CA2885081C - Steam generation system - Google Patents
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- CA2885081C CA2885081C CA2885081A CA2885081A CA2885081C CA 2885081 C CA2885081 C CA 2885081C CA 2885081 A CA2885081 A CA 2885081A CA 2885081 A CA2885081 A CA 2885081A CA 2885081 C CA2885081 C CA 2885081C
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Abstract
A steam generation system for producing steam from water for use in hydrocarbon extraction is provided. The system comprises a direct contact heater for producing a pressurized heated water from water input thereto and air/gas constituents and a flash tank in fluid communication with the direct contact heater for receiving the pressurized heated water and generating steam based on a pressure differential between the pressure of the flash tank and the pressurized heated water.
Description
, , Steam Generation System Technical Field The invention relates to systems for generating steam for use in hydrocarbon extraction.
Background Steam is used in hydrocarbon production in a number of different thermal recovery well systems for aiding in the extraction or production of hydrocarbons from a hydrocarbon reservoir. For ex-ample, hydrocarbons, such as heavy oil or bitumen, from a reservoir, such as from oil sands, may be recovered using a thermal in-situ recovery process, such as steam-assisted gravity drainage (SAGD), expanding solvent steam-assisted gravity drainage (ES-SAGD), cyclic steam stimula-tion (CSS), steam flooding, solvent-assisted cyclic steam stimulation, toe-to-heel air injection (THAI), or a solvent aided process (SAP). The generation of steam is a sizable investment in any of the thermal recovery well systems.
A number of systems and methods are traditionally used for generating steam for use in hydro-carbon thermal recovery. One problem associated with steam generation is the quality of water needed to produce the steam while minimizing fouling of the components such as boilers, heat exchangers, piping, etc. When produced water is used, the produced water contains a number of minerals and impurities which foul the components of the steam generation system and produced water typically requires expensive treatment, such as ion exchange treatment and/or softening, before the water is processed into steam. To avoid expensive treatment processes, systems have been developed that allow for the use of produced water despite the relatively high concentration of contaminants.
One such system is referred to as Flash Steam Generation (FSG), for example, wherein high quality steam is generated, without the need for boiling water and while avoiding the deposit of undesirable solids on equipment, by decoupling heating and phase changing processes during a staged heat transfer approach starting from a feed water containing solid particles and mineral materials.
A schematic of an FSG system is shown generally at 100 in Figure 1. A water supply such as produced water is input at 150 and heated via a staged heat transfer system 110 that comprises a plurality of heat exchangers, for example three heat exchangers 115, 120 and 125, that gradually heat the water under pressure so as not to vapourize the water thereby causing fouling of the pip-ing and/or heat exchangers 115, 120 and 125. Water pressure is typically around 18 MPa. The pressurized heated water is input into a flash tank 105 at a lower pressure, generally around 10 MPa where the pressure differential results in the flash vapourizing of the heated water into steam. Impurities in the water are precipitated and may be removed from the flash tank 105 as waste 135 while the steam is expelled at 140 from the flash tank 105. Steam quality may be up to about 25%, meaning that 75% water is left behind in the flash tank while 25% of the input wa-ter is vapourized into steam. The remaining water may be recycled at 145 and passed through the staged heat transfer system 110 again.
Some problems associated with FSG include the difficulty of establishing and operating a staged heat transfer; such a system is complex and can require significant maintenance. Staged heat transfer can easily result in localized vapourizing zones that foul the piping, the heat exchanger or both, and the process can result in further overheating of the associated components and fur-ther fouling thereof Maintenance can therefore be more frequently required for FSG operations if fouling occurs. In addition, increased expenses can be associated with establishing and main-taining a high pressure system.
An alternative system that avoids a staged heat transfer is referred to as a rocket boiler or direct fire(d) boiler and is shown generally in Figure 2 at 200. Air 210, fuel 215 and water 220 are in-put into the rocket boiler 205 where they are directly fired to vapourization wherein impurities in the water precipitate and may be removed as waste 225. The generated steam may be expelled at 230. However, due to the direct firing of the water and air, both CO2 and N2 are generated and expelled with the steam at 230. When the steam and gas mixture is injected into a steam cham-ber, the nitrogen can act as an insulating barrier in the steam chamber thereby preventing proper steam chamber formation. CO2 injected with the steam into the hydrocarbon formation may also generate a number of problems, potentially including acting as an insulating layer in the steam chamber, resulting in reduced efficiency of hydrocarbon extraction. One method of reducing nitrogen and other non-condensable gas emissions is to replace the air 210 with pure oxygen;
however, this solution is impractical on an industrial scale such as in hydrocarbon extraction.
