Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
METHODS AND SYSTEMS FOR REAL-TIME WATER CUT MEASUREMENT
FIELD
[0001] This disclosure relates generally to systems and methods for
determining
the ratio of water to a total volume of liquid in a produced fluid stream
(commonly
referred to as the 'water cut'), and more specifically to systems and methods
for
determining water cut based on heat capacities of water and hydrocarbon
mixtures.
INTRODUCTION
[0002] Various systems and methods are known to measure the water cut
of
produced fluids for conventional and heavy oil process. Water cut measurements
may
be considered important for e.g. process control and/or fulfilling regulatory
reporting
requirements.
[0003] For example, water cuts may be measured during periodic
testing, in
which one or more wells are queued for test. Such testing typically requires
two-phase
or three-phase separators, which may be considered relatively expensive. Where
a row
of multiple wells are put on test, an accounting of the water cut typically
cannot be
performed on a well-by-well basis. As a result, troubleshooting and/or
surveillance may
be more challenging. Also, in some cases it may not be practical to hold
multiple wells
'on test' at the same time.
[0004] As another example, water cut may be measured using an oil
water meter,
such as those available from Agar Corporation of Houston, Texas. Such water
cut
meters may be based on microwave absorption, Near Infrared (NIR) measurements,
guided radar, or gamma ray based instruments. However, such meters may not
have a
desired precision and/or accuracy. For example, the density of certain
produced fluids
may not provide sufficient contrast to enable accurate water cut measurements.
Also,
the presence of air bubbles and/or frothing of the produced fluid may
adversely affect
the performance of such meters.
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SUMMARY
[0005] The following introduction is provided to introduce the reader
to the more
detailed discussion to follow. The introduction is not intended to limit or
define any
claimed or as yet unclaimed invention. One or more inventions may reside in
any
combination or sub-combination of the elements or process steps disclosed in
any part
of this document including its claims and figures.
[0006] In accordance with one broad aspect of this disclosure, there
is provided a
system for determining a water cut for fluid produced from at least one
wellbore, the
system comprising: a conduit for conveying fluid produced from at least one
wellbore; a
flow rate sensor configured to determine a flow rate for produced fluid
flowing through
the conduit; a heat source configured to transfer thermal energy to produced
fluid
flowing through the conduit; a first temperature sensor configured to
determine a first
temperature value for produced fluid downstream of the heat source; and a
processor
operatively coupled to the flow rate sensor, the heat source, and the first
temperature
sensor, the processor configured to: determine a temperature change across the
heat
source, based on the first temperature value and a temperature value for
produced fluid
upstream of the heat source; and determine a water cut for produced fluid
flowing
through the conduit, based on the determined flow rate, a rate of thermal
energy
transfer for the heat source, the temperature change, a specific heat capacity
value for
water, and a specific heat capacity value for at least one hydrocarbon present
in the
produced fluid.
[0007] In some embodiments, the system further comprises a second
temperature sensor configured to determine the temperature value for produced
fluid
upstream of the heat source.
[0008] In some embodiments, the first temperature sensor comprises a first
thermocouple or a first set of thermocouples.
[0009] In some embodiments, the second temperature sensor comprises a
second thermocouple or a second set of thermocouples.
[0010] In some embodiments, the heat source comprises a heat
exchanger.
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[0011] In some embodiments, the flow rate determined by the flow rate
sensor is
a mass flow rate.
[0012] In some embodiments, the flow rate sensor is positioned
upstream of the
heat source.
[0013] In some embodiments, the processor is further configured to:
periodically
log, in a data file, determined water cuts for produced fluid flowing through
the conduit,
and time values corresponding to when the water cuts were determined.
