CA3097892A1 - Adjustment of solvent injection rate based on storage temperature fluctuation in steam-solvent assisted recovery process for hydrocarbon recovery - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
In a process of recovering hydrocarbons from a subterranean reservoir with co-injection of steam and solvent, steam and a solvent are injected into the reservoir, and a rate of steam injection is adjusted based on real-time fluctuation of a storage temperature of the solvent to be injected. The solvent storage temperature may be dependent on fluctuation in solar energy transferred to the solvent, and the rate of steam injection may be adjusted to, at least in part, compensate for the fluctuation in the solar energy transferred to the solvent.
Date Recue/Date Received 2020-11-02

Description

ADJUSTMENT OF SOLVENT INJECTION RATE BASED ON STORAGE
TEMPERATURE FLUCTUATION IN STEAM-SOLVENT ASSISTED RECOVERY
PROCESS FOR HYDROCARBON RECOVERY
FIELD
[0001] The present disclosure relates generally to hydrocarbon recovery from subterranean reservoirs, and particularly to solvent injection control in in situ steam-solvent hydrocarbon recovery.
BACKGROUND

[0002] Steam and a solvent can be co-injected into a subterranean reservoir of bituminous sands (also commonly referred to as oil sands) to assist, drive, or aid hydrocarbon recovery from the reservoir (referred to herein as a steam-solvent recovery process).

[0003] Typically, in a steam-solvent recovery process a desired ratio of solvent to steam (solvent-to-steam ratio) in the injection stream and the desired injection temperature and pressure are pre-determined, and the steam and solvent are mixed at constant respective amounts or rates according to these pre-determined values before injection by separately controlling the injection rate of steam and the injection rate of solvent so that the ratio of the solvent injection rate to the steam injection rate is the same as the desired solvent-to-steam ratio in the injection mixture, which has been determined to provide the desired temperature and pressure in the injection mixture.
For example, for a given solvent injection rate (e.g. 35 t/d), the steam injection rate may be selected and controlled (e.g. selected to be 15 t/d) to obtain a weight percentage of the solvent (e.g. 70 wt% solvent) in the injection mixture that corresponds to the desired solvent to steam ratio (e.g. =3:7), which provides the desired mixture temperature and pressure. The solvent to steam ratio may be based Date Recue/Date Received 2020-11-02 on weight/mass, volume, mole, or a combination thereof, and may be expressed or indicated in the form of relative ratios, or percentages such as weight percentages, volume percentages, or molar percentages.

[0004] In a typical arrangement in a steam-solvent recovery process, an input stream of steam and an input stream of solvent may be provided through separate pipelines and mixed at a junction of the pipelines at surface before injection into the injection well, where the flow rate in each of the input pipeline is regulated to achieve a pre-selected target flow rate. The target flow rates are typically pre-determined according to the desired ratio of solvent to steam in the injection stream and injection temperature/pressure. For example, the target values of the required flow rates in the steam input pipeline and the solvent input pipeline for a given weight ratio of solvent to steam and a selected injection temperature can be pre-determined. The flow in each of the input pipelines may be controlled to achieve and maintain the pre-determined flow rate for that input line.
SUMMARY

[0005] It has been recognized by the present inventor(s) that maintaining the same flow rate of injected steam over a long period of time to achieve a constant target solvent-to-steam ratio in the injection mixture in a steam-solvent recovery process may not provide the optimal, e.g. more economical outcome in some situations. For example, it has been recognized that when the temperature of the input solvent before mixing or injection with the steam is fluctuating, injecting the steam at a correspondingly lower or higher rate depending on whether the input solvent temperature is higher or lower may reduce or avoid steam wastage and may optimize steam injection. Thus, it would be beneficial to adjust the steam injection rate at least in part based on the real-time fluctuation of the solvent storage temperature.

[0006] Thus, in an aspect of the present disclosure, there is provided a method of injecting steam and solvent into a subterranean reservoir to assist recovery of Date Recue/Date Received 2020-11-02 hydrocarbons therefrom, the method comprising injecting steam and a solvent into the reservoir; and adjusting a rate of steam injection based on real-time fluctuation of a storage temperature of the solvent to be injected.

[0007] In various embodiments, the storage temperature of the solvent may be dependent on fluctuation in solar energy transferred to the stored solvent such as through direct sunlight or other solar radiation, and the rate of steam injection may be adjusted to, at least in part, compensate for the fluctuation in the solar energy transferred to the stored solvent. In this process, a first stream comprising steam at a first temperature and a second stream comprising the solvent at a second temperature may be mixed to form a third stream comprising steam and the solvent at a third temperature. The first stream may flow at a first flow rate and the second stream may flow at a second flow rate, the first and second flow rates may be selected based on a target temperature for the third stream, and the second temperature may be dependent on the storage temperature. The first flow rate of the first stream may be dynamically adjusted to compensate for real-time fluctuation in the second temperature of the second stream to reduce a difference between the target temperature and the third temperature of the third stream. The third stream may be then injected at the third temperature into the reservoir. Adjustment of the first flow rate may be based on actual fluctuation in the second temperature. The actual fluctuation in the second temperature may be measured in real-time. Adjustment of the first flow rate may also be based on an expected change of the second temperature.
The solvent may be stored in a container exposed to solar radiation such as sunlight during daytime, and the expected change of the second temperature may be determined at least in part based on expected natural fluctuations in the sunlight over time. The natural fluctuations in the sunlight may comprise daily fluctuations and seasonal fluctuations. An exterior surface of the container may be coated with a light absorbing coating to increase heat energy absorbed by the container from the sunlight, for increasing the second temperature. A solar panel may be provided and heat energy may be transferred from the solar panel to the container to increase the second temperature. More broadly, the solvent may be stored in a container receiving heat from an energy source, and the expected change of the second temperature is Date Recue/Date Received 2020-11-02 determined at least in part based on expected fluctuations of the amount of heat received from the energy source. The energy source may be an external energy source (including an environmental thermal energy source), or an internal energy source (e.g. integrated with the storage container).

[0008] In a further aspect, there is provided a system for injecting steam and solvent into a subterranean reservoir to assist recovery of hydrocarbons therefrom, the system comprising: a first conduit for supplying a first stream comprising steam; a second conduit for supplying a second stream comprising a solvent; a third conduit connected to the first and second conduit for mixing the first and second streams to form a third stream and supplying the third stream comprising steam and the solvent for injection into the reservoir; a flow regulator in the first conduit for regulating a first flow rate of the first stream in the first conduit; a controller connected to the flow regulator, the controller configured and programmed to control the flow regulator to adjust the first flow rate of the first stream based on fluctuation in the second temperature of the second stream.

