TECHNICAL FIELD

[0001 ] The technical field generally relates to recovering hydrocarbons or fluids, such as heavy hydrocarbons, from a subsurface formation, and more particularly to systems and methods for recovering hydrocarbons from a subsurface formation aided by a geothermal well. The technical field also relates to the use of wells for recovering geothermal heat from a subterranean formation for use at surface.

BACKGROUND

[0002 ] The general principle of recovering hydrocarbons, such as heavy hydrocarbons, from a subsurface formation involves heating the heavy hydrocarbons or otherwise reducing the viscosity, thereby facilitating recovery via a production well. Existing thermal processes for recovering heavy hydrocarbons typically require a large surface footprint with significant infrastructure, notably for steam generation. For example, steam-assisted gravity drainage (SAGD) processes require water and natural gas to generate steam at the surface so that the steam can be injected into the injection well for heating the heavy hydrocarbons. These processes have drawbacks, such as energy consumption, notable capital expenditure requirements, and CO2 generation.

[0003 ] There is therefore a need for improved technologies for recovering hydrocarbons from subsurface reservoirs and for leveraging geothermal heat sources for various uses.

SUMMARY

[0004 ] Various systems and methods are described herein for recovering heavy hydrocarbons from a subsurface formation while leveraging geothermal heat present in a lower zone of the formation. Drawing the geothermal heat up to the heavy hydrocarbon zone using a geothermal well can facilitate mobilization and recovery of the heavy hydrocarbons. Various implementations, aspects and applications of the technology are described in further detail herein. [0005 ] In some aspects, there is provided a system for recovering heavy hydrocarbons from a subsurface formation, the system comprising: a geothermal well comprising: a heat-receiving well section extending within a geothermal zone of the formation and being configured to be heated by geothermal heat in the geothermal zone and transmit heat upward; and a heat-transmission well section extending from the heat-receiving well section and extending into at least a heavy hydrocarbon zone of the formation located above the geothermal zone, the heat-transmission well section being configured to receive heat from the heat-receiving well section and transmit heat into the heavy hydrocarbon zone to promote mobilization of the heavy hydrocarbons; and a production well located in the heavy hydrocarbon zone and configured to receive mobilized heavy hydrocarbons for recovery to surface.

[0006 ] In some aspects, the heavy hydrocarbons may include heavy hydrocarbons, such as heavy oil, and/or bitumen. The hydrocarbons could also include oil or other hydrocarbon fluids.

[0007 ] In some aspects, the geothermal well can include an elongated component located in a corresponding wellbore and composed of a heat conductive material, and the heat is transmitted upward from the heat-receiving well section by conduction.

[0008 ] In some aspects, the geothermal well can include a supercritical fluid located in the heat-receiving well section and heat-transmission well section, and the heat is transmitted upward from the heat-receiving well section to the heat-transmission well section by conduction.

[0009 ] The geothermal well can include an insulated casing, which can be a vacuum insulated tubing casing.

[0010 ] In some aspects, the geothermal well can further include an upper well section that extends from the heat-transmission well section to the surface. [0011 ] The geothermal well can be configured to receive an injection fluid that is injectable downhole from the surface via the upper well section, and enters the heavy hydrocarbon zone via the heat-transmission well section. The injection fluid may be heated in the heat-transmission section and/or heat-receiving well section to form a heated fluid, and the heated fluid is injected into the heavy hydrocarbon zone via the heat-transmission well section. In some aspects, the injection fluid is not preheated at the surface. The injection fluid may include a gas, a liquid, or a mixture thereof. The gas can include steam or CO2, while the liquid can include water.

[0012 ] The geothermal well may be configured so that the inj ection fluid is heated the heatreceiving well section to form a heated fluid, the heated fluid being circulated to the heattransmission well section and injected into the heavy hydrocarbon zone via the heat-transmission well section.

[0013 ] The geothermal well may be configured to receive a first injection fluid that is injectable downhole from the surface via the upper well section, and is transported to the heatreceiving well section to form a heated first injection fluid, the heated fluid being circulated to the heat-transmission well section; and a second injection fluid that is heated in the heat-transmission to form a heated second injection fluid, and the heated second injection fluid is injected into the heavy hydrocarbon zone via the heat-transmission well section. The first injection fluid may be a supercritical fluid.

[0014 ] In some aspects, the geothermal well may be configured such that steam is generated upon heating of the water in the heat-transmission well section, and the steam is injected into the heavy hydrocarbon zone from the heat-transmission well section.

[0015 ] In some aspects, the heat-transmission well section includes a tubular liner that includes perforations for injection of the injection fluid into the heavy hydrocarbon zone.

[0016 ] The geothermal well may include at least one valve or packer located in a downhole region of the heat-transmission well section to prevent flow of the injection fluid further downhole. The at least one valve or packer may be located at a downhole end of the heat-transmission well section to prevent flow of the injection fluid into the heat-receiving well section. [0017 ] The geothermal well may also include at least one control valve located at an uphole region of the heat-transmission well section or in the upper well section to control the injection fluid entering the heat-transmission well section.

[0018 ] In some aspects, the heat-receiving well section may be configured to receive a hot native fluid from the geothermal zone of the formation, and transport the hot native fluid uphole into the heat-transmitting well section. The hot native fluid may be injected into the heavy hydrocarbon zone via the heat-transmission well section. The hot native fluid may include a gas, a liquid, or a mixture thereof. The gas may include steam or CO2, whereas the liquid may include water.

[0019 ] In some aspects, the geothermal well may be configured such that lower pressures that are present ascending up the geothermal well cause the water to flash to form steam which is injected into the heavy hydrocarbon zone via the heat-transmission well section.

[0020 ] The geothermal well may include at least one stop valve or packer located in an uphole region of the heat-receiving well section to prevent flow of the native fluid further up the geothermal well.

[0021 ] The geothermal well may also include a flow control valve that is located at an uphole region of the heat-receiving well section and configured to control flow of the hot native fluid into the heat-transmission well section. The at least one flow control valve may control the amount of the native fluid entering the heat-transmission well section.

[0022 ] In some aspects, the heat-receiving well section may be configured to transmit the heat by conduction to the heat-transmission well section, and the heat-transmission well section is configured to transmit the heat into the heavy hydrocarbon zone by conduction, in the absence of fluid injection into the heavy hydrocarbon zone.

[0023 ] In some aspects, the heat-receiving well section may be configured to prevent flow of a native fluid from the geothermal zone of the formation uphole into the heat-transmission well section. [0024 ] In some aspects, the heat-transmission well section may be horizontal and overly at least a portion of the production well. The heat-transmission well section may also be parallel with and vertically spaced apart from the production well.

[0025 ] In some aspects, the heat-receiving well section may substantially be perpendicular with respect to the heat-transmission well section. The heat-receiving well section may be generally vertical. The heat-receiving well section may also be generally inclined.

[0026 ] In some aspects, the heavy hydrocarbon zone and the geothermal zone are vertically separated from each other by at least one barrier zone of the formation.

[0027 ] In some aspects, the heat-receiving well section may have branched well sections or may be a linear well section.

[0028 ] In some aspects, there may be a plurality of the geothermal wells associated with one or more production wells. A plurality of the production wells may also be associated with the geothermal well.

[0029 ] In some aspects, there is provided a method for recovering heavy hydrocarbons from a subsurface formation, the method comprising: heating a heavy hydrocarbon zone of the formation and mobilizing heavy hydrocarbons contained therein with geothermal heat obtained from a geothermal zone of the formation, wherein the geothermal heat is obtained by a geothermal well comprising: a heat-receiving well section extending within the geothermal zone of the formation, and being configured to be heated by geothermal heat in the lower geothermal zone and transmit heat upward; a heat-transmission well section extending from the heat-receiving well section and extending into at least the heavy hydrocarbon zone of the formation located above the geothermal zone, the heat-transmission well section being configured to receive heat from the heat-receiving well section and transmit heat into the heavy hydrocarbon zone to promote mobilization of the heavy hydrocarbons; and recovering the mobilized heavy hydrocarbons to surface.

[0030 ] In some aspects, the heating and the recovering are performed simultaneously; or wherein the heating is performed as a pretreatment step prior to recovering the mobilized heavy hydrocarbons from the subsurface formation.

[0031 ] In some aspects, the heating of the heavy hydrocarbon zone may be performed by conduction of the geothermal heat through the heat-receiving well section and the heattransmission well section and into the heavy hydrocarbon zone in the absence of fluid injection into the geothermal well.

[0032 ] In some aspects, the heating of the heavy hydrocarbon zone may be performed by conduction of the geothermal heat from the heat-receiving well section to the heat-transmission well section, and by downhole injection of an injection fluid that is heated in the heat-transmission well section and then injected into the heavy hydrocarbon zone.