Background Steam is used in hydrocarbon production in a number of different thermal recovery well systems for aiding in the extraction or production of hydrocarbons from a hydrocarbon reservoir. For ex-ample, hydrocarbons, such as heavy oil or bitumen, from a reservoir, such as from oil sands, may be recovered using a thermal in-situ recovery process, such as steam-assisted gravity drainage (SAGD), expanding solvent steam-assisted gravity drainage (ES-SAGD), cyclic steam stimula-tion (CSS), steam flooding, solvent-assisted cyclic steam stimulation, toe-to-heel air injection (THAI), or a solvent aided process (SAP). The generation of steam is a sizable investment in any of the thermal recovery well systems.
A number of systems and methods are traditionally used for generating steam for use in hydro-carbon thermal recovery. One problem associated with steam generation is the quality of water needed to produce the steam while minimizing fouling of the components such as boilers, heat exchangers, piping, etc. When produced water is used, the produced water contains a number of minerals and impurities which foul the components of the steam generation system and produced water typically requires expensive treatment, such as ion exchange treatment and/or softening, before the water is processed into steam. To avoid expensive treatment processes, systems have been developed that allow for the use of produced water despite the relatively high concentration of contaminants.
One such system is referred to as Flash Steam Generation (FSG), for example, wherein high quality steam is generated, without the need for boiling water and while avoiding the deposit of undesirable solids on equipment, by decoupling heating and phase changing processes during a staged heat transfer approach starting from a feed water containing solid particles and mineral materials.
A schematic of an FSG system is shown generally at 100 in Figure 1. A water supply such as produced water is input at 150 and heated via a staged heat transfer system 110 that comprises a plurality of heat exchangers, for example three heat exchangers 115, 120 and 125, that gradually heat the water under pressure so as not to vapourize the water thereby causing fouling of the pip-ing and/or heat exchangers 115, 120 and 125. Water pressure is typically around 18 MPa. The pressurized heated water is input into a flash tank 105 at a lower pressure, generally around 10 MPa where the pressure differential results in the flash vapourizing of the heated water into steam. Impurities in the water are precipitated and may be removed from the flash tank 105 as waste 135 while the steam is expelled at 140 from the flash tank 105. Steam quality may be up to about 25%, meaning that 75% water is left behind in the flash tank while 25% of the input wa-ter is vapourized into steam. The remaining water may be recycled at 145 and passed through the staged heat transfer system 110 again.
Some problems associated with FSG include the difficulty of establishing and operating a staged heat transfer; such a system is complex and can require significant maintenance. Staged heat transfer can easily result in localized vapourizing zones that foul the piping, the heat exchanger or both, and the process can result in further overheating of the associated components and fur-ther fouling thereof Maintenance can therefore be more frequently required for FSG operations if fouling occurs. In addition, increased expenses can be associated with establishing and main-taining a high pressure system.
An alternative system that avoids a staged heat transfer is referred to as a rocket boiler or direct fire(d) boiler and is shown generally in Figure 2 at 200. Air 210, fuel 215 and water 220 are in-put into the rocket boiler 205 where they are directly fired to vapourization wherein impurities in the water precipitate and may be removed as waste 225. The generated steam may be expelled at 230. However, due to the direct firing of the water and air, both CO2 and N2 are generated and expelled with the steam at 230. When the steam and gas mixture is injected into a steam cham-ber, the nitrogen can act as an insulating barrier in the steam chamber thereby preventing proper steam chamber formation. CO2 injected with the steam into the hydrocarbon formation may also generate a number of problems, potentially including acting as an insulating layer in the steam chamber, resulting in reduced efficiency of hydrocarbon extraction. One method of reducing nitrogen and other non-condensable gas emissions is to replace the air 210 with pure oxygen;
however, this solution is impractical on an industrial scale such as in hydrocarbon extraction.
2 A need therefore exists to provide a steam generation system that overcomes or mitigates one or more of the downsides outlined above or as observed in the art or in the industry.
