Underground Infrastructure - February 2023 - 34

CIGMAT Report
Electrical resistivity of the smart spacer fl uids was measured
using the conductivity probe and digital resistivity meter. To
assure repeatability of the measurements, the initial resistivity
was measured at least three times for each smart spacer fl uid
and the average resistivity is reported.
A commercially available conductivity probe was used to
measure conductivity (inverse of resistivity), at a range of 0.1
μS/cm to 100 mS/cm, representing a resistivity of 0.1Ω.m to
10,000 Ω.m.
Digital resistivity meter (used in the oil industry) was used
to measure the resistivity of the smart spacer fl uid directly, at
a range of 0.01 Ω-m to 400 Ω-m.
In the study, high-frequency alternative current (AC) measurement
was adopted to overcome the interfacial problems
and minimize the contact resistances.
Electrical resistance (R) was measured using an LCR meter,
which measures the inductance (L), capacitance (C) and
resistance (R)), during all the cleaning tests. Th is device has
at least a count of 1 μΩ for electrical resistance and measures
the impendence (resistance, capacitance and inductance) in
the frequency range of 20 Hz to 300 kHz.
Based on the impedance (z)-frequency (f) response, it was
determined that the smart spacer fl uid was a resistive material.
Hence the resistance was measured at 300 kHz using the twoprobe
method during the entire testing time.
Density. Th e density of the spacer fl uid was 8.46 ppg.
With the addition of 0.5% and 1% nanoFe2
O3
O3
O3
(based on total
weight of the spacer fl uid), density increased to 8.51 and 8.55
ppg, respectively. Adding 0.5% nanoFe2
sity by 0.6%; adding 1% nanoFe2
increased it by 1%.
Th e water-based drilling fl uid was prepared by adding 8%
bentonite by weight of water. Th e density and resistivity of the
drilling fl uid were 8.2 ppg and 7 Ω-m.
Temperature. Th e spacer fl uids with and without
were subjected to a temperature of 25°C to 75°C
nanoFe2O3
to investigate the change in the fl uid's electrical resistivity.
Resistivity of the smart spaced fl uid increased with the addition
of more nanoFe2
er fl uid with 0%, 0.5% and 1% nanoFe2
O3 (FIGURE 2). Th e resistivity of the spacO3
was
0.2 Ω-m, 0.202
Ω-m and 0.207 Ω-m. At 25°C temperature, the increase in the
electrical resistivity was 3.5%, with addition of 1% nanoFe2
Resistivity of the smart spacer fl uid at 50°C increased linearly
with addition of nanoFe2O3 content (FIGURE 2). With
0%, 0.5% and 1% nanoFe2
O3
O3
.
, resistivity was 0.182 Ω-m, 0.187
Ω-m and 0.193 Ω-m, respectively. At 50°C temperature, electrical
resistivity increased 6%, with addition of 1% nanoFe2
O3
Th e resistivity of the smart spacer fl uid increased with
the addition of nanoFe2
1% nanoFe2O3
O3
.
O3 (FIGURE 2). With 0%, 0.5% and
resistivity was 0.169 Ω-m, 0.172 Ω-m and
0.176 Ω-m, respectively. At 75°C temperature, electrical resistivity
increased about 4%, with addition of 1% nanoFe2
Th e electrical resistivity of the smart spacer fl uid decreased
from 0.2 Ω-m to 0.169 Ω-m, a 15% decrease ,with the increase
in temperature from 25°C to 75°C.
Piezoresistivity. Smart spacer fl uid with and without
FIGURE 2: Temperature effect on electrical resistivity of spacer fluid
with different nanoFe2
O3
content.
was subjected to pressure up to 500 psi in the
high-pressure high-temperature (HPHT) chamber to investigate
the piezoresistive behavior. Equation (8) predicted the
results very well.
nanoFe2O3
.
increased the denFIGURE
3: Measured and predicted stress-resistivity relationship
for smart spacer fluid with different nanoFe2
O3
content.
34 FEBRUARY 2023 | UndergroundInfrastructure.com
FIGURE 4: Shear stress-shear strain rate relationship for spacer fluid
with different nanoFe2
O3
content.
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