[0033 ] In some aspects, the heating of the heavy hydrocarbon zone may include introducing a circulation fluid downhole into the geothermal well, wherein the circulation fluid is circulated through the heat-receiving well section to be heated to form a heated fluid, and then the heated fluid is transported to the heat-transmission well section for injection into the heavy hydrocarbon zone or for indirect heating of the heavy hydrocarbon zone. The circulation fluid may include a gas, a liquid, or a mixture thereof. The gas may include steam or CO2, whereas the liquid may include water. In some aspects, steam may be generated as the heated fluid upon heating of the water in the heat-receiving well section, and the steam is injected into the heavy hydrocarbon zone from the heat-transmission well section.

[0034 ] In some aspects, the heating of the heavy hydrocarbon zone may be performed by conduction of the geothermal heat from the heat-receiving well section to the heat-transmission well section, and by injection of a hot native fluid that is received from the geothermal zone of the formation through heat-receiving well section, transported uphole to the heat-transmission well section, and then injected into the heavy hydrocarbon zone. The native fluid may include a gas, a liquid, or a mixture thereof. The gas may include steam or CO2, whereas the liquid may include water. [0035 ] In some aspects, lower pressures that are present ascending up the geothermal well cause the water to flash to form steam which is injected into the heavy hydrocarbon zone via the heat-transmission well section.

[0036 ] In some aspects, the recovering of the mobilized heavy hydrocarbons may be performed by gravity drainage.

[0037 ] In some aspects, there is provided a method for recovering hydrocarbons from a subsurface formation, the method comprising transferring geothermal heat from a geothermal zone of the formation to a hydrocarbon zone located above the geothermal zone by conduction to promote mobilization of the hydrocarbons for production thereof to surface. The hydrocarbons may include heavy hydrocarbons.

[0038 ] In some aspects, there is provided a method for recovering hydrocarbons from a subsurface formation, the method comprising transferring geothermal heat from a geothermal zone of the formation to a hydrocarbon zone located above the geothermal zone without transferring the geothermal heat to surface to promote mobilization of the hydrocarbons for production thereof to the surface. The hydrocarbons may include heavy hydrocarbons.

[0039 ] In some aspects, there is provided a method for heating and recovering a fluid in a subsurface formation, the method comprising: heating a fluid-containing zone of the formation with geothermal heat obtained from a geothermal zone of the formation, wherein the geothermal heat is obtained by a geothermal well comprising: a heat-receiving well section extending within the geothermal zone of the formation, and being configured to be heated by geothermal heat in the lower geothermal zone and transmit heat upward; a heat-transmission well section extending from the heat-receiving well section and extending into at least the fluid-containing zone of the formation located above the geothermal zone, the heat-transmission well section being configured to receive heat from the heat-receiving well section and transmit heat into the fluid-containing zone to heat fluids contained therein; and recovering heated fluid to surface.

[0040 ] In some aspects, there is provided a system for recovering hydrocarbons from a subsurface formation, the system comprising: a geothermal well comprising: a heat-receiving well section extending within a geothermal zone of the formation and being configured to be heated by geothermal heat in the geothermal zone and transmit heat upward; a heat-transmission well section extending from the heat-receiving well section and extending into at least a hydrocarbon zone of the formation located above the geothermal zone, the heat-transmission well section being configured to receive heat from the heat-receiving well section and transmit heat into the hydrocarbon zone to promote mobilization of the hydrocarbons; and a production well located in the hydrocarbon zone and configured to receive mobilized hydrocarbons for recovery to surface.

[0041 ] In some aspects, there is provided a method for recovering hydrocarbons from a subsurface formation, the method comprising: heating a hydrocarbon zone of the formation and mobilizing hydrocarbons contained therein with geothermal heat obtained from a geothermal zone of the formation, wherein the geothermal heat is obtained by a geothermal well comprising: a heat-receiving well section extending within the geothermal zone of the formation, and being configured to be heated by geothermal heat in the lower geothermal zone and transmit heat upward; a heat-transmission well section extending from the heat-receiving well section and extending into at least the hydrocarbon zone of the formation located above the geothermal zone, the heat-transmission well section being configured to receive heat from the heat-receiving well section and transmit heat into the hydrocarbon zone to promote mobilization of the hydrocarbons; and recovering the mobilized hydrocarbons to surface.

[0042 ] In some aspects, there is provided a system for recovering heavy hydrocarbons and geothermal heat from a subsurface formation, the system comprising: a geothermal well comprising: a heat-receiving well section extending within a geothermal zone of the formation and being configured to be heated by geothermal heat in the geothermal zone and transmit heat upward; a heat-transmission well section extending from the heat-receiving well section and extending into at least a heavy hydrocarbon zone of the formation located above the geothermal zone, the heat-transmission well section being configured to receive geothermal heat from the heat-receiving well section and transmit a first portion of the geothermal heat into the heavy hydrocarbon zone to promote mobilization of the heavy hydrocarbons; an upper well section extending from the heat-transmission well section to the surface, the upper well section being configured to receive a second portion of the geothermal heat from the heat-transmission well section for recovery to the surface; and a production well located in the heavy hydrocarbon zone and configured to receive mobilized heavy hydrocarbons for recovery to the surface.

[0043 ] The geothermal well may include an elongated component located in a corresponding wellbore and composed of a heat conductive material, and the geothermal heat is transmitted upward from the heat-receiving well section by conduction. [0044 ] The geothermal well may include a supercritical fluid located in the heat-receiving well section and heat-transmission well section, and the heat is transmitted upward from the heatreceiving well section to the heat-transmission well section by conduction.

[0045 ] The geothermal well may include an insulated casing, which may be a vacuum insulated tubing casing.

[0046 ] The geothermal well may be configured such that the heat-receiving well section is configured to receive a hot native fluid from the geothermal zone of the formation, and transport the hot native fluid uphole into the heat-transmission well section and to the surface.

[0047 ] The geothermal well may be configured such that a first portion of the hot native fluid is transported into the heat-transmission well section and injected into the heavy hydrocarbon zone; and a second portion of the hot native fluid is transported into the heat-transmission well section and further into the upper well section for recovery to the surface. The hot native fluid may include a gas, a liquid, or a mixture thereof. The gas may include steam or CO2. The liquid may include water.

[0048 ] The geothermal well may be configured such that the second portion of the hot native fluid comprises steam that is used for generating electricity at or just below the surface.

[0049 ] The geothermal well may be configured such that the geothermal heat recovered to the surface is used for generating electricity and/or steam.

[0050 ] In some aspects, there is provided a system for recovering geothermal heat and/or a hot native fluid from a subsurface formation, the system comprising: a geothermal well comprising: a heat-receiving well section extending within a geothermal zone of the formation and being configured to transport the geothermal heat and/or hot native fluid in the geothermal zone upward; and an upper well section extending from the heat-receiving well section to the surface, the upper well section being configured to receive the geothermal heat and/or hot native fluid from the heat-receiving well section for recovery to the surface.

[0051 ] The geothermal well may include an elongated component located in a corresponding wellbore and composed of a heat conductive material, and the geothermal heat is transmitted upward from the heat-receiving well section by conduction.

[0052 ] The geothermal well may include a supercritical fluid located in the heat-receiving well section and heat-transmission well section, and the heat is transmitted upward from the heatreceiving well section to the heat-transmission well section by conduction.

[0053 ] The geothermal well may include an insulated casing, which may be a vacuum insulated tubing casing.

[0054 ] The hot native fluid may include a gas, a liquid, or a mixture thereof. The gas may include steam or CO2. The liquid may include water..

[0055 ] The geothermal well may be configured such that the hot native fluid comprises steam that is used for generating electricity at or just below the surface.

[0056 ] The geothermal well may be configured such that the geothermal heat recovered to the surface is used for generating electricity and/or steam.

[0057 ] In some aspects, there is provided a method for recovering hydrocarbons, geothermal heat, and/or hot native fluid from a subsurface formation, the method comprising: heating a hydrocarbon zone of the formation and mobilizing hydrocarbons contained therein with geothermal heat and/or hot native fluid obtained from a geothermal zone of the formation, wherein the geothermal heat and/or hot native fluid is obtained by a geothermal well comprising: a heat-receiving well section extending within the geothermal zone of the formation, and being configured to be heated by geothermal heat and/or hot native fluid in the lower geothermal zone and transmit heat upward; a heat-transmission well section extending from the heat-receiving well section and extending into at least the hydrocarbon zone of the formation located above the geothermal zone, the heat-transmission well section being configured to receive geothermal heat and/or hot native fluid from the heat-receiving well section and transmit a first portion of the geothermal heat and/or hot native fluid into the hydrocarbon zone to promote mobilization of the hydrocarbons; an upper well section extending from the heat-transmission well section to the surface, the upper well section being configured to receive a second portion of the geothermal heat and/or hot native fluid from the heat-transmission well section for recovery to the surface; and recovering the mobilized hydrocarbons and the geothermal heat to the surface.

