American Oil and Gas Reporter - June 2016 - 55

SpecialReport: Permian Basin Update
well 3 being shut in, indicating the timezero connectivity observed between these
two wells no longer existed. This leads
to a key hypothesis that connectivity observed during initial flowback does not
necessarily mean wells are spaced too
closely because of the potential rapid

degradation of the connected flow paths.
Figure 5 shows another time-zero interference test, but also includes interwell
pressure interaction during completion,
and adds a third stacked landing interval
to the well configuration. Well 2 is landed
in the Lower-B, wells 1 and 3 are in the

FIGURE 3
Spraberry and Wolfcamp Targets in Midland Basin

U. Spraberry
M. Spraberry
L. Spraberry
Jo Mill Sand
L. Spraberry
Shale
Dean
Wolfcamp A
Wolfcamp B1
Wolfcamp B2

Upper B

Wolfcamp B3

Lower B

Wolfcamp C1

Wolfcamp C2
Wolfcamp D
Strawn

FIGURE 4A
Time-Zero Interwell Connectivity from Shut-In Pressure Responses
(Horizontal Wells Gun-Barrel View)
#1 Open

WC Upper-B
#4

#2 Open
#1 & #2
Choke
changes
#3 Open

Bottom-Hole Pressure

stacked targets for developing horizontal
wells. Introducing this third, vertical dimension increases the complexity and
importance of determining optimal well
spacing and understanding well-to-well
interference and its impact on well performance.
Figure 3 shows a type log illustrating
the number of potential targets that may
exist at a single well location. With the
statistical variability in well performance,
it would take 50-100 wells to determine
an optimal spacing and stacking strategy
in a given area, based on well performance
alone. Given the geomechanical variability
throughout the field, these pilots would
have to be repeated in multiple study
areas, requiring hundreds to thousands
of wells to fully optimize spacing and
stacking across a large acreage position.
Getting up the learning curve quickly
in regard to spacing and stacking has required analyzing and integrating multiple
engineering and geoscience datasets, with
interwell pressure interference at the top
of the list.
Figure 4A illustrates how measured
BHP and interference tests can be used
to quantify magnitude and direction of
"time-zero" well connectivity (or the connectivity observed between wells during
initial flowback). In this case, the shut-in
BHP response from well No. 5 is shown
as four surrounding wells are opened.
Pressure begins to decline as soon as
well No. 1 is opened, indicating connectivity with the offset well. The pressure
decline steepens as well No. 2 is opened,
again during well 1 and 2 choke changes,
and again when wells 3 and 4 are opened.
This valuable data conclusively indicates that interwell connectivity exists
simultaneously in each of four directions
around the No. 5 well.
The observed time-zero connectivity
may or may not degrade with time, as
demonstrated in Figure 4B, using three
wells from the example shown in Figure
4A. An additional interference test was
conducted four months after time-zero
connectivity was observed. Well Nos. 4
and 5 were shut in, BHP was monitored
during pressure buildups, and surrounding
wells were kept producing. After extended
and stable pressure buildups were observed, well No. 3 was shut in also. Well
4 responded immediately with a more
rapid pressure buildup and a step change
increase in pressure derivative, indicating
sustained connectivity with well 3.
However, well 5 did not respond to

#2
WC Lower-B

#3

#5
(Gauge)

#1

Shut-in pressure
#4 Open
#5 Open

#5
Choke
change

Flaming
pressure

Time

JUNE 2016 55
American Oil and Gas Reporter - June 2016

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