CA3090168C - Methods and systems for real-time water cut measurement - Google Patents

Abstract

Methods and systems for determining a water cut for fluid produced from at least one wellbore are disclosed. Methods include transferring thermal energy to a sample of fluid; determining a temperature change for the sample of fluid due to a 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. In some methods, a sample of fluid is diverted to a vessel.

Description

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.

Date Recue/Date Received 2020-08-14 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.

Date Recue/Date Received 2020-08-14

[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.

Date Recue/Date Received 2020-08-14

[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.

Date Recue/Date Received 2020-08-14

[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;

Date Recue/Date Received 2020-08-14

[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 Date Recue/Date Received 2020-08-14 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 Date Recue/Date Received 2020-08-14 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.

Date Recue/Date Received 2020-08-14

[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:

Date Recue/Date Received 2020-08-14 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 Date Recue/Date Received 2020-08-14 ¨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.

Date Recue/Date Received 2020-08-14

[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 Date Recue/Date Received 2020-08-14 (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 Date Recue/Date Received 2020-08-14 (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 Date Recue/Date Received 2020-08-14 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, Date Recue/Date Received 2020-08-14 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 Date Recue/Date Received 2020-08-14 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 Date Recue/Date Received 2020-08-14 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.

Date Recue/Date Received 2020-08-14

Claims (20)

CLAIMS:

1. A system for determining a water cut for fluid produced from at least one wellbore, the system comprising:
a conduit for conveying produced fluid from the 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 flowing through the conduit 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 value 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.

2. The system of claim 1, further comprising:
a second temperature sensor configured to determine the temperature value for produced fluid upstream of the heat source.

3. The system of claim 1 or claim 2, wherein the first temperature sensor comprises a first thermocouple or a first set of thermocouples.

Date Recue/Date Received 2021-03-09

4. The system of claim 2, wherein the second temperature sensor comprises a second thermocouple or a second set of thermocouples.

5. The system of any one of claims 1 to 4, wherein the heat source comprises a heat exchanger.

6. The system of any one of claims 1 to 5, wherein the flow rate determined by the flow rate sensor is a mass flow rate.

7. The system of any one of claims 1 to 6, wherein the flow rate sensor is positioned upstream of the heat source.

8. The system of any one of claims 1 to 7, wherein the processor is further configured to:
periodically log, in a data file, determined water cut values for produced fluid flowing through the conduit, and time values corresponding to when the water cut values were determined.

9. 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 produced fluid from the 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 a quantity of thermal energy being transferred to the sample, based on the two or more temperature values; and determine a water cut value for the sample of fluid, based on the quantity of thermal energy transferred to the sample of fluid from the heat source, the temperature change of the sample Date Recue/Date Received 2021-03-09 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.

10. The system of claim 9, further comprising:
an inlet valve upstream of the vessel, the inlet valve in communication with a conduit conveying produced fluid from the at least one wellbore, and configured to selectively divert produced fluid from the 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 the diverted fluid from an outlet of the vessel to the conduit.

11. The system of claim 9 or claim 10, wherein the temperature sensor comprises a thermocouple or a set of thermocouples.

12. The system of any one of claims 9 to 11, wherein the heat source comprises a heat exchanger.

13. The system of any one of claims 9 to 12, wherein the processor is further configured to:
periodically log, in a data file, determined water cut values for samples of fluid, and time values corresponding to when the water cut values were determ ined.

14. 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 produced fluid from the at least one wellbore;

Date Recue/Date Received 2021-03-09 determining, using at least one temperature sensor, a temperature change for the sample of produced fluid due to the transfer of thermal energy; and determining a water cut value for the sample of produced fluid, based on a quantity of thermal energy transferred to the sample of produced fluid, 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 produced fluid; and a mass of the sample of produced fluid.

15. The method of claim 14, wherein, during the transferring, the sample of produced fluid is in a vessel.

16. The method of claim 15, further comprising:
diverting the sample of produced fluid to the vessel, using an inlet valve in communication with a conduit conveying produced fluid from the at least one wellbore and in communication with an inlet of the vessel; and releasing the sample of produced fluid from the vessel to the conduit, using an outlet valve in communication with the conduit and with an outlet of the vessel.

17. The method of claim 14, wherein, during the transferring, the sample of produced fluid is flowing through a conduit for conveying produced fluid from the at least one wellbore, wherein 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 a heat source, and wherein determining the water cut value for the sample of produced fluid is further based on the determined flow rate.

18. The method of claim 17, wherein the determined flow rate is a mass flow rate.

Date Recue/Date Received 2021-03-09

19. The method of any one of claims 14 to 18, wherein the sample of produced fluid comprises at least 90% water and hydrocarbons.

20. The method of any one of claims 14 to 19, wherein the specific heat capacity value for at least one hydrocarbon present in the produced fluid is between 2 and 2.5 kJ/(Kg-K).

Date Recue/Date Received 2021-03-09