American Oil and Gas Reporter - December 2016 - 62

SpecialReport: Well Stimulation & Completion Technology
Delaware Basin Field Test
The horizontal well selected for the
field test targeted a Bone Spring sand interval at ±8,000 feet true vertical depth
in the Delaware Basin. The completion
plan called for multistage hydraulic fracturing using 16 plug-and-perf stages, with
detectable 20/40-mesh proppant pumped
in stage 16 (the final stage). It was hoped
that placing detectable proppant in the
last stage closest to the heel of the wellbore
would allow the EM source tool to be
placed as close as possible to perforations
without requiring tractoring. Figure 1
shows the positioning of the current
source injection point relative to the perforation interval for stage 16. Tool deployment was accomplished using a single-conductor e-line cable.
An earth model was constructed of
the stratigraphic column using resistivity
data from an electric open-hole log of a
pilot hole in the area. Forward modeling
of the resistivity profile from formation
depth to surface was used to design the
surface receiver array, including the optimum number and positioning of sensors.
Each receiver station consisted of two
horizontal electric field dipoles orthogonal
to each other, with one of the dipoles oriented in the same direction as the wellbore's longitudinal axis.
Based on a balance of availability, cost
and forward modeling, a total of 20 receiver
stations were designed. In addition to
measuring e-field signals, the design team
also was interested in capturing magnetic
field signals, since a signal response in
the b-field was predicted to be higher by
one of the models. Therefore, two of the
20 stations also incorporated horizontal
magnetic coil sensors (oriented orthogo-

FIGURE 2
Sensor Array Design at Delaware Basin Well Site

nally) to capture the b-field response.
Figure 2 shows the sensor array design.
The yellow squares indicate e-field dipole
receiver stations, and red squares indicate
a combination of e-field dipole pairs and
b-field sensor pairs. Black dots are the location of negative return electrodes (grounding points) and green dots are offset wells
(both active and inactive). The purple lines

FIGURE 3
Proposed EM Measurement Sequence and Timeline
≈ days

≈ hours

≈ days

D
Time

Fracture stage with
enhanced propant

Frac company on site
= EM data collect (borehole
current source activated)
62 THE AMERICAN OIL & GAS REPORTER

show section boundaries, while the blue
line connects the surface well coordinates
with total depth coordinates. The black
"rings" represent 0.5-kilometer contour
radii from the wellhead.
EM Measurements
In an effort to maximize the current
transmitted to the source tool, experiments
were conducted with two grounding-point
locations: one at the edge of the well
pad, and the other one kilometer from
the well site. EM noise impact on nearby
sensor stations also was evaluated. The
analysis predicted that more than 10 amps
of current would be transmitted to the
current source tool at depth, given expected
e-line cable resistance.
Several additional transmission aspects
were important, including the duration
of the transmission, the transmission
waveform/character, and the number (and
timing) of the measurements taken. The
final determination of each of these issues
entailed balancing the technical merits
with the associated time and cost, and
eventually led to the final recommendation
of four measurements (Figure 3).

American Oil and Gas Reporter - December 2016

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