CA3022786A1

CA3022786A1 - Process and system for processing a produced stream from a solvent hydrocarbon recovery operation

Info

Publication number: CA3022786A1
Application number: CA3022786A
Authority: CA
Inventors: Michael Patrick Mckay
Original assignee: Cenovus Energy Inc
Current assignee: Cenovus Energy Inc
Priority date: 2017-11-30
Filing date: 2018-10-31
Publication date: 2019-05-30

Abstract

A system and process for recovering hydrocarbons from a reservoir formation is disclosed and involves injecting a vaporized solvent stream into the reservoir formation, the solvent reducing a viscosity of the hydrocarbons to facilitate recovery in a produced stream including hydrocarbons, solvent, and water. The process involves separating water from the produced stream to generate a dewatered stream which is heated prior to recovering gaseous solvent to generate a hydrocarbon product stream. A portion of the heating is provided by extracting heat from the gaseous solvent recovered from the dewatered stream. The process involves treating the gaseous solvent to generate a liquefied solvent stream and to separate residual water and reservoir gas and generating thermal energy through combustion of a fuel gas for vaporizing the liquefied solvent stream for re-injecting into the reservoir formation as the vaporized solvent stream, the combustion of fuel gas resulting in discharge of a hot exhaust stream. The process involves directing the exhaust stream through a heat exchanger causing a vaporized water portion of the exhaust stream to condense to a liquid releasing latent energy, which is transferred to a heated thermal fluid for the heating of the dewatered stream.

Description

PROCESS AND SYSTEM FOR PROCESSING A PRODUCED STREAM FROM A SOLVENT HYDROCARBON
RECOVERY OPERATION
BACKGROUND
1. Field This disclosure relates generally to hydrocarbon recovery from a reservoir formation and more particularly to recovery of hydrocarbons using a solvent and processing of a produced stream from the recovery operation.

2. Description of Related Art Heavy oil hydrocarbon recovery from a reservoir formation may require reducing viscosity of the heavy hydrocarbons to increase mobility to facilitate production to the surface. The heavy oil hydrocarbons may include bitumen, which is generally very viscous and difficult to mobilize within the reservoir formation.
One such recovery technique uses a solvent such as propane or butane injected into the reservoir at relatively low temperatures when compared to other recovery techniques such as steam assisted gravity drainage (SAGD). The viscosity of the heavy hydrocarbons is reduced due to mixing with the solvent and through a slight rise in temperature. The reduced viscosity hydrocarbons will have improved mobility within the reservoir formation thus facilitating production to the surface.
There remains a need for systems and processes for treating the produced stream to recover solvent and separate the hydrocarbon product stream from water and other produced fluids.
SUMMARY
In accordance with one disclosed aspect there is provided a process for recovering hydrocarbons from a reservoir formation. The process involves injecting a vaporized solvent stream into the reservoir formation, the solvent being operable to reduce a viscosity of the hydrocarbons to facilitate recovery in a produced stream including hydrocarbons, solvent, and water. The process also involves separating a substantial portion of the water from the produced stream to generate a dewatered stream, and heating the dewatered stream prior to recovering gaseous solvent from the dewatered stream to generate a hydrocarbon product stream. A portion of the heating is provided by extracting heat from the gaseous solvent recovered from the dewatered stream. The process further involves treating the gaseous solvent to generate a liquefied solvent stream and to separate residual water and reservoir gas. The process also involves generating thermal energy through combustion of a fuel gas for vaporizing the liquefied solvent stream for re-injecting into the reservoir formation as the vaporized solvent stream, the combustion of fuel gas resulting in discharge of a hot exhaust stream. The process further involves directing the hot exhaust stream through a heat exchanger operably configured to cause a vaporized water portion of the exhaust stream to condense to a liquid thereby releasing latent energy, the released latent energy being transferred to a heated thermal fluid for the heating of the dewatered stream.
Injecting may involve injecting the vaporized solvent stream into the reservoir formation at an injection pressure, the vaporized solvent stream having a temperature at or above the saturation point for the vaporized solvent at the injection pressure.
The solvent may include propane and the injection temperature may be at or above about 70 C, the hot exhaust stream may have a temperature of at least about 120 C, and the latent energy may be operable to heat the thermal fluid to a temperature of at least about 80 C.
The process may involve compressing the gaseous solvent prior to extracting heat, the compression being operable to cause an increase in temperature of the gaseous solvent.
Generating thermal energy may involve causing a boiler to heat a thermal fluid circulating through a heat exchanger disposed within a vaporizer vessel, the heat exchanger being operable to heat the liquefied solvent.
The process may involve maintaining a pressure within the vaporizer vessel sufficient to cause at least a portion of solvent within the vaporizer vessel to remain liquefied and in thermal communication with a heat transfer surface of the heat exchanger thereby facilitating thermal energy transfer to the liquefied solvent portion while generating a saturated vaporized solvent stream at an outlet of the vaporizer vessel, and injecting the vaporized solvent stream may involve injecting the vaporized solvent stream at a reduced pressure less than the pressure within the vaporizer vessel to cause the solvent to become superheated to compensate for heat losses during injection.

-3-The pressure within the vaporizer vessel may be selected based on a maximum enthalpy of the vaporized solvent stream at saturation thereby preventing development of a liquid phase when injecting the vaporized solvent stream at the reduced pressure.
The solvent may include propane and the pressure within the vaporizer vessel may be in the range of between about 2750 kPa and about 3000 kPa.
Reducing the pressure of the vaporized solvent stream may involve reducing the pressure to between about 2000 kPa and about 2200 kPa.
The process may involve treating a water stream including at least one of the portion of water separated from the produced stream and the residual water separated from the recovered solvent to remove entrained hydrocarbons and to generate a treated water stream.
Treating the water stream may involve causing mixing between the water stream and an injected gas in a flotation vessel at a pressure high enough to cause the injected gas to induce flotation of entrained hydrocarbons within the water stream, the induced flotation being operable to cause hydrocarbons to separate from the water stream and float upwardly within the flotation vessel to facilitate collection while a treated water stream having reduced hydrocarbon content is drawn off from the vessel.
The injected gas may include a fuel gas and the process may further involve recovering at least a portion of the fuel gas from the collected hydrocarbons in a subsequent process.
The flotation vessel may include a plurality of separation zones each zone being operably configured to cause mixing between the water stream and the injected gas and having an outlet for drawing off collected hydrocarbons, and the water stream remaining at each zone may form an inlet stream to the next zone for providing successive treatment of the water stream through the flotation vessel.
The solvent may include one of propane and butane.
In accordance with another disclosed aspect there is provided a process for recovering hydrocarbons from a reservoir formation. The process involves injecting a vaporized solvent stream into the reservoir formation, the solvent being operable to reduce a viscosity of the hydrocarbons to facilitate recovery in a produced

-4-stream including hydrocarbons, solvent, and water. The process also involves separating a substantial portion of the water from the produced stream to generate a dewatered stream, and heating the dewatered stream to a temperature above a critical temperature associated with the solvent. The process further involves receiving the dewatered stream in a first separation vessel operated under supercritical conditions, the separation vessel being operable to facilitate separation of the dewatered stream by density into a supercritical liquefied solvent and a hydrocarbon stream. The process further involves treating the supercritical liquefied solvent to separate reservoir gas and to generate a liquefied solvent stream, and vaporizing the liquefied solvent stream for re-injecting into the reservoir as the vaporized solvent stream.
The process may involve discharging the hydrocarbon stream from the separation vessel, receiving the hydrocarbon stream in a second separation vessel operated at a pressure lower than the supercritical pressure and being operable to cause further solvent to vaporize for collection as a gaseous solvent, and discharging a remaining hydrocarbon portion as a hydrocarbon product stream.
The process may involve causing production of the produced stream at a pressure above the critical pressure associated with the solvent and maintaining the pressure above the critical pressure while generating the dewatered stream.
Vaporizing the liquefied solvent stream may involve causing a boiler to heat a thermal fluid circulating through a heat exchanger disposed within a vaporizer vessel, the heat exchanger being operable heat the liquefied solvent.
The process may involve maintaining a pressure within the vaporizer vessel sufficient to cause at least a portion of solvent within the vaporizer vessel to remain liquefied and in thermal communication with a heat transfer surface of the heat exchanger thereby facilitating thermal energy transfer to the liquefied solvent portion while generating a saturated vaporized solvent stream at an outlet of the vaporizer vessel, and injecting the vaporized solvent stream may involve injecting the vaporized solvent stream at a reduced pressure less than the pressure within the vaporizer vessel to cause the solvent to become superheated to compensate for heat losses during injection.
The pressure within the vaporizer vessel may be selected based on a maximum enthalpy of the vaporized solvent stream at saturation thereby preventing development of a liquid phase when injecting the vaporized solvent stream at the reduced pressure.