[0014] In accordance with another broad aspect of this disclosure,
there is
provided a system for determining a water cut for fluid produced from at least
one
wellbore, the system comprising: a vessel for receiving a sample of fluid
produced from
at least one wellbore; a heat source configured to transfer thermal energy to
the sample
of fluid; a temperature sensor configured to determine two or more temperature
values
for the sample of fluid; and a processor operatively coupled to the heat
source and the
temperature sensor, the processor configured to: determine a temperature
change of
the sample of fluid in response to thermal energy being transferred to the
sample,
based on the two or more temperature values; and determine a water cut for the
sample
of fluid, based on a quantity of thermal energy transferred to the sample of
fluid from the
heat source, the temperature change of the sample of fluid, a specific heat
capacity
value for water, a specific heat capacity value for at least one hydrocarbon
present in
the produced fluid, and at least one of: the total volume of the sample of
fluid; and a
determined mass of the sample of fluid.
[0015] In some embodiments, the system further comprises an inlet
valve
upstream of the vessel, the inlet valve in communication with a conduit
conveying fluid
produced from at least one wellbore, and configured to selectively divert
fluid produced
from at least one wellbore to an inlet of the vessel; and an outlet valve
downstream of
the vessel, the outlet valve in communication with the conduit, and configured
to
selectively release fluid from an outlet of the vessel to the conduit.
[0016] In some embodiments, the temperature sensor comprises a
thermocouple
or a set of thermocouples.
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[0017] In some embodiments, the heat source comprises a heat
exchanger.
[0018] In some embodiments, the processor is further configured to:
periodically
log, in a data file, determined water cuts for samples of fluid, and time
values
corresponding to when the water cuts were determined.
[0019] In accordance with another broad aspect of this disclosure, there is
provided a method for determining a water cut for fluid produced from at least
one
wellbore, the method comprising: transferring thermal energy to a sample of
fluid
produced from at least one wellbore; determining, using at least one
temperature
sensor, a temperature change for the sample of fluid due to the transfer of
thermal
energy; and determining a water cut for the sample of produced fluid, based on
a
quantity of thermal energy transferred to the sample, the temperature change,
a specific
heat capacity value for water, a specific heat capacity value for at least one
hydrocarbon present in the produced fluid, and at least one of: a volume of
the sample
of fluid; and a mass of the sample of fluid.
[0020] In some embodiments, during the transferring, the sample of fluid is
in a
vessel.
[0021] In some embodiments, the method further comprises: diverting
the sample
of fluid to the vessel, using an inlet valve in communication with a conduit
conveying
fluid produced from the at least one wellbore and in communication with an
inlet of the
vessel; and releasing the sample of fluid from the vessel to the conduit,
using an outlet
valve in communication with the conduit and with an outlet of the vessel.
[0022] In some embodiments, during the transferring, the sample of
fluid is
flowing through a conduit for conveying fluid produced from at least one
wellbore, and
the method further comprises: determining, using a flow rate sensor, a flow
rate for
produced fluid flowing through the conduit; and wherein the temperature change
is
determined for a location downstream of the heat source, and wherein
determining the
ratio of water to a total volume of produced fluid is further based on the
determined flow
rate.
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[0023] In some embodiments, the determined flow rate is a mass flow
rate.
[0024] In some embodiments, the sample of fluid comprises at least
90% water
and hydrocarbons.
[0025] In some embodiments, the specific heat capacity value for at
least one
hydrocarbon present in the produced fluid is between 2 and 2.5 kJ/(Kg-K).
[0026] It will be appreciated by a person skilled in the art that a
method or
apparatus disclosed herein may embody any one or more of the features
contained
herein and that the features may be used in any particular combination or sub-
combination.
