CA2974752C - System and method for recovering solvents used during bitumen production - Google Patents

Abstract

A solvent recovery process is described, which can be used to recover relatively heavier, more valuable solvents used during an in-progress or recently completed continuous bitumen production process. The solvent recovery process operates by using a solvent that is relatively lighter than the previously used solvent to increase recovery of one or more of the heavier, more expensive solvents stranded or otherwise retained in the reservoir. The relatively lighter solvent remains in the vapour phase when injected in the chamber and maintains pressure in the reservoir, which acts to i) lower the partial pressure of the heavier solvent that is being targeted for recovery, resulting in vaporization of that solvent, and ii) displace the heavier solvent that is in the vapour phase. This can improve cost-effectiveness of various in situ bitumen recovery processes that use solvent at least in part, such as, for example, processes that use solvent with steam and/or electromagnetic heating.

Description

SYSTEM AND METHOD FOR RECOVERING SOLVENTS USED DURING BITUMEN
PRODUCTION
TECHNICAL FIELD
[0001] The following relates to systems and methods for recovering solvents used during bitumen production.
BACKGROUND

[0002] Bitumen is known to be considerably viscous, does not flow like conventional crude oil, and can be present in an oil sand reservoir. As such, bitumen is recovered using what are considered non-conventional methods. For example, bitumen reserves are typically extracted from a geographical area using either surface mining techniques, wherein overburden is removed to access the underlying pay (e.g., oil sand ore-containing bitumen) and transported to an extraction facility; or using in situ techniques, wherein subsurface formations (containing the pay) are heated such that the bitumen is caused to flow into one or more wells drilled into the pay while leaving formation rock in the reservoir in place. Both surface mining and in situ processes produce a bitumen product that is subsequently sent to an upgrading and refining facility, to be refined into one or more petroleum products, such as gasoline and jet fuel.

[0003] Bitumen reserves that are too deep to feasibly permit bitumen recovery by mining techniques are typically accessed by drilling wellbores into the hydrocarbon bearing formation (i.e. the pay) and implementing an in situ technology. There are various in situ technologies available, such as steam driven-based techniques (e.g., Steam Assisted Gravity Drainage (SAGD) and Cyclic Steam Stimulation (CSS)), steam-solvent co-injection techniques (e.g., expanding solvent-SAGD (ES-SAGD)) and waterless solvent-based techniques (e.g., N-Solv, Enhanced Solvent Extraction Incorporating Electromagnetic Heating (ESEIEH) also known as "EASE".

[0004] In a typical implementation of the SAGD method, a pair of horizontally oriented wells are drilled into the bitumen reserve, such that the pair of horizontal wells are vertically aligned with respect to each other and separated by a relatively small distance, typically in the order of several meters. The well installed closer to the surface and above the other well is generally referred to as an injector well, and the well positioned below the injector well is referred to as a producer well. The injector well and the producer well are then connected to various equipment installed at a surface site. The injector well facilitates steam injection into the reservoir. The injected steam propagates vertically and laterally into the reservoir in a formation referred to as a steam chamber. Latent heat released by the injected steam mobilizes the bitumen, which 23177848.1 drains due to gravity and is produced continuously along with condensed water in the producer well (i.e., continuous bitumen recovery process). SAGD can be used to achieve high production rates, but requires a continuous water supply and generates CO2 emissions due to the natural gas combusted for steam generation.

[0005] Solvent-steam co-injection methods involve co-injecting with steam a hydrocarbon solvent, which propagates into the reservoir along with steam in the vapour phase and condenses at the vapour liquid interface. Dilution of oil by the condensed solvent further reduces the viscosity of bitumen and the co-injected solvent may then be partially recovered with the production fluids and reused. For example, ES-SAGD involves co-injection with steam solvents having a close saturation temperature to that of steam (e.g., hexanes and diluents).

[0006] Waterless or "non-steam" solvent-based techniques rely on one or more solvents to mobilize the bitumen in the absence of steam. The solvent is typically injected as a vapour into the reservoir at a predetermined pressure. The solvent is typically, but not always, selected to be at the vapour boiling point at the bitumen chamber's temperature and pressure. As the solvent condenses it releases its latent heat, thereby both warming and dissolving the bitumen.
The combination of warming and liquid solvent dilution mobilizes the bitumen permitting it to flow.