-5-The solvent may include propane and the pressure within the vaporizer vessel may be in the range of between about 2750 kPa and about 3000 kPa.
Reducing the pressure of the vaporized solvent stream may involve reducing the pressure to between about 2000 kPa and about 2200 kPa.
The process may involve treating the portion of the water separated from the produced stream to remove entrained hydrocarbons and to generate a treated water stream.
Treating the water stream may involve causing mixing between the water stream and an injected gas in a vessel at a pressure high enough to cause the injected gas to induce flotation of entrained hydrocarbons within the water stream, the induced flotation being operable to cause hydrocarbons to separate from the water stream and float upwardly within the vessel to facilitate collection while a treated water stream having reduced hydrocarbon content is drawn off from the vessel.
The injected gas may include a fuel gas and the process may further involve recovering at least a portion of the fuel gas from the collected hydrocarbons in a subsequent process.
The flotation vessel may include a plurality of separation zones each zone being operably configured to cause mixing between the water stream and the injected gas and having an outlet for drawing off collected hydrocarbons, and the water stream remaining at each zone may form an inlet stream to the next zone for providing successive treatment of the water stream through the vessel.
The solvent may include one of propane and butane.
In accordance with another disclosed aspect, in a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream including hydrocarbons, solvent, and water, there is provided a process for generating heat for processing the produced stream. The process involves separating a substantial portion of the water from the produced stream to generate a dewatered stream, and heating the dewatered stream prior to recovering gaseous solvent from the dewatered stream to generate a hydrocarbon product stream, a

-6-portion of the heating is provided by extracting heat from the gaseous solvent recovered from the dewatered stream.
The process may involve compressing the gaseous solvent prior to extracting heat, the compression being operable to cause an increase in temperature of the gaseous solvent.
The solvent may include one of propane and butane.
In accordance with one disclosed aspect, in a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream including hydrocarbons, solvent, and water, there is provided a system for generating heat for processing the produced stream. The system includes a separation vessel operable to receive the produced stream and to separate a substantial portion of the water from the produced stream to generate a dewatered stream, and a heat exchanger for heating the dewatered stream prior to recovering gaseous solvent from the dewatered stream to generate a hydrocarbon product stream.
The heat exchanger is operably configured to extract heat from the gaseous solvent recovered from the dewatered stream for heating the dewatered stream.
The solvent may include one of propane and butane.
In accordance with one disclosed aspect, in a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream including hydrocarbons, solvent, and water, there is provided a process for generating heat for processing the produced stream. The process involves generating thermal energy through combustion of a fuel gas for vaporizing a liquefied solvent stream for injecting into the reservoir as a vaporized solvent stream, the combustion of fuel gas resulting in discharge of a hot exhaust stream. The process also involves directing the hot exhaust stream through a heat exchanger operably configured to cause a vaporized water portion of the exhaust stream to condense to a liquid thereby releasing latent energy, the released latent energy being transferred to a thermal fluid used for heating of the produced stream during processing to recover solvent and generate a hydrocarbon product stream.

-7-Injecting may involve injecting the vaporized solvent stream into the reservoir formation at an injection pressure, the vaporized solvent stream having a temperature at or above the saturation point for the vaporized solvent at the injection pressure.
The solvent may include propane and the injection temperature may be at or above about 70 C, the hot exhaust stream may have a temperature of at least about 120 C, and the latent energy may be operable to heat the thermal fluid to a temperature of at least about 80 C.
The solvent may include one of propane and butane.
In accordance with one disclosed aspect, in a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream including hydrocarbons, solvent, and water, there is provided a system for generating heat for processing the produced stream. The system includes a gas-fired burner operable to generate thermal energy through combustion of a fuel gas for vaporizing a liquefied solvent stream for injecting into the reservoir as a vaporized solvent stream, the combustion of fuel gas resulting in discharge of a hot exhaust stream. The system also includes a heat exchanger operably configured to receive the exhaust stream and to cause a vaporized water portion of the exhaust stream to condense to a liquid thereby releasing latent energy, the released latent energy being transferred to a thermal fluid used for heating of the produced stream during processing to recover solvent and generate a hydrocarbon product stream.
The solvent may include one of propane and butane.
In accordance with one disclosed aspect, in a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream, there is provided a process for heating solvent to an injection temperature. The process involves generating thermal energy to heat a heat transfer surface in thermal communication with a liquefied solvent within a vaporizer vessel. The process also involves maintaining a pressure within the vaporizer vessel sufficient to cause at least a portion of solvent within the vaporizer vessel to remain liquefied and in thermal communication with the heat transfer surface thereby facilitating thermal energy transfer to the liquefied solvent portion while generating a saturated vaporized solvent stream at an outlet of the vaporizer vessel. The process further involves injecting the vaporized solvent stream at a reduced pressure

-8-less than the pressure within the vaporizer vessel to cause the solvent to become superheated to compensate for heat losses during injection.
The pressure within the vaporizer vessel may be selected based on a maximum enthalpy of the vaporized solvent stream at saturation thereby preventing development of a liquid phase when injecting the vaporized solvent stream at the reduced pressure.
The solvent may include propane and the pressure within the vaporizer vessel may be in the range of between about 2750 kPa and about 3000 kPa.
Reducing the pressure of the vaporized solvent stream may involve reducing the pressure to between about 2000 kPa and about 2200 kPa.
The solvent may include one of propane and butane.
In accordance with one disclosed aspect, in a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream, there is provided a system for heating solvent to an injection temperature. The system includes a vaporizer vessel operably configured to receive a liquefied solvent, the vaporizer vessel having a heat transfer surface disposed in thermal communication with the liquefied solvent.
The system also includes a heat source operable to generate thermal energy for heating the heat transfer surface while maintaining a pressure within the vaporizer vessel sufficient to cause at least a portion of solvent within the vaporizer vessel to remain liquefied and in thermal communication with the heat transfer surface thereby facilitating thermal energy transfer to the liquefied solvent portion while generating a saturated vaporized solvent stream at an outlet of the vaporizer vessel. The system further includes a solvent injector operably configured to inject the vaporized solvent stream into the reservoir formation at a reduced pressure less than the pressure within the vaporizer vessel to cause the solvent to become superheated to compensate for heat losses during injection.
The solvent may include one of propane and butane.
In accordance with one disclosed aspect, in a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced

-9-stream including hydrocarbons, solvent, and water, there is provided a process for separating solvent from the produced stream. The process involves separating a substantial portion of the water from the produced stream to generate a dewatered stream, heating the dewatered stream to a temperature above a critical temperature associated with the solvent, and receiving the dewatered stream in a separation vessel operated under supercritical conditions, the separation vessel being operable to facilitate separation of the dewatered stream by density into a supercritical liquefied solvent and a hydrocarbon stream.
The process may involve discharging the hydrocarbon stream from the separation vessel, receiving the hydrocarbon stream in a second separation vessel operated at a pressure lower than the supercritical pressure and being operable to cause further solvent to vaporize for collection as a gaseous solvent, and discharging a remaining hydrocarbon portion as a hydrocarbon product stream.
The process may involve causing production of the produced stream at a pressure above the critical pressure associated with the solvent and maintaining the pressure above the critical pressure while generating the dewatered stream.
The solvent may include one of propane and butane.
In accordance with one disclosed aspect, in a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream including hydrocarbons, solvent, and water, there is provided a system for separating solvent from the produced stream. The system includes a separation vessel operably configured to separate a substantial portion of the water from the produced stream to generate a dewatered stream. The system also includes a heat exchanger operably configured to heat the dewatered stream to a temperature above a critical temperature associated with the solvent, and a supercritical separation vessel operably configured to receive the dewatered stream, the supercritical separation vessel being operated under supercritical conditions and being operable to facilitate separation of the dewatered stream by density into a supercritical liquefied solvent and a hydrocarbon stream.
The solvent may include one of propane and butane.
Other aspects and features will become apparent to those ordinarily skilled in the art upon review of the following description of specific disclosed embodiments in conjunction with the accompanying figures.