[0027] These and other aspects and features of various embodiments will be
described in greater detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] For a better understanding of the described embodiments and to
show
more clearly how they may be carried into effect, reference will now be made,
by way of
example, to the accompanying drawings in which:
[0029] Figure 1 is an exemplary schematic diagram of a well pad
facility that
includes a separator and flow meters for taking water cut measurements;
[0030] Figure 2 is an exemplary schematic diagram of another well pad
facility
that includes a water cut meter and mass flow meter for taking water cut
measurements;
[0031] Figure 3 is an exemplary schematic diagram of a well pad
facility that
includes apparatus for determining water cut based on heat capacity, in
accordance
with one embodiment;
[0032] Figure 4 is an exemplary schematic diagram of a well pad
facility that
includes apparatus for determining water cut based on heat capacity, in
accordance
with another embodiment;
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[0033] Figure 5 is a plot of bitumen-diluent-water mixture heat
capacity for a
range of water cuts and diluent concentrations;
[0034] Figure 6 is a plot of heat capacities for mixtures of bitumen-
diluent-water
for a constant water cut and changing diluent concentration;
[0035] Figure 7 is a plot of heat capacities for mixtures of bitumen-
diluent-water
for a constant diluent concentration and changing water cut;
[0036] Figure 8 is a plot of the heat capacity of certain paraffins
over a range of
temperatures;
[0037] Figure 9 is a simplified process flow diagram for a method for
determining
a ratio of water to a total volume of liquid in fluid produced from at least
one wellbore in
accordance with one embodiment; and
[0038] Figure 10 is a simplified process flow diagram for a method
for
determining a ratio of water to a total volume of liquid in fluid produced
from at least one
wellbore in accordance with another embodiment.
[0039] The drawings included herewith are for illustrating various examples
of
articles, methods, and apparatuses of the teachings of the present
specification and are
not intended to limit the scope of what is taught in any way.
DESCRIPTION OF EXAMPLE EMBODIMENTS
[0040] Various apparatuses, methods and compositions are described
below to
provide an example of an embodiment of each claimed invention. No embodiment
described below limits any claimed invention and any claimed invention may
cover
apparatuses and methods that differ from those described below. The claimed
inventions are not limited to apparatuses, methods and compositions having all
of the
features of any one apparatus, method or composition described below or to
features
common to multiple or all of the apparatuses, methods or compositions
described
below. It is possible that an apparatus, method or composition described below
is not an
embodiment of any claimed invention. Any invention disclosed in an apparatus,
method
or composition described below that is not claimed in this document may be the
subject
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matter of another protective instrument, for example, a continuing patent
application,
and the applicant(s), inventor(s) and/or owner(s) do not intend to abandon,
disclaim, or
dedicate to the public any such invention by its disclosure in this document.
[0041] Furthermore, it will be appreciated that for simplicity and
clarity of
illustration, where considered appropriate, reference numerals may be repeated
in a
figure or among different figures to indicate corresponding or analogous
elements. In
addition, numerous specific details are set forth in order to provide a
thorough
understanding of the example embodiments described herein. However, it will be
understood by those of ordinary skill in the art that the example embodiments
described
herein may be practiced without these specific details. In other instances,
well-known
methods, procedures, and components have not been described in detail so as
not to
obscure the example embodiments described herein. Also, the description is not
to be
considered as limiting the scope of the example embodiments described herein.
[0042] Figure 1 is a schematic diagram of an example well pad
facility that
includes a separator and flow meters for taking water cut measurements. In the
illustrated example, two wells 10a and 10b are shown (which may be referred to
collectively as 10a/b herein), although it will be appreciated that three or
more wells
may be present. During normal operation, gasses produced from each well 10a/b
are
directed to an outlet conduit 25, via conduit segments 11 and 15, and a valve
13. Outlet
conduit 25 may be in fluid communication with one or more compressors and/or
multi-
phase pumps. Concurrently, liquids from each well 10a/b are directed to a
valve 18 (e.g.
a Remote Operated Valve, or ROV), via a conduit segment 12, a valve 14, and a
conduit segment 16. Valve 18 may direct produced liquid to an output conduit
26, which
may be in fluid communication with a trunk line for the well pad facility.
[0043] Valve 18 may be operated to selectively divert produced liquid to a
test
separator 22 via a conduit 20. For example, valve 18 may divert produced
liquid to
separator 22 at predetermined time intervals. After undergoing separation, a
fluid
stream 22a comprising a substantial portion, and preferably all, of the
hydrocarbons
present in the produced liquid entering separator 22 is directed through a
flow meter 24
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to output conduit 26. Also, a fluid stream 22b comprising a substantial
portion, and
preferably all, of the water present in the produced liquid entering separator
22 is
directed through a flow meter 24 to output conduit 26. The water cut may then
be
determined based on the volume flow rate of water 22b and hydrocarbons 22a
determined by the flow meters 24.