[0009] In various embodiments, the system may comprise a steam source connected to the first conduit for supplying steam at selected temperature, pressure and steam quality. The flow regulator may comprise one or more valves. The system may comprise a solvent source connected to the second conduit for supplying the solvent at a selected second flow rate. The solvent source may comprise a container exposed to sunlight during daytime, and the controller may be programmed to determine expected change in the second temperature at least in part based on expected natural changes in the sunlight over time, and to adjust the first flow rate based on the expected change in the second temperature. An exterior surface of the container may comprise a light absorbing coating for increasing heat energy absorbed by the container from the sunlight. The system may further comprise a solar panel connected to the solvent source for generating heat energy from sunlight and providing the heat energy to the solvent source to increase the second temperature.
The system may comprise a temperature sensor associated with the second conduit for detecting the second temperature, wherein the controller is programed to adjust the Date Recue/Date Received 2020-11-02 first flow rate based on fluctuation in the detected second temperature. The controller may comprise a processor or a computer. The third conduit may be in fluid communication with an injection well penetrating the reservoir for injecting the third stream into the reservoir through the injection well.

[0010] Other aspects, features, and embodiments of the present disclosure will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the disclosure in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In the figures, which illustrate, by way of example only, embodiments of the present disclosure:

[0012] FIG. 1 is a schematic side view of a hydrocarbon reservoir and a pair of wells penetrating the reservoir for recovery of hydrocarbons.

[0013] FIG. 2 is schematic block diagram of a possible arrangement in the surface injection facility shown in FIG. 1, according to an embodiment of the present disclosure.

[0014] FIG. 3 is a line graph showing representative temperature profiles of a solvent stored in a solvent storage tank and corresponding temperature profile of the local environmental temperature over a period of about a week.

[0015] FIG. 4 is a line graph showing representative temperature profiles of the corresponding steam/solvent mixture and the stored solvent, in response to the local environmental temperature fluctuation as shown in FIG. 4.

[0016] FIG. 5 is a schematic block diagram of a control system for control the steam and solvent injection in the system of FIG. 2.
Date Recue/Date Received 2020-11-02

[0017] FIG. 6 is a line graph illustrating corresponding profiles of electricity usage in a power supply system and electricity usage for intermittent heating of the production zone in an embodiment of the present disclosure.
DETAILED DESCRIPTION

[0018] Selected embodiments of the present disclosure relate to methods of hydrocarbon recovery from a reservoir of bituminous sands assisted by injection of steam and solvent as mobilizing agents into the reservoir (referred to as steam-solvent recovery processes), and methods of controlling injection of steam and solvent into the reservoir in such processes.

[0019] In overview, it has been recognized by the present inventor(s) that an improved recovery outcome may be achieved by adjusting the steam injection rate based on the real time temperature fluctuation in the solvent storage temperature, in comparison to injecting the steam at a constant rate that is determined based on the desired solvent to steam ratio in the injection mixture. In particular, it is expected that in an embodiment disclosed herein comparable recovery performance, e.g., instant or cumulative oil or hydrocarbon production rates or both may be achieved at a reduced amount of overall steam injection.

[0020] Reducing the amount of injected steam not only can reduce operational costs associated with heating, storage, transportation, and injection of steam, but can also have positive environmental effects due to reduced consumption energy and reduced emission.

[0021] Another possible benefit is that, for a given oil production site with a steam generation plant having a limited steam generation capacity, where the total amount or rate of steam generation by the steam generation plant cannot exceed the capacity of the plant, if the steam usage for injection of the solvent is reduced, the saved steam Date Recue/Date Received 2020-11-02 may be redirected and used for other purposes or functions in the recover process at the same site. Thus, better steam utilization may be achieved with little or no increase in steam generation cost.

[0022] As used herein in various embodiments, the term "reservoir" refers to a subterranean or underground formation containing recoverable hydrocarbons (oil); and the term "reservoir of bituminous sands" refers to such a formation wherein at least some of the hydrocarbons are viscous or immobile in their native state, and are disposed between or attached to sands.

[0023] In various embodiments, the terms "oil", "hydrocarbons" or "hydrocarbon"
relate to mixtures of varying compositions comprising hydrocarbons in the gaseous, liquid or solid states, which may be in combination with other fluids (liquids and gases) that are not hydrocarbons. For example, "viscous hydrocarbons", "heavy oil", "extra heavy oil", and "bitumen" refer to hydrocarbons occurring in semi-solid or solid form and having a viscosity in the range of about 1,000 to over 1,000,000 centipoise (mPa.s or cP) measured at the native in situ reservoir temperature. In this specification, the terms "hydrocarbons", "oil", and "bitumen" may be used interchangeably unless otherwise specified. Depending on the in situ density and viscosity of the hydrocarbons, the hydrocarbons may include, for example, a combination of oil, heavy oil, extra heavy oil, and bitumen. The term "oil" when used generally may include "light"
oil, hydrocarbons mobile at typical reservoir conditions. Heavy crude oil, for example, may include any liquid petroleum hydrocarbon having an American Petroleum Institute (API) Gravity of less than about 20 such as lower than 6 , and a viscosity greater than 1,000 mPa.s. Extra heavy oil, for example, may have a viscosity of over 10,000 mPa.s and about 10 API Gravity. The API Gravity of bitumen typically ranges from about 12 to about 6 or about 7 and the viscosity of bitumen is typically greater than about 1,000,000 mPa.s.

[0024] The term "solvent" is also used herein in the broad sense. A
suitable solvent may be propane or butane. Other solvents may also be used in different embodiments.
Suitable solvents may also include diluents or condensates, such as natural gas Date Recue/Date Received 2020-11-02 condensates or natural gas liquids. The diluent may be selected from diluents suitable for use as additives to the produced hydrocarbons to facilitate transportation of the produced hydrocarbons by pipeline. The condensates may include condensates produced from the same reservoir formation or a different reservoir formation, and thus may also be readily available on site. Suitable solvents may include hydrocarbons such as, propane, butane, pentane, or hexane, or heavier hydrocarbons. A
combination of solvents may also be suitable in some embodiments.

[0025] An example embodiment of the present disclosure relates to a steam-solvent recovery for recovering hydrocarbons from a subterranean reservoir as illustrated in FIG. 1.

[0026] FIG. 1 schematically illustrates a typical well pair configuration in a hydrocarbon reservoir formation 100, which can be operated to implement an embodiment of the present disclosure. The well pair may be configured and arranged similar to a typical well pair configuration for steam-assisted-gravity-drainage (SAGD) operations, or a conventional steam-solvent recovery process.

[0027] The reservoir formation 100 contains viscous or heavy hydrocarbons below an overburden 110. Under the native conditions before any treatment, a reservoir of bituminous sands is typically at a relatively low temperature, such as about 12 C, and the formation pressure may be from about 0.1 to about 4 MPa, depending on the location and other characteristics of the reservoir.

[0028] The overburden 110 may be a cap layer or cap rock. Overburden 110 may be formed of a layer of impermeable material such as clay or shale. A region in the formation 100 just below and near overburden 110 may be considered as an interface region.

[0029] In example embodiments, the well pair includes an injection well 120 and a production well 130, which have horizontal sections extending substantially horizontally in reservoir formation 100, and are drilled and completed for producing hydrocarbons from reservoir formation 100. Wells 120 and 130 may be configured and Date Recue/Date Received 2020-11-02 completed according to any suitable techniques for configuring and completing horizontal in situ wells known to those skilled in the art. Injection well 120 and production well 130 may also be referred to as the "injector" and "producer", respectively.