-10-BRIEF DESCRIPTION OF THE DRAWINGS
In drawings which illustrate disclosed embodiments, Figure 1 is a block diagram of a system for recovering and processing hydrocarbons from a reservoir formation;
Figure 2 is a schematic view of a system for system for implementation of a dewatering and degassing process and solvent recovery process in accordance with one disclosed embodiment;
Figure 3 is a schematic view of a system for implementation of the dewatering and degassing process and solvent recovery process in accordance with an alternative disclosed embodiment;
Figure 4 is a schematic view of a system for implementation of a solvent treatment process in accordance with one disclosed embodiment;
Figure 5 is a schematic view of a system for implementation of a solvent treatment process in accordance with another disclosed embodiment;
Figure 6 is a schematic view of a system for implementation of a solvent vaporization process in accordance with one disclosed embodiment; and Figure 7 is a schematic view of a system for implementation of a water treatment process in accordance with one disclosed embodiment.
DETAILED DESCRIPTION
Referring to Figure 1, a system for recovering hydrocarbons from a reservoir formation 100 is shown generally at 102. In this embodiment two horizontally drilled wellbores extend into the reservoir formation 100, including an upper wellbore 104 and a lower wellbore 106. A vaporized solvent stream 108 is introduced into the upper wellbore 104 via an injection process 110. The vaporized solvent stream 108 will generally be at a higher temperature than the reservoir formation 100 and mixes with in-situ hydrocarbons.
The solvent is operable to reduce a viscosity of the hydrocarbons by causing an increase in temperature and

-11-by dissolving in the hydrocarbons. In one embodiment the temperature of the vaporized solvent stream 108 is selected such that when the solvent reaches the hydrocarbons within the reservoir formation 100, the vaporized solvent condenses thus releasing latent heat. In one embodiment the solvent may be propane, but in other embodiments butane, diluent, and/or other solvents may make up the vaporized solvent stream 108.
In one embodiment, the temperature of the vaporized solvent stream 108 may be significantly lower than steam temperatures required in thermal in-situ hydrocarbon recovery processes such as, but not limited to, steam-assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS) hydrocarbon recovery processes.
The lower temperature reduces losses during injection through an overburden 118 between the surface 116 and the reservoir formation 100, reducing the energy required to recover the hydrocarbons from the reservoir formation 100.
In embodiments where the reservoir formation 100 includes deposits of heavy hydrocarbons such as bitumen, the increased viscosity provided by the solvent increases the mobility of the heavy hydrocarbons to facilitate recovery in a produced stream 114. The produced stream 114 is produced to the surface 116 of the reservoir formation 100 via a production process 112. In one embodiment an electric submersible pump is operated within the lower wellbore 106 to pump the produced stream 114 to the surface. The produced stream 114 will generally include hydrocarbons, water, condensed liquid solvent, entrained gaseous solvent and reservoir gas. Asphaltenes, sulphur, and metals within the reservoir formation 100 may be more difficult to mobilize and at least a portion of these undesirable products would advantageously remain in the reservoir formation 100. The water in the produced stream 114 may be connate water from the reservoir formation 100. In other embodiments, steam may be injected into the reservoir formation 100 via the upper wellbore 104 to establish conditions suitable for production prior to injection of the vaporized solvent stream 108. In such cases the water portion of the produced stream 114 may include recovered water previously injected as steam.
In other embodiments, recovery of hydrocarbons may be only through solvent injection i.e. a solvent only recovery process.
A surface facility for processing the produced stream 114 to remove water and separate and treat the solvent for re-injection into to the reservoir formation 100 is shown in Figure 1 at 120 as a series of processing steps. Water and solvent are separated from the produced stream 114 leaving a hydrocarbon product stream 122, which may be transported by pipeline or other means to a refining facility. It is desirable to recover a significant proportion of the solvent from the produced stream 114 to reduce the

-12-amount of solvent required for the recovery operation and to prevent transportation of entrained solvent within the hydrocarbon product stream 114. A small proportion of entrained solvent may remain in the hydrocarbon product stream 122 and may be substantially vented while accumulating the hydrocarbon product stream in, for example, a sales oil tank, prior to transportation.
The produced stream 114 initially goes through a dewatering and degassing process 124, in which a substantial portion of the water, some gaseous phase solvent, and other reservoir gasses and water vapor are separated from the produced stream 114 to generate a dewatered stream 126.
The water is discharged as separated water 130, which may still include hydrocarbons, some solvent, and other impurities and may be subjected to a water treatment process 132. The water treatment process 132 may involve further de-oiling of the water, for example in a skim tank, and results in a treated water stream 134. The treated water stream 134 may be used in other hydrocarbon recovery operations or may be accumulated in a pond for further settlement. Vaporized solvent and other reservoir gasses are separated in a gaseous stream 128. In some embodiments the dewatering and degassing process 124 may be implemented using a three-phase separation vessel commonly known as a free water knock out (FWKO).
The dewatered stream 126 may still include a substantial portion of liquid solvent and entrained gaseous solvent still to be removed in a solvent recovery process 136. In one embodiment, solvent is recovered through one or more flash evaporation processes in a flash vessel where the dewatered stream undergoes a reduction in pressure causing liquid solvent to vaporize for removal as recovered solvent 138. The recovered solvent 138 will generally also include a smaller proportion of reservoir gas and water vapor. The remaining hydrocarbons may be subjected to a further flash evaporation processes at further reduced pressure to drive off a remaining portion of the solvent, leaving the hydrocarbon product stream 122. The hydrocarbon product stream 122 may be suitable for transport or may be further treated, for example by addition of a diluent, to make the product stream suitable for pipeline transport.
The recovered solvent 138 in the gaseous phase may include some water vapor and/or reservoir gasses such as methane and hydrogen sulfide. The recovered solvent 138 is subjected to a solvent treatment process 140, in which the gaseous solvent is pressurized to generate a liquefied solvent stream 142. During pressurization, water vapor within the recovered gaseous solvent 138 also condenses and is collected as residual water 144 for processing in the water treatment process 132.

