Intervention process for geothermal wells

Abstract

A method for extracting thermal energy from a geothermal reservoir having one or more features extending through the geothermal reservoir includes analyzing subsurface data to determine a measured depth of a feature of the one or more that intersects a production well, running a downhole tool along the production well to a location corresponding to the measured depth of the feature, and performing an intervention at the location using the downhole tool, wherein the intervention includes injecting a reactive solution into the feature, wherein the reactive solution is configured to penetrate the feature to a desired depth and according to a desired pattern based on an injection rate of the reactive solution into the feature and a reaction rate of the reactive solution with the feature.

Description

INTERVENTION PROCESS FOR GEOTHERMAL WELLSCROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority from US Appl. No. 18 / 678,911 filed on May 30, 2024, which is a continuation-in-part of US Appl. No. 18 / 479,187 filed on October 2, 2023 and claims priority to US Provisional Appl. No. 63 / 504,797 filed on May 30, 2023, each of which are herein incorporated by reference in their entirety.FIELD

[0002] The present disclosure relates to geothermal systems that extract thermal energy from a geothermal reservoir.BACKGROUND

[0003] Geothermal systems that extract thermal energy (e.g., heat) from a geothermal reservoir are generating considerable interest. A conventional geothermal reservoir is a volume of subsurface rock that contains a natural source of pressurized geothermal fluid that is heated by natural geological processes below the Earth's surface. The pressurized geothermal fluid can include hot water or brine. The pressurized geothermal fluid is used as a source of thermal energy. A production well is drilled from the surface into and through the conventional geothermal reservoir, and may intersect one or more naturally-occurring fractures in the subsurface rock of the conventional geothermal reservoir. These naturally-occurring fractures provide a flow path of the pressurized geothermal fluid into the production well where it flows through the production well to the surface. The thermal energy from the geothermal fluid that flows to the surface can be extracted and used by an energy conversion plant for power generation, large scale heating or cooling, industrial / agricultural processes, or other geothermal applications.SUMMARY

[0004] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0005] In an embodiment, a method for extracting thermal energy from a geothermal reservoir having one or more features extending through the geothermal reservoir includes analyzing subsurface data to determine a measured depth of a feature of the one or more that intersects a production well, running a downhole tool along the production well to a location corresponding to the measured depth of the feature, and performing an intervention at the location using the downhole tool, wherein the intervention includes injecting a reactive solution into the feature, wherein the reactive solution is configured to penetrate the feature to a desired depth and according to a desired pattern based on an injection rate of the reactive solution into the feature and a reaction rate of the reactive solution with the feature.

[0006] In another embodiment, a method for increasing a heat transfer capacity of a geothermal reservoir including analyzing subsurface data to determine a measured depth of one or more features that intersect a geothermal well, running a downhole tool along the geothermal well to a position corresponding to the measured depth of a feature of the one or more features, and performing an intervention at the position using the downhole tool, wherein the intervention includes injecting a reactive solution into the feature, wherein the reactive solution is configured to penetrate the feature to a desired depth based on a reaction rate of the reactive solution with the subsurface rock of the geothermal reservoir and penetrate the feature according to a desired pattern based on an injection rate of the reactive solution into the feature, wherein the desired pattern corresponds to a ramified wormhole.

[0007] In another embodiment, a system includes a conveyance system configured to deploy a downhole tool within a geothermal well that intersects a geothermal reservoir, the downhole tool configured to perform an intervention at an intersection of the geothermal well with a feature of the geothermal reservoir, and a control system configured to control operation of the conveyance system to run the downhole tool to a position of the intersection, and operate the downhole tool to inject a reactive fluid into the feature to generate a ramified wormhole within the geothermal reservoir.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The subject disclosure is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of the subjectdisclosure, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

[0009] FIG. 1 is a schematic diagram of an embodiment of a geothermal system having a production well that intersects and / or connects to one or more features extending through a geothermal reservoir, in accordance with aspects of the present disclosure;

[0010] FIG. 2 is a schematic diagram of an embodiment of a geothermal system having a production well and an injection well that intersect and / or connect to one or more features extending through a geothermal reservoir, in accordance with aspects of the present disclosure;

[0011] FIG. 3 is a flowchart of an embodiment of a method for an intervention process used to enhance flow of pressurized geothermal fluid from a geothermal reservoir and / or increase a heat transfer capacity of a geothermal reservoir, in accordance with aspects of the present disclosure;

[0012] FIG. 4 is a flowchart of an embodiment of a method for selectively treating one or more features of a geothermal reservoir with an acid-based solution to enhance the flow rate of pressurized geothermal fluid from a geothermal reservoir and / or to increase a heat transfer capacity of a geothermal reservoir, in accordance with aspects of the present disclosure; and

[0013] FIG. 5 is a schematic diagram of an embodiment of one or more patterns that may be generated during an intervention process, in accordance with aspects of the present disclosure.DETAILED DESCRIPTION

[0014] The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the subject disclosure only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the subject disclosure. In this regard, no attempt is made to show structural details in more detail than is necessary for the fundamental understanding of the subject disclosure, the description taken with the drawings making apparent to those skilled in the art how the several forms of the subject disclosure may be embodied in practice. Furthermore, like reference numbers and designations in the various drawings indicate like elements.

[0015] As used herein, the term “near wellbore region” refers to a rock formation within lessthan 5 feet from a wellbore surface. That is, a production wellbore having a 12-inch diameter includes a near wellbore region with an 11-foot diameter that is centered in the production wellbore.

[0016] As used herein, the term “feature” refers to a portion of a rock formation within the near wellbore region that includes pressurized geothermal fluid that may be accessed by a production wellbore.

[0017] As used herein, the term “aperture” refers to an opening or space in the near wellbore region that connects a feature to a production well at the intersection of the feature and the production well.

[0018] As used herein, the term “fracture” refers to a feature within the near wellbore region that is in fluid communication with the production well via one or more apertures.

[0019] As used herein, the term “opening a feature” means enhancing or increasing flow of geothermal fluid carried by a feature into a production well by enlarging an aperture that connects the feature to the production well or opening new flow channels that are fluidly connected to the feature or unblocking or improving the flow of geothermal fluid through an aperture that connects the feature to the production well.

[0020] As used herein, the term “near the intersection of the feature” means within less than 30 feet of a center of the intersection of the feature with the production well.

[0021] Geothermal reservoirs contain a natural source of pressurized geothermal fluid (e.g., hot water, brine, steam) that may be utilized as a source of thermal energy. For example, one or more production wells may be drilled from the surface into and through the geothermal reservoir, and the production wells may intersect one or more features in the subsurface rock of the geothermal reservoir. In certain instances, these features may naturally provide a flow path of the pressurized geothermal fluid into the production well(s), thereby enabling the pressurized geothermal fluid to be directed to the surface via the production well(s). For example, the features may correspond to fractures within the subsurface rock that are in fluid communication with the production well(s) via one or more apertures. The thermal energy from the pressurized geothermal fluid (e.g., hot fluid) that flows to the surface may be extracted and used by an energy conversionplant for power generation, large scale heating and cooling, industrial / agricultural processes, or other geothermal applications.

[0022] Additionally, or alternatively, a fluid (e.g., water) may be introduced into the geothermal reservoir to exchange heat with the geothermal reservoir. For example, a thermal energy-depleted fluid may be injected or discharged into the geothermal reservoir (e.g., via a production well, via an injection well). The geothermal reservoir may generally be at a higher temperature and / or pressure than the thermal energy -depl eted fluid, such that as the thermal energy-depleted fluid is directed through the geothermal reservoir (e.g., into features of the geothermal reservoir), geothermal heat may be transferred to the thermal energy-depleted fluid. Thus, the geothermal reservoir may function as a heat exchanger to place the thermal energy- depleted fluid into a heat exchange relationship with the geothermal reservoir, thereby enabling the thermal energy-depleted fluid to transition to a thermal energy-charged fluid, which may be extracted and used by an energy conversion plant, as described above.