[0030] As illustrated, wells 120 and 130 are connected to respective corresponding surface facilities, which typically include an injection surface facility 140 and a production surface facility 150. Surface facility 140 is configured and operated to supply injection fluids, including steam and at least one solvent, into injection well 120, and will be further described in more detail below. Surface facility 150 is configured and operated to produce fluids collected in production well 130 to the surface. Each of surface facilities 140, 150 includes one or more fluid pipes or tubing for fluid communication with the respective well 120 or 130.

[0031] As better illustrated in FIG. 2, the surface facility 140 includes a steam source such as a steam generation plant 402, and a supply line such as fluid pipe 404 connected to the steam generation plant 402 for supplying steam to injection well 120 for injection into the reservoir formation 100. A fluid flow regulator such as a valve 406 is provided in the fluid pipe 404 for regulating the fluid flow rate in the fluid pipe 404.
Devices and equipment for driving steam flow and measuring steam properties such as steam temperature and pressure may be provided in the steam generation plant 402 or along pipe 404, but for simplicity these devices and equipment are not shown in FIG. 2, as details of these devices and equipment are not necessary for understanding the present disclosure. For illustration purposes only, a flow meter 408 may be provided in the steam supply line, such as at fluid pipe 404 as depicted in FIG. 2, for measuring the steam flow rate in the steam supply line.

[0032] The surface facility 140 also includes a solvent source such as a solvent storage tank 412 and a supply line such as fluid pipe 414 for supplying the solvent to the injection well 120 for co-injection with steam. A flow regulator such as a valve 416 is provided in pipe 414 for regulating the fluid flow in pipe 414. A flow meter 418 is also Date Recue/Date Received 2020-11-02 provided to measure the fluid flow rate through pipe 414. Optionally, a pump 420 is provided to drive the fluid flow in pipe 414.

[0033] Valves 406, 416 may be any suitable fluid flow control valves for use under the particular operation conditions in a given embodiment. Existing valves used in steam and solvent supply lines in conventional steam-solvent recovery processes may be used. Valves 406 and 416 may be of the same type or be different, and may be selected so that valve 406 is suitable for controlling steam flow at the expected steam temperature and pressure ranges, and valve 416 is suitable for controlling flow of the particular solvent to be used.

[0034] Flow meters 408 and 418 may be any suitable fluid flow meters. They may be the same or of different types and measurement ranges selected for the particular application.

[0035] Optionally, surface facility 140 may include a heating facility (not separately shown) for pre-heating the solvent before injection.

[0036] Heating devices or heat insulation (not separately shown) may also be provided in one or more of the supply lines (e.g. pipes 404 and 414) for control or maintain the temperatures of the supplied fluids such as steam and solvents.

[0037] Both pipes 404 and 414 are connected to a mixing junction 422, which is connected to the injection well 120 through an input pipe 424, for mixing the steam and solvent before the mixture of steam and the solvent is injected into the reservoir formation 120.

[0038] As depicted, the mixing junction 422 is located at surface. However, in different embodiments, the mixing junction 422 may be located at surface, near or in the well head of injection well 120, or inside a section of the injection well 120. The input pipe 424 may be a separate pipe connected to the injection well, or may be a part of the injection well 210.
Date Recue/Date Received 2020-11-02

[0039] A temperature sensor 426 may be provided at the mixing junction 422 or downstream of the mixing junction 422 along the input pipe 424 for measuring the temperature in the mixture of steam and the solvent to be injected.
Temperature sensor 426 is selected and located to measure the temperature in the steam/solvent mixture in the mixing junction 422 or in the input pipe 424 near the mixing junction 422.

[0040] A temperature sensor 428 is also provided at the solvent storage, such as tank 412, for measuring the solvent storage temperature in real time.
Temperature 428 may be located at any suitable location in or adjacent tank 412 for measuring the storage temperature of the solvent. In an alternative embodiment, a temperature sensor such as sensor 418 may be provided in or along pipe 414 for measuring the solvent temperature before mixing.

[0041] The temperature sensors 426 and 428 may be any suitable sensors for detecting and measuring the fluid temperatures at the expected temperature ranges and pressures for the respective fluids (solvent or mixture of steam and solvent). For example, the temperature sensors may be selected from thermocouples, resistance temperature detectors (RTD), thermistors, thermometers, infrared temperature sensors, digital temperature sensors such as semiconductor based temperature sensing integrated circuit (IC), and the like.

[0042] When the mixing junction 422 is located downhole in the injection well 120, a distributed temperature sensing (DTS) device may also be used to detect the temperature or temperature changes in the mixture of steam and the solvent.

[0043] Optionally, one or more additional supply lines may be provided for supplying other fluids, additives or the like for co-injection with steam or the solvent.

[0044] While not expressly depicted, it should be understood that each supply line may be connected to a corresponding source of supply, which may include, for example, a boiler, a fluid mixing plant, a fluid treatment plant, a truck, a fluid tank, or the like. In some embodiments, co-injected fluids or materials may be pre-mixed Date Recue/Date Received 2020-11-02 before injection. In other embodiments, co-injected fluids may be separately supplied into injection well 120.

[0045] Surface facility 150 may include a fluid transport pipeline for conveying produced fluids to a downstream facility (not shown) for processing or treatment.
Surface facility 150 also includes necessary and optional equipment (not separately shown) for producing fluids from production well 130, as can be understood by those skilled in the art.

[0046] Other necessary or optional surface facilities 160 may also be provided, as can be understood by those skilled in the art. For example, surface facilities 160 may include one or more of a pre-injection treatment facility for treating a material to be injected into the formation, a post-production treatment facility for treating a produced material, a control or data processing system for controlling the production operation or for processing collected operational data.

[0047] Surface facilities 140, 150 and 160 may also include recycling facilities for separating, treating, and heating various fluid components from a recovered or produced reservoir fluid. For example, the recycling facilities may include facilities for recycling water and solvents from produced reservoir fluids.

[0048] Injection well 120 and production well 130 may be configured and completed in any suitable manner as can be understood or is known to those skilled in the art, so long as the wells are compatible with injection, and optionally recovery, of a selected solvent to be used in a steam-solvent recovery process as will be disclosed below.

[0049] For example, in different embodiments, the well completions may include perforations, slotted liner, screens, outflow control devices such as in an injection well, inflow control devices such as in a production well, or a combination thereof known to one skilled in the art.

[0050] FIG. 1 shows wells 120, 130 in formation 100 during a recovery process where a vapour chamber 360 has formed.

Date Recue/Date Received 2020-11-02

[0051] As illustrated, each of injection well 120 and production well 130 has a casing 220, 230 respectively. An injector tubing may be positioned in injector casing 220 and connected to input pipe 424 for receiving the mixture of steam and the solvent to be injected into the reservoir formation 100. The use of the injector tubing can be understood by those skilled in the art, and will be described below.

[0052] For simplicity, other necessary or optional components, tools or equipment that are installed in the wells are not shown in the drawings as they are not particularly relevant to the present disclosure.

[0053] In operation, wells 120 and 130 may be operated to produce hydrocarbons from reservoir formation 100 according to a process disclosed herein.

[0054] For example, in an embodiment the wells 120 and 130 may be initially operated as in a conventional SAGD process, or a suitable variation thereof, as can be understood by those skilled in the art. In this initial process, steam may be the only or the dominant injection fluid.