-13-The solvent treatment process 140 may further include treatment to separate reservoir gas 146 such as methane and hydrogen sulfide from the solvent. Methane has a substantially lower vaporization temperature than a solvent such as propane, and in proportions greater than about 1% to 2% may dominate the vapor space of the vaporized solvent stream 108, thus reducing the efficacy of the solvent for increasing hydrocarbon viscosity on injection into the upper wellbore 104. In one embodiment, the solvent treatment process 140 may further include treatment to separate the hydrogen sulfide in the reservoir gas stream 146 from methane, which can be used as a combustible fuel source for other processes. Hydrogen sulfide when combusted in the presence of oxygen produces Sulphur dioxide, a sulfuric acid precursor that acts as an acid rain contributor. The hydrogen sulfide may be treated with a specialty chemical from a group of chemicals known as triazines, which bind irreversibly to hydrogen sulfide acting as a sulfide removal agent. Alternatively, the hydrogen sulfide may be treated to form a solid of sulfur, if there are sufficient quantities of hydrogen sulfide in the reservoir gas stream 146.
Alternatively, other suitable hydrogen sulfide removal processes may be implemented.
The liquefied solvent stream 142 then goes through a solvent vaporization process 148, in which the solvent stream is heated to a target injection temperature causing vaporization of the solvent. Vaporized solvent is collected and forms the vaporized solvent stream 108 for injection into the reservoir formation 100. Heating of the liquefied solvent stream 142 may be provided through combustion of a fuel gas 150. In one embodiment the fuel gas 150 may be natural gas provided at least in part through recovery of methane during the solvent treatment process 140.
Heat integration Referring to Figure 2, a system for implementation of the dewatering and degassing process 124 and solvent recovery process 136 in accordance with one embodiment is shown generally at 200. The system 200 includes a three phase separation vessel 202, which receives the produced stream 114 at an inlet 204.
The separation vessel 202 provides for separation by density between a less dense hydrocarbon portion 206 and a more dense water portion 208 of the produced stream 114. The hydrocarbon portion 206 is discharged at an outlet 210 as the dewatered stream 126, which still includes solvent. The water portion 208 is discharged through a lower outlet 212 as separated water 130 for further treatment.
In one embodiment, the produced stream 114 may be received at a production pressure of between about 2000 kPa and 2500 kPa. The production pressure is generated in the production process 112, for example by operation of the downhole electric submersible pump (not shown). The produced stream 114 may have

-14-been heated to a temperature of about 70 C, depending on the solvent injection temperature which may be above 70 C for a propane solvent. In one embodiment the separation vessel 202 may be operated at a pressure similar to the production pressure. Under these conditions some of the condensed liquid solvent may evaporate from the surface of the hydrocarbon portion 206 and along with reservoir gas and water vapor is discharged at an outlet 214 as the gaseous stream 128. For a produced stream temperature of about 70 C, the collected gaseous solvent and other reservoir gas may be discharged at the outlet 214 at a temperature of about 70 C and at a pressure similar to the produced pressure.
The system 200 also includes a valve 216 in communication with the outlet 210.
The dewatered stream 126 is fed through a pressure letdown valve, which reduces the pressure of the dewatered steam. The pressure letdown causes vaporization of a portion of the liquid solvent in the dewatered stream and the resulting Joule-Thomson effect will reduce the temperature of this stream. In one embodiment the dewatered stream after the valve 216 may be at a pressure of about 1200 kPa and under these conditions the temperature of the dewatered stream may reduce from about 70 C to about 30 C.
The system 200 also includes a first heat exchanger 226 and a second heat exchanger 228, which are used to reheat the dewatered stream prior to recovering gaseous solvent from the dewatered stream in a high pressure flash evaporator vessel 218. The flash evaporator vessel 218 has an inlet 220 for receiving the heated dewatered stream, an outlet 222 for discharging vaporized solvent, and an outlet 224 for discharging a liquid stream. In the flash evaporator vessel 218, a liquid portion 230 accumulates and the let-down pressure causes liquid solvent within the liquid portion to vaporize to accumulate above a surface of the liquid portion. Vaporized solvent is discharged from the outlet 222 and the system 200 includes a compressor 232 for compressing the vaporized solvent to a pressure similar to the produced pressure. The work done by the compressor 232 in compressing the vaporized solvent increases the temperature, in one embodiment to about 70 C. The liquid stream discharged from the outlet 224 will include hydrocarbons but would still include some liquid solvent portion for recovery.
In the embodiment shown in Figure 2, the system 200 also includes a low pressure flash evaporator vessel 234 having an inlet 236 for receiving the liquid stream from the outlet 224 of the flash evaporator vessel 218, an outlet 238 for discharging vaporized solvent, and an outlet 240 for discharging the hydrocarbon product stream 122. The liquid stream discharged from the flash evaporator vessel 218 at the outlet 224 passes through a pressure letdown valve 242 and is heated by a heat exchanger 244 before being received at the inlet 236 of the low pressure flash evaporator vessel 234. In one embodiment the pressure in the

-15-flash evaporator vessel 218 may be at about 1200 kPa and the pressure in the low pressure flash evaporator vessel 234 may be in the region of about 200 kPa. The pressure reduction in this specific case would be about 1000 kPa, but in other embodiments may be between about 200 kPa and 2000 kPa. In the flash evaporator vessel 234, a liquid portion 246 accumulates and the let-down pressure causes further liquid solvent within the liquid portion to vaporize to accumulate above a surface of the liquid portion. The vaporized solvent is discharged from the outlet 238. The system 200 also includes a compressor 248 for compressing the vaporized solvent at the outlet 238 to a pressure similar to the produced pressure. The work done by the compressor 248 in compressing the vaporized solvent increases the temperature, in one embodiment to about 70 C.
Following the low pressure flash evaporation in the flash evaporator vessel 234, a significant proportion of the liquid solvent will have been recovered. The stream discharged at the outlet 240 should thus have only a small proportion of entrained liquid solvent and provides the hydrocarbon product stream 122.
In the embodiment shown, a portion of the heating for the first heat exchanger 226 may be provided by extracting heat from the recovered gaseous solvent at the outlet 214, the compressor 232, and the compressor 248. These recovered gaseous solvent streams are combined to form the recovered solvent 138, which as described above goes through a further solvent treatment process 140. However, in this embodiment the combined stream is also used to act as a thermal fluid for heating the dewatered stream .. passing through the first heat exchanger 226. In one embodiment the first heat exchanger 226 may be implemented as a shell and tube heat exchanger, in which the thermal fluid (i.e. recovered solvent 138) is channeled through tubes in a shell vessel and transfers thermal energy from the recovered gaseous solvent to the dewatered stream passing through the shell. The recovered solvent 138 will also generally include a significant water vapor portion with which to provide heating through condensation within the first heat exchanger 226. Since the recovered solvent 138 will generally be cooled during the solvent treatment process 140 (shown in Figure 1) the excess thermal energy associated with the recovered solvent would be otherwise dissipated. Use of the excess thermal energy thus reduces the overall thermal heating requirement for operating the system 200, in some embodiments by about 15 %
based on process design simulations for the disclosed system.
In the embodiment shown in Figure 2, the first heat exchanger 226 heated by the recovered solvent 138 only provides a portion of the required heating for the dewatered stream 126 prior to processing in the flash evaporator vessel 218. The second heat exchanger 228 and the heat exchanger 244 for heating the

-16-stream being received at the inlet 236 of the low pressure flash evaporator vessel 234 are heated by a thermal fluid 250 such as circulating glycol or heating oil that is heated by a heat source such as a boiler or by other means as described later herein.
Supercritical solvent separation Referring to Figure 3, a system for implementation of the dewatering and degassing process 124 and solvent recovery process 136 in accordance with an alternative embodiment is shown generally at 300. The system 300 includes a three phase separation vessel 302, which receives the produced stream 114 at an inlet 304 and operates generally as described above discharging the dewatered stream 126 at an outlet 306 and separated water 130 at an outlet 308. However, in this embodiment, the produced stream 114 is received at an elevated production pressure above a critical pressure associated with the solvent. For the example of a propane solvent, the critical pressure is in the region of 4500 kPa and in this case the production process 112 may involve operating an electric submersible pump at the elevated pressure to cause production of the produced stream 114 at a pressure above the critical pressure. The three phase separation vessel 302 thus operates a pressure above the critical pressure while generating the dewatered stream 126. The temperature of the dewatered stream 126 would still be commensurate with the temperature of the produced stream 114 (for example 70 C for a propane solvent) and would thus remain under sub-critical conditions.
Recovered solvent 310 is discharged from the three phase separation vessel 302 at an outlet 312, but in this embodiment the recovered solvent will be at the elevated pressure. Similarly, the dewatered stream 126 at the outlet 306 will be at the elevated pressure.
The system 300 also includes a heat exchanger 314 for heating the dewatered stream 126 to a temperature above a critical temperature associated with the solvent. The heat exchanger 314 is heated by a thermal fluid 316 such as oil or glycol, and in one embodiment may heat the dewatered stream 126 to above 100 C
for a propane solvent.
The system 300 also includes a supercritical separation vessel 318 having an inlet 320 for receiving the dewatered stream 126, which in this case is at supercritical pressure and temperature. The supercritical separation vessel 318 thus operates under supercritical conditions and facilitates separation of the dewatered stream 126 by density into a less dense supercritical liquefied solvent, which is discharged at an outlet 322, and a more dense liquid hydrocarbon stream, which is discharged at an outlet 324.