[0044] Figure 2 is a schematic diagram of an example well pad
facility that
includes a water cut meter and a flow meter for taking water cut measurements.
In this
example, apparatus upstream of valve 18 is the same as the example illustrated
in
Figure 1. In the example of Figure 2, during normal operation, valve 18 may be
operated to selectively divert produced liquid to a water cut meter 28 via a
conduit 20.
For example, valve 18 may divert produced liquid to water cut meter 28 at
predetermined time intervals. After passing the water cut meter, the diverted
fluid
stream is directed through a flow meter 24 to output conduit 26. The water cut
may then
be determined based on data from the water cut meter 28 and the mass and/or
volume
flow rate determined by flow meter 24. For example, flow meter 24 may
determine a
mass flow rate (e.g. a Coriolis meter with mass flow rate readings and
density) or a
volume flow rate (e.g. a simple turbine meter that provides volumetric flow
rate).
[0045] While system such as the examples illustrated in Figures 1 and
2 can be
used to take water cut measurements, such systems may have one or more
disadvantages. For example, an oil-water separator 22 may be considered
relatively
expensive, particularly if it only being used for water cut measurements. As
another
example, known oil-water meters may not have a desired precision and/or
accuracy
(e.g. the presence of air bubbles and/or frothing of the produced fluid may
adversely
affect the performance of such meters).
[0046] In contrast to systems and methods for determining water cut based
on
physical separation (e.g. as in the example of Figure 1) or by using water cut
meters
that are based on dielectric measurements using radio or microwave frequency
(e.g. as
in the example of Figure 2), systems and methods disclosed herein may be used
to
determine the water cut of a produced fluid stream based on specific heat
capacity.
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[0047] The specific heat capacity for a mixture of liquids is based
on the specific
heat capacities of the components in the mixture and their relative proportion
of the
mixture. That is:
Cpj = WC,72 x Cp,water (1 ¨ WCin) x Cp,Hc (1)
where Cpi is the specific heat capacity for the mixture, Cp,water is the
specific heat
capacity for water, Cp,Hc is the specific heat capacity for hydrocarbons
present in the
mixture, and WC,72 is the mass-based water cut.
[0048] The specific heat capacity for a mixture of liquids can also
be empirically
determined based on an observed temperature change for a known mass (or
volume) of
mixture resulting from the application of a known quantity of heat energy to
the mixture
sample. For example, for a flowing fluid mixture:
CP,mix _________________________________________________________________ (2)
(rh x AT)
where Cpi is the specific heat capacity for the mixture, 61 is the output rate
of a heat
source providing thermal energy to the mixture,
is the mass flow rate of the mixture,
and AT is the temperature change across the heat source.
[0049] Combining equations (1) and (2), the water cut WC,, for a
flowing mixture
of produced fluids may be expressed as:
WC,72 x Cp,water + (1 ¨ WC172) x Cp,Hc =(m. _________ x AT) (3)
¨ (Cp,Hc x x AT)
W in = (4)
CP,water X ill X AT) ¨ (Cp,Hc x rh x AT)
Thus, the water cut WC,72 may be determined based on measurements of 61, ñi,
and AT
and known or assumed values for Cp,Hc and Cp,water- It will be appreciated
that the
mass-based water cut WC,72 can be converted to a volumetric water cut WC
relatively
simply by using density values for water and for hydrocarbons present in the
mixture.
[0050] As another example, for a fixed volume of sample fluid:
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CP,mix _________________________________________________________________ (5)
(m x AT)
where Cpi is the specific heat capacity for the mixture, Q is the total heat
transferred
to the mixture, and m is the mass of the sample mixture.