[0023] In certain traditional systems, flow loss may occur where the feature(s) intersect and fluidly couple to the production well(s) of the system. Specifically, the aperture of a feature at the intersection of the production well can act as a flow restrictor that limits fluid flow through the feature (e.g., fracture, rock matrix) and into the production well. This can limit the amount of heat captured by the system and delivered to the surface and thus decrease the productivity of the system. Additionally, or alternatively, certain features of a geothermal reservoir may not enable sufficient geothermal heat transfer with a fluid introduced into the geothermal reservoir. For example, in certain traditional systems, fractures may be formed via conventional fracking methods to form an artificial geothermal reservoir configured to transfer geothermal heat to a thermal energy-depleted fluid. However, the fractures that are formed via conventional fracking methods may extend through the geothermal reservoir in a manner that limits an amount of heat transfer between the geothermal reservoir and the thermal energy -depleted fluid. Thus, it is now recognized that improved systems and methods for accessing pressurized geothermal fluid and / or encouraging pressurized geothermal fluid flow into a production well are desired. Similarly, improved systems and methods for increasing geothermal heat transfer between a geothermal reservoir and a fluid introduced into the geothermal reservoir (e.g., increasing the heat transfer capacity of a geothermal reservoir) are desired.

[0024] Accordingly, embodiments of the present disclosure are directed toward boosting or improving the performance of geothermal systems that include a geothermal reservoir. More particularly, embodiments of the present disclosure may employ an intervention process (e.g., acidization process) that employs a reactive solution (e.g., an acid-based solution, alkaline solution) configured to enhance and / or increase the flow of pressurized geothermal fluid from the geothermal reservoir into the production well. In certain embodiments, the intervention process (e.g., the reactive solution) may be configured increase an amount of heat transfer between the geothermal reservoir and a fluid (e.g., thermal energy-depleted fluid) introduced into the geothermal reservoir. For example, the intervention process may include developing a chemical composition for a reactive fluid (e.g., reactive treatment fluid, acidic treatment fluid, acid-based solution, an alkaline treatment fluid, alkaline solution) that may be deployed into the geothermal reservoir to stimulate or treat features (e.g., fractures, natural fractures, hydraulic fractures, rock matrices) within the geothermal reservoir. The reactive fluid may be designed to withstand elevated temperatures associated with the geothermal reservoir.

[0025] Upon developing the chemical composition for the reactive fluid, the chemical composition of the reactive fluid may be optimized to achieve a desired reactivity with features of the geothermal reservoir. For example, the desired reactivity may be optimized and / or designed to enable the reactive fluid to penetrate the feature and / or rock formation to a desired depth. The intervention process may further include determining an injection rate for the reactive fluid, where the injection rate, along with the optimized chemical composition, are configured to provide a desired reaction pattern within the geothermal reservoir to enhance and / or increase the flow rate of pressurized geothermal fluid into the production well of the system. In certain embodiments, the injection rate, along with the chemical composition, may be configured to provide a desired reaction pattern within the geothermal reservoir that increases a heat transfer capacity of the geothermal reservoir. After determining an appropriate injection rate, the intervention process may include modeling and / or simulating the intervention process via one or more computer models. In certain embodiments, during the modeling and / or simulating step, one or more operating parameters (e.g., injection rate) may be adjusted before reaching an execution phase of the intervention process in which the reactive fluid is directed toward a target location (e.g., target feature). As noted above, the reactive fluid may be directed toward certain features of the geothermal reservoir to enhance and / or increase the flow rate of pressurized geothermal fluid fromthe feature into the production well and / or to increase a heat transfer capacity of the geothermal reservoir. It should be appreciated that during the execution phase, certain parameters may be monitored and / or adjusted as needed to increase flow of pressurized geothermal fluid from a geothermal reservoir and / or to increase a heat transfer capacity of a geothermal reservoir, as discussed in greater detail below.

[0026] With the preceding in mind, FIG. 1 is a schematic view of an embodiment of a geothermal system 10. The geothermal system 10 may include various components configured to access thermal energy from a geothermal reservoir 12 of the geothermal system 10, which may correspond to a volume of subsurface rock that contains a natural source of pressurized geothermal fluid (e.g., hot water, brine, steam). For example, the geothermal system 10 may include a production well 14 drilled from the surface 16 into and through the geothermal reservoir 12, where the production well 14 intersects one or more features 18 in the subsurface rock of the geothermal reservoir 12. In certain embodiments, the subsurface rock (e.g., rock matrix) itself (or a portion thereof) within the near wellbore region may correspond to a feature 18, as described in greater detail below. Each of the one or more features 18 may contain pressurized geothermal fluid, and the geothermal system 10 may be configured to provide a fluid flow path from each of the one or more features 18 into the production well 14, thereby enabling the pressurized geothermal fluid to be directed along the fluid flow path, into the production well 14, and toward the surface 16. In certain embodiments, the geothermal system 10 may perform one or more interventions to enhance and / or increase the flow of pressurized geothermal fluid from the one or more features 18 into the production well 14, as discussed in greater detail below. The thermal energy from the geothermal fluid that flows to the surface 16 may be extracted and used by an energy conversion system 11 (e.g., energy conversion plant) for power generation, large scale heating or cooling, industrial and / or agricultural processes, or other geothermal applications. For example, the energy conversion system 11 may include a steam turbine driven by the pressurized geothermal fluid, wherein the steam turbine drives an electrical generator.

[0027] Additionally, or alternatively, the geothermal reservoir 12 may be used as a heat exchanger to transfer heat to a fluid (e.g., thermal energy -depl eted fluid, cold water) introduced into the geothermal reservoir 12 (e.g., into features 18 of the geothermal reservoir 12). That is, that natural properties of the geothermal reservoir 12 (e.g., temperature, pressure) and / or thenatural properties of the pressurized geothermal fluid within the geothermal reservoir 12 may enable one or more of the features 18 to facilitate heat transfer between the geothermal reservoir 12 and a thermal fluid introduced into the geothermal reservoir 12. For example, in certain embodiments, the geothermal system 10 may correspond to and / or be arranged in a huff and puff configuration. In such embodiments, the energy conversion system 11 may be configured to direct (e.g., pump) a thermal energy-depleted fluid (e.g., cold water) along an injection line 13 (e.g., injection conduit) under pressure into the production well 14, thereby enabling the thermal energy- depleted fluid to flow into one or more of the features 18 (e.g., during an inflation phase). The production well 14 may then be sealed or closed off (e.g., via a valve disposed along the injection line 13) for a threshold amount of time, thereby enabling the geothermal reservoir 12 to pressurize and / or increase the temperature of the thermal energy-depleted fluid disposed within the features 18 of the geothermal reservoir 12. For example, natural properties of the geothermal reservoir 12 (e.g., temperature and / or pressure of the subsurface rock) may be greater than the operating properties of the thermal energy -depl eted fluid (e.g., temperature and pressure of the thermal energy-depleted fluid). Additionally, or alternatively, a temperature of the pressurized geothermal fluid within the subsurface rock (e.g., within the features 18) of the geothermal reservoir 12 may be greater than a temperature of the thermal energy-depleted fluid introduced into the geothermal reservoir 12 during the injection phase. As such, the geothermal reservoir 12 may function as a heat exchanger in which the warmer subsurface rock and / or pressurized geothermal fluid deposits heat to the cooler thermal energy-depleted fluid, thereby increasing the temperature of the thermal energy-depleted fluid.