Summary of the Invention In one embodiment there is provided a steam generation system for producing steam from water, the system comprising:
a direct contact heater for producing a pressurized heated water from a water input there-to and air/gas constituents; and a flash tank, in fluid communication with the direct contact heater, for receiving the pres-surized heated water and generating steam based on a pressure differential between the pressure of the flash tank and the pressurized heated water.
In another embodiment of the steam generation system or systems outlined above, the system or systems further including a separator in communication with the flash tank and the direct contact heater for separating the air/gas constituents from the pressurized heated water.
In another embodiment of the steam generation system or systems outlined above, the system or systems further include a recycled water conduit in communication with the flash tank and the direct contact heater for transferring water remaining in the flash tank to the direct contact heater.
In another embodiment of the steam generation system or systems outlined above, the flash tank comprises a waste outlet for outputting precipitated impurities from the water upon steam gener-ation.
In another embodiment of the steam generation system or systems outlined above, the flash tank is in fluid communication with a steam injection well of a hydrocarbon thermal recovery well system.
In another embodiment of the steam generation system or systems outlined above, the direct con-tact heater produces a pressurized heated water having a temperature above the atmospheric boil-ing point of the water but at a suitable pressure to be saturated water in liquid phase.
Summary of the Invention In one embodiment there is provided a steam generation system for producing steam from water, the system comprising:
a direct contact heater for producing a pressurized heated water from a water input there-to and air/gas constituents; and a flash tank, in fluid communication with the direct contact heater, for receiving the pres-surized heated water and generating steam based on a pressure differential between the pressure of the flash tank and the pressurized heated water.
In another embodiment of the steam generation system or systems outlined above, the system or systems further including a separator in communication with the flash tank and the direct contact heater for separating the air/gas constituents from the pressurized heated water.
In another embodiment of the steam generation system or systems outlined above, the system or systems further include a recycled water conduit in communication with the flash tank and the direct contact heater for transferring water remaining in the flash tank to the direct contact heater.
In another embodiment of the steam generation system or systems outlined above, the flash tank comprises a waste outlet for outputting precipitated impurities from the water upon steam gener-ation.
In another embodiment of the steam generation system or systems outlined above, the flash tank is in fluid communication with a steam injection well of a hydrocarbon thermal recovery well system.
In another embodiment of the steam generation system or systems outlined above, the direct con-tact heater produces a pressurized heated water having a temperature above the atmospheric boil-ing point of the water but at a suitable pressure to be saturated water in liquid phase.
3 In another embodiment of the steam generation system or systems outlined above, the direct con-tact heater is in fluid communication with a produced water source for receiving produced water to be heated.
In another embodiment of the steam generation system or systems outlined above, the direct con-tact heater is a direct contact boiler operated at a pressure suitable to maintain the water in liquid phase upon heating past the atmospheric boiling point of the water.
In another embodiment of the steam generation system or systems outlined above, the direct con-tact heater comprises a waste outlet for outputting precipitated impurities from the water upon heating.
In a further embodiment there is provided a method of generating steam from water comprising the steps of:
heating the water in a direct contact heater to a temperature above the atmospheric boil-ing point of the water at a pressure suitable to maintain the water in liquid phase to generate a pressurized heated water and air/gas constituents;
removing the air/gas constituents from the direct contact heater;
transferring the pressurized heated water to a flash tank at a lower pressure than the pres-surized heated water at a suitable pressure differential to generate steam upon transfer of the pressurized heated water into the flash tank; and expelling the steam generated in the flash tank.
In another embodiment of the method or methods of generating steam outlined above, the meth-od or methods further comprise the step of:
removing impurities precipitated from the pressurized heated water upon steam genera-tion from the flash tank.
In another embodiment of the method or methods of generating steam outlined above, the meth-od or methods further comprise the step of:
In another embodiment of the steam generation system or systems outlined above, the direct con-tact heater is a direct contact boiler operated at a pressure suitable to maintain the water in liquid phase upon heating past the atmospheric boiling point of the water.
In another embodiment of the steam generation system or systems outlined above, the direct con-tact heater comprises a waste outlet for outputting precipitated impurities from the water upon heating.