[0058 ] In some aspects, there is provided a method for recovering geothermal heat and/or hot native fluid from a subsurface formation, the method comprising: obtaining geothermal heat and/or hot native fluid contained within a geothermal zone of the subsurface formation, wherein the geothermal heat and/or hot native fluid is obtained by a geothermal well comprising: a heat-receiving well section extending within the geothermal zone and being configured to transport the geothermal heat and/or hot native fluid in the geothermal zone upward; and an upper well section extending from the heat-receiving well section to the surface, the upper well section being configured to receive the geothermal heat and/or hot native fluid from the heat-receiving well section for recovery to the surface; using the geothermal heat and/or hot native fluid at the surface.

[0059 ] In some aspects, there is provided a method for recovering geothermal heat and/or hot native fluid from a subsurface formation, the method comprising: obtaining geothermal heat and/or hot native fluid contained within a geothermal zone of the formation, wherein the geothermal heat and/or hot native fluid is obtained by an abandoned well, and wherein the abandoned well is configured to receive the geothermal heat and/or the hot native fluid from the geothermal zone; and recovering at least a portion of the geothermal heat and/or at least a portion of the hot native fluid to the surface.

[0060 ] In some aspects, at least a downhole portion of the abandoned well is located in the geothermal zone of the formation.

[0061 ] In some aspects, the method further comprises drilling downhole into the abandoned well to extend the abandoned well and reach the geothermal zone of the formation.

[0062 ] In some aspects, the abandoned well receives an elongated component composed of a heat conductive material, and the geothermal heat is transmitted uphole in the well by conduction through the elongated component.

[0063 ] In some aspects, the abandoned well comprises a supercritical fluid, and the geothermal heat is transmitted uphole in the well by conduction.

[0064 ] In some aspects, the abandoned well comprises an insulated casing, which may be a vacuum insulated tubing casing.

[0065 ] In some aspects, the abandoned well receives a hot native fluid from the geothermal zone of the formation, and transports the hot native fluid uphole in the well to the surface. The hot native fluid may include a gas, a liquid, or a mixture thereof. The gas may include steam or CO2. The liquid may include water..

[0066 ] In some aspects, the abandoned well is an abandoned production well or and abandoned injection well.

[0067 ] In some aspects, the hot native fluid comprises steam that is used for generating electricity at or just below the surface. [0068 ] In some aspects, the geothermal heat recovered to the surface is used for generating electricity and/or steam.

[0069 ] In some aspects, there is provided a use of geothermal heat recovered by the system defined herein or by the method defined herein, for generating electricity and/or steam, or for reinjection into a geothermal well for recovering heavy hydrocarbons from the subsurface formation and/or a second subsurface formation.

[0070 ] In some aspects, there is provided a system for geothermally heating and recovering an injection fluid, the system comprising: a geothermal well comprising: a heat-receiving well section extending within a geothermal zone of a subsurface formation and being configured to transport the injection fluid in the geothermal zone downward; and an upper well section extending from the heat-receiving well section to the surface, the upper well section being configured to receive an injection fluid that is injectable downhole from the surface via the upper well section; wherein the geothermal well is configured so that the injection fluid is heated in the geothermal zone to form a geothermally-heated fluid and wherein the heat-receiving well section is configured to receive the geothermally-heated fluid for recovery to the surface.

[0071 ] In some aspects, there is provided a method for geothermally heating and recovering an injection fluid, the method comprising: injecting an injection fluid into a geothermal well comprising: a heat-receiving well section extending within a geothermal zone of a subsurface formation and being configured to transport the injection fluid in the geothermal zone downward; and an upper well section extending from the heat-receiving well section to the surface, the upper well section being configured receive the injection fluid that is injectable downhole from the surface via the upper well section; wherein the geothermal well is configured so that the injection fluid is heated in the geothermal zone to form a geothermally-heated fluid and wherein the heatreceiving well section is configured to receive the geothermally-heated fluid for recovery to the surface; and recovering the geothermally-heated fluid at the surface.

[0072 ] In some aspects, there is provided a use of geothermally-heated injection fluid recovered by the system defined herein or by the method defined herein, for generating electricity and/or steam, or for reinjection into a geothermal well for recovering heavy hydrocarbons from the subsurface formation and/or a second subsurface formation.

[0073 ] In some aspects, there is provided a method for recovering hydrocarbons from one or more subsurface formations, the method comprising: injecting an injection fluid into a geothermal well comprising: a heat-receiving well section extending within a geothermal zone of a subsurface formation and being configured to transport the injection fluid in the geothermal zone downward; and an upper well section extending from the heat-receiving well section to the surface, the upper well section being configured receive the injection fluid that is injectable downhole from the surface via the upper well section; wherein the geothermal well is configured so that the injection fluid is heated in the geothermal zone to form a geothermally-heated fluid and wherein the heatreceiving well section is configured to receive the geothermally-heated fluid for recovery to the surface; recovering the geothermally-heated fluid at the surface; and inj ecting the geothermally-heated fluid into one or more geothermal wells or production wells for recovering heavy hydrocarbons from the subsurface formation and/or a second subsurface formation

BRIEF DESCRIPTION OF THE DRAWINGS

[0074 ] For a better understanding of the aspects and implementations described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings which show exemplary implementations, and in which:

[0075 ] Fig. 1 is a side view schematic of a system for recovering heavy hydrocarbons according to one example implementation. The system comprises a geothermal well comprising a heat-receiving well section and a heat-transmitting well section, where the geothermal well heats the heavy hydrocarbons by conduction (wavy lines) of heat from a hot geothermal zone up to the heavy hydrocarbon zone. Heated heavy hydrocarbons are then recovered to the surface via a production well.

[0076 ] Fig. 2 is a side view schematic of the system for recovering heavy hydrocarbons according to a second example implementation. The system comprises a geothermal well comprising a heat-receiving well section and a heat-transmitting well section, where the geothermal well heats the heavy hydrocarbons by conduction of heat from a hot geothermal zone up to the heavy hydrocarbon zone, as well as by injection of a fluid (dashed arrows; white arrows represent colder fluid and black arrows represent heated fluid) from the surface that is heated in heat-transmitting well section and injected into the heavy hydrocarbon zone. Heated heavy hydrocarbons are then recovered to the surface via a production well.

[0077 ] Fig. 3 is a side view schematic of the system for recovering heavy hydrocarbons according to a third example implementation. The system comprises a geothermal well comprising a heat-receiving well section and a heat-transmitting well section, where the geothermal well heats the heavy hydrocarbons by conduction of heat (solid arrows) from a hot geothermal zone up to the heavy hydrocarbon zone. In addition, a hot native fluid (dashed arrows) from the hot geothermal zone flows into the geothermal well and is transported from the heat-receiving well section up to the heat-transmission well section for injection into the heavy hydrocarbon zone. Heated heavy hydrocarbons are then recovered to the surface via a production well.

[0078 ] Fig. 4 is a close-up side view schematic of the heat-receiving well section, according to one example implementation.

[0079 ] Fig. 5 is a close-up side view schematic of the upper well receiving section, according to one example implementation.

[0080 ] Fig. 6 is a close-up side view schematic of the heat-transmitting well section, according to one example implementation.

[0081 ] Fig. 7 is a close-up side view schematic of the heat-transmitting well section, according to one example implementation.

[0082 ] Fig. 8 is a side view schematic of the system of Figs. 1 to 3, whereby the hot native fluid (dashed arrows from the hot geothermal zone) from the hot geothermal zone and injection of a fluid (dashed arrows from the surface; white arrows represent colder fluid and black arrows represent heated fluid) from the surface is transported to the heat-transmitting well section and injected into the heavy hydrocarbon zone.

[0083 ] Fig. 9 is a side view schematic of the system of Fig. 2 and 3, whereby the hot native fluid (dashed arrows from the hot geothermal zone) from the hot geothermal zone and/or injection of a fluid (dashed arrows from the surface; white arrows represent colder fluid and black arrows represent heated fluid) from the surface is transported to the heat-transmitting well section and injected into the heavy hydrocarbon zone, in the absence of conduction.

[0084 ] Fig. 10 is a side view schematic of the system of Fig. 2, wherein injection of a fluid (dashed arrows from the surface; white arrows represent colder fluid and black arrows represent heated fluid) from the surface is transported to the heat-receiving well section for heating in the geothermal zone, circulated to the heat-transmission well section, and injected into the heavy hydrocarbon zone, in the absence of conduction. [0085 ] Fig. 11 is a side view schematic of the system of Fig. 1, wherein the geothermal well includes supercritical fluid (wavy arrows) that conducts geothermal heat from the heatreceiving well section to the heat-transmission well section, in the absence of an elongated component.

[0086 ] Fig. 12 is a side view schematic of the system of Fig. 1, wherein the geothermal well includes supercritical fluid (wavy arrows) that conducts geothermal heat and/or a hot native fluid (dashed arrows from the hot geothermal zone) from the heat-receiving well section to the heat-transmission well section, in the absence of an elongated component. Hot native fluid is then injected into the hydrocarbon zone via the heat-transmission well section.