[0028] As the temperature of the thermal energy -depl eted fluid increases, the thermal energy- depleted fluid may transition to a thermal energy-charged fluid, which may be retrieved by the energy conversion system 11. For example, upon opening the production well 14 (e.g., transitioning the valve from a closed position to an open position, during a deflation phase), the natural properties of the geothermal reservoir 12 may generate a pressure differential between the geothermal reservoir 12 and the surface 16, thereby enabling the geothermal reservoir 12 to drive the thermal energy-charged fluid toward the surface 16. That is, the subsurface rock may have a natural tendency to migrate back to an deflated position (e.g., due to the increased pressures associated with a geothermal reservoir 12), such that thermal energy-depleted fluid introduced into the one or more features 18 during an inflation phase is discharged out of the one or more features18 as thermal energy-charged fluid 18 during a deflation phase. The thermal energy -charged fluid may be directed out of the production well 14 and along an extraction line 15 to the energy conversion system 11 to be used for energy conversion, as discussed above. It should be appreciated that, in certain embodiments, a single line (e.g., injection line 13) may be used as both the injection line 13 and the control line 15.

[0029] Multiple types of features 18 are shown in the illustrated embodiment. For example, the geothermal reservoir 12 may include one or more first fractures 20 (e.g., first fracture type, natural fracture, pre-existing fracture, naturally-occurring fracture) and one or more second fractures 22 (e.g., second fracture type, conventional fracture, hydraulic fracture) extending through the geothermal reservoir 12 (e.g., subsurface rock), where the second fractures 22 collectively define an artificial geothermal reservoir 23. For example, the second fractures 22 may be formed via conventional fracking methods, whereby the fractures 22 increase a permeability of the subsurface rock of the geothermal reservoir 12 to form the artificial geothermal reservoir 23 from which fluid may be extracted, as described in greater detail below. Each of the first and second fractures 20, 22 may be fluidly coupled to the production well 14 via an aperture 24. Additionally, one or more of the features 18 may correspond to a matrix 26 (e.g., rock matrix, portion) of the subsurface rock within the near wellbore region that may include pressurized geothermal fluid. However, unlike the first and second fractures 20, 22, the matrix 26 does not naturally connect to (e.g., is not in fluid communication with) the production well 14, for example, without one or more interventions that enhance, boost, and / or enable flow of geothermal fluid from the rock matrix into the production well 14, as described in greater detail below.

[0030] In the illustrated embodiment, the first fracture 20 has a surface depth 28 that is a vertical distance from the surface 16, and a measured depth 30 along the production well 14 that is a length of the production well 14 to the aperture 24 of the first fracture 20. As may be appreciated, the measured depth 30 may be different than the surface depth 28 based at least in part on a pathway of the production well 14 and / or on a pathway of the first fracture 20. The artificial reservoir 23 also has a surface depth 32 that is a vertical distance from the surface 16, and a measured depth 34 along the production well 14 that is a length of the production well 14 to the apertures 24 of the second fracture(s) 22. As may be appreciated, the measured depth 34 may be different than the surface depth 32 based at least in part on a pathway of the production well 14and / or on a pathway of the second fracture(s) 22 (e.g., pathway of the artificial reservoir 23). Similarly, the rock matrix 26 has a surface depth 36 that is a vertical distance from the surface 16, and a measured depth 38 along the production well 14 that is a length of the production well 14 to the rock matrix 26. In the illustrated embodiment, the wellbore of the production well 14 is completed with a perforated liner 40 (e.g., slotted liner) with perforations in the intervals of the production well 14 that intersect the features 18. In alternate embodiments, the wellbore of the production well 14 may be completed with a perforated casing (e.g., cemented perforated casing) or as an open wellbore.

[0031] It should be appreciated that while the production well 14 is illustrated as intersecting one first fracture 20 and two second fractures 22 (e.g., one artificial geothermal reservoir 23), in other embodiments, the production well 14 may intersect any number of first fractures (e.g., zero, two, three, four, or more) and any number of second fractures 22 (e.g., one, three, four, five, or more) and / or artificial geothermal reservoirs 23. Further, while one rock matrix 26 is illustrated, it should be understood that any portion of the subsurface rock of the geothermal reservoir 12 within the near wellbore region may correspond to a rock matrix 26 that can be treated by an intervention process to increase and / or enhance the flow of pressurized geothermal fluid from the geothermal reservoir 12.

[0032] FIG. 2 is a schematic diagram of an embodiment of a geothermal system 50 arranged and / or configured in an injector / producer well configuration. The geothermal system 50 may include similar features to the geothermal system 10. For example, the geothermal system 50 includes the energy conversion system 11 and the geothermal reservoir 12 having the one or more features 18 (e.g., first fractures 20, second fractures 22 of an artificial geothermal reservoir 23, rock matrices 26) extending through the subsurface rock of the geothermal reservoir 12. In the illustrated embodiment, the geothermal system 50 also includes a producer well 52 (e.g., extraction well) and an injector well 54 fluidly coupled to the energy conversion system 11 (e.g., via the injection line 13 and the extraction line 15), where the producer well 52 and the injector well 54 intersect the one or more features 18 of the geothermal reservoir 12. The geothermal system 50 may be configured to introduce thermal energy-depleted fluid into the geothermal reservoir 12 (e.g., into features of the geothermal reservoir 12), thereby enabling the geothermal reservoir 12 to function as a heat exchanger to transfer heat to the thermal energy-depleted fluid. In this way,the thermal energy-depleted fluid may transition to a thermal energy-charged fluid, which may be retrieved by the geothermal system 50 and used for energy production.

[0033] For example, the energy conversion system 11 may be configured to direct (e.g., inject) thermal energy-depleted fluid (e g., cold water) into the injector well 54. The thermal energy- depleted fluid may flow through the injector well 54 and into the one or more features 18. As the thermal energy-depleted fluid flows into the one or more features 18, the natural properties of the geothermal reservoir 12 may increase the temperature and / or pressure of the thermal energy- depleted fluid, thereby causing the thermal -energy depleted fluid to transition to a thermal energy- charged fluid. For example, a temperature of the pressurized geothermal fluid within the one or more features 18 and / or a temperature of the subsurface rock of the geothermal reservoir 12 may be greater than a temperature of the thermal energy-depleted fluid introduced into the one or more features 18 via the injector well 54. As such, the geothermal reservoir 12 may function as a heat exchanger in which the warmer pressurized geothermal fluid and / or subsurface rock deposits heat to the cooler thermal energy-depleted fluid, thereby increasing the temperature of the thermal energy-depleted fluid.

[0034] Thereafter, the thermal energy-charged fluid may be retrieved by the producer well 52 and directed toward the surface 16 to be used by the energy conversion system 11. For example, the producer well 52 may be configured to provide the energy conversion system 1 1 with a flow of thermal energy-charged fluid (e.g., water, fluid having thermal energy). The energy conversion system 11 is configured to receive the thermal energy-charged fluid and extract the thermal energy from the fluid, whereby the thermal energy may be converted into electrical and / or mechanical energy. Once the thermal energy has been extracted, the energy conversion system 11 may be configured to direct the thermal energy-depleted fluid back through the injector well 54 to repeat the cycle.

[0035] In the illustrated embodiment, the producer well 52 includes a generally vertical well portion 52A and a generally horizontal well portion 52B (e.g., lateral well portion), and the injector well 54 includes a generally vertical well portion 54A and a generally horizontal well portion 54B. The horizontal well portion 52B of the producer well 52 and the horizontal well portion 54B of the injector well 54 may be offset by a distance 56 (e.g., geological formation gap), therebyforming an open loop between the injector well 54 and the producer well 52. As fluid is introduced into the geothermal reservoir 12 (e.g., into features 18 of the geothermal reservoir 12), the fluid may be directed along the distance 56 through the geothermal reservoir 12 (e.g., through the features 18) from the horizontal well portion 54B of the injector well 54 to the horizontal well portion 52B of the producer well 52, whereby geothermal heat is transferred to the fluid. Thus, fluid flowing through the producer well 52 is generally hot, whereas fluid flowing through the injector well 54 is generally cold. The temperatures of the hot and cold fluid, and the temperature difference, may depend on the depth of the producer and injector wells 52 and 54 and other considerations (e.g., natural properties of the geothermal reservoir 12).