[0007] For example, in heated solvent-based techniques, bitumen mobilized by a heated solvent (e.g., propane or butane) flows under the influence of gravity, to a production well. In ESEIEH/EASE techniques, radio frequency is used to heat an in situ bitumen reservoir and a solvent is provided to facilitate mobilization of the bitumen.

[0008] Hydrocarbon recovery techniques that utilize solvent at least in part facilitate mobilization of hydrocarbons at lower temperatures than are required for SAGD, at least because the viscosity of the bitumen is reduced by being dissolved by the solvent. However, the solvents used for dissolving bitumen can be considered expensive.

[0009] Partial recovery of solvents is possible. For example, the portion of the solvent present in the mobilized bitumen which is produced may be collected. However, a portion of the solvent is typically expected to not be recoverable, because it will have condensed into a liquid form and remain in the chamber, e.g., in the unrecovered bitumen reservoir and/or in the reservoir pore space, thereby reducing cost-efficiency of the bitumen recovery operation.
23177848.1 SUMMARY

[0010] In one aspect, there is provided a method for recovering solvent used during bitumen production, the method comprising: subsequent to injecting a first solvent into a bitumen reservoir to reduce the viscosity of the bitumen in the bitumen reservoir during a continuous bitumen production process, injecting a second solvent into the bitumen reservoir, wherein the second solvent is lighter than the first solvent, wherein the second solvent remains in the vapour phase when injected in a vapour chamber in the bitumen reservoir, wherein the second solvent maintains pressure in the bitumen reservoir, and wherein a bitumen containing fluid produced using the second solvent at least in part comprises a portion of the first solvent.

[0011] An advantage of the solvent recovery method described herein stems from the injection of a relatively lighter solvent after the injection of a relatively heavier solvent during a bitumen recovery process, to enable greater recovery of the previously injected solvent. As the chamber pressure decreases, either during a continued production process or after commencing wind-down or blowdown, at least one relatively lighter solvent is injected, allowing a greater proportion of the heavier and more valuable solvent to be recovered.
In an implementation of the method, a plurality of solvents, each being progressively lighter than one previously injected can be injected.

[0012] This transition from heavier to lighter solvents during a continuous production process allows for a greater recovery of previously used heavier solvent(s), at least because these heavier solvents can be recovered during the bitumen recovery process rather than at the end of the recovery process. .

[0013] The lightest solvent can be disposed at the end of the process using, for example, a non-condensable gas such as carbon dioxide (CO2). This can contribute both to additional recovery of solvent, and to sequestering CO2 in the formation.

[0014] The subsequent injection of relatively lighter solvents can be combined with other heat sources such as conductive heating, e.g., electrical, radio frequency antennae, hot oil closed loop, etc. It can also be appreciated that in other implementations, steam can be used in place of, or in conjunction with such a relatively lighter solvent to recover a previously injected solvent.
BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Embodiments will now be described by way of example only with reference to the appended drawings wherein:
23177848.1

[0016] FIG. 1 is a cross-sectional elevation view of a well pair used for a continuous solvent based oil recovery process;

[0017] FIG. 2 is a cross-sectional elevation view of a set of three well pair in a bitumen reservoir;

[0018] FIG. 3(a) is a cross-sectional elevation view of a well pair and surrounding region of solvent in a first solvent injection phase;

[0019] FIG. 3(b) is a is a cross-sectional elevation view of a well pair and surrounding region of solvent in a second solvent injection phase;

[0020] FIG. 3(c) is a is a cross-sectional elevation view of a well pair and surrounding region of solvent in a third solvent injection phase; and

[0021] FIG. 4 is a flow chart illustrating operations performed in a non-steam solvent-based continuous bitumen production process using a progression from heavier to lighter solvents.
DETAILED DESCRIPTION

[0022] A solvent recovery process is described herein, which can be used to recover relatively heavier, more valuable solvents used during an in-progress or recently completed bitumen production process. The solvent recovery process operates by using a solvent that is relatively lighter than the previously used solvent to increase recovery of one or more of the heavier, more expensive solvents stranded or otherwise retained in the reservoir. The relatively lighter solvent remains in the vapour phase when injected in the chamber and maintains pressure in the reservoir, which acts to i) lower the partial pressure of the heavier solvent that is being targeted for recovery, resulting in vaporization of that solvent, and ii) displace the heavier solvent that is in the vapour phase. This can improve cost-effectiveness of various in situ bitumen recovery processes that use solvent at least in part, such as, for example, processes that use solvent with steam and/or electromagnetic heating.

