American Oil and Gas Reporter - November 2019 - 53

SpecialReport: Marcellus/Utica Activity

Perforating Approach
Optimizes Proppant Distribution,
Improves Well Performance
By Matt Fry
and Adam Altieri
CANONSBURG, PA.-Reduced stage
spacing has been demonstrated to improve
well performance, but it also adds additional stages to a well, thereby increasing
completion cost. The mechanics of why
reduced stage spacing improves well performance are unclear, but observations
from distributed acoustic sensing may
shed light on one potential mechanism:
a tendency for heel-ward bias in the
treatment of a stage, where dominant
clusters in the heel of a stage take the
majority of the treatment, independent
of the number of perforation clusters or
cluster spacing.
This results in proppant distribution
along the length of a well mimicking a
sine wave, where higher sand loading is
associated with the dominant clusters in
the stage's heel, and lower corresponding
to the understimulated toe clusters. Reduced state spacing increases the uniformity of proppant distribution along the
length of a lateral by effectively decreasing
the period of the sine wave, thereby compressing the over- and understimulated

intervals (Figure 1A). However, a more
straightforward way of distributing proppant uniformly is to decrease the amplitude
of the sine wave (Figure 1B).
Rockdale Marcellus LLC conducted
a study to demonstrate how a perforating
scheme using variable shot cluster (VSC)
and limited entry (LE) techniques can
accomplish this by mitigating heel-ward
bias in an attempt to provide the same
production uplift as reduced stage spacing.
The study's objective was to generate
more uniform fracture half-lengths by
preventing uncontrolled half-length growth
associated with dominant heel-ward clusters taking the majority of the treatment,
thereby ensuring that all perforations
were treated and achieved uniform proppant distribution.
Effective Flow Area
A downhole camera was utilized on
multiple wells to inspect perforations for
evidence of erosion and perform a semiquantitative ranking of the amount of
proppant passing through each perforation.
Multiple VSC perforating schemes were
observed to help ascertain which variables
controlled the distribution of proppant

FIGURE 1A
Decreasing Period of Sine Wave

Heel

FIGURE 1B
Decreasing Amplitude of Sine Wave
A)

RSS

Heel

Standard

Above Average

Above Average

Standard

along the length of a stage. Results demonstrate that effective flow area (EFA) is
the controlling factor determining which
perforations accept fluid and proppant.
In nearly all stages, perforation efficiency is 100% until such a point is
reached where perforations no longer accept significant volumes of proppant.
Limiting the number of perforations to
the treatable EFA is required to ensure
all perforations in a stage are treated,
and an arithmetic model is constructed
for calculating an appropriate VSC perforating scheme to promote uniform proppant distribution among each cluster.
A cost-effective and tangible method
is presented to evaluate uniformity of
proppant distribution. Uniform cluster
treatment and proppant distribution potentially may replace less direct and costly
practices such as RSS and diverters for
improving well production, and offers
the added benefit of potentially limiting
outsized fracture half-length growth associated with dominant clusters. This
study was performed in the Marcellus
Shale, but generally applies to all unconventional plays that utilize plug-and-perf
slickwater hydraulic fracturing treatments.

Heel

B)

Ideal

Heel

Toe

Toe

Average
Below Average

Below Average

Average

Toe

Toe

NOVEMBER 2019 53
American Oil and Gas Reporter - November 2019

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