-17-In the embodiment shown, the system also includes a heat exchanger 326 which extracts heat to reduce the temperature of the supercritical liquefied solvent discharged at the outlet 322. The heat exchanger 326 is also configured to cause a letdown in pressure causing the solvent 328 to remain in the liquid phase, but at sub-critical conditions due to the reduction to sub-critical temperature and pressure. A cooling medium 330 provided to the heat exchanger 326 will be heated by the supercritical liquefied solvent and may be used to provide other heating requirements for the system 300.
In the embodiment shown in Figure 3, the system 300 also includes a low pressure flash evaporator vessel 332 having an inlet 334 for receiving the liquid hydrocarbon stream from the outlet 324 of the flash evaporator vessel 318, an outlet 336 for discharging vaporized solvent, and an outlet 338 for discharging the hydrocarbon product stream 122. The liquid hydrocarbon stream discharged from the outlet 324 of the flash evaporator vessel 218 passes through a pressure letdown valve 340 and is heated by a heat exchanger 344 before being received at the inlet 334 of the low pressure flash evaporator vessel 332. In the flash evaporator vessel 334, a liquid portion 346 accumulates and the let-down pressure causes further liquid solvent within the liquid portion to vaporize to accumulate above a surface of the liquid portion. The vaporized solvent is discharged from the outlet 336. The system 300 also includes a compressor 348 for compressing the vaporized solvent at the outlet 336 to produce a recovered solvent stream 350.
In one embodiment the recovered solvent stream 350 is compressed to an elevated pressure at which liquefaction of the solvent would occur. The recovered solvent 310 from the three phase separation vessel 302 would also be at elevated pressure in this embodiment. The streams 310, 328 and 350 together make up the recovered solvent 138 that will still undergo the solvent treatment process 140 shown in Figure 1 and described in more detail below.
In other embodiments, the produced stream 114 may be produced at a pressure lower than the supercritical pressure for the solvent, and processing through the three phase separation vessel 302 and heat exchanger 314 may be at the lower pressure, the supercritical pressurization being provided by an in-line charge pump (not shown) between the heat exchanger 314 and the supercritical separation vessel 318.
Following the low pressure flash evaporation in the vessel 332, a significant proportion of the liquid solvent will have been recovered. The stream discharged at the outlet 338 should thus have only a small proportion of entrained liquid solvent and provides the hydrocarbon product stream 122.

-18-One advantage associated with the system 300 is that a substantial portion of the solvent is removed as a supercritical liquid, avoiding the need to vaporize and compress vaporized solvent. This embodiment thus eliminates the compressor 232 in the Figure 2 embodiment, thus reducing the requirement for rotating equipment.
Solvent treatment Referring to Figure 4, a system for implementation of the solvent treatment process 140 in accordance with one embodiment is shown generally at 400. The system 400 is configured for treatment of the recovered solvent 138 made up by the streams 310, 328, and 350 generated by the solvent recovery system shown in Figure 3. In this embodiment the recovered solvent streams 310 and 350 are processed differently to the recovered solvent stream 328, which is generated under supercritical conditions. The recovered solvent streams 310 and 350 include vaporized solvent, water vapor, and reservoir gases.
The system 400 includes an air cooler 402 and a three phase separation vessel 404. The streams 310 and 350 are received at an inlet 406 of the separation vessel 404 following cooling by the air cooler 402. The stream received at the inlet 406 following cooling comprises liquefied and vaporized solvent, liquid water, and reservoir gases. For a propane solvent at about 4000 kPa and 40 C, the solvent will be primarily liquefied and the separation vessel 404 separates liquid water from the liquid solvent and discharges the liquid water at an outlet 408. The water from the outlet 408 may be sent to the water treatment process 132 for further processing. The liquid solvent is discharged at an outlet 412, while a remaining gaseous phase portion is vented via an outlet 410. The gaseous phase portion at the outlet 410 will be primarily reservoir gasses such as methane and hydrogen sulfide.
The system 400 also includes a distillation column 414, which has an inlet 416 for receiving the liquid solvent from the outlet 412 of the separation vessel 404. The distillation column 414 also includes an inlet 418 for receiving the recovered solvent stream 328. In one embodiment, both of the streams received at the inlets 416 and 418 will be primarily liquid phase solvent having some entrained vaporized solvent and reservoir gas. The distillation column 414 separates the vapor phase including reservoir gasses from the liquefied solvent. The vapor phase is discharged from an outlet 420. The distillation column 414 includes a reboiler 422 for re-boiling liquid at the bottom of the column and liquefied solvent is discharged from an outlet 424 as the liquefied solvent stream 142 for further processing in the solvent vaporization process 148.

-19-The gaseous streams at the outlet 410 of the separation vessel 404 and the outlet 420 of the distillation column 414 are combined and processed through a scavenger 426 to remove hydrogen sulfide, leaving primarily methane for use as fuel gas 150.
Referring to Figure 5, a system for implementation of the solvent treatment process 140 in accordance with another embodiment is shown generally at 500. The system 500 is configured for treatment of the recovered solvent stream 138 generated by the system 200 shown in Figure 2. In an embodiment where the solvent is propane, the recovered solvent 138 may be at a pressure of about 1500 kPa and a temperature below 70 C following heating of the first heat exchanger 226 as shown in Figure 2. The system 500 includes an air cooler 502 and a three phase separation vessel 504.
The recovered solvent 138 is received at an inlet 506 of the separation vessel 504 following cooling by the air cooler 502. The stream received at the inlet 506 comprises vaporized solvent, liquefied solvent, liquid water, and reservoir gases.
The air cooler 502 further cools the recovered solvent 138 prior to being received in the separation vessel 504, which separates liquid water from the liquid solvent and discharges the liquid water at an outlet 508.
The stream received at the inlet 506 may have a temperature of about 40 C and a pressure of 1500 kPa.
The water from the outlet 508 may be sent to the water treatment process 132 for further processing. The liquid solvent is discharged at an outlet 512, while a remaining gaseous phase portion is vented via an outlet 510. The gaseous phase portion at the outlet 510 includes vaporized solvent and reservoir gasses such as methane and hydrogen sulfide.
The system 500 also includes a compressor 514, which further compresses the gaseous phase portion at the outlet 510 and feeds the compressed stream through a cooler 516 before undergoing a second separation stage in a separation vessel 518. In the embodiment shown the coolers 502 and 516 are shown as air coolers, but in other embodiments a cooling medium other than air may be used. The separation vessel 518 receives a compressed cooled stream from the cooler 516 at an inlet 520. The stream received at the inlet 520 comprises liquefied and vaporized solvent, liquid water, and reservoir gases and for a propane solvent at a pressure of about 4000 kPa and a temperature of about 40 C, would be primarily liquefied. The separation vessel 518 again separates liquid water from the liquid solvent and discharges the liquid water at an outlet 522. The water from the outlet 522 may be sent to the water treatment process 132 for further processing. The liquid solvent is discharged at an outlet 524.