[0023] Turning now to the figures, FIG. 1 illustrates an example of a bitumen production site at a surface location 12 in a particular geographical region. The production site 10 is positioned to allow one or more well-pairs 14 to be drilled from the surface location 12 towards a bitumen reservoir (i.e., the pay 24). The one or more well-pairs 14 include an injector well 16 configured to inject solvent into the pay 24, positioned above a producer well 18 configured to recover a bitumen-containing fluid that has been mobilized by the injected solvent. The injector well 16 is typically located about 4 to 6 meters above the producer well 18, although a shorter or 23177848.1 longer distance is possible, as is a lateral offset. The one or more well-pairs 14 are drilled vertically into the overburden 22 towards and into the underlying pay 24, and as they are drilled become oriented substantially horizontally, such that the producer well 18 is above but near the formation 26 underlying the pay 24 (hereinafter the "underlying formation 26"). The one or more well pairs 14 are operated using surface production equipment 20. After determining the surface location 12 and production site 10, and determining where the one or more well-pairs 14 will be located at the production site 10 (e.g., by conducting typical computer simulations using geological and reservoir data), the corresponding locations of the production site 10 are drilled, as is known in the art.

[0024] After drilling the wells 16, 18, the surface production equipment 20 is installed in one or more production facilities for operating the one or more well pairs 14.
Completing a particular well for production can involve several steps, as is known in the art, and includes the installation of solvent injection apparatus for injecting solvent via the injector well 16, and can include the installation of other equipment for introducing an additional heat source into the injector well 16, e.g., steam and/or an electrical based heat source.

[0025] Typically, multiple well pairs 14 are drilled from the surface location 12 into the subsurface hydrocarbon-bearing formation to recover bitumen within the particular geographical area. FIG. 2 illustrates multiple well pairs 14 used to extract a targeted region of the pay 24, the view in FIG. 2 being towards and along the ends of the horizontal portions of the injector and producer wells 16, 18. It will be appreciated that three well pairs 14 are shown for illustrative purposes only and more or fewer well pairs 14 can be employed in different implementations.
as shown in FIG. 2.

[0026] Generally, the solvent recovery process described herein is applied after the injection of a first solvent into a bitumen reservoir during a bitumen production process. The first solvent can have been applied in a solvent-only process or a process that utilizes the first solvent with another source of heat, such as steam or an electrical heat source. The solvent recovery process described herein can be applied during the production process that utilizes the first solvent, or can be applied thereafter, e.g., after commencing wind-down or blowdown, in order to increase recovery of the first solvent. In one implementation, the solvent recovery process is combined with another in situ bitumen recovery process such as ESEIEH/EASE
that uses electromagnetic heating. It can be appreciated that in other implementations, the solvent recovery process can be combined with other heat sources such as conductive heating, e.g., electrical, radio frequency antennae, hot oil closed loop, etc. It can also be appreciated that in 23177848.1 other implementations, steam can be used in place of, or in conjunction with a relatively lighter hydrocarbon solvent to recover a previously injected solvent.

[0027] In an implementation, the method can be applied to a system comprising a well pair as shown in FIG. 1, with the first solvent having been injected as a vapour or liquid into the pay 24 from an injector well 16, preferably as a vapour. The first solvent is typically, but not always, selected to be at the vapour boiling point at the operating temperature and pressure of the chamber. The first solvent propagates vertically and laterally into the bitumen reservoir and condenses at the vapour liquid interface. Bitumen is mobilized by the condensation of, and latent heat released by, the first solvent, which dissolves a portion of the bitumen in the reservoir, thereby forming a first fraction comprising the first solvent and the mobilized bitumen. The mobilized bitumen then drains under the effect of gravity and is produced along with the first solvent from a producer well 18.

[0028] In the method disclosed herein, at a later time during the well life, e.g., during continued production or therefore, such as after commencing wind-down or blowdown, solvent injection is transitioned from the first solvent to a second solvent, or restarted using the second solvent. The second solvent is lighter than the first solvent, and remains in the vapour phase when injected in the chamber. This allows for the increased recovery of the first relatively heavier solvent, by maintaining pressure in the reservoir, acting to lower the partial pressure of the heavier first solvent being targeted for recovery resulting in vaporization of the relatively heavier solvent, and to displace the first relatively heavier solvent out of the chamber enabling its recovery. Over time, the second solvent can substantially replace the first solvent in the bitumen reservoir as the first solvent is displaced.