[0087 ] Fig. 13 is a side view schematic of the system of Fig. 2, wherein the geothermal well includes supercritical fluid (wavy arrows) that conducts geothermal heat from the heatreceiving well section to the heat-transmission well section, in the absence of an elongated component. Injection of an injection fluid (dashed arrows from the surface; white arrows represent colder fluid and black arrows represent heated fluid) from the surface is transported into the heattransmission well section to be heated and injected into the heavy hydrocarbon zone.

[0088 ] Fig. 14 is a side view schematic of the system of Fig. 2, wherein injection of a supercritical fluid (wavy arrows) from the surface is transported to the heat-receiving well section for heating in the geothermal zone, circulated to the heat-transmission well section, in the absence of an elongated component. Injection of another fluid (dashed arrows from the surface; white arrows represent colder fluid and black arrows represent heated fluid) from the surface is transported into the heat-transmission well section to be heated by the circulating supercritical fluid and injected into the heavy hydrocarbon zone.

[0089 ] Fig. 15 is a side view schematic of the system of Fig. 1 and 3 whereby geothermal heat (solid arrows) and/or hot native fluid (dashed arrows) from the hot geothermal zone up is further transported to the surface.

[0090 ] Fig. 16 is a side view schematic of the system of Fig. 12, whereby supercritical fluid (wavy arrows) and/or hot native fluid (dashed arrows) from the hot geothermal zone up is further transported to the surface, in the presence of conduction with a supercritical fluid (wavy arrows),.

[0091 ] Fig. 17 is a side view schematic of the system for recovering geothermal heat (solid arrows) and/or hot native fluid (dashed arrows) from a subsurface formation, in the presence or absence of conduction with an elongated component, using a geothermal well or an abandoned well.

[0092 ] Fig. 18 is a side view schematic of the system for recovering geothermal heat and/or hot native fluid (dashed arrows) from a subsurface formation, in the presence of conduction with a supercritical fluid (wavy arrows), using a geothermal well or an abandoned well.

[0093 ] Fig. 19 is a side view schematic of the system for recovering geothermally-heated injection fluid from a subsurface formation, wherein injection of a fluid (dashed arrows from the surface; white arrows represent colder fluid and black arrows represent heated fluid) from the surface is transported to the heat-receiving well section for heating in the geothermal zone, circulated to the heat-transmission well section, and recovered to the surface, using a geothermal well or an abandoned well.

[0094 ] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Nevertheless, for disclosure purposes, it should be understood that the relative proportions of the various elements as shown in the figures are disclosed.

DETAILED DESCRIPTION

[0095 J The present description relates to systems and methods for recovering heavy hydrocarbons from a subsurface formation, as shown for example in Figs. 1-4, as well as systems and methods for retrieving heat from a subterranean formation and using the heat at surface and/or in a subterranean zone.

[0096 ] In some implementations, the systems and methods described herein leverage the use of a geothermal well to obtain geothermal heat from a low zone of the formation and transport that heat up to a heavy hydrocarbon zone to heat and mobilize the hydrocarbons to facilitate recovery. The geothermal heat can be sent directly from the geothermal zone to the heavy hydrocarbon zone by conduction via completion equipment in the well and/or by allowing hot native fluid to flow up through the well for inj ection into the heavy hydrocarbon zone. Optionally, a fluid can be injected from surface and can be heated by the geothermal heat and injected into the reservoir.

[0097 ] More particularly, the system can include a geothermal well that brings heat from the hot geothermal zone up to the heavy hydrocarbon zone for heating the heavy hydrocarbons, thereby reducing the viscosity of the heavy hydrocarbons for facilitated recovery to the surface by a nearby production well. The systems and methods described herein harness geothermal heat for directly heating hydrocarbons, and therefore provide enhancements in terms of efficiency and environmental sustainability.

[0098 J Referring now to Figs. 1 to 4, the present technology relates to a system 10 for recovering heavy hydrocarbons 12 from a subsurface formation. The system 10 includes a geothermal well 14 that includes a heat-receiving well section 16 and a heat-transmission well section 18, and the system 10 also includes a production well 20. The heat-receiving well 16 section extends within a geothermal zone 22 of the formation and is configured to be heated by geothermal heat in the geothermal zone 22 and to transmit the heat upward. The heat-transmission well section 18 extends from the heat-receiving well section 16 into at least a heavy hydrocarbon zone 24 of the formation located above the geothermal zone 22. The heat-transmission well section 18 is configured to receive heat from the heat-receiving well section 16 and to transmit the heat into the heavy hydrocarbon zone 24 to promote mobilization of the heavy hydrocarbons 12. The production well 20 is located in the heavy hydrocarbon zone 24 and is configured to receive mobilized heavy hydrocarbons 12 for recovery to the surface 26.

[0099 ] As used herein, the term “hydrocarbons” may refer to any hydrocarbon that is present in a subsurface formation for recovery to the surface. The hydrocarbons may in include “heavy” hydrocarbons having a relatively high viscosity that would create difficulties for in situ recovery. Heavy hydrocarbons may include heavy oil, crude oil and bitumen, for example. Hydrocarbons may be localized in subsurface formations termed “hydrocarbon zones” or reservoirs. In some cases, heavy hydrocarbons have a low API (American Petroleum Institute) gravity. In some cases, the heavy hydrocarbons have an API gravity that is lower than 30, 25, 20, 15, or 10. The heavy hydrocarbons can be recovered as oil-water emulsions, due to native water or injected water or steam. It is noted that the present technology may be useful for the recovery and/or production of various hydrocarbon fluids, including light crude oil, shale oil, or vapour phase hydrocarbons such as natural gas, where geothermal heating can provide one or more benefits. It is also possible to apply the techniques described herein to heat other types of fluids that are present in formations, such as water, brine, and the like.

[00100 ] As used herein, the terms “subsurface formation”, “underground reservoir”, and “subterranean zone” may be used interchangeably. The subsurface formations described herein may be localized offshore or onshore and at any depth. Subsurface formations may include hydrocarbons and hydrocarbon zones. Furthermore, subsurface formations may include geothermal zones containing geothermal heat.

[00101 ] As used herein, the term “surface” may refer to the uppermost level of land (ground) or sea, or to a region just below the surface (i.e., near surface).

[00102 ] As used herein, the term “supercritical fluid” may refer to a single or a mixture of different fluids.

[00103 ] As used herein, the term “mobilized” refers to hydrocarbons that have a reduced viscosity for facilitated recovery. Heating, for example, may be one method for reducing the viscosity of hydrocarbons and promoting their mobilization. In some implementations, heating hydrocarbons to at least 100°C may be sufficient for promoting mobilization. Optimal temperature ranges for mobilization may be at least within 150°C to 300°C, however, in areas of higher pressure, a lower temperature (<100°C) may be sufficient to heat and mobilize the hydrocarbons. In some implementations, the resulting viscosity of mobilized hydrocarbons is preferably less than about 1000 cP (centipoise), less than about 750 cP, less than about 500 cP, less than about 250 cP, less than about 100 cP, or less than about 50 cP.

[00104 ] The subsurface formations including the heavy hydrocarbon zones 24 may be located at various distances from a geothermal zone 22, and may be separated by one or more barriers. Barrier layers may include a low-permeability stratum in the formation, and may be formed of shale or mud, for example. The geothermal well 14 may be configured to increase or decrease the length of the heat-receiving well section 16 and/or the heat-transmission well section 18 depending on the position of the heavy hydrocarbon zone 24 with respect to the geothermal zone 22. In some cases, the heavy hydrocarbon zone 24 and the geothermal zone 22 are vertically separated from each other. Alternatively, the heavy hydrocarbon zone 24 and the geothermal zone 22 are horizontally separated from each other.

[00105 ] In some implementations, the heat-receiving well section 16 is generally perpendicular with respect to the heat-transmission well section 18, especially when the heattransmission well section 18 is generally horizontal and the heat-receiving well section 16 is generally vertical. The heat-receiving well section 16 may be generally vertical or generally inclined, horizontal, or directional. In some implementations, the heat-receiving well section 16 has branched well sections or is an unbranched well section.

[00106 ] In some implementations, the heat-transmission well section 18 is horizontal and overlies at least a portion of the production well 20. In some cases, the heat-transmission well 18 section is parallel with and vertically spaced apart from the production well 20, and forms a well pair configuration with the production well 20. The heat-transmitting well section 18 may also have branched well sections or may be an unbranched well section. While the well pair confirmation is shown in the figures, it is also noted that the heat-transmission well section 18 can be located above one or more production wells 20 and oriented at various angles rather than being directly above and parallel with the production well 20.

[00107 ] In some implementations, the geothermal well 14 includes an upper well section 28 that extends from the heat-transmission well section 18 to the surface 26. The upper well section 28 is formed during the initial drilling of the geothermal well 14 and may simply be kept as a wellbore access. In some cases, the upper well section 28 is used to inject an injection fluid 32 downhole into the heat-transmitting well section 16, as will be described in further detail below.