-20-As in the Figure 4 embodiment, the system 500 includes a distillation column 526 having an inlet 528 for receiving the liquid solvent from the outlet 524 of the separation vessel 518.
The distillation column 526 also includes an inlet 530. Liquid solvent separated in the separation vessel 504 at the outlet 512 is fed through a charge pump 532 to provide an increased pressure liquid solvent stream at the inlet 530. In one embodiment the charge pump 532 pressurizes the liquid solvent to a pressure of about 4000 kPa. The streams received at the respective inlets 528 and 530 will be primarily liquid phase solvent having some entrained vaporized solvent and reservoir gasses. The distillation column 526 separates the vapor phase including reservoir gasses from the liquefied solvent. The vapor phase is discharged from an outlet 534 and processed through a scavenger 540 to remove hydrogen sulfide, leaving primarily methane for use as fuel gas 150. The distillation column 526 includes a reboiler 536 for re-boiling liquid at the bottom of the column and liquefied solvent is discharged from an outlet 538 as the liquefied solvent stream 142 for further processing in the solvent vaporization process 148.
Condensing boiler Referring to Figure 6, a system for implementation of the solvent vaporization process 148 in accordance with one embodiment is shown generally at 600. The system 600 includes a boiler 602, having a burner 604 that generates thermal energy through combustion of fuel gas 150 for vaporizing the liquefied solvent stream 142 for re-injecting into the reservoir formation 100. The boiler includes a tubing circuit 608 heated by the burner 604.
The system 600 includes a vaporizer vessel 610 having in inlet 612 for receiving the liquefied solvent stream 142. During recovery operations some of the solvent will be lost, for example through discharge in the treated water stream, entrainment in the hydrocarbon stream or separated reservoir gasses, or dissipation within the reservoir formation. In this embodiment, losses are compensated by introducing make up solvent 616 as required. The vaporizer vessel 610 includes a heat exchanger 618 disposed within the vaporizer vessel and being operable to heat liquefied solvent received at the inlet 612 and accumulated within the vessel. The heat exchanger 618 is heated by a thermal fluid that circulates through the heat exchanger and is returned via a pump 620 to the tubing circuit within the boiler 602. The heat exchanger 618 heats the liquefied solvent causing vaporization, and vaporized solvent is discharged at an outlet 622 to .. form the vaporized solvent stream 108 for injection into the reservoir formation 100 via the injection process 110.

-21-The combustion of fuel gas in the burner 604 results in discharge of a hot exhaust stream 606 via a flue 624 of the boiler 602. The flue 624 channels the hot exhaust stream 606 through a condensing section 626.
The hot exhaust stream 606 includes a significant water vapor portion due to combustion of the fuel gas 150. In one embodiment the hot exhaust stream may be at a temperature above 100 C, which maintains the water in the vapor phase. The condensing section 626 includes a heat exchanger 628, which receives the hot exhaust stream 606 and causes a vaporized water portion of the exhaust stream to condense to a liquid thereby releasing latent energy. The released latent energy is transferred to the thermal fluid 250 circulating through the heat exchanger 628, which may be used for heating requirements within the various disclosed systems herein. For example, the thermal fluid 250 is used for heating the second heat exchanger 228 and heat exchanger 244 shown in Figure 2. Condensed water may be collected from the condensing section 626 at an outlet 630 and treated in the water treatment process 132.
Solvent vaporization The vaporizer vessel 610 shown in Figure 6 may be maintained at a pressure sufficient to cause at least a portion of solvent within the vessel to remain liquefied, as shown at 632. The liquefied solvent remains in thermal communication with a heat transfer surface of the heat exchanger 618, thereby facilitating thermal energy transfer to the liquefied solvent portion while generating a saturated vaporized solvent stream at the outlet 622 of the vaporizer vessel. In one embodiment sufficient heating is provided by the heat exchanger 618 to cause the vaporized solvent stream at the outlet 622 to have a temperature at the saturation point for the vaporized solvent at the injection pressure.
However in other embodiments, it may be desired to cause the vaporized solvent to be superheated for injection into the reservoir formation 100 to compensate for any injection heat losses. Superheating a vaporized solvent within the vaporizer vessel 610 would however require a significantly larger heat transfer area than the heat exchanger 618 required for heating the liquefied solvent to lower than superheated temperatures. Rather than attempt to superheat the vaporized stream, the vaporized solvent stream may be injected at a reduced pressure, less than the pressure within the vaporizer vessel 610, causing the vaporized solvent to become superheated to compensate for heat losses during injection. In one embodiment the pressure within the vaporizer vessel 610 is selected based on a maximum enthalpy of the vaporized solvent stream at saturation thereby preventing development of a liquid phase when injecting the vaporized solvent stream at the reduced pressure. As an example, for a propane solvent the pressure may be in the region of 2750 kPa to 3000 kPa, facilitating generation of a substantially saturated vaporized solvent (i.e. having a vapor quality x=1). In the embodiment shown in Figure 6, the system 600 includes a

-22-solvent injector 634 operable to implement the injection process 110. An injection pressure produced in the solvent injector 634 may be reduced to between about 2000 kPa and about 2200 kPa, causing a vaporized solvent stream 636 to be superheated at the lower pressure for injection into the upper wellbore 104 of the system 102 shown in Figure 1.
Water Treatment Referring to Figure 7, a system for implementation of the water treatment process 132 in accordance with one embodiment is shown generally at 700. The system includes a flotation vessel 702 and a reject separator vessel 704. The flotation vessel 702 has a water inlet 706 for receiving the separated water stream 130 and/or residual water stream 144 generated in the respective dewatering and degassing process 124 and solvent treatment process 140. In the embodiment shown, the water inlet 706 is disposed to cause a generally tangential flow within the flotation vessel as indicated by the arrow 708. The flotation vessel 702 also includes a gas inlet 710 for injecting a gas into the flotation vessel. In one embodiment the gas injected at the gas inlet 710 may be a fuel gas such as methane. The flotation vessel 702 also includes a water outlet 712 disposed at the bottom of the vessel for discharging the treated water stream 134 and an outlet 714 at the top of the vessel for discharging a separated hydrocarbon stream 720.
The water streams 130 and 144 will generally include some dissolved gasses such as gaseous solvent and reservoir gasses and may also include significant impurities in the form of dissolved solids such as silica, hardness ions such as calcium and magnesium, other salts and dissolved organic compounds.
The water 130, 144 received at the water inlet 706 combines with the injected gas at the gas inlet 710 causing mixing between the water stream and the injected gas in a flotation region 716. The flotation vessel 702 is maintained at a pressure high enough to cause the injected gas to induce flotation of entrained hydrocarbons within the water stream 130, 144. The induced flotation in combination with flotation provided by dissolved gasses entrained within the water stream causes hydrocarbons to separate from the water stream and float upwardly within the flotation vessel 702. The hydrocarbons being less dense than the water accumulate in a region 718 above the flotation region 716, facilitating collection by the outlet 714 as the separated hydrocarbon stream 720. The separated hydrocarbon stream 720 may include solvent, fuel gas, and liquid hydrocarbon products. Within a treated water region 722 below the region 716, the water has a reduced hydrocarbon content and may be drawn off via the water outlet 712 as the treated water stream 134.

-23-The treated water region 722 may be sized to permit bubbles generated by the injected gas to float upwardly through the flotation region 716 thereby reducing the dissolved gas content in the treated water at the water outlet 712. In one embodiment the flotation vessel 702 may include guide vanes 724 between the flotation region 716 and the treated water region 722 to provide separation between the regions and to direct the injected gas upwardly within the flotation vessel 702.
The reject separator vessel 704 has an inlet 726 for receiving the separated hydrocarbon stream 720, an outlet 728 for collecting a separated gaseous portion and an outlet 730 for drawing off a hydrocarbon portion. The less dense gaseous portion separates from the hydrocarbon portion within the reject separator vessel 704 to produce a gaseous stream 732. The gaseous stream 732 may include vaporized solvent and reservoir gasses, and may be combined with recovered solvent 138 generated in either of the systems 200 or 300 described above. A hydrocarbon portion 734 drawn off at the outlet 730 may be further processed in the solvent recovery process 136 to remove further solvent.
While the separated water 130 and residual water 144 may be conventionally treated in a skim tank at low pressures near atmospheric pressure, gaseous hydrocarbons would generally need to be collected and compressed rather than vented. To permit sufficient settling and residence time, the skim tank would thus need to be relatively large. The flotation vessel 702 provides a compact alternative to a skim tank and the injection of the fuel gas causes rapid separation of hydrocarbons through the induced flotation thus reducing a residence time in the flotation vessel. In some embodiments a multi-stage flotation vessel having a plurality of separation zones may be used. Each zone would be configured generally as shown in Figure 7 to cause mixing between the water stream and the injected gas and would have an outlet for drawing off collected hydrocarbons. The water stream remaining at each zone would form an inlet stream to the next zone for providing successive treatment of the water stream through the flotation vessel to provide several stages of separation within a single compact flotation vessel.
While specific embodiments have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.