[0029] Optionally, at a later time, when the concentration of the first solvent in the recovered fluid has further decreased, the second solvent can be replaced with a third solvent, the third solvent being lighter than the second solvent, to allow for the increased recovery of the second solvent according to the mechanism discussed above.
Over time, the third solvent can substantially replace the second solvent in the bitumen reservoir as the second solvent is displaced.

[0030] An example of the presently described solvent recovery process would be with or following a thermal solvent recovery process that uses butane as the first solvent. During 23177848.1 the start-up and primary production phases, butane is injected, and a certain percentage of the injected butane would remain in the reservoir, either in liquid or gaseous form. Later on in the life of the well, some or all of the injected butane would be replaced by a lighter solvent, such as ethane, methane or CO2, allowing for the stranded butane to be produced to surface over a period of time, reducing the amount of this more valuable solvent being stranded in the reservoir. The application of this solvent recovery process would also allow for more bitumen to be produced by maintaining pressure in the reservoir that would have otherwise dropped, once butane injection ceases.

[0031] Optionally, at one or more later times, additional and subsequently lighter solvents may replace the heavier solvents previously injected into the bitumen reservoir, thereby facilitating continuous mobilization of bitumen in the pay 24, continuous production of bitumen and recovery of the heavier solvent(s) during the recovery process.
Transitioning to, or restarting injection with, progressively lighter solvent(s) may progress in succession or it may skip one or more compounds in the succession. In an implementation, transition to lighter solvents ends with a non-condensable gas such as, for example, nitrogen, methane or carbon dioxide; which can be left behind or "sequestered"
in the reservoir upon completion of the process.

[0032] The presently described method of solvent recovery can utilize a set of multiple solvents having different "weights" (i.e. being relatively lighter and relatively heavier), each of the solvents having a corresponding boiling point. An example of such a set of solvents is a set of alkane-based solvents. The method of solvent recovery can contribute to various bitumen recovery processes, while minimizing loss of heavier and more costly solvents by progressing from heavier to lighter solvents as the pressure in the vapour chamber decreases. The method of solvent recovery can achieve this by utilizing solvents from the set according to the relative weight of the solvent compared to a previously injected solvent. For example, with a relatively heavier alkane such as octane (i.e. relatively higher carbon solvent) that was injected into the bitumen reservoir at an early stage, at subsequent stages in the well life, progressively lighter alkanes such as butane, etc. (i.e. progressively lower carbon solvent) can be injected to maintain the pressure in the bitumen reservoir and act to vaporize the previous solvent and displace that previous solvent that is in the vapour phase.

[0033] An example of a set of solvents is a set of alkanes ranging from a relatively lighter alkane such as methane to a relatively heavier alkane such as octane, e.g., a set of solvents 23177848.1 including methane (CH4), ethane (02H8), propane (C3H8), butane (C4I-110), pentane (C51-112), hexane (C6-114), heptane (07H16), octane (C81118) etc. Other examples of sets of solvents can be selected from n (normal) and iso-alkanes according to the boiling points of such solvents.
Similarly, other sets of solvents can be chosen from the following solvents, based on the boiling points and, in some cases the costs, of the respective solvents, for example:
naphtha, toluene, xylene, benzene, diesel, natural gas, etc.

[0034] The solvent recovery process can occur with or without an additional heat source, such as steam injected into the reservoir The solvent can be injected in a liquid state and penetrates the pay 24 surrounding the injector wells 16 before vapourizing at deeper zones, thereby creating a region of solvent 40a around the injector well 16 as shown in FIG. 3(a).
FIGS. 3(a)-3(c) illustrate regions of solvent 40a, 40b, 40c that develop during the solvent recovery process described herein, as lighter and lighter solvents are successively injected (with the region of solvent 40 being larger, the lighter the solvent). The region of solvent 40a in FIG.
3(a) has a diffusion boundary 42a at the periphery of the region 40a. The diffusion boundary 42a represents substantially the outermost boundary of the region of solvent 40a, within which diffusion of the solvent occurs. The diffusion boundary 42a can be used to determine a relative volume that would be consumed, for different solvents being injected (as described in greater detail below). The region of solvent 40b in FIG. 3(b) has a diffusion boundary 42b at the periphery of the region 40b. The region of solvent 40c in FIG. 3(c) has a diffusion boundary 42c at the periphery of the region 40c. The diffusion boundaries 42a, 42b, 42c are progressively deeper into the pay 24 as the progressively heavier solvents are injected. The larger the region of solvent 40 defined by the diffusion boundary 42, the larger the volume of solvent that penetrates the pay 24, and the higher volume of solvent that would be consumed. As such, injected solvents having a closer diffusion boundary 42 and smaller region of solvent 40 consume less injected solvent.