[0036] Referring to FIGS. 1 and 2, in certain embodiments, a downhole tool may be deployed into the production well 14, the producer well 52, and / or the injector well 54, and the downhole tool may be operated to perform one or more interventions configured to enhance and / or increase the flow rate of pressurized geothermal fluid from the geothermal reservoir 12 (e.g., from the one or more features 18) into the production well 14 of the geothermal system 10 and / or the producer well 52 of the geothermal system 50. For example, the interventions discussed herein may be configured to enlarge and / or open a first fracture 20 and / or second fracture 22, thereby enabling pressurized geothermal fluid contained within the first fracture 20 and / or second fracture 22 to readily flow into the production well 14 and / or producer well 52. In certain embodiments, the interventions may be configured to enlarge an aperture 24 of first fracture 20 and / or a second fracture, thereby reducing pressure loss at the aperture 24 while increasing the flow area and / or flow rate of pressurized geothermal fluid into the production well 14 and / or producer well 52. Additionally, or alternatively, the interventions discussed herein may be configured to provide a fluid flow path from a rock matrix 26 into the production well 14 and / or the producer well 52, thereby enabling the rock matrix 26 to direct pressurized geothermal fluid into the production well 14 and / or the producer well 52. For example, in certain embodiments, the intervention may be configured to increase a permeability of the rock matrix 26, thereby increasing a flow rate of pressurized geothermal fluid from the rock matrix 26 into the production well 14 and / or producer well 52.

[0037] Further still, in certain embodiments, the interventions discussed herein may be configured to enhance and / or increase a heat transfer capacity of the geothermal reservoir 12 (e.g.,enhance and / or increase a heat transfer capacity of one or more of the features 18). For example, the interventions discussed herein may be configured to target one or more of the features 18 to generate a fluid network (e.g., artificial network, artificial reservoir) within the features 18 of the geothermal reservoir 12 and / or within the subsurface rock of the geothermal reservoir 12 that facilitates heat transfer between the geothermal reservoir 12 and a thermal fluid introduced into the geothermal reservoir 12. In certain embodiments, an intervention may be performed at the first fractures 20 to increase the permeability of the first fractures 20, thereby generating a fluid network (e.g., artificial reservoir) associated with the first fractures 20. By increasing the permeability of the first fractures 20 (e.g., by generating the fluid network), increased amounts of thermal fluid may be introduced into the geothermal reservoir 12 to receive heat from the geothermal reservoir 12. Further, as the permeability increases, a heat transfer capacity of the first fractures 20 may also increase based on the increase in the heat exchange surface area (e g., based on increased amounts or volumes of subsurface rock being exposed via the fluid network). Similarly, an intervention may be performed at the second fractures 22 to increase the permeability of the second fractures 22 and / or the artificial geothermal reservoir 23. In this way, a fluid network associated with the second fractures 22 may also be generated, whereby the fluid network is capable of receiving increased amounts of thermal fluid and / or has an increased heat transfer capacity. In certain embodiments, the interventions may be configured to enlarge and / or open an aperture 24 of a first fracture 20 and / or second fracture 22 fluidly coupling the first fracture 20 and / or second fracture 22 to the injector well 54, thereby enabling increased amounts (e.g., volumes) of thermal energy-depleted fluid to be introduced into the geothermal reservoir 12.

[0038] Further still, an intervention may be performed at a rock matrix 26 to provide a fluid flow path from the rock matrix 26 into the production well 14 or producer well 52 and / or to increase the permeability of the rock matrix 26 (e.g., to generate a fluid network within the rock matrix 26). Similar to the discussion above with respect to the first and second fractures 20, 22, by increasing the permeability of the rock matrix 26, increased amounts of thermal fluid may be introduced into the geothermal reservoir 12 (e.g., into the rock matrix) to receive heat from the geothermal reservoir 12. Further, as the permeability increases, a heat transfer capacity of the rock matrix 26 may also increase based on the increase in the heat exchange surface area (e.g., based on increased amounts or volumes of subsurface rock being exposed via the fluid network). It should be appreciated that in certain embodiments, the intervention process employed by thegeothermal system 10 may be different based at least in part on aspects of the feature 18 being targeted (e.g., whether the feature 18 is a first fracture 20, a second fracture 22, or a rock matrix 26, a composition of the feature 18, etc.), as discussed in greater detail below.

[0039] FIG. 3 is a flowchart of an example process 100 or workflow having an intervention that may be utilized by the geothermal system 10 and / or the geothermal system 50 to open a feature (e.g., features 18 of FIG. 1) that intersects a well (e.g., production well 14, producer well 52, injector well 54) or otherwise enhances or increases the flow rate of pressurized geothermal fluid into the production well or producer well of the system (e.g., geothermal system 10 of FIG. 1). Additionally, or alternatively, the process 100 may be performed to increase the heat transfer capacity of the geothermal reservoir 12. In certain embodiments, certain steps of the process 100 may be performed by downhole equipment, whereas other steps of the process 100 may be performed by a processor-based computing device or controller or any other suitable computing device(s) or controller(s). Furthermore, the blocks of the process 100 may be performed in the order disclosed herein or in any other suitable order. For example, certain blocks of the process 100 may be performed concurrently. In addition, in certain embodiments, one or more of the blocks of the process 100 may be repeated or omitted.

[0040] In block 102, a geothermal well or wellbore (e.g., production well 14, producer well 52, injector well 54) is drilled, such that the geothermal well intersects one or more features of a geothermal reservoir (e.g., features 18 of the geothermal reservoir 12). As noted above, the one or more features may extend through the geothermal reservoir. In certain embodiments, one or more of the features may be fluidly coupled to the geothermal well(s) (e.g., fractures 20, 22 that couple to the geothermal well via one or more apertures 24), while other of the features may be fluidly isolated from the geothermal well(s) (e.g., a rock matrix intersected by the production well that is not yet in fluid communication with the production well). The one or more features may contain pressurized geothermal fluid (e.g., hot water, brine, steam), which may be collected by the geothermal well(s) and delivered to the surface to be used as thermal energy. In certain embodiments, the geothermal well(s) may be configured to introduce a thermal fluid into the one or more features, where the thermal fluid receives geothermal heat from the geothermal reservoir. Thereafter, the heated thermal fluid may be extracted and delivered to the surface to be used as thermal energy, as discussed in greater detail below. In certain embodiments, the geothermalwell(s) may be completed, for example with a perforated liner, a perforated casing, or as an open wellbore at least in the interval(s) that intersect the one or more features of the geothermal reservoir. As discussed herein, each of a casing and liner may be referred to as a tubular completion component.

[0041] In block 104, well log data (e.g., subsurface data) may be analyzed (e.g., by a processorbased computing device) to determine a position of each of the one or more features intersected by the production well drilled in block 102. For example, borehole pressure measurements, caliper measurements, resistivity measurements, acoustic or ultrasonic borehole imaging measurements, and / or other downhole measurements may be analyzed to determine a wellbore depth (e.g., position, measured depth) for each of the one or more features. These measurements may be performed while drilling or by a wireline tool after drilling. For example, borehole pressure measurements may be analyzed for pressure loss while drilling. When the drilling crosses or otherwise intersects a feature, the borehole pressure will decrease. The depth of such pressure loss can be detected and used as the measured depth (e.g., position) of the feature in the geothermal well. In certain embodiments, the measured depth may correspond to a wellbore depth of an aperture of a fracture (e.g., feature) in the geothermal well. In other embodiments, the measured depth may correspond to a wellbore depth of a rock matrix in the geothermal well. In certain embodiments, the subsurface data may be obtained from direct measurement of the geothermal well, from surface measurements, or from offset wells.