[0051] Combining equations (1) and (5), the mass-based water cut WCõ,
for a
mixture of produced fluids may be expressed as:
w cm x Cp,water + (1 ¨ WC772) x Cp,Hc =(6)
(m x AT)
Q ¨ (Cp,Hc x m x AT)
W Cm = __________________________________________________________________ (7)
(
CP,water X m X AT) ¨ (Cp,Hc X Ill X AT)
Thus, the water cut WCõ, may be determined based on measurements of Q, m, and
AT
and known or assumed values for Cp,Hc and Cp,water- Again, the mass-based
water cut
WCõ, can be converted to a volumetric water cut WC by using density values for
water
and for hydrocarbons present in the mixture. It will be appreciated that,
similarly, a
volumetric water cut WC can be converted to a mass-based water cut WCm. As
such,
the term "water cut" as used herein is a dimensionless value that can be based
on
either mass or volumetric ratios.
[0052] Figure 5 illustrates the relative effects of changes in water
content (shown
as mass percentage) and changes in hydrocarbon composition (shown as diluent
mass
percentage) on specific heat capacity for a mixture Cp,mix. For changes in
hydrocarbon
composition, it is presumed that most ¨ if not all ¨ of the variation in heat
capacity will
be due to variation in the concentration of diluent in the produced fluid
stream, rather
than, e.g. variation in the relative concentrations of various hydrocarbons in
the
produced fluid stream.
[0053] Also, with reference to Figure 8, the specific heat capacity
for
hydrocarbons changes with molar mass and temperature. However, the range of
values
reported in the literature for various paraffins (e.g. (heptane, decane,
tridecane,
pentadecane, hexadecane, octadecane) is relatively narrow, from about 2 to
about 2.5
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¨KJ. In contrast, the specific heat capacity for water is about 4.2 ¨KJ, or
about twice that
KG=K KG=K
of hydrocarbons. This relative difference in specific heat capacities is
another reason
why the relative concentrations of various hydrocarbons in the produced fluid
stream
may be ignored (or assumed to have an insignificant impact) when calculating
specific
heat capacities of water/hydrocarbon mixtures Cp;mix.
[0054]
To determine Cp,Hc, a compositional analysis may be performed on fluid
produced from a well. Alternatively, Cp,Hc may be estimated based on an
assumed
composition of hydrocarbons in a formation and/or an assumed concentration of
diluent.
It will be appreciated that produced fluid may be periodically sampled and
Cp,Hc updated
as necessary.
[0055]
Figures 6 and 7 are also illustrative of the relative effects of changes in
water content and changes in diluent concentration on specific heat capacity
for a
mixture Cp;mix. In Figures 6 and 7, data points relating to a water cut of 20%
are labelled
"20", data points relating to a water cut of 50% are labelled "50", and data
points relating
to a water cut of 80% are labelled "80". For example, with reference to Figure
7, for a
water cut of 20%, the specific heat capacity for the mixture Cp,mi, is between
about 2.3
and 2.6 ¨KJ, for a water cut of 50%, the specific heat capacity for the
mixture Cp,mi, is
KG=K
between about 3 and 3.25 ¨KJ, and for a water cut of 80%, the specific heat
capacity for
KG=K
the mixture
is between about 3.7 and 3.75 -1 K. In contrast, with reference to
Figure 6, for a diluent concentration of 20%, the specific heat capacity for
the mixture
is between about 2.3 and 3.7 ii(Gfic. As Figures 6 and 7 illustrate, water
content
has a more significant impact on the specific heat capacity for a mixture
Cp,mi, than
compositional change in the hydrocarbon phase (e.g. changes in diluent
concentration).
[0056]
Returning to Figure 3, a schematic diagram of an example well pad facility
that is configured to determine water cut based on heat capacity. In the
illustrated
example, two wells 10a and 10b are shown, although it will be appreciated that
only
one, or three or more wells may be present.
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[0057] During normal operation, gasses produced from each well 10a/b
are
directed to an outlet conduit 25, via conduit segments 11, 15, and a valve 13.
Outlet
conduit 25 may be in fluid communication with one or more compressors and/or
multi-
phase pumps. Concurrently, liquids from each well 10a/b are directed to an
output
conduit 26 via a conduit segment 16. Output conduit 26 may be in fluid
communication
with a trunk line for the well pad facility.
[0058] In the illustrated example, each conduit segment 16 is in
selective fluid
communication with sampling apparatus via valves 36, 37, which may be ROVs.