[00108 ] In some implementations, the system includes a plurality of geothermal wells 14 associated with one or more production wells 20. The geothermal wells 14 can be provided in various arrangements and patterns with respect to each other and with respect to the production wells 20. The system may include a combination of different geothermal wells, as shown by different implementations herein, associated with one or more production wells 20. For example, one geothermal well 14 can be configured for fluid injection, while another geothermal well 14 can be configured to transfer geothermal heat by conduction without fluid injection. In addition, there may be a plurality of production wells associated with a geothermal well. Finally, the systems, methods, or geothermal wells described herein may be partially or completely combined with existing in situ recovery systems and methods for recovering heavy hydrocarbons, such as but not limited to the SAGD process. For example, one or more SAGD well pairs could be located close to and associated with one or more of the geothermal wells 14.

First Implementation

[00109 ] Fig. 1 illustrates the system 10 that includes the geothermal well 14 which heats the heavy hydrocarbons 12 by conduction of heat from the hot geothermal zone 22 to the heavy hydrocarbon zone 24 where fluid does not flow into the heat-transmission section 18 from the surface or from the heat-receiving section 16.

[00110 ] According to this example implementation, the geothermal well 14 includes an elongated component 30 located in the wellbore of the geothermal well and composed of a heat conductive material, and the heat is transmitted upward (or “uphole” as depicted by the arrows in Fig. 1) from the heat-receiving well section 16 by conduction. The elongated component 30 may be, but is not limited to, a rod, a cable or a tubular. The elongated component 30 can be constructed so as to promote heating from the geothermal zone, conducting heat up to the heat-transmission section 18, and then releasing the heat into the heavy hydrocarbon zone 24. The elongated component 30 can have an outer surface that is in direct contact with the inner wall of the wellbore at locations where heat is transported into the hydrocarbon zone 24, and it can be insulated from the formation in locations where heat transmission to the outer formations is to be minimized (e.g., through barrier zones or any zones that are in between the geothermal zone and the heavy hydrocarbon zone). The heat conductive material may be a metal, such as to steel. The elongated component 30 may extend between a lower part of the heat-receiving well section 16 to an upper part of the heat-transmitting well section 18, although it can have various dimensions and constructions depending on the application. Heat released by the heat-transmitting well section 18 into the reservoir is depicted as wavy lines in Fig. 1.

[00111 ] The geothermal well 14 may further include an insulated casing. The insulating casing may enclose the elongated component 30 to prevent heat loss in certain locations. The insulated casing may be a vacuum insulated tubing (VIT) casing. The insulated casing surface may therefore be in direct contact with the inner wall of the wellbore at locations where heat is transported into the hydrocarbon zone 24, to minimize heat loss from the wellbore to the outer formation. The insulation can thus be provided in between the heat-receiving and heat-releasing sections of the geothermal well.

[00112 ] The geothermal well 14 also includes the upper well section 28 that extends from the heat-transmission well section 18 to the surface 26. The upper well section 28 is formed during drilling and may be completed in various ways depending on the desired use. For example, for this example implementations, the upper well section 28 may simply be a wellbore access (e.g., for inspection, maintenance or measurements) and thus is not equipped for injection or production. The upper well section 28 could also be completed so that little to no geothermal heat or fluid can travels up from the heat-transmission well section 18, and therefore could be provided with appropriate equipment for this purpose.

Second Implementation

[00113 ] Fig. 2 illustrates the system 10 which includes the geothermal well 14 which heats the heavy hydrocarbons 12 by conduction of heat from the hot geothermal zone 22 to the heavy hydrocarbon zone 24, and in this sense is similar to the system 10 according to the first implementation, but it also involves providing an injection fluid 32 from the surface 26. The injection fluid 32 is provided from the surface 26 downhole and into the heat-transmitting well 18 section. The injection fluid 32 is heated by the heat-transmitting well 18 section, which has received geothermal heat, and is injected into the heavy hydrocarbon zone 24. This implementation therefore includes geothermal heating as well as fluid injection from the surface to help mobilize the heavy hydrocarbons 12. [00114 ] According to this example implementation, the injection fluid 32 is introduced via the upper well section 28 and flows down into the heat-transmitting well section 18. The upper well section 28 may therefore be coupled to injection equipment at surface 26 which can be configured depending on the type and state of the injection fluid (e.g., vapor, liquid, heated, ambient). The injection fluid 32 is then heated by the heat-transmitting well section 18, which is heated geothermally by conduction as described herein. The heated injection fluid 32 is then injected into the heavy hydrocarbon zone 24 to help mobilize the heavy hydrocarbons 12. The heavy hydrocarbons 12 may therefore be heated by conduction of geothermal heat from the heattransmitting well section 18 into the hydrocarbon zone, as well as by contact with the heated injection fluid 32 entering the hydrocarbon zone 24. The injection fluid 32 can help mobilize the heavy hydrocarbons by heating and also be other mechanisms as some injection fluids can mix with the hydrocarbons and help reduce viscosity.

[00115 ] For this implementation, the heat-transmitting well section 18 is configured to allow the injection fluid to flow into the heavy hydrocarbon zone 24, and thus provides fluid communication between the wellbore and the surrounding reservoir. For instance, the heattransmitting well section 18 may include perforations 34 for releasing the heated injection fluid 32 into the heavy hydrocarbon zone 24, as shown in Fig. 6. The perforations 34 can be provided through a tubular liner that facilitates transmission of the geothermal heat. The heat-transmitting well section 18 may include flow control devices 35 or other completion systems to enable injection of the heated injection fluid 32 into the heavy hydrocarbon zone 24, as shown schematically in Fig. 7. The heat-transmitting well section 18 may include a steel tubing that is perforated for injection of the injection fluid 32. The injection fluid 32 can be delivered from surface using a pump or a compressor, for example, depending on the type of injection fluid introduced into the geothermal well.

[00116 ] The injection fluid 32 may include a gas, liquid, or a mixture of gas and liquid. The gas may include steam or CO2. The liquid may include water. In some implementations, the injection fluid 32 is not preheated prior to downhole injection. In some cases, the injection fluid 32 is a liquid (e.g., liquid comprising water) which is introduced as a liquid and is heated in the heat-transmitting well section 18 and is thus converted partially or completely into a gas (e.g., steam) which is injected into the heavy hydrocarbon zone 24. This downhole vaporization of the injection fluid is enabled by the geothermal heat in the heat-transmitting well section 18. Alternatively, the injection fluid can be in liquid phase when introduced into the geothermal well and also when injected into the reservoir.

[00117 ] When fluid is injected into the reservoir, it can form a mixture with the mobilized heavy hydrocarbons 12, which is then recovered as the production fluid. The production fluid can include hydrocarbons, injection fluid as well as other native fluids such as water and light gases. The production fluid is treated at surface. Heavy hydrocarbons 12 may be separated from the other components of the production fluid by various methods, such as by using separators (e.g., gas separator, oil/water separator, vapor/liquid separators, etc.). In some implementations, the produced water and/or gas/CCb that is separated from the hydrocarbons may be treated and reused as part of the injection fluid 32. In general, the production fluid can be treated to remove the injection fluid for reuse in the system 10.

[00118 [ In the second implementation, the geothermal well 14 can be equipped to allow the injection fluid to pass from the surface, into the heat-transmission well section, and into the reservoir without flowing further down the geothermal well 14. For example, the geothermal well can have a packer, valve or another device that prevents fluid flow from the heat-transmission well section 18 down into the heat-receiving well section 16. The flow prevention device can be deployed at a downhole end of the heat-transmission well section 16, for example. Examples of such a packer 40 and valve 38 are schematically illustrated in this arrangement in Fig. 6.

Third Implementation

[00119 ] Fig. 3 illustrates the system 10 which includes the geothermal well 14 that heats the heavy hydrocarbons 12 by conduction of heat from the hot geothermal zone 22 to the heavy hydrocarbon zone 24, and in this sense is similar to the system 10 according to the first implementation, but it also involves allowing a hot native fluid to flow from the geothermal zone 22 through the geothermal well 14 and into the heavy hydrocarbon zone 24. The hot native fluid 36 is obtained from the hot geothermal zone 22 and is transported uphole from the heat-receiving well section 16 into the heat-transmission well section 18 for injection into the heavy hydrocarbon zone 24. [00120 ] According to this example implementation, the hot native fluid 36 is fluid that is originally present in hot geothermal zone 22. The heat-receiving well section 16 may comprise a fluid inlet 41 (see Fig. 4) that receives the hot native fluid 36 from the hot geothermal zone 22 and due to pressure differential the hot native fluid 36 flows up to the heat-transmitting well section 18. The fluid inlet 41 could be configured to be operable between an open position and a closed position to control whether the hot native fluid can enter the geothermal well 14. The fluid inlet 41 may be configured to work independently or in conjunction with the elongated component 30 (heat conductive material). The native fluid is at a higher pressure compared to the heat-transmitting well section 18 and thus the heat-receiving well section 16 provides a conduit for passage of the native fluid to the lower pressure region. The hot native fluid 36 may then be injected into the heavy hydrocarbon zone 24 via the perforations 34 or other flow control devices 35of the heattransmitting well section 18. The heavy hydrocarbons 12 may therefore be heated by conduction of geothermal heat via the heat-transmitting well 18 section, and by injecting the hot native geothermal fluid 36 that is transported uphole into the heat-transmitting well section 18.