[0042] Additionally, or alternatively, the well-log data may be analyzed to identify physical and / or operating characteristics of each of the one or more features and / or the geothermal reservoir. For example, resistivity measurements, acoustic or ultrasonic borehole imaging measurements, and / or other downhole measurements may be analyzed to identify the physical and / or operating characteristics of each of the features intersected by the geothermal well(s). The physical characteristics may include, but are not limited to, a size (e.g., length, depth, volume) of the feature, a size (e.g., diameter, circumference) of an aperture fluidly coupling the feature to the production well, a material composition of the feature (e.g., whether the feature includes scale deposits and / or the type of scale deposits, a type of subsurface rock in the geothermal reservoir), and the like. The operating characteristics, which may be at least partially defined by the physical characteristics, may include a flow rate of pressurized geothermal fluid from the feature into the geothermalwell(s) (e.g., before an intervention process is performed), a flow rate of fluid into the feature from the geothermal well(s) (e.g., a capacity or ability of the feature to receive treatment fluid, a capacity or ability of the feature to receive a thermal energy-depleted fluid), a heat transfer capacity of the feature, and the like.

[0043] In certain embodiments, other types of data may be analyzed in block 104 to identify the location and / or characteristics of the one or more features. For example, in certain embodiments, one or more of the features may change or adjust over time (e.g., as a result of pressurized geothermal fluid flowing out of the feature(s), as a result of thermal fluid being injected into the one or more features, based on an intervention process targeting one or more of the features). Accordingly, in certain embodiments, real-time data may be analyzed (e.g., data received from electrical and / or optical telemetry cables extending along the geothermal well(s)) to identify the changes to the physical and / or operating characteristics of the one or more features. Such real-time data may be utilized by the process 100 to adjust certain operating parameters, thereby increasing the efficiency of the process 100.

[0044] In block 106, a downhole tool may be located in the geothermal well(s) at a measured depth corresponding to the position of the feature as determined in block 104. The downhole tool may be located in the geothermal well via a conveyance system (e.g., drill pipe, coiled tubing, or wireline). For example, the conveyance system may be configured to deploy the downhole tool into a geothermal well at a position corresponding to a target feature. In certain embodiments, the conveyance system may include a controller (e.g., a processor-based control system) configured to operate the downhole tool to perform an intervention at the position corresponding to the target feature, as described in greater detail below. Accurately positioning the downhole tool for the intervention at or near the feature (e.g., at or near the intersection of a feature and the geothermal well) increases the effectiveness of the intervention. That is, an intervention performed within less than three feet, less than two feet, or less than one foot of the feature that intersects the production well can greatly improve the efficacy of the intervention to reduce the pressure loss of the pressurized geothermal fluid and / or to increase the flow rate of the pressurized geothermal fluid into the geothermal well.

[0045] In block 108, the downhole tool can be operated to perform an intervention that opensthe feature or otherwise enhances and / or increases the flow rate of pressurized geothermal fluid into the geothermal well(s) of the system. For example, the intervention may be configured to open the feature, which may increase the flow area and / or reduce the pressure loss at the intersection of feature (e.g., at an aperture of a fracture) and the geothermal well(s). Additionally, or alternatively, the intervention may be configured to enhance the heat transfer capacity of the geothermal reservoir (e.g., of features of the geothermal reservoir). For example, the intervention may generate a fluid network within the geothermal reservoir that is configured to facilitate heat transfer between the geothermal reservoir and a fluid introduced into the geothermal reservoir. As discussed in greater detail below, the intervention may correspond to a treatment process (e.g., acidizing process, alkalinizing process, reactive fluid process) that introduces a reactive fluid (e.g., reactive treatment fluid, acidic treatment fluid, acid-based solution, alkaline treatment fluid, alkaline solution) having a particular composition into the features of the geothermal reservoir at a desired flow rate to generate openings and / or fluid networks within the geothermal reservoir having a particular geometry and / or configuration (e.g., having a desired pattern) that facilitates retrieval of pressurized geothermal fluid from the geothermal reservoir and / or enhances the heat transfer capacity of the geothermal reservoir.

[0046] In optional block 110, the operations of blocks 106 and 108 may be repeated with respect to additional feature(s) that intersect the production well in order to increase the flow rate of pressurized geothermal fluid into the production well. In optional block 112, debris resulting from the intervention of block 108 may be cleaned out and / or removed from the production well (e.g., via coiled tubing), thereby further increasing the flow rate of pressurized geothermal fluid into the production well.

[0047] FIG. 4 is a flowchart of an example process 200 for stimulating (e.g., treating, acidizing, alkalinizing) a geothermal reservoir to open features within a geothermal reservoir or otherwise enhance and / or increase the flow rate of pressurized geothermal fluid into the geothermal well(s) (e.g., production well 14, producer well 52, injector well 54) of a geothermal system (e.g., geothermal system 10, geothermal system 50). Additionally, or alternatively, the process 200 may be utilized to enhance the heat transfer capacity of a geothermal reservoir and / or one or more features of the geothermal reservoir. In certain embodiments, one or more steps of the process 200 may correspond to certain steps performed during the intervention in block 108 ofFIG. 3 to stimulate portions of the geothermal reservoir (e.g., intervals of the geothermal well(s) that intersect features of the geothermal reservoir), thereby increasing the flow area of a feature, reducing the pressure loss associated with a feature, and / or enhancing the heat transfer capacity of a feature of the geothermal reservoir. In this way, the flow rate of pressurized geothermal fluid carried by the feature into the geothermal well may increase and / or the amount of heat received by a thermal fluid introduced into the geothermal reservoir may increase, thereby increasing productivity of the geothermal system.

[0048] In certain embodiments, the stimulation (e.g., intervention, acidizing, alkalinizing) may be localized with respect to a particular feature within the geothermal reservoir by setting inflatable packers (e.g., straddle packers) in the wellbore at measured depths above and below the feature (e.g., axially opposite sides of the feature relative to an axis of the wellbore. Further, the stimulation may extend about the circumference of the geothermal well (e.g., wellbore), for example, in the case where the feature intersects the geothermal well about the circumference of the geothermal well. The extent of the stimulation (e.g., radial length of the acidizing and / or alkalinizing in a radial direction away from the geothermal well (e.g., relative to an axis of the wellbore) and into the geothermal reservoir) may be limited by the design and operation of the downhole tool and / or by the reactive fluid itself (e.g., chemical composition of the reactive fluid, injection rate at which the reactive fluid is directed toward the feature). In certain embodiments, the extent of the stimulation may extend radially in the range of one foot to fifty feet into the formation at or near a feature. Further, in certain embodiments, the stimulation may be configured to create a fluid flow path (e.g., fluid network) from one geothermal well (e.g., injector well 54) to another geothermal well (e.g., producer well 52). That is, in certain embodiments, the process 200 may be configured to provide a fluid network that extends for a distance (e g., distance 56) between a first geothermal well (e.g., injector well) and a second geothermal well (e.g., producer well), where the fluid network is configured to direct the thermal energy-depleted therethrough, thereby enabling the geothermal reservoir to deposit heat to the thermal energy-depleted fluid.

[0049] In certain embodiments, certain steps of the process 200 may be performed by a processor-based computing device or controller or any other suitable computing device(s) or controller(s), whereas other steps of the process 200 may be performed by downhole equipment. Furthermore, the blocks of the process 200 may be performed in the order disclosed herein or inany other suitable order. For example, certain blocks of the process 200 may be performed concurrently. In addition, in certain embodiments, one or more of the blocks of the process 200 may be repeated or omitted.