In a further embodiment there is provided a method of generating steam from water comprising the steps of:
heating the water in a direct contact heater to a temperature above the atmospheric boil-ing point of the water at a pressure suitable to maintain the water in liquid phase to generate a pressurized heated water and air/gas constituents;
removing the air/gas constituents from the direct contact heater;
transferring the pressurized heated water to a flash tank at a lower pressure than the pres-surized heated water at a suitable pressure differential to generate steam upon transfer of the pressurized heated water into the flash tank; and expelling the steam generated in the flash tank.
In another embodiment of the method or methods of generating steam outlined above, the meth-od or methods further comprise the step of:
removing impurities precipitated from the pressurized heated water upon steam genera-tion from the flash tank.
In another embodiment of the method or methods of generating steam outlined above, the meth-od or methods further comprise the step of:
4 recycling water remaining in the flash tank to the direct contact heater following steam generation.
Brief Description of the Drawings Figure 1 is a schematic of a prior art system for steam generation referred to as Flash Steam Generation (F SG);
Figure 2 is a schematic of a prior art system for steam generation referred to as Direct Steam Generation (DSG); and Figure 3 is a schematic illustrative of one embodiment of a system for steam generation.
Detailed Description It will be appreciated that the methods, systems, apparatuses, techniques, examples and embodi-ments described herein are for illustrative purposes intended for those skilled in the art, and are not meant to be limiting in any way. All reference to dimensions, capacities, embodiments or ex-amples throughout this disclosure, including the figures, should be considered a reference to an illustrative and non-limiting dimension, capacity, embodiment, or an illustrative and non-limiting example.
One example of a steam generation system that avoids the use of a staged heat transfer while also reducing or even removing CO2 content in the steam is disclosed herein with reference to Figure 3 wherein the system is shown generally at 300. A direct contact heater 305, such as a direct fire boiler, is used to directly heat water 360, such as produced water, input into the direct contact heater 305. For the purposes of this disclosure, the boiler will be referred to as a direct contact heater as the water therein is under pressure and therefore is heated with minimal to no vapourization. It is believed that some evaporation may occur; however, the direct contact heater is not intended to vapourize the water, but rather to heat the water, for example, above the at-mospheric boiling point. In one embodiment, a rocket boiler may be used as the direct contact heater. Rocket boilers, or direct steam generation boilers are well known in the art and will not be described further.
Both air 345 and fuel 350 are input into the heater 305 for use in providing combustion fuel for the heater 305 for heating the water 360. The water 360 is pressurized in the heater 305 such that the heated water is kept in the liquid phase and expelled together at 340 as pressurized heated water with typical air/gas constituents such as CO2, N2 and other non-condensable gases. The stream 340 of pressurized heated water and air/gas constituents expelled from the heater 305 is directed to a separator 310 to separate the air/gas constituents from the pressurized and saturated heated water. The air/gas constituents are expelled at 330 from the separator 310 and the pressur-ized heated water is expelled at 325 from the separator 310. Optionally, at least a portion of the air/gas constituents may be expelled at 375 from the direct contact heater 305 and the pressurized heated water 340 may be routed directly into the flash tank 315 without passing through a sepa-rator, such as 310. It will be appreciated that some trace amounts of air/gas constituents may be present in the pressurized heated water 340. This option may be useful in the event the non-condensable gases may be expelled directly from the direct contact heater 305.
It is also with the concept of the invention, to remove air/gas constituents from both the direct contact heater 305 at 375 and also from the separator 310.
It will be appreciated that the air 345 may be replaced with 02. The cost of using 02 is somewhat prohibitive, but using 02 instead of air would reduce or even avoid mixing and reacting of 02 with gases such as nitrogen, thereby limiting the formation of nitrogen oxides and emissions thereof As the air/gas constituents are expelled at 330 from the separator 310, the pressurized heated wa-ter is output at 325 free or substantially free of CO2 and other non-condensable gases, including N2 or oxides thereof The pressurized heated water at 325 is input into a flash tank 315 wherein steam is generated. The flash tank 315 is at a lower pressure than the pressurized heated water therein and therefore the pressurized heated water is at least partially vapourized into a saturated steam fraction. The saturated steam is expelled at 335 for eventual use, for example, in a thermal recovery process such as a SAGD operation. The remaining water fraction may be expelled at 320 and recycled through the system for further steam generation. The water expelled at 320 may be routed directly to the heater 305 or may be combined at 380 with the feed water 360. Option-ally, a re-pressurization pump 355 may be used to pressurize the water fraction before recycling the water fraction to the heater 305.