Claims

What is claimed is:

1. A process for recovering hydrocarbons from a reservoir formation, the process comprising:
injecting a vaporized solvent stream into the reservoir formation, the solvent being operable to reduce a viscosity of the hydrocarbons to facilitate recovery in a produced stream including hydrocarbons, solvent, and water;
separating a substantial portion of the water from the produced stream to generate a dewatered stream;
heating the dewatered stream prior to recovering gaseous solvent from the dewatered stream to generate a hydrocarbon product stream, wherein a portion of the heating is provided by extracting heat from the gaseous solvent recovered from the dewatered stream;
treating the gaseous solvent to generate a liquefied solvent stream and to separate residual water and reservoir gas;
generating thermal energy through combustion of a fuel gas for vaporizing the liquefied solvent stream for re-injecting into the reservoir formation as the vaporized solvent stream, the combustion of fuel gas resulting in discharge of a hot exhaust stream; and directing the hot exhaust stream through a heat exchanger operably configured to cause a vaporized water portion of the exhaust stream to condense to a liquid thereby releasing latent energy, the released latent energy being transferred to a heated thermal fluid for the heating of the dewatered stream.

2. The process of claim 1 wherein injecting comprises injecting the vaporized solvent stream into the reservoir formation at an injection pressure, the vaporized solvent stream having a temperature at or above the saturation point for the vaporized solvent at the injection pressure.

3. The process of claim 2 wherein the solvent comprises propane and wherein the injection temperature is at or above about 70 °C, the hot exhaust stream has a temperature of at least about 120 °C, and wherein the latent energy is operable to heat the thermal fluid to a temperature of at least about 80 °C.

4. The process of claim 1 further comprising compressing the gaseous solvent prior to extracting heat, the compression being operable to cause an increase in temperature of the gaseous solvent.

5. The process of claim 1 wherein generating thermal energy comprises causing a boiler to heat a thermal fluid circulating through a heat exchanger disposed within a vaporizer vessel, the heat exchanger being operable heat the liquefied solvent.

6. The process of claim 5 further comprising:
maintaining a pressure within the vaporizer vessel sufficient to cause at least a portion of solvent within the vaporizer vessel to remain liquefied and in thermal communication with a heat transfer surface of the heat exchanger thereby facilitating thermal energy transfer to the liquefied solvent portion while generating a saturated vaporized solvent stream at an outlet of the vaporizer vessel; and wherein injecting the vaporized solvent stream comprises injecting the vaporized solvent stream at a reduced pressure less than the pressure within the vaporizer vessel to cause the solvent to become superheated to compensate for heat losses during injection.

7. The process of claim 6 wherein the pressure within the vaporizer vessel is selected based on a maximum enthalpy of the vaporized solvent stream at saturation thereby preventing development of a liquid phase when injecting the vaporized solvent stream at the reduced pressure.

8. The process of claim 6 wherein the solvent comprises propane and wherein the pressure within the vaporizer vessel is in the range of between about 2750 kPa and about 3000 kPa.

9. The process of claim 8 wherein reducing the pressure of the vaporized solvent stream comprises reducing the pressure to between about 2000 kPa and about 2200 kPa.

10. The process of claim 1 further comprising treating a water stream including at least one of the portion of water separated from the produced stream and the residual water separated from the recovered solvent to remove entrained hydrocarbons and to generate a treated water stream.

11. The process of claim 10 wherein treating the water stream comprises:
causing mixing between the water stream and an injected gas in a flotation vessel at a pressure high enough to cause the injected gas to induce flotation of entrained hydrocarbons within the water stream, the induced flotation being operable to cause hydrocarbons to separate from the water stream and float upwardly within the flotation vessel to facilitate collection while a treated water stream having reduced hydrocarbon content is drawn off from the flotation vessel.

12. The process of claim 11 wherein the injected gas comprises a fuel gas and further comprising recovering at least a portion of the fuel gas from the collected hydrocarbons in a subsequent process.

13. The process of claim 11 wherein the flotation vessel comprises a plurality of separation zones each zone being operably configured to cause mixing between the water stream and the injected gas and having an outlet for drawing off collected hydrocarbons, and wherein the water stream remaining at each zone forms an inlet stream to the next zone for providing successive treatment of the water stream through the flotation vessel.

14. The process of claim 1 wherein the solvent comprises one of propane and butane.

15. A process for recovering hydrocarbons from a reservoir formation, the process comprising:
injecting a vaporized solvent stream into the reservoir formation, the solvent being operable to reduce a viscosity of the hydrocarbons to facilitate recovery in a produced stream including hydrocarbons, solvent, and water;
separating a substantial portion of the water from the produced stream to generate a dewatered stream;
heating the dewatered stream to a temperature above a critical temperature associated with the solvent;
receiving the dewatered stream in a separation vessel operated under supercritical conditions, the separation vessel being operable to facilitate separation of the dewatered stream by density into a supercritical liquefied solvent and a hydrocarbon stream;
treating the supercritical liquefied solvent to separate reservoir gas and to generate a liquefied solvent stream; and vaporizing the liquefied solvent stream for re-injecting into the reservoir as the vaporized solvent stream.

16. The process of claim 15 further comprising:
discharging the hydrocarbon stream from the separation vessel;
receiving the hydrocarbon stream in a second separation vessel operated at a pressure lower than the supercritical pressure and being operable to cause further solvent to vaporize for collection as a gaseous solvent; and discharging a remaining hydrocarbon portion as a hydrocarbon product stream.

17. The process of claim 15 further comprising causing production of the produced stream at a pressure above the critical pressure associated with the solvent and maintaining the pressure above the critical pressure while generating the dewatered stream.

18. The process of claim 15 wherein vaporizing the liquefied solvent stream comprises causing a boiler to heat a thermal fluid circulating through a heat exchanger disposed within a vaporizer vessel, the heat exchanger being operable heat the liquefied solvent.

19. The process of claim 18 further comprising:
maintaining a pressure within the vaporizer vessel sufficient to cause at least a portion of solvent within the vaporizer vessel to remain liquefied and in thermal communication with a heat transfer surface of the heat exchanger thereby facilitating thermal energy transfer to the liquefied solvent portion while generating a saturated vaporized solvent stream at an outlet of the vaporizer vessel; and wherein injecting the vaporized solvent stream comprises injecting the vaporized solvent stream at a reduced pressure less than the pressure within the vaporizer vessel to cause the solvent to become superheated to compensate for heat losses during injection.

20. The process of claim 19 wherein the pressure within the vaporizer vessel is selected based on a maximum enthalpy of the vaporized solvent stream at saturation thereby preventing development of a liquid phase when injecting the vaporized solvent stream at the reduced pressure.

21. The process of claim 19 wherein the solvent comprises propane and wherein the pressure within the vaporizer vessel is in the range of between about 2750 kPa and about 3000 kPa.

22. The process of claim 21 wherein reducing the pressure of the vaporized solvent stream comprises reducing the pressure to between about 2000 kPa and about 2200 kPa.

23. The process of claim 15 further comprising treating the portion of the water separated from the produced stream to remove entrained hydrocarbons and to generate a treated water stream.