[0050] In block 202, a reactive fluid (e.g., reactive treatment fluid, acidic treatment fluid, acidbased solution, alkaline treatment fluid, alkaline solution) may be developed that is configured to withstand elevated temperatures associated with a geothermal reservoir. For example, the reactive fluid may correspond to chemical solution (e.g., acid-based solution, alkaline solution) configured to chemically react with the subsurface rock of the geothermal reservoir and / or with scales embedded within the subsurface rock of the geothermal reservoir (e.g., carbonaceous scale, siliceous scale). In certain embodiments, the specific chemical solution that is developed and utilized to extract thermal energy from a geothermal reservoir may be based on a type of subsurface rock included within the geothermal formation and / or a type of scale embedded within one or more of the features of the geothermal formation. For example, in carbonate dominant formations, the reactive fluid may include hydrogen chloride (HC1) acid-based solutions (e.g., hydrochloric acids, retarded hydrochloric acids), organic acid solutions, hydrogen fluoride (HF) acid-based solutions (e.g., hydrofluoric acids, retarded hydrofluoric acids), mud acid solutions (e.g., mud acids), chelant mixtures, surfactants, or any combination thereof, that are configured to react with the carbonate dominant formation to increase the heat transfer capabilities of the carbonate dominant formation and / or to increase a flow rate of pressurized geothermal fluid into a geothermal well.

[0051] In sandstone or silica dominant formations, a single sandstone acid (SSA) solution may be developed to increase the heat transfer capabilities of the silica or sandstone dominant formation and / or to increase a flow rate of pressurized geothermal fluid into a production well. In certain embodiments, the SSA solution may correspond to a mixture of various solutions that enable the SSA solution to react with the silica or sandstone dominant formation in a desired manner, as discussed in greater detail below. For example, the SSA solution (e.g., the reactive fluid) may include hydrogen fluoride (HF) acid-based solutions (e.g., hydrofluoric acids, retarded hydrofluoric acids), hydrochloric (HC1) acid-based solutions (e.g., hydrochloric acids, retarded hydrochloric acids), organic acids, chelant mixtures, scale inhibitor components, or any combination thereof. In certain embodiments, the hydrofluoric acid solution component and / or the hydrochloric acid solution component may be configured to solubilize aluminosilicates. Incertain embodiments, the hydrofluoric acid solution component and / or the hydrochloric acid solution component may be generated using respective precursors. For example, the hydrofluoric acid solution component may be formed from precursors such as ammonium fluoride, ammonium bifluoride, or a fluoropolymer, whereas the hydrochloric acid solution component may be formed from precursors such as chloro-polymers. The SSA solution may also include a scale inhibitor component configured to block formation of precipitates, such as calcium fluoride, magnesium fluoride, amorphous silica, and / or fluorosilicates. Further, the SSA solution may include an organic component (e.g., blend of organic acid(s)), such as one or more chelants, configured to balance dissolution capacity, overall potential of hydrogen (pH), and system stability while limiting risks associated with secondary and / or tertiary precipitation.

[0052] In still other embodiments, the subsurface rock may correspond to a granitoid dominant formation. For example, while granitoid formations may be largely inert (e.g., the subsurface rock of the granitoid formation does not react and / or minimally reacts with an acid-based solution), granitoid formations may include natural fractures filled with scale (e.g., carbonaceous scale, siliceous scale) or other components that may react with an acid-based solution. Thus, in certain embodiments, a reactive solution (e.g., acid-based solution, alkaline solution) may be developed based on a type of scale embedded within a granitoid formation, thereby increasing the heat transfer capabilities of the granitoid formation and / or increasing a flow rate of pressurized geothermal fluid (e.g., hot water, brine, steam) into a geothermal well. For example, formations having carbonaceous scale may be treated with one or more of the reactive solutions used to treat carbonate dominant formations (e.g., hydrogen chloride (HC1) acid-based solutions, hydrogen fluoride (HF) acid-based solutions, mud acid solutions, chelant mixtures, organic acid solutions, surfactants), whereas formations having siliceous scale may be treated with the SSA solutions described above (e.g., mixture having various components including an acidic component such as hydrofluoric acid or hydrochloric acid, a scale inhibitor component, and an organic acid component).

[0053] It should be appreciated that the type of subsurface rock that defines the one or more features and / or that is present within the geothermal reservoir may be determined by analyzing well log data and / or real-time data (e.g., block 104 of process 100). Notably, each of the types of subsurface rock discussed above that may be accessed by a geothermal system using the process200 discussed herein may contain less than a threshold amount of hydrocarbon, such that the process 200 does not extract hydrocarbon from the geothermal reservoir. That is, the process 200 is not utilized to extract hydrocarbon products, but rather, to extract pressurized geothermal fluid (e.g., hot water, brine, steam) from the geothermal reservoir and / or to increase a heat transfer capacity of the geothermal reservoir, as discussed in greater detail below.

[0054] In block 204, after developing the appropriate reactive solutions for each of the abovedescribed subsurface rock types and / or formation types, the reactive solutions may be tested and optimized to achieve a particular reaction rate with the geothermal reservoir. For example, in block 204, computed tomography (CT) scanning and / or core testing may be utilized to determine a rate of reaction of the reactive solution with the one or more features (e.g., the particular type of subsurface rock present within the one or more features, type of subsurface rock that defines the one or more features). In certain embodiments, the reactive solutions may be optimized to achieve a target reaction rate with the features that penetrates the subsurface rock to a desired depth. For example, as noted above, the reactive solutions that are developed in block 202 may be configured to react with the features (e.g., subsurface rock that defines the features) and / or with portions of the subsurface rock that include scale, thereby increasing a flow rate of pressurized geothermal fluid from the features and / or increasing a heat transfer capacity of the features. In certain instances, when the reactivity (e.g., reaction rate) between the reactive solution and a feature exceeds an upper limit threshold value, the reactive solution may be spent or consumed at a rate that does not enable the reactive solution to penetrate the feature (e.g., penetrate the subsurface rock) to a desired depth. Similarly, when the reactivity between the reactive solution and the feature is below a lower limit threshold value, the reactive solution may not be reactive enough to penetrate the feature to a desired depth. Thus, the reactive solution may be tested and optimized to achieve a particular reaction rate that penetrates the feature in a desired manner (e.g., to a desired depth).

[0055] In certain embodiments, the desired penetration depth may correspond to a distance between geothermal wells employed by a geothermal system. For example, in an injector producer configuration, the target reaction rate for the reactive solution may be configured to penetrate the subsurface rock for a distance (e.g., depth) that corresponds to the distance between an injector well and a producer well of the geothermal system (e.g., distance 56). That is, the reaction ratemay be tested and optimized such that the reactive solution penetrates the geothermal formation from the injector well to the producer well, thereby generating a fluid flow path for thermal fluid to flow therethrough (e.g., from the injector well to the producer well).

[0056] In block 206, after the reactive solution has been developed and optimized to achieve a particular reaction rate with the geothermal reservoir (e.g., penetrate the geothermal reservoir to a desired depth), an injection rate of the reactive solution may be tested and optimized. For example, in block 206, additional CT scanning and / or core testing may be utilized to identify an appropriate injection rate of the reactive solution that achieves a desired pattern within the geothermal reservoir. In certain embodiments, the injection rate of the reactive solutions may be tested and optimized to achieve a ramified wormhole pattern within the subsurface rock (e.g., a series of channels and / or a fluid network) that facilitates retrieval of pressurized geothermal fluid and / or increases a heat transfer capacity of the geothermal reservoir. For example, FIG. 5 illustrates the differences between a dominant wormhole 250 and a ramified wormhole 260, where the ramified wormhole 260 is configured to increase the heat transfer capacity of a geothermal formation , such as the geothermal reservoir 12, and / or to increase or enhance flow of pressurized geothermal fluid into a geothermal well (e.g., production well 14, producer well 52, injector well 54).

[0057] As shown in the illustrated embodiment, the dominant wormhole 250 extends for a depth 251 into the geological formation 12 and includes a primary or dominant channel 252 having a number of branches 254 (e.g., secondary branches) extending therefrom. Meanwhile, the ramified wormhole 260 may extend for a depth 261 into the geothermal reservoir 12. In certain embodiments, the depth 251 at which the dominant wormhole 250 extends into the geothermal reservoir 12 may be greater than the depth 261 at which the ramified wormhole 260 extends into the geothermal reservoir 12. Further, as illustrated, the ramified wormhole 260 may not include a primary channel, and instead may include a series of interconnected channels 262 that collectively define a network 264 of channels 262. For example, the ramified wormhole 260 may include at least a threshold number of interconnections between the channels 262, thereby generating the network 264 of channels 262. As shown in the illustrated embodiment, a number of connections between various channels 262 of the ramified wormhole 260 may be greater than a number of connections between channels 252 and / or branches 254 of the dominant wormhole 250. In thisway, the ramified wormhole 260 may enable greater heat transfer across the network relative to the heat transfer achieved by the dominant wormhole. In certain embodiments, the network 264 of the ramified wormhole 260 may also facilitate retrieval of a greater volume of pressurized geothermal fluid relative to the dominant wormhole 250 (e.g., by increasing a flow area within the geothermal reservoir 12).