It will be appreciated that the water 360 may be produced water which includes typical impuri-ties that have not been removed by way of typical water treatments such as ion exchange and/or softening because impurities are precipitated in the flash tank 315 and removed as a waste prod-uct at a waste product outlet 370. Furthermore, it will be appreciated that the produced water provided to the system 300 may not require a de-oiling treatment to remove residual oil. The residual oil present in the produced water may serve as a fuel source for the direct contact heater 305, and as such may not require prior removal. Optionally, any impurities that precipitate out of the water heated in the heater 305 may be removed as a waste product at a waste product out-let 365 in the event that some steam is produced or that some evaporation occurs.
In addition, because at the heater 305, the separator 310, or both, CO2 and other non-condensable gases in the gas phase are removed or substantially removed from the pressurized heated water, the steam produced at 335 from the flash tank 315 is free or substantially free of CO2 and other non-condensable gases. By removing or substantially removing the CO2 and other non-condensable gases from the steam generated by the flash tank 315, the steam may be injected into a reservoir without incurring the potential negative effects associated with CO2 or other non-condensable gases possibly acting as an insulating layer and barrier to forming a proper steam chamber. Similarly, nitrogen may also act as an insulating layer and barrier to forming a proper steam chamber and can be removed from the steam at 330 before the steam is injected into the reservoir.
It is important to note that the pressurized heated water in the heater 305 should be kept at a suit-able pressure and/or temperature to remain in the liquid phase to allow for separation of the CO2 and other non-condensable gases at 330 without significant loss of water as water vapour or steam along with the gases expelled from the separator 310.
The pressure differential between the pressurized heated water entering the flash tank 315 and the flash tank 315 should be suitable to allow for steam generation upon input of the pressurized heated water into the flash tank 315. A vapour quality approaching, for example, 25% may be obtained. Depending on the use of the steam 335 expelled from the flash tank 315, the steam may be at a pressure of about 4 MPa for direct injection into an injection well, for example, a SAGD well, or the steam may be at a pressure of about 10 MPa if further transportation or man-, agement is necessary before reservoir injection or end use. Depending on the pressure require-ments for the expelled steam at 335, the pressure level of the pressurized heated water expelled from the heater 305 may be determined to ensure a sufficient pressure differential of the pressur-ized heated water 325 input into the flash tank 315. For example, the heater 305 may produce pressurized heated water 325 at a pressure of about 18 MPa while flash tank 315 is maintained below 18 MPa and the steam expelled from the flash tank 315 is below 18 MPa, for example at MPa.
It will be appreciated that any suitable piping and/or valve setup may be implemented to carry out steam generation from water including produced water as described herein.
The setup shown in the schematic of Figure 3 is not intended to be limiting but is merely illustrative of one em-bodiment for carrying out steam generation using a combination of a direct contact heater for heating the water and a flash tank for generating steam from the pressurized heated water. Pres-sure valves, flow control valves, manual valves, automated valves, etc., may be used in control-ling, characterizing and/or monitoring the water, pressurized heated water, air, fuel, waste, CO2, N2, or other air/gas constituents as desired or required throughout the steam generation system.
In addition, flow measurement instruments and sampling instruments may be used as necessary or desired throughout the system to collect information on fluid flow, corrosion, or other charac-teristics of the water, steam, pressurized heated water, fuel, waste, air, etc., to allow for operation and optimization of the system.
It will be appreciated that reference to a hydrocarbon reservoir includes any hydrocarbon deposit suitable for production of hydrocarbons including for example, but not limited to, a bitumen de-posit, oil sands, heavy oil deposit, etc. It will also be appreciated that hydrocarbons, such as heavy oil or bitumen, from a reservoir, such as from oil sands, may be recovered using a thermal in-situ recovery process, such as but not limited to: steam-assisted gravity drainage (SAGD), ex-panding solvent steam-assisted gravity drainage (ES-SAGD), cyclic steam stimulation (CSS), steam flooding, solvent-assisted cyclic steam stimulation, toe-to-heel air injection (THAI), or a solvent aided process (SAP).
It will also be appreciated that the water 360, including produced water, may be provided from multiple sources at one or more well pads and may be combined for input into the system 300 and/or heater 305.
The steam generated by the system 300 may be used as needed or desired for example in a ther-mal recovery process in one or more well pads implementing one or more thermal recovery techniques.