[00121 ] The hot native fluid 36 may include gas, liquid, or a mixture of gas and liquid, depending on the fluids native to the particular geological formation. Due to lower pressures that are present ascending up the geothermal well 14, the hot native fluid 36, which may begin as a liquid (e.g., water), may flash to form a gas (e.g., steam) which is injected into the heavy hydrocarbon zone 24 via the heat-transmission well section 18. The hot native fluid 36 may include steam from its initial phase within the hot geothermal zone 22 and be injected as steam and/or hot water in the heat-transmission well section 18. In some instances, the hot native fluid 36 is kept hot or is further heated by simultaneous conduction of geothermal heat in the heat-receiving well section 16 and heat-transmitting well section 18, as described in the first implementation.

[00122 ] When native fluid is allowed to flow up and into the hydrocarbon zone, it can form a mixture with the mobilized heavy hydrocarbons 12, which is then recovered as the production fluid. The production fluid can include hydrocarbons, native fluid from the geothermal zone, as well as native fluids from the hydrocarbon zone. The production fluid is treated at surface. Heavy hydrocarbons 12 may be separated from the other components of the production fluid by various methods, such as by using separators (e.g., gas separator, oil/water separator, vapor/liquid separators, etc.). In some implementations, the produced water and/or gas/CCh that is separated from the hydrocarbons may be treated and disposed of or used as injection fluid in another well.

[00123 ] In the third implementation, the geothermal well 14 can be equipped to allow the hot native fluid to pass from the geothermal zone, up through the heat-receiving well section, into the heat-transmission well section, and then into the reservoir without flowing further up the geothermal well 14. For example, the geothermal well can have an uphole packer 40a, an uphole valve 38a or another device that prevents fluid flow from the heat-transmission well section 18 up the upper section of the geothermal well. The flow prevention device can be deployed at an uphole end of the heat-transmission well section 16, for example. Examples of such a packer 40a and valve 38a are schematically illustrated in this arrangement in Fig. 7.

Variant implementations

[00124 ] While three example implementations have been described above, it is noted that one or more of the implementations can be used over time for a given system. For example, a geothermal well 14 could be initially operated according to the first implementation with no fluid injection from the surface or the geothermal zone, and then the geothermal well could be subsequently operated according to the second or third implementation by allow the appropriate fluid flow and injection. For instance, the geothermal well could be equipped with valves that could be operated manually or remotely in an open or closed position to allow fluid to flow from surface or from the geothermal zone into the heat-transmission well section and then into the hydrocarbon zone. The geothermal well could also be recompleted to switch operation to another implementation.

[00125 ] It is also possible for a given geothermal well to switch operation between the second and third implementations. For instance, referring to Figs. 4-7, the geothermal well 14 could be operated with fluid injection from the surface where the uphole valve 38a is open and the downhole valve 38 is closed; and then the operating mode could be switched by ceasing fluid injection from the surface, closing the uphole valve 38a, opening the downhole valve 38, and opening the fluid inlet 41 to allow native fluid flow into the geothermal well 14. It may be of interest to begin the hydrocarbon recovery process using the third implementations to leverage the hot native fluids present in the geothermal zone, and then if or when the hot native fluids become depleted the process can switch to fluid injection from the surface. In this manner, the operating mode of the geothermal well 14 could be modified between the first, second and third implementations, if desired.

[00126 ] In addition, the systems according to the first, second and third implementations may be used alone or in combination for heating and/or recovery heavy hydrocarbons. For example, Fig. 8 describes a combination of the systems according to the first, second and third implementations, whereby geothermal heat is transmitted by conduction (with the elongated component 30) and transmission of a hot native fluid 36, and whereby an injection fluid 32 is provided from the surface 26. In some cases, for both the hot native fluid 36 and the injection fluid 32 to be injected into the hydrocarbon zone 24 by the heat-transmission well section, pressures in the heat-receiving well section 16/geothermal zone 22 and upper well section 28 must be higher than the pressure in the heat-transmission well section 18/hydrocarbon zone 24.

[00127 [ Furthermore, Fig. 9 generally discloses systems in which the geothermal well is configured to provide geothermal heat to a target subterranean zone (e.g., hydrocarbon zone 24), via a hot native fluid 36 and/or injection fluid 32, in the absence of conduction. The geothermal well 14, therefore, could be configured without an elongated component for heat conduction. The hot native fluid 36 (e.g., air or steam) may travel from the heat-receiving well section 16 to the heat-transmission well section 18 to be injected into the subterranean zone, such as for mobilization of the hydrocarbons 12. Similarly, the injection fluid 32, which may or may not be pre-heated, may flow into the heat-transmission well section 18 for injection into the subterranean zone. In some cases, the injection fluid 32 is heated downhole in the subterranean zone. For Example, in scenarios where an injection fluid 32 is provided for injection into the hydrocarbon zone 24 in the absence of conduction or hot native fluid 36, the injection fluid 32 may be transported downhole into the heat-receiving well section 16 to be heated by the geothermal zone 22, and subsequently circulated to the heat-transmission well section 18 for injection (Fig. 10). In some cases, the injection fluid 32 is released into the hot geothermal zone 22, and is heated and recovered by the heat-receiving well section 16 (Fig. 10).

[00128 ] In some scenarios, in the absence of an elongated component 30, supercritical fluid 42 may be used to conduct geothermal heat and/or hot native fluid in the geothermal well 14, such as in the systems of Fig. 11-14. The heat-receiving 16 and heat-transmission 18 well sections of the geothermal well 14 may be filled with the supercritical fluid 42 to conduct geothermal heat from the heat-receiving well section 16 to the heat-transmission well section 18 (Fig. 11). A hot native fluid 36 may be transported from the heat-receiving well section 16 to the heat-transmission well section 18 for injection into the hydrocarbon zone (Fig. 12). In some scenarios, an injection fluid 32 from the surface 26 may then be injected and transported into a reservoir within the heattransmission well section 18 that is surrounded by the supercritical fluid 42 to be heated, and then injected into the hydrocarbon zone 24 for mobilization of the hydrocarbons 18, as described in Fig. 13. In some scenarios, the supercritical fluid 42 may be circulated in the geothermal well for heating the injection fluid 32. For example, described in Fig. 14 is a system 10, wherein injection of the supercritical fluid 42 from the surface 26 is transported to the heat-receiving well section 16 for heating in the geothermal zone, and is then circulated to the heat-transmission well section 18. Furthermore, injection of the injection fluid 32 from the surface 26, optionally in a separate compartment than the supercritical fluid 42, is transported into the heat-transmission well section to be heated by the circulating supercritical fluid 42 and is injected into the hydrocarbon zone 24 for mobilization of hydrocarbons 12.

[00129 ] The systems described herein may also be used alone or in combination with other conventional systems used for heating and/or recovery of heavy hydrocarbons. Preferably, the systems described herein do not utilize surface boilers or steam as an injection fluid. The systems described herein preferably minimize the use of non-renewable energy sources for heating and/or recovering heavy hydrocarbons.

[00130 [ In some cases, the system 10 according to the first implementation is used alone. Therefore, the heat-receiving well section 16 is configured to transmit the heat by conduction to the heat-transmission well section 18, and the heat-transmission well section 18 is configured to transmit the heat into the heavy hydrocarbon zone 24 by conduction, in the absence of fluid injection (either of hot native fluid 36 or injection fluid 32) into the geothermal well 14 and the heavy hydrocarbon zone 24.

[00131 ] As mentioned above, the geothermal well 14 may include one more valves and/or packers, or other completion devices, to control uphole or downhole flow of fluids. The one or more valves and/or packers may be located at various points of the heat-receiving well section 16, heat-transmitting well section 18, and/or the upper well section 28, as shown in Figs. 4-7.

[00132 ] The geothermal well 14 may include at least one downhole valve 38 or packer 40 located in a downhole region of the heat-transmission well section 18 to prevent flow of the injection fluid 32 further downhole. The at least one downhole valve 38 or packer 40 may be located at a downhole end of the heat-transmission well section 18 to prevent flow of the injection fluid 32 into the heat-receiving well section 16. It is also possible to provide multiple downhole isolation devices, such as valves or packers, at various locations along the heat-transmission well section 18 and/or the heat-receiving well section 18, and to operate the downhole isolation devices to achieve desired fluid injection effects.