[0058] It should be appreciated that, in certain embodiments and / or depending on a type of geothermal system being employed, different steps may be performed to achieve the ramified wormhole 260 pattern illustrated in FIG. 5. For example, returning to FIG. 4, in carbonate dominant formations, block 206 may involve a two-step process in which the injection rate is optimized to achieve a first pattern (e.g., dominant wormhole 250), and then the injection rate is adjusted and optimized to achieve a second pattern (e.g., ramified wormhole 260) from the first pattern.

[0059] In block 208, computer modeling may be performed to further optimize, test, and / or adjust the injection rate determined in block 206. For example, the modeling in block 208 may include obtaining and inputting site information and stimulation parameters (e.g., reactivity, injection rate) into a computer model or system that determines and outputs an array of expected outcomes based on the applied information and parameters. In certain embodiments, the computer model may correspond to an optimization model that includes, for instance, a machine learning (ML) model. As used herein, a “machine learning model” refers to a computer algorithm or model (e.g., classification model, regression model) that can be tuned (e.g., trained) based on training input to approximate unknown functions. For example, an ML model may refer to a neural network or other machine learning algorithm or architecture that learns and approximates complex functions and generates outputs based on a plurality of inputs provided to the machine learning model. In certain embodiments, an ML system, model, or neural network described herein is an artificial neural network. In certain embodiments, an ML system, model, or neural network described herein is a convolutional neural network. In certain embodiments, an ML system, model, or neural network described herein is a recurrent neural network. In at least one embodiment, an ML system, model, or neural network described herein is a Bayes classifier. As used herein, a “machine learning system” may refer to one or multiple ML models that cooperatively generate one or more outputs based on corresponding inputs. For example, an MLsystem may refer to any system architecture having multiple discrete ML components that consider different kinds of information or inputs.

[0060] In block 208, the reactivity of the reactive solution, the injection rate of the reactive solution, the geothermal profile of the geothermal reservoir, and / or other parameters may be utilized as inputs in the model, thereby enabling the model to generate outputs that may quantify and / or simulate an expected outcome of the reactive solution with the geothermal reservoir. For example, the model may utilize the data to generate a simulation that depicts the manner in which the reactive solution reacts with the geothermal reservoir. In certain embodiments, the model may quantify an amount of pressurized geothermal fluid that may be extracted by a geothermal well. Additionally, or alternatively, the model may quantify a heat exchange capacity of the geothermal reservoir. Using the model in block 208, the process 200 may repeat blocks 204 and 206 to further refine and / or adjust the reactivity and / or injection rate of the reactive solution to achieve a desired outcome (e.g., to generate a desired pattern in the geothermal reservoir, to increase and / or enhance flow of geothermal fluid from the geothermal reservoir, to increase and / or enhance a volume of subsurface rock that may be utilized as a heat exchanger).

[0061] After modelling the stimulation in block 208, the process 200 may proceed to block 210, in which a downhole tool is deployed into the geothermal well to stimulate the geothermal reservoir using the parameters and modelling as determined in blocks 204, 206, and 208. That is, block 210 may correspond to an execution phase in which the reactive solution having the desired reactivity determined in block 204, and the desired injection rate determined in block 206 (each of which are further optimized by the modelling in block 208) is introduced to the geothermal reservoir. In certain embodiments, block 210 may correspond to blocks 106 and 108 described above. For example, in block 210 a downhole tool may located in the geothermal well(s) at a measured depth corresponding to the position of a target feature (e.g., as determined in block 104 of the process 100). Thereafter, the downhole tool may operated to inject a reactive solution into the target feature, whereby the reactive solution has been designed, tested, and modelled (e.g., optimized) to increase a heat transfer capacity of the geothermal reservoir and / or to increase flow of pressurized geothermal fluid from the geothermal reservoir geothermal well (e.g., based on the physical and / or operating characteristics of the geothermal reservoir).

[0062] In certain embodiments, the downhole tool may be operated to direct the reactive solution into the target feature and / or geothermal reservoir at a desired injection rate as determined in block 206, thereby enabling the reactive solution to penetrate the feature in a desired manner. For example, a reactive solution configured to penetrate the geothermal reservoir to a desired depth as determined in block 204 may be directed into the geothermal reservoir and / or target feature at the injection rate determined in block 206 (e.g., based on a type of subsurface rock of the geothermal reservoir, based on a type of scale within one or more features of the geothermal reservoir), thereby enabling the downhole tool to generate one or more ramified wormholes within the geothermal reservoir. As discussed above, the ramified wormholes may be configured to increase the heat transfer capacity of the geothermal reservoir and / or to increase a flow of pressured geothermal fluid from the reservoir.

[0063] It should be appreciated that the process 200 may repeat various of the blocks discussed above for different features within the geothermal reservoir. That is, in certain embodiments, characteristics (e.g., physical characteristics, operating characteristics) of a particular feature may be identified, a reactive solution capable of reacting with the geothermal reservoir based on the characteristics (e.g., composition of the subsurface rock, type of scale embedded within one or more features) of the geothermal reservoir may be selected, the reactive solution may be optimized and tested to determine an appropriate injection rate into the geothermal reservoir, and the reactive solution may be injected into the geothermal reservoir via the downhole tool at the determined injection rate. Thereafter, the downhole tool may be relocated to another position corresponding to a different feature that intersects the geothermal well. Notably, if the different feature has different characteristics than the previously stimulated feature, the composition of the reactive solution and / or the injection rate of the reactive solution may be adjusted based on the differing characteristics (e.g., based on a different subsurface rock type within the geothermal reservoir).

[0064] In certain embodiments, downhole fiber optic telemetry may be utilized to monitor and / or track the response and / or reaction between the reactive solution and the geothermal reservoir. Data collected by the fiber optic telemetry may be returned to the model in block 208 to further train or tune the model. Additionally, in certain embodiments, data indicative of the response and / or reactivity between the acid-based solution and the geothermal reservoir may be utilized to further optimize the reaction rate determined in block 204 and / or the injection ratedetermined in block 206.

[0065] Technical effects of the present disclosure include systems and methods for treating one or more features of a geothermal reservoir with a reactive solution that has been tested and optimized to achieve a particular reaction rate and / or a particular reaction pattern within the geothermal reservoir, thereby increasing a heat transfer capacity of the geothermal reservoir and / or increasing an amount of pressurized geothermal fluid retrieved from the geothermal reservoir. For example, present embodiments may employ an intervention process configured to develop a reactive solution (e.g., reactive fluid, acid-based solution, alkaline solution) based on a type of subsurface rock present within the geothermal formation and / or a type of scale embedded within features of the geothermal reservoir. In certain embodiments, the reactive solutions that are developed may be configured to withstand elevated temperatures associated with a geothermal reservoir. After developing the reactive solution, the reactive solution may be tested and optimized to achieve a desired reaction rate with the geothermal reservoir (e.g., with the subsurface rock, with the one or more features, with scale embedded within the one or more features). In certain embodiments, the target or desired reaction rate may be configured to penetrate the geothermal reservoir to a desired depth.