[0035] As illustrated in FIG. 4, the solvent recovery process described herein can include determining a transition point during a continuous production process or a restart point for injecting the second solvent at step 104. It can be appreciated that in an implementation, commencement of the production process can correspond to such a transition point, wherein a first, relatively heavy solvent is selected. The relatively lighter solvent to be used for a period of time following the transition or restart point is selected at step 106 and is injected at the injector well 16 at step 108. A bitumen containing fluid can then be recovered at step 110 via the 23177848.1 producer well 18, and if applicable (i.e. during injection of the second or a subsequent solvent), previously injected solvent can be recovered from the bitumen containing fluid at step 112.

[0036] The solvent is injected in the liquid state, e.g., from a truck at surface 12. It is expected that near the end of the injection stage for a particular solvent, due to an increase in temperature surrounding the injector wells 16, the solvent will be in a gaseous state where the temperature is higher than the condensation temperature of the solvent under a given pressure.
As such, the liquid solvent initially diffuses into the formation at a larger flux due a larger concentration that is exposed to the bitumen. Once the solvent is vapourized, the flux of solvent diffusion decreases due to less solvent being available at the interface with the bitumen. The mobilized bitumen, due to solvent dissolution in the surrounding bitumen is produced in a mixture of liquid solvent and bitumen.

[0037] For constant boundary conditions, the diffusion boundary (45Diff ) can be defined as opiff = V4Dt , where 6Diff is the diffusion length, boundary or front (referred to herein as "diffusion boundary"), and D is a diffusion coefficient or diffusivity in dimensions of [length2 time-1], for example m2/sec . The diffusion boundary provides a measure of how far the concentration has propagated in the x-direction by diffusion in time t (Bird, R.B., Stewart, W.E., Lightfoot, E.N., "Transport Phenomena", John Wiley & Sons, 1976).

[0038] The Wilke-Chang equation (Wilke C.R., Chang, P., "Correlation Of Diffusion Coefficients in Dilute Solutions", A.I.Ch.E. Journal, 1:264-270, 1955) can be used for estimating the diffusivity of nonelectrolytes (i.e., hydrocarbon solvent) in an infinitely dilute solution (i.e., bitumen):
VITIMB,õ _________________ (T + 273.15)

[0039] D = 7.4 x =
P. vSolv

[0040] where D is diffusion coefficient (cm2/sec), (1) is association factor of bitumen, MBitu is molecular weight of bitumen (i.e., 500-550), 1.4.8 is viscosity of the bitumen (cP) and VSolv is molal volume of solvent at normal boiling point (cc/g.mole). Based on current available data, the temperature dependence of the diffusion coefficient can be assumed to be linear.
Linear correlation is proposed in other correlations such as Stokes-Einstein (Einstein, Albert, Ann. Phys. 17, 549, 1905 and Miller C.C., "The Stokes-Einstein Law for Diffusion in Solution", Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, Vol. 106, No. 740, pp. 724-749, 1924) or close to linear in other 23177848.1 correlations such as in Sitaraman (Sitaraman R., Ibrahim S. H., Kuloor N. R.
"A Generalized Equation for Diffusion in Liquids" J. Chem. Eng. Data, 1963,8 (2), pp 198-201 doi:10.1021/je60017a017). The formulae suggested above for calculating the diffusion coefficient are expected to hold true for low-viscosity liquids but to introduce error for a high-viscosity solvent. However, the solute (i.e., bitumen) the solvents use in the present diffusion controlled mobilization process are light and less than 10 cP viscosity.

[0041] The Wilke-Chang equation shows that by increasing the temperature surrounding the infill well, the diffusion increases linearly. It is noted that since the diffusion is increasing inversely by viscosity of the bitumen ( ,,,u ), the diffusion reduces for higher temperatures.

