US 2024/0393280 A1 · MEASURING SYSTEM AND MEASURING METHOD FOR CONDUCTIVITY OF SUPERCRITICAL GEOTHERMAL FLUID

Abstract

The invention pertains to a measuring system for the conductivity of supercritical geothermal fluid, featuring a reaction control unit with a reaction vessel lined with corundum ceramic and containing a stirrer, a pressure control unit including a booster pump connected to Ar gas and an air compressor, a flow control unit with a flowmeter, and a temperature control unit comprising a heating furnace with thermocouples both inside and outside the reaction chamber. An electrical signal monitoring unit with electrodes fitted through a corundum capillary into the ceramic lining measures current and voltage. The invention also details a method for measuring conductivity, highlighting how water-rock interactions in supercritical geothermal fluids affect conductivity changes.

A measuring method for conductivity of a supercritical geothermal fluid, adopting a measuring system for conductivity of the supercritical geothermal fluid, comprising a reaction control unit, a pressure control unit, a flow control unit, a temperature control unit and an electrical signal monitoring unit;

the reaction control unit comprises a reaction vessel, the reaction vessel is equipped with a corundum ceramic lining, a stirrer is set in a reaction chamber of the reaction vessel, and a rotational speed/temperature control instrument for controlling a water-rock reaction process is externally connected to the reaction chamber;
the pressure control unit comprises a booster pump and a back pressure valve arranged on the reaction vessel, the booster pump is also connected to an Ar gas and an air compressor respectively;
the flow control unit comprises a flowmeter, and a reaction gas is introduced into the reaction chamber through the flowmeter;
the temperature control unit comprises a heating furnace wrapped outside the reaction vessel, and thermocouples for monitoring temperature are arranged inside and outside the reaction chamber of the reaction vessel, the electrical signal monitoring unit comprises two pairs of electrodes opposite to two sides of the reaction vessel, a corundum capillary tube is pressed into the corundum ceramic lining, the electrodes are set in the corundum capillary tube, and relative electrodes are connected to measure a current and a voltage.
a method is as follows:
establishing a fluid conductivity σ1 model based on a temperature T, a density ρ, and a fluid salinity Θ, a governing equation is as follows:
log
⁡
(
σ
l
)
=
-
1.706
-
93.78
/
T
+
0.8075
log
⁡
(
Θ
)
+
3.0781
log
⁡
(
ρ
)
+
log
⁡
(
Λ
⁡
(
T
,
p
)
)
where Λ (T, p) is a molar conductivity controlled by temperature and pressure, it is related to a solution viscosity μ, the formula is as follows:
Λ
=
A
+
B
⁢
μ
-
1
+
C
⁢
μ
-
2
where coefficients A, B, and C are functions of a molar concentration m, the coefficients A, B, and C are as follows:
A
=
a
1
+
(
a
2
-
a
1
)
[
1
+
(
m
a
3
)
⁢
a
4
]
-
1
B
-
1
=
[
b
1
+
(
b
2
-
b
1
)
[
1
+
(
m
b
3
)
b
4
]
-
1
]
-
10
6
C
=
c
1
+
c
2
⁢
m
where a1, a2, a3, a4, b1, b2, b3, b4, c1, c2 are coefficients;
the solution viscosity u is controlled by the salinity Θ, the temperature T and the pressure P, and an equation is as follows:
μ
⁡
(
P
,
T
,
Θ
)
=
μ
H
2
⁢
O
(
T
,
P
)
⁢
(
1
+
3
⁢
Θ
)
⁢
(
800
-
T
800
)
9
(
800
-
T
800
)
9
+
(
T
800
)
9
+
(
μ
H
2
⁢
O
(
T
,
P
)
⁢
(
1
-
Θ
)
+
μ
NaCl
800
⁢
Θ
)
⁢
(
T
800
)
9
(
800
-
T
800
)
9
+
(
T
800
)
9
where μH2O (T, P) is a pure water viscosity at a given temperature and pressure state, μNaCl800 is a melt viscosity at 800° C.;
the solution density is as follows:
ρ
NaCl
,
l
=
ρ
NaCl
,
l
0
1
-
0.1
ln
⁡
(
1
+
10
⁢
P
⁢
λ
NaCl
,
l
)
where a reference density under 1 bar pressure:
ρ
NaCl
,
l
0
=
m
0
m
1
+
m
2
⁢
T
+
m
3
⁢
T
2
a solution compressibility coefficient:
λ
NaCl
,
l
=
m
4
+
m
5
⁢
T
where m0, m1, m2, m3, m4, m5 are coefficients;
a whole-rock conductivity is estimated by an Archie formula:
σ
r
=
1
α
⁢
σ
l
⁢
ϕ
m
⁢
s
l
n
where σr is a conductivity of fluid-bearing rock, φ is a porosity of rock, s1 is a saturation of salt water, m is a relevant parameter of rock, n is a saturation index, and α is a coefficient factor.

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Measuring system and measuring method for conductivity of supercritical geothermal fluid

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Measuring system and measuring method for conductivity of supercritical geothermal fluid

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Abstract

Claims4