[0055] Alternatively, steam and a solvent may be co-injected at the start of the production stage after the start-up stage.

[0056] In any event, both steam and one or more solvents are injected during at least one period of the production stage, and the following description is focused on such injection period. Optionally, a non-condensable gas such as methane may also be injected with the steam and the solvent.

[0057] Steam is supplied by steam generator 402 to junction 422 through pipe 404, and a solvent such as propane is supplied by solvent tank 412 to junction 422 through pipe 414, as illustrated in FIG. 2. The steam flow may be driven by steam generator 402 and regulated by valve 406. The steam flow rate may be measured using flow meter 408. The solvent flow may be driven by pump 420 and regulated by both valve 416 and pump 420. The solvent may be supplied to junction 422 in the liquid phase or gas phase, or in both phases. The solvent may be compressed during storage. In an embodiment, the solvent may be supplied to pipe 414 as a liquid. In a different Date Recue/Date Received 2020-11-02 embodiment, the solvent may be stored in a liquid state and supplied to pipe 414 as a vapor, or heated and vaporized in pipe 414 before the solvent is supplied to junction 422. The solvent flow rate is measured by flow meter 418. The solvent temperature (Ts01) is detected by temperature sensor 428. The temperature (Tm) in the mixed stream and solvent after junction 422 is detected by temperature sensor 426.

[0058] For steam-solvent co-injection, at given injection temperature and pressure of the injected mixture, and given expected average solvent storage temperature and steam supply conditions (including steam temperature, pressure and quality), the initial or base solvent injection rate and steam injection rate may be determined.

[0059] Determination of the base injection rates may be based on a selected solvent-to-steam ratio in the injection stream in pipe 414 for optimal production performance or other considerations, as can be understood by those skilled in the art.
For example, a target solvent to steam ratio may be selected according to the techniques disclosed in CA 3,027,274. The target solvent to steam ratio may be determined in consideration of a number of factors as will be understood by those skilled in the art, and further explained below.

[0060] For a given solvent to steam ratio, a corresponding target temperature, Tt, in the injection stream (mixture) in pipe 424 can also be determined. It is noted that the actual temperature in the injection stream (mixture) in pipe 424 may vary over time and is not necessarily the same as the target temperature Tt at any given time.

[0061] As some flow characteristics and thermodynamic properties of steam and solvent flows in pipe 404 and 414 can affect the dependency of lion the target solvent to steam ratio, the actual relevant flow characteristics and thermodynamic properties of steam and the solvent may also be determined or obtained. For example, the steam temperature and pressure and steam quality may be measured or already known based on information obtained from the steam generation process at steam generator 402. It is also possible to measure actual steam temperature and pressure in pipe 404 using suitable temperature and pressure sensors (not shown) installed in pipe 404.

Date Recue/Date Received 2020-11-02

[0062] The solvent temperature may be determined based on the storage temperature of the solvent in storage tank 412 as detected by temperature sensor 428.
The solvent pressure may also be determined or measured based on the storage pressure of the solvent in storage tank 412 or the pump pressure at pump 420, depending on the situation, using a pressure sensor (not shown). The pressure of the solvent may also be determined based on the solvent temperature without directly measurement using a pressure sensor.

[0063] In different embodiments, the solvent temperature and pressure may also be measured in pipe 414 using suitable sensors (not shown).

[0064] The flow rate of the solvent stream in pipe 414 can be directly measured using flow rate meter 418.

[0065] Some of these quantities or operation parameters may be obtained based on estimation or modeling and do not need to be directly measured in some embodiments. For example, the flow rate or pressure of the solvent may be estimated based on the pumping speed of pump 420.

[0066] For illustration purposes only, in a simple case, the temperature of a mixture of two fluids may be calculated as follows in Equation (1), assuming there is no phase change (e.g., no evaporation or condensation) and no other net energy loss/gain in the system during mixing:
Tfinal = M1 C1 T1 + 1772 C2 T2, (1) where "mi" represents the mass of each input fluid "i", "c" represents the specific heat of the input fluid, Ti"" represents the temperature of the input fluid before it is mixed with the other fluid, and "7-final" is the temperature of the mixture of the two fluids.

[0067] The solvent to steam ratio in a mixture of steam and solvent may be calculated by mseiven / t. Msteam , where mseivent and Msteam are the masses of solvent and steam in the mixture respectively, or by rseivent/rsteam, where rseivent and rsteam are the injection rates of solvent and steam respectively. Equation (1) may be thus rewritten as Date Recue/Date Received 2020-11-02 Equation (2) to provide the relation between the target mixture temperature and the selected solvent to steam ratio:
Tr = grsolvent/rsteam) ci Ti + C2 T23 rSteaM
= [(solvent to steam ratio) ci Ti + c2 T2,) rsteam. (2)

[0068] The relationship or correlation between the temperatures and the target solvent to steam ratio can be more complicated in practice, such as when more fluids are involved, or in non-ideal situations such as when there is heat loss/gain or phase change during mixture.

[0069] The more complicated relationships can be determined using models or using known techniques, including computer modeling software products commercially available.

[0070] As can be appreciated by those skilled in the art, the target temperature Tt at temperature sensor 426 can be determined based on the target solvent to steam ratio, and the relevant flow and thermodynamic characteristics and properties determined/obtained as described above. For example, a person skilled in the art would understand how to calculate the target temperature Tt for a given solvent to steam ratio (on the basis of weight, volume, or molar percentages) and the relevant flow and thermodynamic information of the input streams. For example, the temperature of the mixture may be affected by the temperatures of the input steam and solvent, the solvent to steam ratio (or in weight/molar percentages of the solvent) in the mixture, the steam quality and the phase(s) of the input solvent and the phase(s) of the solvent in the mixture. As can be understood, the solvent to steam ratio is directly dependent on the flow rates of input steam and solvent.

[0071] The target temperature Tt may be previously known, and may be a constant over a period of time, but may also be dynamically determined in real time from time to Date Recue/Date Received 2020-11-02 time, continuously, at regular intervals, or periodically based on detected or other input values that may fluctuate or change over time.

[0072] For example, the injection temperature may be selected in part based on the selected solvent and its thermodynamic properties and the target pressure in the injection stream. For instance, in some embodiments, gaseous propane may be injected, as a minimum criteria, at 2 MPa and 60 C or 70 C, or at 3 MPa and C. When the steam pressure is 3.1 MPa with the temperature of 303 C, and the downhole pressure is 3.2 MPa, propane may be injected at an injection rate of 1.3 t/hr and steam may be injected at an injection rate of 2.17 t/hr, with the overall mixture temperature of 185 C.

[0073] It is also possible to determine the correlation between the steam flow rate R
in pipe 404 and the temperature (T) in pipe 414 based on the known flow and thermodynamic characteristics/properties of the input streams. This correlation may be calculated based on a theoretical or a simulation model, or may be empirically determined based on experimental or field data, or may be based on both. For example, the correlation may be completely based on calculation using known flow dynamic and thermodynamic relationships and measured input data. The correlation may be completely based on testing using direct flow rate measurements under the same or similar flow and thermodynamic conditions. Some correlation information may be extrapolated from calculations or testing data for higher or lower flow rates.

