American Oil and Gas Reporter - June 2016 - 56

SpecialReport: Permian Basin Update
Upper-B, and well 4 is in the Wolfcamp
A. Wells 1 and 2 were completed first
and had tubing and bottom-hole gauges
installed in time to monitor shut-in pressure
during a portion of well 3's completion.
Interference between wells was observed clearly through changes in measured pressure trends associated with offset
fracturing operations, placing offset wells
on production, and in extreme cases by
changing chokes on offset wells.
In this example, the observation is
that the Upper-B and Lower-B have
time-zero connectivity, but Upper-B and

A do not complement our understanding
of variable rock strength between these
three landing targets and those rocks'
ability to act as frac barriers during
completion.
Differences in these early responses
provide insights to the shape and directionality of the induced fracture system,
and can guide development optimization
by making spacing, stacking and completion adjustments to wells with the
strongest connectivity, especially if those
interactions do not degrade adequately
with time.

FIGURE 4B
Degraded Time-Zero Interwell Connectivity from Pressure Buildup Data

Pressure Derivative

Bottom-Hole Pressure

#3
Shut-in

#5

ildups

Shut-in

bu
pressure

(Horizontal Wells Gun-Barrel View)
WC Upper-B

#4

#4
(Shut-in)

#5

#3
(Producing)

#2
(Producing)

#5
(Shut-in)

WC Lower-B

#1
(Shut-in)

Pressure de
rivatives

#4

Time

FIGURE 5
Directionality of Time-Zero Connectivity Among Multiple Stacked Wells
Using Shut-In Pressure Responses
#3 Completion

- #2 Opens choke
- #1 Pressure decline steepens

- #3 Opened
- #2 Pressure decline steepens
- #4 Does not respond
- #1 Does not respond

Bottom-Hole Pressure

- #3 Completion
- #2 Reacts more than #1

#3
Opens choke

#4
Opened

(Horizontal Wells Gun-Barrel View)
Variables connectivity

WC A

#1 Opens choke

Weak
#3

WC Upper-B

ro
n

#2

St

g

n
ro
St

g

#1

N

on

e

#4

WC Lower-B

Time

56 THE AMERICAN OIL & GAS REPORTER

#3
Opens choke

Horizontal Well Depletion
Figure 6 shows how a vertical well
can be used to assist in understanding
distance and directionality of horizontal
well depletion. The vertical well in this
example had been completed previously
in multiple zones above, in and below
the Wolfcamp, and had produced for 10
months.
A retrievable, multigauge assembly
was installed in preparation for offset
horizontal well activity. This assembly
consisted of multiple downhole gauges
isolated between packers for monitoring
zonal shut-in pressure. A TEC line connected each gauge in series and ran up to
surface, where real-time monitoring was
recorded at a surface box.
One of the most important, yet difficult,
challenges in optimizing well spacing
and stacking is determining how much
depletion is occurring a certain distance
laterally and vertically away from a horizontal well. This multigauge assembly
is designed to utilize vertical wells to
quantify the shape and character of the
depleting reservoir volume around a horizontal well.
The multigauge assembly was installed
while an offset horizontal well was being
drilled in very close proximity to the vertical well. The corresponding pressure
buildup is shown in the bottom left of
Figure 6.
Next, pressures from each gauge increased abruptly with varying degrees of
intensity as a response to the horizontal
well completion. There is a short period
between completing and opening the horizontal well, and then pressure decline
steepens when the horizontal well opens.
Pressure continues to decline as the horizontal well produces.
The red pressure curve shows the most
depletion and sustained connectivity with
the horizontal well, followed by the green
and blue pressure curves. The purple and
orange pressure curves increase during
the horizontal well completion, but have
very little depletion response from horizontal well production. The minimal pressure decline of these two gauges may be
dominated by leak-off of post-frac, supercharged pressure, or by minor communication with other gauges through a
possible micro-annulus outside the vertical
wellbore.
The varying degree of response among
the five gauges provides drastically increased understanding of horizontal well
depletion with respect to distance, direction
American Oil and Gas Reporter - June 2016

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