American Oil and Gas Reporter - July 2020 - 55

faults are crossed by a particular well
and the volume of water produced.
Most of the wells that cross the red
faults, or faults that penetrate from the
Wolfcamp into the shallower Bone Spring,
show a greater amount of water produced
over six months than those that cross
only the blue intra-formational faults and
fractures. However, it is important to note
that since the study used publicly-sourced
well data, the depth to which these unconventional wells penetrate is unknown,
as are other factors that may contribute
to the produced water volumes.
Knowing that wells crossing the red
inter-formational faults produce more water
than wells not crossing faults that penetrate
into a shallower interval creates a greater
understanding of how faults and fractures
can result in increased water production
in unconventional wells. A methodology
then can be used to determine which faults
and fractures may create a higher risk for
water production, as seen in Figure 3A.
This is a map view of an arbitrary
point in the Wolfcamp formation using a
red-orange-yellow measure to indicate
the corresponding high-medium-low risk
assessment of the faults and fractures at
this surface or target level. Having the
ability to glance at a target location or
interval with this fault risk assessment
can help drive the placement of a lateral
or determine where to create a bypass
zone during hydraulic fracturing.

Figure 3B illustrates how a well could
be placed to minimize the risk of increased
water production. This example of a well
path crosses two yellow, low-risk faults
in the Upper Wolfcamp formation. If the
well were to be placed in the high-risk
red faults on the left side of the seismic
image, increased cost and a high water
cut could be a significant detriment to
producing hydrocarbons.
The right side of the seismic image
indicates the water-saturated zones and
the hydrocarbon-bearing intervals, as illustrated in Figure 2A, to further emphasize
the risk factors associated with faults and
fractures that cross multiple intervals.
Additionally, understanding the fault
and fracture network, along with a petrophysical analysis of the rocks (Figures 2A
and 3B), can help determine where faults
and fractures penetrate water-saturated
zones and where connected networks also
can result in increased water production.
The Delaware Basin study illustrates
how fault and fracture networks, when
imaged in a processed 3-D seismic volume,
can be analyzed in a variety of intervals,
areas and sizes. Understanding the fault
and fracture networks in an unconventional
asset can increase estimated ultimate recovery by reducing produced water, increasing production efficiency, reducing
impacts on the environment and decreasing
cost per well.
Analyzing fault and fracture networks

FIGURE 3A
Color-Coded Risk Assessment of Faults
and Fractures at Arbitrary Point in Wolfcamp

for potential produced water volume
should be a fundamental step in understanding (and valuing) an unconventional
resource play asset.
r
Editor's note: The authors acknowledge CGG Multi-Client for granting permission to show seismic data from its
Avalon 3-D survey in Reeves County, Tx.

SANDRA MAREK formerly served
as a reservoir geoscientist with CGG
Reservoir Americas. Prior to that she
worked for BP Americas, and has six
years of experience in exploration,
seismic reservoir characterization,
seismic interpretation, and stratigraphy
in a variety of onshore and offshore
fields. Marek holds a B.S. in geology
from Stephen F. Austin State University
and an M.S. in geology with a focus
on carbonate geology, from Texas
A&M University.
GRAHAM SPENCE is regional
technical manager for CGG Reservoir
Americas. With 14 years of experience
in reservoir characterization, predominately in the Lower 48, Spence has
developed bespoke geoscience solutions
for both conventional and unconventional reservoirs. He holds a B.S. in
geosciences.

FIGURE 3B
Example of Well Placement to Minimize
Increased Water Production Risk

Legend
High risk - upward
intersecting faults
Medium risk - downward
intersecting faults

Low risk - intraformational faults

JULY 2020 55

American Oil and Gas Reporter - July 2020

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