Valves
36, 37 may be operated to selectively divert produced liquid to a test vessel
or chamber
40 (e.g. an insulated cylinder). For example, valves 36 and 37 may be operated
consecutively or concurrently to divert produced liquid from well 10a/b to a
test vessel
40 at predetermined time intervals.
[0059] After being diverted from conduit segment 16, the fluid sample
may be
heated using a heat source 38 (e.g. a heater or heat exchanger). For example,
the fluid
sample may be heated after it has been introduced into the test vessel 40.
Alternatively,
or additionally, the fluid sample may be heated before it reaches the interior
of test
vessel 40 (e.g. an inlet to the vessel may include one or more heating
elements).
[0060] Optionally, valve 36 and/or 37 may function as a pressure
control valve
(PCV) to control fluid pressure within test vessel 40 in order to inhibit, and
preferably
prevent, flashing and/or vaporization of light hydrocarbons, which may
otherwise lead to
e.g. the formation of gas bubbles. For example, the presence of gas affect the
efficiency
of the heat source 38 in delivering energy to the produced fluid in test
vessel 40.
Alternatively, or additionally, a separate PCV (not shown) may be provided.
[0061] Also, after the diverted fluid sample has been heated, a
temperature
measurement may be obtained using a temperature sensor 34 (e.g. a
thermocouple).
For example, temperature sensor 34 may be used to determine a temperature
after it
has been introduced into the test vessel 40, and/or as it is exiting the
vessel.
Additionally, an initial temperature measurement for the diverted fluid sample
may be
obtained using temperature sensor 34 before the diverted fluid sample has been
heated
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(e.g. immediately after its introduction to test vessel 40. Alternatively, an
initial
temperature for the diverted sample may be based on e.g. a temperature
measurement
taken upstream of valve 36, such as a temperature for liquid exiting the well
10a/b.
[0062] Optionally, the mass of the diverted sample in test vessel 40
may be
measured. Alternatively, the mass of the diverted sample may be estimated
based on,
for example, the volume of the fluid sample, its temperature, pressure,
density, and/or
estimated composition.
[0063] The water cut for the diverted sample (and for fluid produced
from the well
10a/b contemporaneously with the diverted sample) may then be determined based
on
e.g. equation (7) above, using the heat output from heater 38 for Q, the mass
of the
sample (determined directly or calculated based on e.g. the volume of the
liquid sample)
for m, temperatures measured using temperature sensor 34 for AT, and known or
assumed values for Cpjic and [0064] After After heating and temperature
measurement, the diverted sample may be
returned to conduit segment 16, e.g. via valve 37, and new sample of produced
fluid
may be diverted from conduit segment 16 to test vessel 40.
[0065] Figure 4 illustrates another example well pad facility that is
configured to
determine water cut based on heat capacity. In the illustrated example, two
wells 10a
and 10b are shown, although it will be appreciated that only one, or three or
more wells
may be present.
[0066] During normal operation, gasses produced from each well 10a/b
are
directed to an outlet conduit 25, via conduit segments 11, 15, and a valve 13.
Outlet
conduit 25 may be in fluid communication with one or more compressors and/or
multi-
phase pumps. Concurrently, liquids from each well 10a/b are directed to an
output
conduit 26 via a conduit segment 16. Output conduit 26 may be in fluid
communication
with a trunk line for the well pad facility.
[0067] In the illustrated example, each conduit segment 16 directs
produced
liquid through a flow meter 24 (e.g. a mass flow meter), and an in-line heat
source 32
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(e.g. a heater or heat exchanger). Temperature sensors 34 are provided to
measure the
produced liquid upstream and downstream of the in-line heater 32.
Alternatively, a
single temperature sensor 34 may be provided downstream of the in-line heater
32, and
a temperature for the fluid entering the in-line heater 32 may be based on
e.g. a
temperature measurement taken upstream of in-line heater 32 and/or flow meter
24,
such as a temperature for liquid exiting the well 10a/b.