[0042] An increase in diffusion means that more solvent is diffusing and 6Diff (diffusion length) can increase by heating up the area surrounding the injector wells 16, e.g., by combining the solvent injection described herein with other non-steam-based recovery processes.

[0043] It can be appreciated that the relative volume of solvent that penetrates the pay 24 can also be modeled according to dispersion of the solvent, which is a combination of diffusion and convection and has a linear relationship with diffusion. That is, the relative volume of each type of solvent can also be modeled by way of a dispersion boundary. Such a dispersion boundary can be estimated using a constant multiplier applied to the above-described diffusion coefficient D, as would be understood by those skilled in the art.

[0044] For simplicity and clarity of illustration, where considered appropriate, reference numerals can be repeated among the figures to indicate corresponding or analogous elements.
In addition, numerous specific details are set forth in order to provide a thorough understanding of the examples described herein. However, it will be understood by those of ordinary skill in the art that the examples described herein can 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 examples described herein. Also, the description is not to be considered as limiting the scope of the examples described herein.

[0045] The examples and corresponding diagrams used herein are for illustrative purposes only. Different configurations and terminology can be used without departing from the principles expressed herein. For instance, components and modules can be added, deleted, modified, or arranged with differing connections without departing from these principles.
23177848.1

[0046] The steps or operations in the flow charts and diagrams described herein are just for example. There can be many variations to these steps or operations without departing from the principles discussed above. For instance, the steps can be performed in a differing order, or steps can be added, deleted, or modified.

[0047] Although the above principles have been described with reference to certain specific examples, various modifications thereof will be apparent to those skilled in the art as outlined in the appended claims.
23177848.1

Claims (18)

Claims:

1. A method for recovering solvent used during bitumen production, the method comprising:
subsequent to a continuous bitumen production process that comprises injecting a first solvent into a bitumen reservoir to reduce the viscosity of the bitumen in the bitumen reservoir, injecting a second solvent into the bitumen reservoir, wherein the second solvent is lighter than the first solvent, wherein the second solvent remains in the vapour phase when injected in a vapour chamber in the bitumen reservoir, wherein the second solvent maintains pressure in the bitumen reservoir, and wherein a fluid produced using the second solvent at least in part comprises a portion of the first solvent.

2. The method of claim 1, wherein the second solvent acts to: i) lower the partial pressure of the first solvent to vaporize at least some of the first solvent, and ii) displace at least some of the first solvent from the vapour chamber in the bitumen reservoir to enable recovery of the first solvent.

3. The method of claim 2, further comprising determining a transition point for switching from the first solvent to the second solvent according to a vapour boiling point at the operating temperature and pressure of the vapour chamber.

4. The method of any one of claims 1 to 3, wherein the fluid produced using the second solvent forms a fraction comprising the second solvent, mobilized bitumen, and the portion of the first solvent.

5. The method of claim 4, wherein over time the second solvent substantially replaces the first solvent in the bitumen reservoir.

6. The method of any one of claims 1 to 5, further comprising producing the fluid.

7. The method of claim 6, further comprising recovering at least some of the first solvent from the produced fluid.

8. The method of any one of claims 1 to 7, further comprising injecting one or more progressively lighter solvents at corresponding progressively later times.

9. The method of any one of claims 1 to 8, wherein the first solvent and second and/or lighter solvents are selected from a plurality of alkanes.

10. The method of any one of claims 1 to 9, further comprising injecting a non-condensable gas after completing solvent injection.

11. The method of claim 10, wherein the non-condensable gas comprises carbon dioxide.

12. The method of any one of claims 1 to 11, wherein a solvent recovery process using the second solvent is applied after commencing a wind-down or a blowdown operation.

13. The method of any one of claims 1 to 11, wherein a solvent recovery process using the second solvent further comprises the application of electromagnetic heating.

14. The method of any one of claims 1 to 11, wherein a solvent recovery process using the second solvent further comprises the application of a conductive heating source.

15. The method of claim 14, wherein the conductive heating source is provided by at least one of electrical heating and closed loop hot oil heating.

16. The method of any one of claims 1 to 15, wherein the continuous production process further comprises the co-injection of steam with the first solvent.

17. The method of any one of claims 1 to 11, wherein a solvent recovery process using the second solvent further comprises the co-injection of steam with the second solvent.

18. The method of any one of claims 6 to 17, wherein the produced fluid is recovered using a production well located beneath an injection well used to inject the first and second solvents.