American Oil and Gas Reporter - November 2015 - 104

SpecialReport: Marcellus/Utica Activity
TABLE 1
Final Staging and Rock Properties
Stage
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

Gas-filled
Porosity

Clay Volume

TOC

Closure Stress
Gradient

Natural Fracture
Density

0.64
0.64
0.68
0.64
0.89
1.0
0.91
0.91
0.88
0.70
0.86
1.0
1.0
0.73
0.95
0.64

0.95
0.95
0.93
0.90
0.83
0.81
0.52
0.52
0.52
0.38
0.48
0.88
0.86
0.38
0.83
1.0

0.56
0.50
0.64
0.56
0.77
0.95
0.76
0.78
0.71
0.49
0.69
1.0
0.92
0.52
0.83
0.47

0.76
0.76
0.76
0.77
0.78
0.78
0.91
0.90
0.87
1.0
0.92
0.74
0.72
0.97
0.78
0.84

0.30
0.60
0.50
0.40
0.30
0.50
0.30
0.40
0.80
0.20
0.40
0.80
0.60
0.80
1.0
0.10

By comparison, well A2 (offset 800
feet to A1) had 13 regular stages and 90
total clusters. Well B1 had 15 total engineered stages (six-eight clusters per stage)
and 104 clusters. Well B2 (offset 750
feet to the B1) had 13 regular stages with
90 total clusters.
The end product of engineered staging
in wells A1 and B1 included stages with
a varying number of clusters. In order to
keep a consistent completion across the
lateral, the amount of sand for each stage
was determined by multiplying the number
of clusters by a base volume of sand per
cluster. This same approach was used
for the A2 and B2 offset wells completed
with regular staging.
The number of perforations per cluster
was determined by keeping the rate per
perforation at two barrels a minute. The

design rate was kept the same for all the
stages to fully utilize the horsepower
available on site. The offset control wells
were completed with 300-foot stage lengths
using seven clusters per stage and the
same amount of sand per cluster as the
corresponding offsets with engineered
staging. Comparing the performance of
both groups of wells is not meaningful
because differences were expected already
because of geology and well configuration
differences (toe-up versus toe-down).
The wells were drilled and completed
with no formation-related operational issues. Well A1 treatment pressures were
compared with average measured closure
stress for each stage. Average pressures
were regulated by optimizing the use of
friction reducer, but are not a good quan-

titative indicator of treatment difficulty.
Instantaneous shut-in pressures (ISIP)
were similar regardless of stage, which
can be explained by the fracture dimensions being greater than the radius of investigation of the sonic tools that acquired
the stress data. Therefore, stresses over
the entire vertical section come into the
observed ISIP. Breakdown pressure is
directly correlated to near-wellbore stresses, but no such correlation was observed
in the Marcellus wells. For example,
stage 10 showed a lower breakdown pressure than stages 13, 14 and 15, even
though the closure stress was measured
highest for all stages.
Production Results
Normalized production at the wellhead
is the best measure of the impact of engineered staging versus regular staging.
Well performance was compared by taking
into account both cumulative production
and productivity index (PI). Because the
sand volume per cluster was the same,
the production evaluation was done using
cluster number normalization. For example, well A1 has 103 clusters while
offset well A2 has 90 clusters. Therefore,
well A1's performance was expected to
be 15 percent better.
Well A1's 400-day cumulative production was 21 percent higher than well
A2 (5 percent normalized uplift from engineered staging). A1 also had a higher
normalized PI, indicating better overall
deliverability, and a shallower PI decline,
indicating higher expected ultimate produced reserves. No interference was detected between wells A1 and A2.
Well B1's 400-day cumulative pro-

FIGURE 4

Coming In December

In the Stimulation & Completion
technology special reports, Callon
Petroleum details how it is integrating multidisciplinary measurements
with 3-D seismic data to optimize
horizontal Wolfcamp Shale completions, Talisman Energy presents new
findings in Eagle Ford well EURs
using staggered lateral downspacing,
and Southwestern Energy's explains
how it is improving Fayetteville production by minimizing stress shadowing effects.
104 THE AMERICAN OIL & GAS REPORTER

Example Log of Grouping Rocks
With Similar Properties and Final Staging

American Oil and Gas Reporter - November 2015

Table of Contents for the Digital Edition of American Oil and Gas Reporter - November 2015