[0074] For a given target solvent to steam ratio, the target temperature Tt and target steam flow rate (Rt) corresponding to the target solvent to steam ratio can be determined based on the correlation.

[0075] The flow rate of the input steam stream and the flow rate of the input solvent stream can be separately measured using flow meters 408 and 418 installed in the input pipes 404 and 414 respectively, and can be regulated or controlled using flow valves 406 and 416 to achieved the selected or desired rates. The flow rates may be manually controlled based on the flow meter readings, or may be automatically controlled. In some embodiments, a flow rate in one of the supply lines may be Date Recue/Date Received 2020-11-02 estimated or determined without using a flow meter in the supply line. For example, the flow rate may be estimated based on the correlation between the flow rates and the temperatures of the input steams and the temperature of the injection stream of the mixed steam and solvent.

[0076] Optionally, a correlation between the temperature in pipe 414 as detected by sensor 426 (T) and the steam flow rate (R) in pipe 404 may be obtained or determined.

[0077] This correlation between T and R may be already known to the operator, may be pre-determined once before or during the control process, or may be determined repeatedly during control process, as will be further discussed below. The correlation may be expressed as a formula (e.g. R = f (T), where "f' represents a mathematical function), a correlation (mapping) table or the like, and may be presented to the operator by any visual devices or calculated by a computer in real-time using an algorithm or routine.

[0078] For example, the correlation between T and R may be determined based on the relevant flow and thermodynamic characteristics of the steam flow and solvent flow in pipes 404 and 414. Relevant flow and thermodynamic characteristics of a flow may include the temperature, pressure, and flow rate, as wells the phase state or quality of the fluid (e.g. vapor or liquid). For a flow of saturated steam, the steam quality is relevant in this context as the steam quality is related to the total enthalpy of the steam stream and can affect the heat transfer and resulting temperature in the steam-solvent mixture after the steam and solvent is mixed. Steam quality refers to the proportion of steam (vapor) in a saturated mixture of steam (vapor) and condensate water (liquid).

[0079] Steam and the solvent can be continuously supplied to pipe 424 at junction 422 at the selected solvent flow rate and an initial steam flow rate, which may be typically below or slightly higher than the target or base steam flow rate (Rt), and the actual mixture temperature Ta in pipe 424 is detected at sensor 426.

Date Recue/Date Received 2020-11-02

[0080] When the solvent temperature and solvent injection rate remain constant over time, the steam flow rate R in pipe 404 may be adjusted based on the detected Ta, and the target temperature Tr. For example, the difference (AT) between the detected temperature Ta and the target temperature Tt in pipe 424 may be calculated as AT = Ta ¨ Tt. If AT < 0, more steam is required to reach the base target temperature Tt to provide the target solvent to steam ratio, the steam flow rate R in pipe 404 is increased by opening up the flow valve 406. If AT> 0, less steam is required to provide the target solvent to steam ratio, the steam flow rate R in pipe 404 is decreased by closing down the flow valve 406. If LIT= 0, or when AT is within an acceptable range, the steam flow rate does not need to be adjusted, and the steam flow rate R in pipe 404 may be maintained at a constant level, i.e., at the target temperature. In practice, the temperature response to the steam flow rate adjustment may not be instantaneous, and a delay time may be required after any adjustment of the steam flow before the temperature T in pipe 424 is stabilized. For more accurate flow adjustments, A T should be calculated based on Ta detected at a time when the temperature Tin pipe 424 is substantially stable. The above adjustment may be repeated until the co-injection operation is terminated or suspended, or the control process is no longer needed in the recovery process.

[0081] As can be appreciated by those skilled in the art, when the steam flow rate R
is adjusted to provide the target temperature Tt, it is expected that the solvent to steam ratio in the injection stream in pipe 424 should be the corresponding target solvent to steam ratio, or is close to the target solvent to steam ratio within an acceptable tolerance range. Therefore, the above process in effect adjusts the steam flow rate R
to reach the target solvent to steam ratio based on the detected Ta, provided that the correlation between R and solvent to steam ratio as reflected through Tt and the correlation between the mixture temperature and the steam flow rate, including the solvent storage (injection) temperature, remain substantially unchanged over the period of injection.

[0082] However, in practice, the solvent storage temperature may not remain substantially constant over a long period of time. For example, significant temperature Date Recue/Date Received 2020-11-02 fluctuation in the solvent storage may occur due to the normal cycles of sun set and sun rise over days, and due to seasonal temperature changes on earth at the storage location.

[0083] FIG. 3 shows a representative temperature profile in a solvent storage tank over time (about a week) and the corresponding environment temperature profile. The storage tank was not temperature controlled, so the solvent storage temperature fluctuates over time with the local environmental temperature and any radiation heating from sunlight, which went through the normal daily cycles.

[0084] As can be seen from FIG. 3, in this particular case, the solvent storage temperature can increase or decrease significantly, by about 15 to 18 C over a day, and more over the time of a week.

[0085] In this case, if the steam injection rate is kept constant for the selected Tt, based on an expected input solvent temperature of, say, 45 C, the same steam injection rate would not be sufficient to achieve the Tt during the night or early morning when the solvent temperature is below about 40 C, but would be too high in the afternoon when the solvent temperature is above about 50 C. That is, in the early morning, insufficient heat energy is provided by the steam, and production performance may be negatively affected; but in the afternoon, an oversupply of heat energy is provided by the steam, which may not cost-effectively increase production performance.

[0086] This effect is illustrated in FIG. 4, where the corresponding temperature of the mixture of steam/solvent also fluctuated when the solvent and steam injection rates were kept constant. The general trend of the change in the mixture temperature correspond to the change in the solvent temperature. Additional minor fluctuations in the mixture temperature seen in FIG. 4 may be due to relatively small changes in the steam supply.

[0087] If the steam injection rate was to be adjusted merely based on the detected Ta to maintain the target temperature Tr, it would not provide the desired target solvent Date Recue/Date Received 2020-11-02 to steam ratio over the period of one day, as in the early morning more steam would be required so the solvent to steam ratio in the early morning is lower than the target solvent to steam ratio and in the afternoon less steam would be required so the solvent to steam ratio in the afternoon is higher than the expected value. In either case, the optimal performance may not be achieved.

[0088] Instead, improved or optimal performance can be achieved according to an embodiment of the present disclosure by taking into account of the real time fluctuation of the solvent temperature, where the steam injection rate is decreased when the solvent temperature is higher than the base solvent temperature used to determine the Tr, and is increased when the solvent temperature is lower than the base solvent temperature, to compensate for the real time fluctuation in the input solvent temperature.

[0089] Considered in an alternative way, in an embodiment of the present disclosure, the goal of adjusting steam flow rate is not to maintain constant the solvent to steam ratio at a target value or to change the target temperature in the mixture, but to maintain the mixture temperature at a selected value such as a target value that has already been reached, in which case the steam flow rate may be adjusted over time in synchronization with the solvent temperature fluctuation, so that the steam injection rate is higher when the solvent temperature is lower and the steam injection rate is lower when the solvent temperature is higher, to compensate for the heat energy the solvent absorbed from or lost to the environment, such as due to the cyclic nature of sunlight.