[00133 ] The geothermal well 14 may include at least one control valve or uphole valve 38a located at an uphole region of the heat-transmission well section 18 or in the upper well section 28. The control valve 38a can be configured and operated to control the injection fluid 32 entering the heat-transmission well section 18. Control of the injection fluid can also be achieved using the surface equipment to control injection rate or pressure of the fluid.

[00134 ] The downhole and/or uphole valves 38/38a or the downhole and/or uphole packers 40/40a can be configured to prevent fluid flow further up the geothermal well 14, which may be desired to stop transfer of heat and/or hot native fluid 36 from the heat-receiving well section 16 or heat-transmitting well section 18 further uphole or for well control purposes. The downhole/uphole valves 38/38a and/or the downhole/uphole packers 40/40a can be located in various parts of the heat-transmission well section 18, as shown in Figs. 6 and 7 for example.

[00135 ] The geothermal well 14 may include a fluid circulation system that allows fluid to circulate without being injected into the reservoir. For example, the geothermal well may be configured such that hot circulation fluid is circulated from the surface down into the heattransmission well section 18 to provide additional heat to the reservoir. The circulation fluid could be steam, but since the steam is not injected into the reservoir the condensate does not require substantial water treatment before being reused to generate additional steam. It is also possible to configure the fluid circulation system to receive the hot native fluid and allow it pass up and through the heat-transmission well section 18 without being injected into the reservoir. [00136 ] The downhole and/or uphole valves 38/38a or the downhole and/or uphole packers 40/40a can also be configured to prevent hot native fluid 36 backflow or injection fluid 32 flow downhole into the geothermal well 14. This may be desired to stop transfer of heat and/or fluid from the heat receiving well section 16 or heat-transmitting well section 18 further downhole, or for well control purposes. The downhole/uphole valves 38/38a and/or the downhole/uphole packers 40/40a can be located in various parts of the heat-receiving well section 16 or the heattransmission well section 18, as shown in Figs. 5-7 for example.

Methods for heating and recovering heavy hydrocarbons

[00137 ] According to another general aspect of the technology, there is described a method for heating and/or recovering heavy hydrocarbons 12 from an underground reservoir.

[00138 ] According to another general aspect of the invention, there is described a method for recovering heavy hydrocarbons 12 from a subsurface formation, the method comprising transferring geothermal heat from a geothermal zone 22 of the formation to a heavy hydrocarbon zone 24 located above the geothermal zone 22 by conduction to promote mobilization of the heavy hydrocarbons 12 for recovery thereof to surface 26.

[00139 ] According to another general aspect of the invention, there is described a method for recovering heavy hydrocarbons 12 from a subsurface formation, the method comprising transferring geothermal heat from a geothermal zone 22 of the formation to a heavy hydrocarbon zone 24 located above the geothermal zone 22 without transferring the geothermal heat to surface 26 to promote mobilization of the heavy hydrocarbons 12 for recovery thereof to the surface 26.

[00140 [ According to one example implementation, there is described a method for recovering heavy hydrocarbons 12 from a subsurface formation, wherein the method includes heating a heavy hydrocarbon zone 24 of the formation and mobilizing heavy hydrocarbons 12 contained therein with geothermal heat obtained from a geothermal zone 22 of the formation, wherein the geothermal heat is obtained by a geothermal well 14. The geothermal well 14 includes a heat-receiving well section 16 extending within the geothermal zone 22 of the formation, and is configured to be heated by geothermal heat in the lower geothermal zone 22 and transmit heat upward. The geothermal well 14 also includes a heat-transmission well section 18 extending from the heat-receiving well section 16 and extending into at least the heavy hydrocarbon zone 24 of the formation located above the geothermal zone 22, the heat-transmission well section 18 being configured to receive heat from the heat-receiving well section 16 and transmit heat into the heavy hydrocarbon zone 24 to promote mobilization of the heavy hydrocarbonsl2. The method further includes recovering the mobilized heavy hydrocarbons 12 to surface 26.

[00141 ] The methods described herein may utilize the systems 10 or geothermal wells 14 according to the example implementations described herein, either alone or in combination.

[00142 ] Recovering mobilized heavy hydrocarbons 12 may involve the use of one or more production wells 20 located nearby or distant to the geothermal wells 14. In some cases, the recovering of the mobilized heavy hydrocarbons 12 is performed by gravity drainage. In some cases, the heating and the recovering are performed simultaneously. Alternatively, the heating is performed as a pretreatment step prior to recovering the mobilized heavy hydrocarbons 12 from the subsurface formation. The geothermal heating methods can be used for starting up a well pair or a well to be used for injection. The geothermal heating methods can be used where the geothermal well operates in conjunction with various other wells and in situ recovery methods, such as SAGD and CSS, where the geothermal well is located above, beside, below or offset with respect to another well that recovers production fluid.

[00143 ] In some implementations, the heating of the heavy hydrocarbon zone 24 is performed by conduction of the geothermal heat through the heat-receiving well section 16 and the heat-transmission well section 18 and into the heavy hydrocarbon zone 24 in the absence of fluid injection into the geothermal well 14 and/or heavy hydrocarbon zone 24.

[00144 ] In some implementations, the heating of the heavy hydrocarbon zone 24 is performed by conduction of the geothermal heat from the heat-receiving well section 16 to the heat-transmission well section 18, and by downhole injection of an injection fluid 32 that is heated in the heat-transmission well section 18 and then injected or released into the heavy hydrocarbon zone 24.

[00145 ] In other implementations, the heating of the heavy hydrocarbon zone 24 is performed by conduction of the geothermal heat from the heat-receiving well section 16 to the heat-transmission well section 18, and by injection of a hot native fluid 36 that is received from the geothermal zone 22 of the formation through heat-receiving well section 16, transported uphole to the heat-transmission well section 18, and then injected into the heavy hydrocarbon zone 24.

[00146 ] In some implementations, the heating of the heavy hydrocarbon zone 24 includes a circulation fluid downhole into the geothermal well 14, wherein the circulation fluid is circulated through the heat-receiving well section 16 to be heated to form a heated fluid 32, and then the heated fluid is transported to the heat-transmission well section 18 for injection into the heavy hydrocarbon zone 24 or for indirect heating of the heavy hydrocarbon zone 24.

Further Implementations and Aspects

[00147 ] Fig. 15 and 16 generally discloses systems in which the geothermal well is configured and operated to not only provide geothermal heat to a target subterranean zone, such as the hydrocarbon zone 24, but also to bring a portion of the heat and/or hot native fluid 36to surface. The geothermal heat brought to surface could then be used for various purposes, including steam generation for surface or subterranean applications, electricity generation, and/or other uses.

[00148 ] Fig. 15 and 16 illustrates the system 10 that includes the geothermal well 14 which may transport geothermal heat by conduction from the hot geothermal zone 22 for recovery to the surface 26. The geothermal well 14 would thus be appropriately completed with equipment for enabling heat conduction into the hydrocarbon zone 24 and up to the surface 26.

[00149 ] According to this example implementation, the geothermal well 14 can include the elongated component 30 or using a supercritical fluid 42, as previously described, located in the wellbore of the geothermal well and composed of a heat conductive material, and the heat is transmitted upward (or “uphole” as depicted by the arrows in Fig. 8) from the heat-receiving well section 16 to the surface 26 by conduction. The elongated component 30 is constructed so as to promote heating from the geothermal zone, conducting heat into the hydrocarbon zone 24 and also uphole to the surface 26. The elongated component 30 may therefore further extend into the upper well section 28 and up to the surface 26. Furthermore, the insulated casing or other insulation equipment may be present in the upper well section 28 of the geothermal well 14 to limit heat loss to the formation that is uphole of the hydrocarbon zone 24 before the heat reaches the surface. In such systems, the insulation can be provided where heat loss is to be minimized and not in the regions where heat is to be received and delivered. Thus, different segments of the elongated component 30 could be insulated while others are exposed to promote heat transfer with the formation or surface equipment. In some aspects, the elongated component 30 may be replaced by a supercritical fluid 42 which is used to conduct geothermal heat from the heatreceiving well section 16 to the heat-transmission well section 18 and further to upper- well section 28 for recovery to the surface 22.

[00150 ] In some implementations, the system 10 also involves allowing a hot native fluid 36 to flow from the geothermal zone 22 through the geothermal well 14 to the surface 26, as also depicted in Fig. 15 and 16. The hot native fluid 36 may be the hot native fluid as previously described. In this scenario, the hot native fluid as well as heat conducted from the geothermal zone would be brought up to the hydrocarbon zone for heating. A portion of the heat can then be conducted up to the surface and/or at least a portion of the hot native fluid can be brought up to surface. The heat that is in the hot native fluid and/or obtained through conduction, can then be used at surface for various applications. In some implementations, the system 10 involves allowing a hot native fluid 36 to flow from the geothermal zone 22 through the geothermal well 14 to the surface 26, in the absence of conduction through a solid medium. Therefore, according to this implementation, the geothermal well 14 may not include the elongated component 30.