[0068] In one or more alternative examples (not shown), heat source
32 may be
provided upstream of flow meter 24, and the one or more temperature sensors 34
may
be positioned in any suitable order, with at least one temperature sensor
positioned
downstream of heat source 32.
[0069] Optionally, valve 14 may function as a pressure control valve
(PCV) to
control fluid pressure within conduit 16 in order to inhibit, and preferably
prevent,
flashing and/or vaporization of light hydrocarbons, which may otherwise lead
to e.g. the
formation of gas bubbles. For example, the presence of gas may interfere with
readings
of the flow meter 24. The presence of gas may also affect the efficiency of
the heat
source 32 in delivering energy to the produced fluid stream. Alternatively, or
additionally, a separate PCV (not shown) may be provided, e.g. upstream of
flow meter
24 and/or heat source 32.
[0070] The water cut for fluid produced from the well 10a/b may then
be
determined based on e.g. equation (4) above, using the heat output of in-line
heater 32
for 6, the flow rate determined by flow meter 24 for the mass flow rate rii
(either
determined directly by a mass flow rate sensor 24, or calculated based on a
volume
flow rate determined by flow meter 24 and a density value for the produced
fluid),
temperatures measured using temperature sensors 34 for AT, and known or
assumed
values for Cp,Hc, and [0071] The The well pad facilities illustrated
schematically in Figures 3 and 4 may
have one or more advantages compared to e.g. the examples illustrated in
Figures 1
and 2. For example, it may be practical and/or economical to provide sampling
apparatus (e.g. flow meter 24, heat source 32, and temperature sensors 34; or
flow
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meter 24, heat source 32, and temperature sensors 34) to determine the water
cut for
each well 10a/b. Such an arrangement may facilitate improved process
analytics,
particularly for solvent-assisted and solvent-dominated recovery processes,
such as
solvent assisted cyclic steam stimulation (SA-CSS), solvent assisted steam
assisted
gravity drainage (SA-SAGD), solvent assisted steam flood (SA-SF), vapor
extraction
process (VAPEX), heated vapor extraction process (H-VAPEX), cyclic solvent
process
(CSP), heated cyclic solvent process (H-CSP), azeotropic heated vapor
extraction
(Azeo H-VAPEX), and the like.
[0072] The type of system provided for a well, or on a header for a
group of wells,
may be based (at least in part) on an expected and/or observed water cut trend
for an
in-situ recovery process. For example, the configuration illustrated in Figure
3 may
facilitate periodic and/or batch water cut measurement of produced fluid. Such
an
arrangement may be particularly suitable for recovery processes that reach a
steady-
state phase with relatively little change to the production profile (e.g. the
water cut can
be expected to remain relatively steady over time). Examples of such recovery
processes include steam assisted gravity drainage (SAGD), SA-SAGD, Enhanced
Bitumen Recovery Technology (EBRT), and other gravity drainage processes.
[0073] As another example, the configuration illustrated in Figure 4
may facilitate
substantially continuous real-time (or near real-time) water cut measurement
of
produced fluid. Such an arrangement may facilitate improved process analytics,
particularly for recovery processes in which the water cut can be expected to
change
significantly over time. Examples of such recovery processes include cyclic
steam
stimulation (CSS), SA-CSS, CSP, and other cyclic processes that exhibit
changes in
water cut during each production cycle. For such processes, it may be
particularly
advantageous to provide continuous and/or real-time (or near real-time) water
cut
measurement.
[0074] In some embodiments, it may be advantageous to provide a
portable
module for both batch and continuous measurement that can be installed for a
well or
on a header for a group of wells. Such a portable module may include a heat
source,
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one or more temperature sensors, and a sensor for determining mass and/or mass
flow
(e.g. depending on whether the portable module is configured for batch or
continuous
measurement).
[0075] The well pad facilities illustrated schematically in Figures 3
and 4 may also
include one or more devices (e.g. computing devices) configured to
periodically log
water cut measurements. For example, a data file storing water cut
measurements and
time values corresponding to when the water cuts were determined may be
regularly
updated (e.g. as new water cuts are determined, and/or periodically on a pre-
determined schedule).