[0090] In further embodiments, additional measures may be taken to account for factors that can affect the solvent storage temperature, or take advantages of the environmental temperature changes or solar energy changes.

[0091] For example, to reduce loss of heat energy from the solvent tank 412 to the environment, and to increase absorption of solar energy from sunlight into the solvent stored in the solvent tank 412, the exterior of the solvent tank 412 may be painted a dark color such as black. Thermal insulation may be provided outside the tank Date Recue/Date Received 2020-11-02 during the winter season, or when the temperature is lower than a certain threshold, and light absorbing materials may be used to absorb sunlight during the day.

[0092] A solvent storage container may also be otherwise coated with a light absorbing coating to increase heat energy absorbed by the container from the sunlight, for increasing the temperature of the stored solvent.

[0093] In alternative embodiments, solar panels may be used to store thermal energy during the day and provide the stored energy to the stored solvent during the night, such that the temperature fluctuation in the storage tank is reduced over the period of a day.

[0094] The injection rates may be regulated and controlled manually, automatically, or semi-automatically. For example, a control system such as the system 500 illustrated in FIG. 5 may be used to control the injection rates.

[0095] As depicted, system 500 includes a controller 502, which may be connected to steam generator 402, valve 406, pump 420, valve 416, flow meter 418 and temperature sensors 426 and 428, for controlling the operation of valves 406, 416, and optionally steam generator 402. Controller 502 may optionally be connected to input devices or sensors (not shown) that can provide data or signal indicative of the properties of the solvent, such as pressure and other information, stored in solvent tank 412. The connection between any two devices may be wired or wireless, and may be direct or through one or more intermediate communication or control devices, as can be understood by those skilled in the art.

[0096] Controller 502 may include one or more processors such as microprocessors or computing units such as one or more central processing units (CPU) or specialized processing circuits units. In some embodiments, a general purpose computer may be used, and is specifically configured and programed to perform the some of the functions and methods described herein.

[0097] For example, in some embodiments, system 500 may include a PID
(proportional integral derivative) controller for controlling temperature, which is Date Recue/Date Received 2020-11-02 connected to sensors 426 and 428 to receive the respective detected temperatures as feedback input, and outputs a control signal to close or open valve 406 as the control element. The target temperature values of Tt may be determined by a processor in controller 502 in real time based on the detected solvent storage temperature from sensor 428, or may be pre-set to vary according to a time-dependent formula or table.

[0098] The PID may be a digital PID or analog PID. In other embodiments, a PD
(proportional-derivative) or PI (proportional-integrated) controller may be used to control the valve 406 based on the detected temperature, depending on the particular application.

[0099] In some embodiments, a programmable controller such as programmable logic controller (PLC) may be included in system 500. A programmable automation controller (PAC) may also be included in system 500.

[00100] In some embodiments, system 500 may be configured as a distributed control system (DCS), and may include a supervisory control computer and a number of controller or control units.

[00101] System 500 may also be configured to provide advanced process control (APC). For example, system 500 may be configured to provide multivariable model predictive control (MPC), including nonlinear MPC. The APC system may be based in part on inferential measurements of some variables, such as one or more of the temperature and pressure of steam in pipe 404, the temperature of the solvent in pipe 414, and the flow rate of the solvent in pipe 414.

[00102]
System 500 may be configured to provide continuous control of valve 406. It is also possible in some embodiments that system 500 is configured and programmed to provide sequential control where valve 406 is controlled and adjusted in time- or event-based automation sequences. For example, a triggering event for an automated control sequence may be a change, either detected or expected based on historical data, in the input solvent temperature due to environmental condition (e.g.
temperature or sunlight) fluctuations or process. Other changes may also trigger a Date Recue/Date Received 2020-11-02 control sequence, including a change in injection condition (such as those dictated by recovery process considerations), a change in the solvent supply (e.g., batch change, truck change, flow rate change or the like), a change in the steam supply (e.g., a temperature or pressure change, or a change in steam quality), or the like. An automated control sequence may also be started at pre-defined times, or after a given time interval, or at regular time intervals, for example to account for daily or seasonal sunlight changes.

[00103] System 500 and controller 502 may also be configured and programmed to provide simulation-based control or optimization of the control of valve 406 for controlling the steam injection rate R.

[00104] Suitable controllers may include controller or control systems configured to run, and installed with, suitable simulation software, such as software available from HoneywellTM under the brand name UNISIMTm.

[00105] One or more reservoir simulation algorithms or software with fluid transport and heat transfer calculations may be used to provide used to provide needed information for control.

[00106] As depicted in FIG. 5, system 500 may also include a computer or processor readable storage media, such as memory 504, for storing both processor executable instructions and data needed to perform the injection control process and optionally other functions or tasks. Memory 504 may include any suitable computer memory devices or storage devices. In particular, memory 504 may store thereon processor executable instructions, which when executed by a processor causes controller 502 to perform the control process.

[00107] System 500 may further include input/output (I/O) interface devices, communication devices (not separately shown) for communication with other connected devices, and for receiving input from a user and for outputting control signals or presenting information to the user.

[00108] In particular, during operation, control system 500 may receive input from Date Recue/Date Received 2020-11-02 a user for determining the target injection temperature Tt. Control system 500 may also communicate with the steam generator 402 or devices associated with the steam generator 402 to obtain operation parameters and information about the input steam, such as its temperature, pressure, steam quality, and the like.

[00109] Controller 502 may also be connected to input devices or sensors such as temperature sensor 428 or flow meter 418, which are associated with the solvent source or a solvent transportation line, such as the solvent tank 412 or pipe line 414.
Controller 502 may receive data or signal indicative of the properties of the solvent, including its temperature and optionally other information, stored in the solvent source such as solvent tank 412, or the transported through the transportation line such as pipe line 414. Alternatively, such information about the solvent may be input by a user or operator.

[00110] Control system 500 may further communicate with flow meter 408, or optionally steam generator 402, to obtain the flow rate of the solvent stream in pipe 404.

[00111] Control system 500 may further communicate with flow meter 418, or optionally pump 420, to obtain the flow rate of the solvent stream in pipe 414.

[00112] Control system 500 may communicate with temperature sensors 426 and 428 directly or indirectly, through wired or wireless connections, to receive the temperature feedback from temperature sensors 426 and 428. Control system 500 may receive a digital or analogue signal from temperature sensors 426 and 428.

[00113] Optionally, control system 500 may be configured and programmed to receive an input of the target solvent to steam ratio, and in response to receiving the target solvent to steam ratio, determine the corresponding base target Tt in pipe 424 based on the target solvent to steam ratio and the current flow and thermodynamic parameters and characteristics, such as by calculation or by searching a data structure (e.g. mapping table) stored in system 500. Optionally, system 500 may be configured and programmed to receive an input from a user or another device that indicates the Date Recue/Date Received 2020-11-02 base target Tt. Control system 500 may be further configured and programmed to adjust target Tt based on historical information or detected temperatures to account for real time fluctuations in the solvent storage temperature.