24. The process of claim 23 wherein treating the water stream comprises:
causing mixing between the water stream and an injected gas in a flotation vessel at a pressure high enough to cause the injected gas to induce flotation of entrained hydrocarbons within the water stream, the induced flotation being operable to cause hydrocarbons to separate from the water stream and float upwardly within the flotation vessel to facilitate collection while a treated water stream having reduced hydrocarbon content is drawn off from the flotation vessel.

25. The process of claim 24 wherein the injected gas comprises a fuel gas and further comprising recovering at least a portion of the fuel gas from the collected hydrocarbons in a subsequent process.

26. The process of claim 24 wherein the flotation vessel comprises a plurality of separation zones each zone being operably configured to cause mixing between the water stream and the injected gas and having an outlet for drawing off collected hydrocarbons, and wherein the water stream remaining at each zone forms an inlet stream to the next zone for providing successive treatment of the water stream through the flotation vessel.

27. The process of claim 15 wherein solvent comprises one of propane and butane.

28. In a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream including hydrocarbons, solvent, and water, a process for generating heat for processing the produced stream, the process comprising:

separating a substantial portion of the water from the produced stream to generate a dewatered stream; and heating the dewatered stream prior to recovering gaseous solvent from the dewatered stream to generate a hydrocarbon product stream, wherein a portion of the heating is provided by extracting heat from the gaseous solvent recovered from the dewatered stream.

29. The process of claim 28 further comprising compressing the gaseous solvent prior to extracting heat, the compression being operable to cause an increase in temperature of the gaseous solvent.

30. The process of claim 28 wherein solvent comprises one of propane and butane.

31. In a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream including hydrocarbons, solvent, and water, a system for generating heat for processing the produced stream, the system comprising:
a separation vessel operable to receive the produced stream and to separate a substantial portion of the water from the produced stream to generate a dewatered stream;
and a heat exchanger for heating the dewatered stream prior to recovering gaseous solvent from the dewatered stream to generate a hydrocarbon product stream, wherein the heat exchanger is operably configured to extract heat from the gaseous solvent recovered from the dewatered stream for heating the dewatered stream.

32. The system of claim 31 wherein solvent comprises one of propane and butane.

33. In a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream including hydrocarbons, solvent, and water, a process for generating heat for processing the produced stream, the process comprising:
generating thermal energy through combustion of a fuel gas for vaporizing a liquefied solvent stream for injecting into the reservoir as a vaporized solvent stream, the combustion of fuel gas resulting in discharge of a hot exhaust stream; and directing the hot exhaust stream through a heat exchanger operably configured to cause a vaporized water portion of the exhaust stream to condense to a liquid thereby releasing latent energy, the released latent energy being transferred to a thermal fluid used for heating of the produced stream during processing to recover solvent and generate a hydrocarbon product stream.

34. The process of claim 33 wherein injecting comprises injecting the vaporized solvent stream into the reservoir formation at an injection pressure, the vaporized solvent stream having a temperature at or above the saturation point for the vaporized solvent at the injection pressure.

35. The process of claim 34 wherein the solvent comprises propane and wherein the injection temperature is at or above about 70 C, the hot exhaust stream has a temperature of at least about 120 C, and wherein the latent energy is operable to heat the thermal fluid to a temperature of at least about 80 C.

36. The process of claim 33 wherein solvent comprises one of propane and butane.

37. In a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream including hydrocarbons, solvent, and water, a system for generating heat for processing the produced stream, the system comprising:
a gas-fired burner operable to generate thermal energy through combustion of a fuel gas for vaporizing a liquefied solvent stream for injecting into the reservoir as a vaporized solvent stream, the combustion of fuel gas resulting in discharge of a hot exhaust stream;
and a heat exchanger operably configured to receive the exhaust stream and to cause a vaporized water portion of the exhaust stream to condense to a liquid thereby releasing latent energy, the released latent energy being transferred to a thermal fluid used for heating of the produced stream during processing to recover solvent and generate a hydrocarbon product stream.

38. The system of claim 37 wherein solvent comprises one of propane and butane.

39. In a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream, a process for heating solvent to an injection temperature, the process comprising:
generating thermal energy to heat a heat transfer surface disposed in thermal communication with a liquefied solvent within a vaporizer vessel;
maintaining a pressure within the vaporizer vessel sufficient to cause at least a portion of solvent within the vaporizer vessel to remain liquefied and in thermal communication with the heat transfer surface thereby facilitating thermal energy transfer to the liquefied solvent portion while generating a saturated vaporized solvent stream at an outlet of the vaporizer vessel; and injecting the vaporized solvent stream at a reduced pressure less than the pressure within the vaporizer vessel to cause the solvent to become superheated to compensate for heat losses during injection.

40. The process of claim 39 wherein the pressure within the vaporizer vessel is selected based on a maximum enthalpy of the vaporized solvent stream at saturation thereby preventing development of a liquid phase when injecting the vaporized solvent stream at the reduced pressure.

41. The process of claim 39 wherein the solvent comprises propane and wherein the pressure within the vaporizer vessel is in the range of between about 2750 kPa and about 3000 kPa.

42. The process of claim 41 wherein reducing the pressure of the vaporized solvent stream comprises reducing the pressure to between about 2000 kPa and about 2200 kPa.

43. The process of claim 39 wherein solvent comprises one of propane and butane.

44. In a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream, a system for heating solvent to an injection temperature, the system comprising:
a vaporizer vessel operably configured to receive a liquefied solvent, the vaporizer vessel having a heat transfer surface disposed in thermal communication with the liquefied solvent;

a heat source operable to generate thermal energy for heating the heat transfer surface while maintaining a pressure within the vaporizer vessel sufficient to cause at least a portion of solvent within the vaporizer vessel to remain liquefied and in thermal communication with the heat transfer surface thereby facilitating thermal energy transfer to the liquefied solvent portion while generating a saturated vaporized solvent stream at an outlet of the vaporizer vessel; and a solvent injector operably configured to inject the vaporized solvent stream into the reservoir formation at a reduced pressure less than the pressure within the vaporizer vessel to cause the solvent to become superheated to compensate for heat losses during injection.

45. The system of claim 44 wherein solvent comprises one of propane and butane.

46. In a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream including hydrocarbons, solvent, and water, a process for separating solvent from the produced stream, the process comprising:
separating a substantial portion of the water from the produced stream to generate a dewatered stream;
heating the dewatered stream to a temperature above a critical temperature associated with the solvent; and receiving the dewatered stream in a separation vessel operated under supercritical conditions, the separation vessel being operable to facilitate separation of the dewatered stream by density into a supercritical liquefied solvent and a hydrocarbon stream.

47. The process of claim 46 further comprising:
discharging the hydrocarbon stream from the separation vessel;
receiving the hydrocarbon stream in a second separation vessel operated at a pressure lower than the supercritical pressure and being operable to cause further solvent to vaporize for collection as a gaseous solvent; and discharging a remaining hydrocarbon portion as a hydrocarbon product stream.

48. The process of claim 46 further comprising causing production of the produced stream at a pressure above the critical pressure associated with the solvent and maintaining the pressure above the critical pressure while generating the dewatered stream.

49. In a hydrocarbon recovery operation in which solvent injection is used to reduce a viscosity of hydrocarbons within a reservoir formation to facilitate recovery in a produced stream including hydrocarbons, solvent, and water, a system for separating solvent from the produced stream, the system comprising:
a separation vessel operably configured to separate a substantial portion of the water from the produced stream to generate a dewatered stream;
a heat exchanger operably configured to heat the dewatered stream to a temperature above a critical temperature associated with the solvent; and a supercritical separation vessel operably configured to receive the dewatered stream, the supercritical separation vessel being operated under supercritical conditions and being operable to facilitate separation of the dewatered stream by density into a supercritical liquefied solvent and a hydrocarbon stream.

50. The system of claim 49 wherein solvent comprises one of propane and butane.