[0076] The following is a description of a method for determining a ratio
of water
to a total volume of liquid in fluid produced from at least one wellbore,
which may be
used by itself or in combination with one or more of the other features
disclosed herein
including the use of any of the apparatus and/or systems disclosed herein.
[0077] Referring to Figure 9, there is illustrated a method 900 for
determining a
ratio of water to a total volume of liquid in fluid produced from at least one
wellbore.
Method 900 may be performed using apparatus described with reference to Figure
3, or
any other suitable apparatus.
[0078] At 910, a sample of produced fluid may be diverted to a
vessel. For
example, fluid may be diverted from a conduit 16 to a vessel 40, e.g. using
one or more
valves 36, 37.
[0079] At 920, thermal energy is transferred to the produced fluid.
For example, a
sample of fluid in vessel 40 may be heated using heat source 38.
[0080] At 930, a temperature change for the produced fluid is
determined. For
example, one or more temperature sensors 34 may be used to measure a
temperature
of sample fluid in vessel 40 before and after heating by heat source 38.
[0081] At 940, a ratio of water to a total volume of liquid in the
produced fluid (i.e.
a water cut) is determined based on specific heat capacity. For example, a
water cut
may be determined based on a quantity of thermal energy transferred to the
produced
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fluid, the mass of the fluid, a temperature change of the fluid, and specific
heat
capacities for water and for the known or assumed composition of hydrocarbons
in the
produced fluid.
[0082] Optionally, at 950, a sample of produced fluid diverted to a
vessel may be
released. For example, fluid in vessel 40 may be released to conduit 16 via
valve 37.
[0083] The following is a description of another method for
determining a ratio of
water to a total volume of liquid in fluid produced from at least one
wellbore, which may
be used by itself or in combination with one or more of the other features
disclosed
herein including the use of any of the apparatus and/or systems disclosed
herein.
[0084] Referring to Figure 10, there is illustrated a method 1000 for
determining a
ratio of water to a total volume of liquid in fluid produced from at least one
wellbore.
Method 1000 may be performed using apparatus described with reference to
Figure 4,
or any other suitable apparatus.
[0085] At 1010, a flow rate for a produced fluid may be determined.
For example,
a flow meter 24 may be provided along a conduit 16 that extends to an output
conduit
26. The measured flow rate may be a mass flow rate or a volumetric flow rate
(which
may be converted to a mass flow rate based on e.g. a density value for the
produced
fluid).
[0086] At 1020, thermal energy is transferred to the produced fluid.
For example,
a produced fluid stream may be heated using heat source 32.
[0087] At 1030, a temperature change for the produced fluid is
determined. For
example, temperature sensors 34 may be used to measure a temperature of
produced
fluid upstream and downstream of heat source 32.
[0088] At 1040, a ratio of water to a total volume of liquid in the
produced fluid
(i.e. a water cut) is determined based on specific heat capacity. For example,
a water
cut may be determined based on a quantity of thermal energy transferred to the
produced fluid, the mass flow rate of the fluid, a temperature change of the
fluid, and
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specific heat capacities for water and for the known or assumed composition of
hydrocarbons in the produced fluid.
[0089] As used herein, the wording "and/or" is intended to represent
an inclusive
- or. That is, "X and/or Y" is intended to mean X or Y or both, for example.
As a further
example, "X, Y, and/or Z" is intended to mean X or Y or Z or any combination
thereof.
[0090] While the above description describes features of example
embodiments,
it will be appreciated that some features and/or functions of the described
embodiments
are susceptible to modification without departing from the spirit and
principles of
operation of the described embodiments. For example, the various
characteristics which
are described by means of the represented embodiments or examples may be
selectively combined with each other. Accordingly, what has been described
above is
intended to be illustrative of the claimed concept and non-limiting. It will
be understood
by persons skilled in the art that other variants and modifications may be
made without
departing from the scope of the invention as defined in the claims appended
hereto. The
scope of the claims should not be limited by the preferred embodiments and
examples,
but should be given the broadest interpretation consistent with the
description as a
whole.
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