American Oil and Gas Reporter - July 2020 - 52

SpecialReport: Geophysics & Computing
produced through connectivity between
a producing interval and a water- and
H2S-bearing interval.

Features in the red and green inter-interval typically vary in size from moderate
to large. These faults and fractures have
significant potential to transmit fluids between formations since they cross from
one formation into another.
The dark red faults typically vary in
size from large to very large. These faults
represent the most easily identified faults
and generally come from deep within
the basin. They also have significant potential to transmit fluids, but since they
typically are deeper than most unconventional wells in the Wolfcamp, the
biggest hazard for encountering issues
associated with these faults is whether
there is connectivity with any of the other
fault and fracture networks that could
allow water or H2S to be transmitted.
No formation micro-imager data was
available within the study wells, which
would be needed to confirm the dominant
orientation and validation of the identified
faults. However, the general north/northwest-to-south/southeast direction of the
observed Upper Wolfcamp faulting follows
the known trend of the Delaware Basin.
Knowing the extent and penetration
of faults and fractures across one or
more intervals is important for understanding how water and/or H2S can be

Petrophysical Analysis
Petrophysical analysis of the stratigraphic column is required to identify
formations hosting high water saturation
(Sw). Petrophysical analysis (Figure 2A)
was performed on a well in central Reeves
County, denoted by the yellow star in
Figure 2B.
Figure 2A highlights the lithological
and Sw interpretation on the Avalon,
Bone Spring and Wolfcamp formations.
All these formations host intervals of
high water saturation and high oil saturation, indicating a challenging scenario
for producers completing the oil-bearing
formations, particularly if they are connected by intra-formational faulting.
For example, producing excessive
water from completing a well in the
Upper Wolfcamp that encounters an intra-formational fault connected to the
high water-saturated Lower Wolfcamp
shows how understanding the connectivity
between the hydrocarbon-bearing and
water-saturated zones can greatly affect
a well's viability. Similarly, a well that
encounters a fault connecting to multiple

FIGURE 2A
Petrophysical Analysis of Well in Study Area

shallower and/or deeper formations may
also supply additional water. In addition,
kerogen content varies throughout this
section, which may supply excess H2S,
but a dedicated geochemical study is required to fully establish those H2S-delivering formations (Type IIS kerogen).
Evaluating Water Production
When these faults and fractures are
overlain with water production data, there
is an apparent correlation between faults
and fractures that penetrate shallower intervals and an increase in produced water.
For example, when a fault crosses from
the Wolfcamp into the Bone Spring, a well
has a greater chance of increased water
production than crossing a fault that is
contained within the Wolfcamp formation.
Figure 2B is an arbitrary top-down
(map) view of the Wolfcamp with the
different color-coded fault and fracture
types. It is overlain with a bubble map of
18 wells showing six-month water production. Each green bubble represents
the volume of water produced over the
interval; the larger the bubble, the greater
the volume of water. The lateral trajectories
of each well are indicated by a red (gasproducing) or green (oil-producing) line.
Thus, the map indicates which types of

FIGURE 2B
Arbitrary Wolfcamp Section Overlain with Faults
and Fractures and Produced Water Bubble Map

Location

Legend
Intra-Formational faults
Upper intersecting faults
Lower intersecting faults
Multi-Interval faults

52 THE AMERICAN OIL & GAS REPORTER

American Oil and Gas Reporter - July 2020

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