American Oil and Gas Reporter - January 2015 - 98

Unconventional Resource Science
clusters. The percentage of frac stage oil
production per cluster is shown in Table
2 according to each perforation scheme
used. Several observations can be made
from the data, assuming that equally
treated clusters will result in equal production among those same clusters in a
frac stage.
First, in the case of the State of North
Dakota 10-3HA where the "6, 6, 6"
scheme was used, the highest oil-producing
cluster was at the shallowest position,
while the lowest oil-producing cluster
was at the deepest position. This is anticipated because one would expect a preference of frac fluid injectivity (therefore,
production) toward the heel-side cluster
when all clusters have the same number
of perforations.
Second, in the case of the 10-3HA
where the "6, 6, 10" scheme was used,
the opposite result was observed, with
the majority of detected production at
the deepest position where the largest
number of holes were used. This suggests
that the difference between number of
holes at the toe-side position to the heel
side and middle positions was larger than
optimal. Last, it is interesting that in the
case of the "6, 6, 8" perforating scheme,
the average oil production at each cluster

Production Logs
Production logs were used to compare
perforation schemes and correlate with
proppant tracer data. The production logging tool consisted of mini-spinners, and
electrical and optical probes positioned
both on a maneuverable arm and the low
side of the tool body. The sensors each
make a direct, localized measurement of
the velocity of the fluid passing through
to enable the calculation of a multiphase
velocity profile. This facilitates detecting
velocity variations in the vertical diameter
of the wellbore that otherwise may be
missed by a single-spinner logging tool.
The No. 10-3HA was logged 42 days
after the fracturing treatment was completed, while the 10-3HW was logged 30
days after treatment. In both cases, the
log was run on coiled tubing and did not
reach total depth. For both wells, approximately 35 percent of the lateral
length was logged.
The 10-3HA utilized three cluster
schemes (number of holes listed from
the heel side to toe side): 6, 6, 6; 6, 6, 8;
and 6, 6, 10, while the 10-3HW utilized
the same cluster scheme on every stage
(6, 6, 8). Perforation schemes were chosen
based on limited-entry principles to more
equally divert fluid flow among perforation

position was identical for both wells and
displayed a more evenly dispersed production distribution.
Spectral gamma ray logs for detecting
proppant tracer can be used to surmise
whether a specific perforation cluster has
been treated. Since both proppant tracer
data and production log data were collected
on the 10-3HA, data were checked for
any possible correlations. Of the three
stages that had proppant tracer added to
the frac fluid slurry, no correlation could
be made with the effectiveness of frac
treatment per cluster in a specific stage
to the ratio of production among clusters
in the same stage. However, a single frac
stage on the 10-3HA showed good proppant tracer coverage across all clusters,
but only one of these clusters had oil
production, according to the production
log. This reinforces the idea that conclusions should be made based on multiple
datasets.
FIGURE 5
Oil- and Water-Soluble
Chemical Tracer Layout
(Including Sampled Offset Wells)

n
Va

6, 6, 8

TABLE 3
Multivariate Predicted Economics (A)
Versus Actual Test Well Performance (B)
CUM oil 180
days (bbl)

EUR
(Mbbl oil)

ROR
(before tax)

A: Bakken, 25 stages, 3.8 MM lbs

121,000

A: Three Forks, 25 stages, 3.8 MM lbs

108,500

B: Bakken, 25 stages, 3.8 MM lbs

127,461

A + up to 15% B + up to 15%

B: Three Forks, 25 stages, 3.8 MM lbs

115,783

C + up to 15%

Target Formation, No. stages, lbs proppant

98 THE AMERICAN OIL & GAS REPORTER

D + up to 15

Dancing Bull 16-21HD

Dancing Bull 16-21HC

Dancing Bull 16-21HZ

6, 6, 8

ll 1

State of ND 10-3HW

Toe side

e
ns

State of ND 10-3HW

Middle

u
Br

State of ND 10-3HA

Heel side

6, 6, 10

Well name

Bakken
Three Forks

Adam Good Bear 15-H

6, 6, 6

Average oil allocation per
cluster position
(%)

Adam Good Bear 15-HX

Frac
stages
logged

Adam Good Bear 15-HW

Perforation
scheme
(No. holes at heel
side, middle, and
toe side cluster)

State of ND 10-3HA

-4

Perforation Scheme and Impact on Oil Production

State of ND 10-3H

TABLE 2

American Oil and Gas Reporter - January 2015

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