formation,
with some thin, higher kerogen value intervals toward the top of the Wolfcamp
B. Calculated effective porosity (PHIE)
varies from 0 to 10 percent throughout
the Wolfcamp.
To identify potential pay intervals
throughout the Wolfcamp, a cutoff of
greater than 5 percent PHIE and less
than 60 percent Sw was applied to the
petrophysical data. Intervals of higher
pay lags were identified within the Wolfcamp A and B, predominately occurring
American Oil and Gas Reporter - September 2017

Table of Contents for the Digital Edition of American Oil and Gas Reporter - September 2017