[00114] System 500 may be configured and programmed to determine a dynamic correlation between the steam flow rate in pipe 404 and the temperature in pipe 414 based on stored information including the flow and thermodynamic parameters and characteristics described herein, and the time-dependent solvent temperature.

[00115] During operation, system 500 may control the steam flow rate in pipeline 404, such as by adjusting the valve 406, or the pumping speed of a pump (not shown) either located along pipeline 404 or at steam generator 402, based on the detected or expected temperature fluctuation in the stored solvent at tank 412. For example, controller 502 may process temperature signals from sensor 428 and adjust the valve 406 to regulate the steam flow rate in pipeline 404 so that the mixture temperature at line 424 is stable at or close to the selected target temperature Tt over time, even when the solvent temperature fluctuates due to changes in the environmental conditions. Alternatively, controller 502 may access stored data on memory 504 to predict the expected solvent temperature in tank 402, and adjust the valve 406 to regulate the steam flow rate in pipeline 404 accordingly.

[00116] In some embodiments, the mixture temperature Tt may optionally vary or be adjusted, such as to provide improved or optimal performance results.
However, in such cases, the steam flow rate is still adjusted to account for the real time temperature fluctuations in the input solvent stream, so as to reduce unnecessary or less efficient steam usage.

[00117] In a further embodiment, the base solvent to steam ratio may be determined based on the expected solvent temperature, which may be referred to as the reference or base solvent temperature. However, since the solvent to steam ratio may be different at different solvent input temperatures, the actual target solvent to steam ratio may be adjusted in view of the actual solvent temperature, and the steam flow rate or the solvent flow rate may be adjusted to maintain the solvent to steam ratio Date Recue/Date Received 2020-11-02 at the optimal value that corresponds to the actual solvent temperature in real time, instead of maintaining the solvent to steam ratio at the fixed value of the base solvent to steam ratio determined based on the reference/base solvent temperature.

[00118] In an example, assume that the solvent may be injected at a rate of 40 lid and the steam may be injected at a rate of 26 t/d to achieve a target mixture temperature of 190 C, and that when the solvent is pre-heated by solar radiation and the solvent and steam are still injected at the same rates, the mixture temperature may reach 200 C. Then, with the pre-heated solvent, it is possible to reduce the steam injection rate to lower the mixture temperature back to 190 C. The steam injection rate may be reduced incrementally, e.g., by 0.1 t/hr at each iteration. The mixture temperature may be monitored and the steam injection rate may be automatically or manually reduced by the selected increment until the mixture temperature reaches the target mixture temperature of 190 C.

[00119] In view of the above factors and considerations, once the solvent has been selected and the conditions of the input materials to the injection stream have been determined, the target injection temperature may be selected, or optionally, the base target solvent to steam ratio may be selected, according to the above descriptions as can be understood by those skilled in the art.

[00120] When the correlation between the mixture temperature and the steam injection rate (such as a baseline rate or reference rates) is established for given injection conditions, e.g., by simulation, calibration, testing, or combination thereof, steam injection rate may be controlled based on the detected mixture temperature and the detected or expected solvent temperature, without determining or calculating the actual solvent to steam ratio (or any weight, volume, or molar percentage of steam or solvent) in the mixture.

[00121] In selected embodiments, the increase and decrease of the steam injection rate may also be controlled taking into account of the electricity costs at the time. For example, when the steam generation and transport require electrical power, reducing the steam injection rate can reduce the instant electrical power consumption.

Date Recue/Date Received 2020-11-02

[00122] It is common that the electricity usage in a power grid will fluctuate over time and have regular peak periods and off-peak periods. Typically, in peak periods when the general demand for electrical power is higher in a power supply network, the electricity cost will be higher, and in the off-peak periods when the demand for electrical power is lower, the electricity cost will be lower. Many utility and electrical power providers will charge a higher rate during the day when electrical power consumption in the local region is higher and a lower rate from after mid-night to early morning when the electrical power consumption in the local region is lower.

[00123] Conveniently, when the steam injection rate is adjusted as described above in view of the daily fluctuation of the solvent storage temperature and the solvent storage temperature fluctuates mainly due to the daily cycle of the sunlight and environmental temperature changes, the steam injection rate is intermittently increased and decreased over daily cycles, where the increased steam injection rate at late night and early morning can be less costly because of the reduced electricity cost at that time, and the decreased steam injection rate during the day can also reduce costs as at the time the electricity cost is relatively higher.

[00124] In some embodiments, the adjustment of the steam injection rate may be further timed to better synchronize with the daily electricity cost changes.
For example, as schematically illustrated in FIG. 8, the steam injection rate (or the overall electricity consumption at the site) may have a profile that tracks or matches the peak and off-peak usage in the power source (e.g. a power grid in this depicted example).
In FIG. 8, the bottom line represents the general electricity usage in a power grid, where ti, t2, t3, t4 and t5 represent different points in time, such as different times in a day. It is also assumed that different electricity costs or charge rates would apply depending on the electricity usage levels at the time. Accordingly, to optimize electricity usage, the steam injection rate, represented by the top line in FIG. 8, may have the profile as shown, to take advantage of the fluctuations of electricity cost over the day.
Such changes in the steam injection may be referred to as intermittent injection.

[00125] In some embodiments, the input solvent may be heated before injection Date Recue/Date Received 2020-11-02 and the heating power used to heat the solvent may also be adjusted in view of the electricity cost fluctuations. In particular, the input solvent may be subjected to intermittent heating.

[00126] Such intermittent injection and intermittent heating may be more economical and, when scheduled appropriately, may not negatively affect the production performance significantly. The process may be, for example operated intermittently so as to reduce or minimize the overall operating expenses (OPEX) associated with electricity usage for the recovery process, including steam generation and injection and any heating of the input materials or even direct electrical heating in the wells.

[00127] For example, the electricity cost to the operator of the recovery process may be substantially reduced during the off-peak period, as compared to the peak period. Cyclically alternating between increased injection/heating and reduced injection/heating over 24 hour cycles as described herein may not significantly affect the injection temperature of the injected mixture and the average temperature in the reservoir.

[00128] Thus, an additional factor for selecting the injection rates and injection rate profiles may include the electricity costs at different time periods during a day or different days of the week or in different seasons.

[00129] As now can be appreciated, the embodiments described above may be modified for application in different contexts or for more general applications.

[00130] To further illustrate embodiments of the present disclosure, some non-limiting and representative examples are discussed below.

[00131] Examples

[00132] Example I

[00133] In a particular example, propane was used as the solvent and injected with steam into a well for recovery of oil from a bitumen reservoir.

Date Recue/Date Received 2020-11-02

[00134] At selected target injection conditions and assuming the solvent would be at room temperature, it was determined that the optimal steam injection rate should be 0.4 ton/hr when the propane injection rate was 1.7 ton/hr for injection at 3 MPa and 80 C.

[00135] However, during injection, it was observed that the resulting mixture temperature of steam and the solvent (Ta) were between about 113 C during the minimum atmospheric temperature and about 121 C at the maximum atmospheric temperature over the period of days in the summer, where the injection pressure was about 3.4 to about 3.7 MPa.