It will be appreciated that various modifications, revisions, adjustments, alterations, substitutions and additions may be made to the systems and methods outlined herein that are within the scope and spirit of the invention and without departing from the scope and spirit of the invention. It is the intention of the inventors that such modifications, revisions, adjustments, alterations, substi-tutions and additions are within the scope of the invention and the appended claims.
Brief Description of the Drawings Figure 1 is a schematic of a prior art system for steam generation referred to as Flash Steam Generation (F SG);
Figure 2 is a schematic of a prior art system for steam generation referred to as Direct Steam Generation (DSG); and Figure 3 is a schematic illustrative of one embodiment of a system for steam generation.
Detailed Description It will be appreciated that the methods, systems, apparatuses, techniques, examples and embodi-ments described herein are for illustrative purposes intended for those skilled in the art, and are not meant to be limiting in any way. All reference to dimensions, capacities, embodiments or ex-amples throughout this disclosure, including the figures, should be considered a reference to an illustrative and non-limiting dimension, capacity, embodiment, or an illustrative and non-limiting example.
One example of a steam generation system that avoids the use of a staged heat transfer while also reducing or even removing CO2 content in the steam is disclosed herein with reference to Figure 3 wherein the system is shown generally at 300. A direct contact heater 305, such as a direct fire boiler, is used to directly heat water 360, such as produced water, input into the direct contact heater 305. For the purposes of this disclosure, the boiler will be referred to as a direct contact heater as the water therein is under pressure and therefore is heated with minimal to no vapourization. It is believed that some evaporation may occur; however, the direct contact heater is not intended to vapourize the water, but rather to heat the water, for example, above the at-mospheric boiling point. In one embodiment, a rocket boiler may be used as the direct contact heater. Rocket boilers, or direct steam generation boilers are well known in the art and will not be described further.
Both air 345 and fuel 350 are input into the heater 305 for use in providing combustion fuel for the heater 305 for heating the water 360. The water 360 is pressurized in the heater 305 such that the heated water is kept in the liquid phase and expelled together at 340 as pressurized heated water with typical air/gas constituents such as CO2, N2 and other non-condensable gases. The stream 340 of pressurized heated water and air/gas constituents expelled from the heater 305 is directed to a separator 310 to separate the air/gas constituents from the pressurized and saturated heated water. The air/gas constituents are expelled at 330 from the separator 310 and the pressur-ized heated water is expelled at 325 from the separator 310. Optionally, at least a portion of the air/gas constituents may be expelled at 375 from the direct contact heater 305 and the pressurized heated water 340 may be routed directly into the flash tank 315 without passing through a sepa-rator, such as 310. It will be appreciated that some trace amounts of air/gas constituents may be present in the pressurized heated water 340. This option may be useful in the event the non-condensable gases may be expelled directly from the direct contact heater 305.
It is also with the concept of the invention, to remove air/gas constituents from both the direct contact heater 305 at 375 and also from the separator 310.
It will be appreciated that the air 345 may be replaced with 02. The cost of using 02 is somewhat prohibitive, but using 02 instead of air would reduce or even avoid mixing and reacting of 02 with gases such as nitrogen, thereby limiting the formation of nitrogen oxides and emissions thereof As the air/gas constituents are expelled at 330 from the separator 310, the pressurized heated wa-ter is output at 325 free or substantially free of CO2 and other non-condensable gases, including N2 or oxides thereof The pressurized heated water at 325 is input into a flash tank 315 wherein steam is generated. The flash tank 315 is at a lower pressure than the pressurized heated water therein and therefore the pressurized heated water is at least partially vapourized into a saturated steam fraction. The saturated steam is expelled at 335 for eventual use, for example, in a thermal recovery process such as a SAGD operation. The remaining water fraction may be expelled at 320 and recycled through the system for further steam generation. The water expelled at 320 may be routed directly to the heater 305 or may be combined at 380 with the feed water 360. Option-ally, a re-pressurization pump 355 may be used to pressurize the water fraction before recycling the water fraction to the heater 305.