[00151 ] The geothermal heat and/or hot native fluid 36 recovered to the surface 26 may be utilized as thermal energy and/or utilized to produce electrical energy. For example, geothermal heat may be used directly for heating, such as for heating homes or for heating nearby or distant oil pipelines to maintain a low oil viscosity at the surface. Depending on the quantity of geothermal heat that is obtained at surface, it can be used to heat pipelines and surface equipment that is located proximate to the well head and/or at remote locations. Geothermal heat may also be used to generate electricity, such as for example by first heating water using the recovered geothermal heat to generate steam, and powering steam turbines. Steam can then be used for heating, as described above. Steam and electricity may be produced at the surface, optionally using steam insulated tanks to prevent cooling of the steam. In some cases, steam is directly obtained from the geothermal well 14 as the hot native fluid 36 from the geothermal zone. The vacuum insulated tubing may be extended in regions of the geothermal well 14, such as in the upper well section 28, to prevent cooling of the hot native fluid 36 (e.g., steam). Furthermore, geothermal heat obtained by embodiments of the system described herein may be used to power a thermoelectric generator to generate electricity..

[00152 ] In some scenarios, as described in Fig. 10, injection fluid 32 may be injected into the geothermal well and is heated by the hot geothermal zone. This geothermally-heated injection fluid may then be recovered to the surface for use as thermal energy, electrical energy, and/or for injection (or reinjection) into a nearby or distant heavy hydrocarbon zone (Fig. 19).

[00153 ] In some case, the recovered geothermal heat, hot native fluid 36, and/or geothermally-heated injection fluid 12 may be recirculated or reinjected into a nearby or distant heavy hydrocarbon zone 24 for heating and recovery of heavy hydrocarbons. In some cases, the recovered geothermal heat and/or hot native fluid is recirculated or reinjected into the same geothermal well 14. In some cases, the recovered geothermal heat and/or hot native fluid is recirculated or reinjected into one or more nearby or distant geothermal wells as described herein, or abandoned, previously used, or repurposed wells (e.g., injection or production well). The recovered recovered geothermal heat, hot native fluid 36, and/or geothermally-heated injection fluid, can therefore be re-injected into a geothermal well or production well for recovering heavy hydrocarbons from the same subsurface formation and/or a second nearby or distant subsurface formation.

[00154 ] In some aspects, the systems described herein may not employ the use of a boiler and/or a heat exchanger at the surface to maintain the temperature of the geothermal heat, hot native fluid, or geothermally-heated injection fluid. The temperature of recovered geothermal heat, hot native fluid, or geothermally-heated injection fluid may be maintained using known thermal insulation techniques and tubing

[00155 ] In some scenarios, a portion of the geothermal heat can be used in a surface facility to generate steam. It is also possible to use a portion of the geothermal heat for steam generation using a near-surface steam generator, as well as steam insulated tanks, located underground but close to the surface (i.e., near surface). [00156 ] In some cases, the geothermal well 14 could be operated in different heat recovery modes over time. For example, the geothermal well could initially be operated in one heat recovery mode where geothermal heat is only brought up to the hydrocarbon zone, and then at a later phase in operations the geothermal well could be switched to operate in another heat recovery mode in which geothermal heat is only brought to surface or is delivered to the hydrocarbon zone and the surface. In this manner, the operation of the geothermal well could be modified over time depending on heat requirements and end-uses. For example, after the hydrocarbon recovery process for a given reservoir has been completed, the geothermal well could be converted to a heat-to-surface well to continue delivering heat to the surface.

[00157 ] In some scenarios, the systems in which the geothermal well 14 is configured and operated to bring geothermal heat from a hot geothermal zone to the surface may be configured and operated in the absence of recovery of hydrocarbons, as depicted in Fig. 17 and 18. Therefore, the geothermal well 14 may not include the heating of a target subterranean zone (e.g., hydrocarbon zone) for the purpose of enhancing recovery of fluid from the zone. According to this implementation, geothermal heat may be recovered to the surface, or near-surface, by conduction (e.g., with the use of the elongated component 30 [Fig. 17] or a supercritical fluid 42 [Fig. 18]). In some cases, a hot native fluid 36 (e.g., steam) from a subterranean zone may be recovered to the surface, or near-surface, in the presence or absence of conduction (i.e., absence of the elongated component 30). The system may include any one of the geothermal wells including one or more the sections described herein. For example, if geothermal heat and/or hot naive fluid is not being delivered into a hydrocarbon zone, the heat-transmission well section may not be necessary and may be configured differently (e.g., it may be insulated to discourage heat transmission into that zone). Recovered fluid and/or heat may be used at surface to generate electricity and/or steam, as previously described.

[00158 ] According to some implementations, the system that is configured and operated to bring geothermal heat from a hot geothermal zone to the surface in the absence of recovery of hydrocarbons, as described in Fig. 17 and 18, may include the use of offshore wells or onshore wells, and such wells may be abandoned or previously-used. Such wells may include production wells, such as oil production wells and/or injection wells, and may or may not be further drilled into to reach deeper and/or hotter geothermal zones. At least a downhole portion of the abandoned well may be located in the geothermal zone of the formation. Initial temperature readings of abandoned wells may be obtained to determine whether the well is suitable for recovering geothermal heat to the surface. Abandoned wells may be configured with the elongated component 30, supercritical fluid 42, and/or insulated tubing, as previously described, extending downhole for recovery of geothermal heat by conduction. Furthermore, a hot native fluid 36 (e.g., steam) may be recovered, in the presence or absence of conduction, using abandoned wells. Recovered fluid and/or heat may be used to generate electricity and/or steam, as previously described.

[00159 ] When abandoned or shut-in well are used, the wells can be recompleted to provide completion equipment suitable for retrieving the geothermal heat. For example, a shut-in well could be recompleted by running in an elongated component with predetermined segments that are insulated and exposed to promote conduction of heat from hot zones up to the surface while inhibiting heat loss to the formation. The elongated component in the upper vertical section of the wells could be insulated, for example, while the deeper parts of the elongated component are exposed to receive geothermal heat. Alternatively, shut-in wells could be leveraged without completion with an elongated component but are configured so that heat that transfers up to the surface is captured and utilized. This could involve surface equipment that is connected to the wellhead to capture heat that is transferred via conduction and/or convection to surface.

Methods for recovering geothermal heat

[00160 ] According to another general aspect of the technology, there is described a method for recovering geothermal heat from a subsurface formation to the surface.

[00161 ] According to this aspect, the method includes recovering geothermal heat obtained by a geothermal well and transporting the geothermal heat by conduction and/or transporting a hot native fluid 36 from the geothermal zone 22, to the surface 26. In some cases, the method utilizes the systems 10 or geothermal wells 14 according to example implementations described herein, either alone or in combination. The method may include heating a heavy hydrocarbon zone 24 of the formation and mobilizing heavy hydrocarbons 12 contained therein with a portion of geothermal heat, and optionally a portion of the hot native fluid 36, obtained from the geothermal zone 22 of the formation, for recovery of the mobilized heavy hydrocarbons 12 to the surface 26 by a nearby production well 20, as previously described.

[00162 ] According to another general aspect, there is described a method for recovering geothermal heat from a subsurface formation using an abandoned well (e.g., production or injection well). At least a downhole portion of the abandoned well may be located in the geothermal zone of the formation. Initial temperature readings of abandoned wells may therefore be obtained to determine whether the well is suitable for recovering geothermal heat to the surface, or near-surface. The method may therefore include an initial step of determining suitable wells to be used as geothermal wells, and the determining step can include temperature sensing. The temperature sensing can use equipment that exists in the well, or instrumentation that is deployed into the abandoned well to obtain temperature and/or pressure readings. The method may also include drilling downhole into the abandoned well to reach a geothermal zone of the formation to extend the well and reach more elevated temperatures. The abandoned well may be configured to receive the elongated component 30 or a supercritical fluid 42, as previously described, to reach the geothermal zone and transmit geothermal heat uphole in the well by conduction. Insulated casing may be applied at any point in the well to prevent heat loss. Furthermore, the abandoned well may be configured to receive a hot native fluid 36 from the geothermal zone of the formation, and transport the hot native fluid uphole in the well to the surface.

[00163 ] It will be appreciated that, for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the Figures to indicate corresponding or analogous elements or steps. In addition, numerous specific details are set forth in order to provide a thorough understanding of the exemplary implementations described herein. However, it will be understood by those of ordinary skill in the art, that the implementations described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the implementations described herein. Furthermore, this description is not to be considered as limiting the scope of the implementations described herein in any way but rather as merely describing the implementation of the various implementations described herein. [00164 ] The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one” but it is also consistent with the meaning of “one or more”, “at least one”, and “one or more than one”.

[00165 ] As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open- ended and do not exclude additional, unrecited elements or method steps.

[00166 ] Other objects, advantages and features of the present description will become more apparent upon reading of the following non-restrictive description of specific implementations thereof, given by way of example only with reference to the accompanying drawings.