American Oil and Gas Reporter - March 2018 - 64

SpecialReport: Advancing Shale Science
Parsley has targeted the overpressured, high-resistivity Upper
Wolfcamp through horizontal drilling in the project area with
great initial success. Although the Wolfcamp is a prolific source
rock and reservoir at Trees Ranch, initial stratigraphic correlations
and geosteering are challenged by limited well control, along
with localized debris flows and chaotic bedding, which are attributed to the proximity to the Central Basin Platform. These
challenges exist throughout both the Bone Spring and Wolfcamp
formations in this area.
Because of these challenges, 3-D seismic and cross-discipline
integration between geology and geophysics have been instrumental to initial geosteering efforts for the company's Permian
Basin horizontal wells, which now are characterized by lateral
lengths averaging more than 9,000 feet.
In order to plan and execute an active horizontal drilling
program in an area such as the Trees Ranch project (Figure 1)
with minimal subsurface well penetrations, 3-D seismic interpretation is integrated with well data to achieve an understanding
of the structural and stratigraphic changes. Known seismic acquisition issues in the southern Delaware Basin and variable
pressure cells can cause velocity anomalies. Therefore, seismic
is used as a general guide for expected structure and faulting
along the lateral.
In undeveloped areas, 3-D seismic depth maps are integrated
with limited log data throughout the development process. Prior
to drilling, the geologist correlates well logs throughout the
area to understand general structure and thickness changes. The
geophysicist integrates these tops into the seismic depth maps
to generate a more accurate subsurface picture, which then aids
the geologist in anticipating formation changes and landing
within the desired target interval.
During the drilling process, the geologist monitors measure-

ment-while-drilling gamma ray. Major formation tops encountered
are correlated back to the seismic and used to adjust the target
landing depth in real time. Throughout the lateral, gamma ray
correlations and mud log data are used to provide more detailed
estimates of formation dip to allow the wellbore to remain in
the preferred flow unit.
In the post-drill analysis, the target zone's formation is
projected from geosteering software and incorporated into the
seismic depth interpretation to update structure maps and assist
in creating directional plans for future laterals. The iterative
process of integrating and re-interpreting 3-D seismic and subsurface well log data is essential to accurate and effective
geosteering of horizontal wells and successful development of
closely spaced target zones in an unconventional play.
Data Integration
Parsley Energy has acquired proprietary 3-D seismic data
across the southern Delaware Basin that is used to produce integrated structure maps utilized for well planning and as an aid
for geosteering. Seismic subsurface imaging in this area is
known to be difficult as a result of shallow, near-surface
variations that must be accounted for during data processing.
Even with lower-frequency content data obtained, seismic
images are invaluable for mapping the Wolfcamp section.
Because of local stratigraphic changes occurring below
seismic resolution, the geologist and the geophysicist work as a
FIGURE 2
Trees State No. 16-1H Pre-Drill Seismic Depth Map

SSTVD
(feet)
7,600
7,614
7,627
7,641
7,654
7,668
7,681
7,695
7,709
7,722
7,736
7,749
7,763
7,776
7,790
7,803
7,817
7,831
7,844
7,858
7,871
7,885
7,898
7,912
7,926
7,939
7,953
7,966
7,980
7,993
8,007
8,021
8,034
8,048
8,061
8,075
8,088
8,102

FIGURE 1
Southern Delaware Basin Wolfcamp Structure Map

Trees Ranch 3-D
Project Area

Central
Basin
Platform

8,120

Trees State 16

Parsley Energy

Southern Delaware Basin

Diablo
Platform

64 THE AMERICAN OIL & GAS REPORTER

Top of Wolfcamp SSTVD Structure
CI=100'

Trees Ranch 3-D
Wolfcamp Pre-Drill Seismic Structure, SSTVD
Pecos and Reeves Co., Tx.
0

Scale = 124,000

2,000

CI = 20 feet, Grid spacing = 500 feet

4,000

6,000 ft

10/9/15
American Oil and Gas Reporter - March 2018

Table of Contents for the Digital Edition of American Oil and Gas Reporter - March 2018
