American Oil and Gas Reporter - September 2023 - 70

SpecialReport: Wellbore Construction
Study Assesses Trends,
Techniques To Mitigate FDIs
In Bakken Infill Development
By Darren Schmidt,
Kyoung Suk Min
and Stephen Guillot
GRAND FORKS, N.D.-As in other
unconventional plays, parent-child well
interactions have a significant effect on
the productivity of Bakken Shale wells.
Development decisions continue to be
driven largely by surface constraints, suggesting
more work is needed to improve
future child well performance and mitigate
fracture-driven interactions (FDIs).
Operators have implemented various
strategies as defensive techniques to mitigate
parent-child well interactions, including
refracturing, increased spacing
and sacrificing stimulation energy into
the nearest child well. Today's most common
mitigation techniques include fracturing
the child well closest to the parent
well first and increasing well spacing.
An Energy & Environmental Research
Center study analyzed pad wells completed
FIGURE 1
Parent Well Location Relative to Infill Wells
by multiple operators in the Williston
Basin from 2017 to 2021, including 230
well pads and 371 parent wells. These
pads were selected to exclude atypical
developments. For instance, only drilling
spacing units (DSUs) where child wells
were drilled parallel to active parent wells
were included.
The five-year period was selected because
parent-child impacts had become
apparent by 2017 and operators were
more likely to implement countermeasures.
Data was assembled to characterize the
parent well, identify whether a discernible
strategy had been implemented to counter
the depletion effect, describe the strategy
and identify any significant production
increase in relation to the parent well.
Parent well location was identified as
either near the edge of the pad or in the
middle, since location can impact completion
strategy. Other parent well characteristics
that were identified included
the number of parent wells within the
unit and whether parent wells were restimulated,
received some intervention
such as fluid loading or had no intervention.
Completion dates were examined
to determine if a stimulation order was
employed based on the position of the
parent well (referred to as a " subsurface "
decision), or if the stimulation order was
simply a " surface " decision, such as completing
the wells in sequence related to
wellhead positioning.
In addition, strategies were inferred
from the data and characterized as stimulating
in order (such as an west-to-east or
east-to-west pattern), stimulating the well
nearest to the parent first, or no strategy
was identifiable. Data was obtained on refractured
wells and used to glean insights.
Within the dataset, analytics were applied
to characterize parent-child well relationships
such as well spacing, stimulation
size, potential reservoir depletion and parent-child
formation sequence (BakkenBakken
or Bakken-Three Forks).
Study Results
More than 2,500 wells were completed
in the Williston Basin between 2017 and
2021. Parent wells were characterized
within the 230-pad dataset. The two most
dominant arrangements include a parent
well located near the edge, or a parent
well located in the middle of the DSU
(Figure 1). Stimulation order can be established
from completion dates and a
strategy can be inferred as to whether the
well nearest to the parent was stimulated
first or last. Parent wells located in the
middle of DSUs comprise 58% of the
data compared with 42% of parent wells
located near the edge.
Comparatively, 40% of the wells were
stimulated beginning closest to the parent
well, 33% were stimulated starting farthest
from the parent well and 27% were identified
as being a surface decision with
stimulation order based on wellhead position.
In addition, 82% of well completion
decisions were attributed to surface decisions
and only 18% to subsurface decisions.
Although a substantial number of
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American Oil and Gas Reporter - September 2023

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