It will be appreciated that the water 360 may be produced water which includes typical impuri-ties that have not been removed by way of typical water treatments such as ion exchange and/or softening because impurities are precipitated in the flash tank 315 and removed as a waste prod-uct at a waste product outlet 370. Furthermore, it will be appreciated that the produced water provided to the system 300 may not require a de-oiling treatment to remove residual oil. The residual oil present in the produced water may serve as a fuel source for the direct contact heater 305, and as such may not require prior removal. Optionally, any impurities that precipitate out of the water heated in the heater 305 may be removed as a waste product at a waste product out-let 365 in the event that some steam is produced or that some evaporation occurs.
In addition, because at the heater 305, the separator 310, or both, CO2 and other non-condensable gases in the gas phase are removed or substantially removed from the pressurized heated water, the steam produced at 335 from the flash tank 315 is free or substantially free of CO2 and other non-condensable gases. By removing or substantially removing the CO2 and other non-condensable gases from the steam generated by the flash tank 315, the steam may be injected into a reservoir without incurring the potential negative effects associated with CO2 or other non-condensable gases possibly acting as an insulating layer and barrier to forming a proper steam chamber. Similarly, nitrogen may also act as an insulating layer and barrier to forming a proper steam chamber and can be removed from the steam at 330 before the steam is injected into the reservoir.
It is important to note that the pressurized heated water in the heater 305 should be kept at a suit-able pressure and/or temperature to remain in the liquid phase to allow for separation of the CO2 and other non-condensable gases at 330 without significant loss of water as water vapour or steam along with the gases expelled from the separator 310.
The pressure differential between the pressurized heated water entering the flash tank 315 and the flash tank 315 should be suitable to allow for steam generation upon input of the pressurized heated water into the flash tank 315. A vapour quality approaching, for example, 25% may be obtained. Depending on the use of the steam 335 expelled from the flash tank 315, the steam may be at a pressure of about 4 MPa for direct injection into an injection well, for example, a SAGD well, or the steam may be at a pressure of about 10 MPa if further transportation or man-, agement is necessary before reservoir injection or end use. Depending on the pressure require-ments for the expelled steam at 335, the pressure level of the pressurized heated water expelled from the heater 305 may be determined to ensure a sufficient pressure differential of the pressur-ized heated water 325 input into the flash tank 315. For example, the heater 305 may produce pressurized heated water 325 at a pressure of about 18 MPa while flash tank 315 is maintained below 18 MPa and the steam expelled from the flash tank 315 is below 18 MPa, for example at MPa.
It will be appreciated that any suitable piping and/or valve setup may be implemented to carry out steam generation from water including produced water as described herein.
The setup shown in the schematic of Figure 3 is not intended to be limiting but is merely illustrative of one em-bodiment for carrying out steam generation using a combination of a direct contact heater for heating the water and a flash tank for generating steam from the pressurized heated water. Pres-sure valves, flow control valves, manual valves, automated valves, etc., may be used in control-ling, characterizing and/or monitoring the water, pressurized heated water, air, fuel, waste, CO2, N2, or other air/gas constituents as desired or required throughout the steam generation system.
In addition, flow measurement instruments and sampling instruments may be used as necessary or desired throughout the system to collect information on fluid flow, corrosion, or other charac-teristics of the water, steam, pressurized heated water, fuel, waste, air, etc., to allow for operation and optimization of the system.
It will be appreciated that reference to a hydrocarbon reservoir includes any hydrocarbon deposit suitable for production of hydrocarbons including for example, but not limited to, a bitumen de-posit, oil sands, heavy oil deposit, etc. It will also be appreciated that hydrocarbons, such as heavy oil or bitumen, from a reservoir, such as from oil sands, may be recovered using a thermal in-situ recovery process, such as but not limited to: steam-assisted gravity drainage (SAGD), ex-panding solvent steam-assisted gravity drainage (ES-SAGD), cyclic steam stimulation (CSS), steam flooding, solvent-assisted cyclic steam stimulation, toe-to-heel air injection (THAI), or a solvent aided process (SAP).
It will also be appreciated that the water 360, including produced water, may be provided from multiple sources at one or more well pads and may be combined for input into the system 300 and/or heater 305.
The steam generated by the system 300 may be used as needed or desired for example in a ther-mal recovery process in one or more well pads implementing one or more thermal recovery techniques.
It will be appreciated that various modifications, revisions, adjustments, alterations, substitutions and additions may be made to the systems and methods outlined herein that are within the scope and spirit of the invention and without departing from the scope and spirit of the invention. It is the intention of the inventors that such modifications, revisions, adjustments, alterations, substi-tutions and additions are within the scope of the invention and the appended claims.