[00136] As noted earlier, propane may be injected at 2 MPa and 70 C, or at 3 MPa and 80 C. However, due to solar radiation heating of the solvent tank, the solvent storage temperature fluctuated over the day as shown in FIG. 3, where the storage temperature of the propane dropped to about 40 C at the lowest point and rose to about 54 C at the highest point. Taking into consideration of these fluctuations of the solvent storage temperature, for injection at a pressure of 2 MPa, the injection propane will only need to be heated by 16 C at the storage temperature of 54 C as compared to by 30 C at the storage temperature of 40 C, to reach the target 70 C.
For injection at the pressure of 3 MPa, the propane temperature would need to be increased by 26 C at the storage temperature of 54 C as compared to by 40 C
at the storage temperature of 40 C, to reach the target 80 C. The steam injection rate could thus be reduced from about 1 ton/hr (at the lower solvent storage temperature) to about 0.4 ton/hr (at the higher storage temperature). The steam injection rate might be adjusted, such as further reduced, as long as the target temperature in the injection mixture of steam and solvent can be achieved.

[00137] The steam injection rate was thus controlled as follows.

[00138] For injection pressure of 3 MPa, the target injection temperature (Tt) was fixed as a constant at 80 C. Propane in the gas phase was mixed with steam.
Date Recue/Date Received 2020-11-02

[00139] The propane storage temperature is monitored, and the steam injection rate was increased when the propane temperature dropped over night, and was decreased when the propane temperature rose during daylight. The steam injection rate was varied and regulated to maintain the target injection temperature Tt.

[00140] The steam injection rate increase and decrease were repeated each day.

[00141] Less than 0.4 ton/hr injection rate was required to maintain the target temperature, and even less is required during daylight time.

[00142] CONCLUDING REMARKS

[00143] Various changes and modifications not expressly discussed herein may be apparent and may be made by those skilled in the art based on the present disclosure.

[00144] It will be understood that any range of values herein is intended to specifically include any intermediate value or sub-range within the given range, and all such intermediate values and sub-ranges are individually and specifically disclosed.

[00145] It will also be understood that the word "a" or "an" is intended to mean one or more" or at least one", and any singular form is intended to include plurals herein.

[00146] It will be further understood that the term "comprise", including any variation thereof, is intended to be open-ended and means "include, but not limited to,"
unless otherwise specifically indicated to the contrary.

[00147] When a list of items is given herein with an "or" before the last item, any one of the listed items or any suitable combination of two or more of the listed items may be selected and used.

Date Recue/Date Received 2020-11-02

[00148] Of course, the above described embodiments are intended to be illustrative only and in no way limiting. The described embodiments are susceptible to many modifications of form, arrangement of parts, details and order of operation. The invention, rather, is intended to encompass all such modification within its scope, as defined by the claims.

Date Recue/Date Received 2020-11-02

Claims (21)

WHAT IS CLAIMED IS:

1. A method of injecting steam and solvent into a subterranean reservoir to assist recovery of hydrocarbons therefrom, the method comprising:
injecting steam and a solvent into the reservoir; and adjusting a rate of steam injection based on real-time fluctuation of a storage temperature of the solvent to be injected.

2. The method of claim 1, wherein the storage temperature of the solvent is dependent on fluctuation in solar energy transferred to the solvent, and the rate of steam injection is adjusted to, at least in part, compensate for the fluctuation in the solar energy transferred to the solvent.

3. The method of claim 1, comprising:
mixing (i) a first stream comprising steam at a first temperature and (ii) a second stream comprising the solvent at a second temperature to form (iii) a third stream comprising steam and the solvent at a third temperature, wherein the first stream flows at a first flow rate and the second stream flows at a second flow rate, the first and second flow rates are selected based on a target temperature for the third stream, and the second temperature is dependent on the storage temperature;
dynamically adjusting the first flow rate of the first stream to compensate for real-time fluctuation in the second temperature of the second stream to reduce a difference between the target temperature and the third temperature of the third stream; and injecting the third stream at the third temperature into the reservoir.

4. The method of claim 3, wherein an adjustment of the first flow rate is based on actual fluctuation in the second temperature.

Date Recue/Date Received 2020-11-02

5. The method of claim 4, wherein the actual fluctuation in the second temperature is measured in real-time.

6. The method of claim 3, wherein an adjustment of the first flow rate is based on an expected change of the second temperature.

7. The method of claim 6, wherein the solvent is stored in a container exposed to sunlight during daytime, and the expected change of the second temperature is determined at least in part based on expected natural fluctuations in the sunlight over time.

8. The method of claim 7, wherein the natural fluctuations in the sunlight comprise daily fluctuations and seasonal fluctuations.

9. The method of claim 7 or claim 8, wherein an exterior surface of the container is coated with a light absorbing coating to increase heat energy absorbed by the container from the sunlight, for increasing the second temperature.

10.The method of any one of claims 7 to 9, further comprising transferring heat energy from a solar panel to the container to increase the second temperature.

11.The method of claim 6, wherein the solvent is stored in a container receiving heat from an energy source, and the expected change of the second temperature is determined at least in part based on expected fluctuations of the amount of heat received from the energy source.

12.A system for injecting steam and solvent into a subterranean reservoir to assist recovery of hydrocarbons therefrom, the system comprising:
a first conduit for supplying a first stream comprising steam;
a second conduit for supplying a second stream comprising a solvent;

Date Recue/Date Received 2020-11-02 a third conduit connected to the first and second conduit for mixing the first and second streams to form a third stream and supplying the third stream comprising steam and the solvent for injection into the reservoir;
a flow regulator in the first conduit for regulating a first flow rate of the first stream in the first conduit;
a controller connected to the flow regulator, the controller configured and programmed to control the flow regulator to adjust the first flow rate of the first stream based on fluctuation in the second temperature of the second stream.

13.The system of claim 12, comprising a steam source connected to the first conduit for supplying steam at selected temperature, pressure and steam quality.

14.The system of claim 12 or claim 13, wherein the flow regulator comprises a valve.

15.The system of any one of claims 12 to 14, comprising a solvent source connected to the second conduit for supplying the solvent at a selected second flow rate.

16.The system of claim 15, wherein the solvent source comprises a container exposed to sunlight during daytime, and the controller is programmed to determine expected change in the second temperature at least in part based on expected natural changes in the sunlight over time, and to adjust the first flow rate based on the expected change in the second temperature.

17.The system of claim 16, wherein an exterior surface of the container comprises a light absorbing coating for increasing heat energy absorbed by the container from the sunlight.

18.The system of any one of claims 14 to 17, further comprising a solar panel connected to the solvent source for generating heat energy from sunlight and providing the heat energy to the solvent source to increase the second temperature.
Date Recue/Date Received 2020-11-02

19.The system of any one of claims 12 to 18, comprising a temperature sensor associated with the second conduit for detecting the second temperature, wherein the controller is programed to adjust the first flow rate based on fluctuation in the detected second temperature.

20.The system of any one of claims 12 to 19, wherein the controller comprises a processor or a computer.

21.The system of any one of claims 12 to 20, wherein the third conduit is in fluid communication with an injection well penetrating the reservoir for injecting the third stream into the reservoir through the injection well.

Date Recue/Date Received 2020-11-02