Claims (12)
1. A steam generation system for producing steam from produced water, the system comprising:
a direct contact combustion heater for producing a pressurized heated water and air/gas constituents from a produced water input thereto; and a flash tank, in fluid communication with the direct contact heater, for receiving the pressurized heated water and generating the steam based on a pressure differential between the pressure of the flash tank and the pressurized heated water.
a direct contact combustion heater for producing a pressurized heated water and air/gas constituents from a produced water input thereto; and a flash tank, in fluid communication with the direct contact heater, for receiving the pressurized heated water and generating the steam based on a pressure differential between the pressure of the flash tank and the pressurized heated water.
2. The steam generation system of claim 1, further including a separator in communication with the flash tank and the direct contact heater for separating the air/gas constituents from the pressurized heated water.
3. The steam generation system of claim 1, further including a recycled water conduit in communication with the flash tank and the direct contact heater for transferring water remaining in the flash tank to the direct contact heater.
4. The steam generation system of any one of claims 1 to 3, wherein the flash tank is in fluid communication with a steam injection well of a hydrocarbon thennal recovery well system.
5. The steam generation system of any one of claims 1 to 4, wherein the direct contact heater produces the pressurized heated water having a temperature above the atmospheric boiling point of the water but at a suitable pressure to be saturated water in liquid phase.
6. The steam generation system of any one of claims 1 to 5, wherein the direct contact heater is in fluid communication with a produced water source for receiving produced water to be heated.
Date Recue/Date Received 2021-10-01
Date Recue/Date Received 2021-10-01
7. The steam generation system of any one of claims 1 to 6, wherein the direct contact heater is a direct contact boiler operated at a pressure suitable to maintain the water in liquid phase upon heating past the atmospheric boiling point of the water.
8. The steam generation system of any one of claims 1 to 7, wherein the flash tank comprises a waste outlet for outputting precipitated impurities from the water upon steam generation.
9. The steam generation system of any one of claims 1 to 7, wherein the direct contact heater comprises a waste outlet for outputting precipitated impurities from the water upon heating.
10. A method of generating steam from produced water comprising the steps of:
heating the produced water in a direct contact combustion heater to a temperature above the atmospheric boiling point of the produced water at a pressure suitable to maintain the water in liquid phase to generate a pressurized heated water and air/gas constituents;
removing the air/gas constituents from the contact heater;
transferring the pressurized heated water to a flash tank at a lower pressure than the pressurized heated water at a suitable pressure differential to generate the steam upon transfer of the pressurized heated water into the flash tank; and expelling the steam generated in the flash tank.
heating the produced water in a direct contact combustion heater to a temperature above the atmospheric boiling point of the produced water at a pressure suitable to maintain the water in liquid phase to generate a pressurized heated water and air/gas constituents;
removing the air/gas constituents from the contact heater;
transferring the pressurized heated water to a flash tank at a lower pressure than the pressurized heated water at a suitable pressure differential to generate the steam upon transfer of the pressurized heated water into the flash tank; and expelling the steam generated in the flash tank.
11. The method of claim 10, further comprising the step of:
removing impurities precipitated from the pressurized heated water upon steam generation from the flash tank.
removing impurities precipitated from the pressurized heated water upon steam generation from the flash tank.
12. The method of claim 10 or 11, further comprising the step of:
recycling water remaining in the flash tank to the direct contact heater following steam generation.
Date Recue/Date Received 2021-10-01
recycling water remaining in the flash tank to the direct contact heater following steam generation.
Date Recue/Date Received 2021-10-01
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US201461954524P | 2014-03-17 | 2014-03-17 | |
| US61/954,524 | 2014-03-17 |
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| Publication Number | Publication Date |
|---|---|
| CA2885081A1 CA2885081A1 (en) | 2015-09-17 |
| CA2885081C true CA2885081C (en) | 2022-07-12 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2885081A Active CA2885081C (en) | 2014-03-17 | 2015-03-17 | Steam generation system |
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| CA (1) | CA2885081C (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA3098744A1 (en) | 2019-11-12 | 2021-05-12 | Innotech Alberta Inc. | Electrical vapor generation methods and related systems |
| CN114353364A (en) * | 2022-01-12 | 2022-04-15 | 西安交通大学 | High-temperature steam generation system and method |
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