[0066] Upon optimizing the reaction rate, an inj ection rate for introducing the reactive solution into the geothermal reservoir may be tested and optimized, thereby enabling the reactive solution to penetrate the geothermal reservoir according to a desired pattern. In certain embodiments, the injection rate may be configured to generate a ramified wormhole within the geothermal formation, whereby the ramified wormhole includes a series of interconnected channels that define a fluid network configured to increase the heat transfer capacity of the geothermal reservoir and / or to increase a flow rate of pressurized geothermal fluid into the production well. After testing and optimizing the reaction rate and the injection rate, the intervention process may include modeling and / or simulating the intervention, thereby enabling certain adjustments (e.g., adjust injection rate) to be made before performing an execution phase of the intervention process in which a downhole tool is deployed to inject the reactive solution according to the tested and optimized injection rate. In certain embodiments, real-time data may be utilized to further tune and / or adjust the intervention process. In this way, the intervention process may increase a heat transfer capacity of a geothermal reservoir and / or increase a flow rate (e.g., mass flow rate) of pressurized geothermal fluid into aproduction well.

[0067] The subject matter described in detail above may be defined by one or more clauses, as set forth below.

[0068] A method for extracting thermal energy from a geothermal reservoir having one or more features extending through the geothermal reservoir includes analyzing subsurface data to determine a measured depth of a feature of the one or more that intersects a production well, running a downhole tool along the production well to a location corresponding to the measured depth of the feature, and performing an intervention at the location using the downhole tool, wherein the intervention includes injecting a reactive solution into the feature, wherein the reactive solution is configured to penetrate the feature to a desired depth and according to a desired pattern based on an injection rate of the reactive solution into the feature and a reaction rate of the reactive solution with the feature.

[0069] The method of the preceding clause, wherein the desired pattern corresponds to a ramified wormhole.

[0070] The method of any preceding clause, wherein the ramified wormhole includes a plurality of channels interconnected to one another to collectively define a fluid network.

[0071] The method of any preceding clause, including selecting a composition of the reactive solution based on a type of subsurface rock that defines the feature.

[0072] The method of any preceding clause, wherein the type of subsurface rock corresponds to a carbonate dominant formation, and wherein the composition of the reactive solution includes a hydrochloric acid, a retarded hydrochloric acid, an organic acid solution, a chelant mixture, a hydrofluoric acid, a mud acid, a surfactant, or any combination thereof.

[0073] The method of any preceding clause, wherein the type of subsurface rock corresponds to a sandstone dominant formation, and wherein the composition of the reactive solution includes a hydrofluoric acid, a hydrochloric acid, a chelant mixture, an organic acid component, a scale inhibitor component, or any combination thereof.

[0074] The method of any preceding clause, comprising generating the hydrofluoric acid usinga hydrogen fluoride precursor.

[0075] The method of any preceding clause, wherein the scale inhibitor component is configured to block formation of one or more precipitates, wherein the one or more precipitates include calcium fluoride, magnesium fluoride, amorphous silica, fluorosilicates, or any combination thereof.

[0076] The method of any preceding clause, wherein the organic acid component includes one or more chelants configured to balance a potential of hydrogen (pH) within the feature, block formation of precipitates, balance a dissolution capacity of the feature, or any combination thereof.

[0077] The method of any preceding clause, including simulating the intervention using the reactive solution and the injection rate before performing the intervention.

[0078] The method of any preceding clause, including receiving real-time data from electrical telemetry cables extending along the production well, wherein the real-time data is indicative of changes to the feature based on injecting the reactive solution into the feature, and adjusting the injection rate of the reactive solution based on the real-time data.

[0079] The method of any preceding clause, including performing a second intervention at a second location in the production well that corresponds to a second measured depth of a second feature of the one or more features, wherein the second feature includes characteristics different than the first feature, and wherein the second intervention includes determining a second injection rate of the reactive solution into the second feature, wherein the second injection rate is configured to penetrate the second feature according to the desired pattern, and injecting the reactive solution into the second feature at the second injection rate to generate the desired pattern within the second feature, wherein the second injection rate is different than the first injection rate based on the characteristics of the second feature being different than the characteristics of the first feature.

[0080] The method of any preceding clause, wherein the first feature corresponds to a natural fracture, and wherein the second feature corresponds to a rock matrix.

[0081] A method for increasing a heat transfer capacity of a geothermal reservoir including analyzing subsurface data to determine a measured depth of one or more features that intersect ageothermal well, running a downhole tool along the geothermal well to a position corresponding to the measured depth of a feature of the one or more features, and performing an intervention at the position using the downhole tool, wherein the intervention includes injecting a reactive solution into the feature, wherein the reactive solution is configured to penetrate the feature to a desired depth based on a reaction rate of the reactive solution with the subsurface rock of the geothermal reservoir and penetrate the feature according to a desired pattern based on an injection rate of the reactive solution into the feature, wherein the desired pattern corresponds to a ramified wormhole.

[0082] The method of the preceding clause, including selecting a composition of the reactive solution based on a type of scale embedded within the feature.

[0083] The method of any preceding clause, including selecting a hydrogen chloride acidbased solution, a hydrogen fluoride acid-based solution, an organic acid solution, a chelant mixture, a surfactant, a mud acid solution, or any combination thereof, for the reactive solution when the type of scale corresponds to carbonaceous scale, or selecting a mixture including a hydrofluoric acid component, a hydrochloric acid component, a scale inhibitor component, an organic acid component, or any combination thereof, for the reactive solution when the type of scale corresponds to siliceous scale.

[0084] The method of any preceding clause, including injecting the reactive solution into the geothermal reservoir to retrieve pressured geothermal fluid from the geothermal reservoir.

[0085] A system includes a conveyance system configured to deploy a downhole tool within a geothermal well that intersects a geothermal reservoir, the downhole tool configured to perform an intervention at an intersection of the geothermal well with a feature of the geothermal reservoir, and a control system configured to control operation of the conveyance system to run the downhole tool to a position of the intersection, and operate the downhole tool to inject a reactive fluid into the feature to generate a ramified wormhole within the geothermal reservoir.

[0086] The system of the preceding clause, wherein the geothermal reservoir corresponds to a volume of subsurface rock having the feature extending therethrough, and wherein a composition of the reactive fluid is selected based on a type of the subsurface rock.

[0087] The system of any preceding clause, including an additional geothermal well positioneda distance from the geothermal well, wherein the feature is positioned between the geothermal well and the additional geothermal well, and wherein the controller is configured to operate the downhole tool to inject the reactive fluid into the feature such that the reactive fluid penetrates the feature to a depth that corresponds to the distance between the geothermal well and the additional geothermal well.

[0088] The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. Moreover, the order in which the elements of the methods described herein are illustrated and described may be re-arranged, and / or two or more elements may occur simultaneously. The embodiments were chosen and described in order to best explain the principals of the disclosure and its practical applications, to thereby enable others skilled in the art to best utilize the disclosure and various embodiments with various modifications as are suited to the particular use contemplated.

[0089] Finally, the techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function]...” or “step for [perform]ing [a function]...”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Claims

CLAIMS:

1. A method for extracting thermal energy from a geothermal reservoir having one or more features extending through the geothermal reservoir, the method comprising: analyzing subsurface data to determine a measured depth of a feature of the one or more that intersects a production well; running a downhole tool along the production well to a location corresponding to the measured depth of the feature; and performing an intervention at the location using the downhole tool, wherein the intervention comprises injecting a reactive solution into the feature, wherein the reactive solution is configured to penetrate the feature to a desired depth and according to a desired pattern based on an injection rate of the reactive solution into the feature and a reaction rate of the reactive solution with the feature.

2. The method of claim 1, wherein the desired pattern corresponds to a ramified wormhole.

3. The method of claim 2, wherein the ramified wormhole comprises a plurality of channels interconnected to one another to collectively define a fluid network.

4. The method of claim 1, comprising selecting a composition of the reactive solution based on a type of subsurface rock that defines the feature.

5. The method of claim 4, wherein the type of subsurface rock corresponds to a carbonate dominant formation, and wherein the composition of the reactive solution comprises a hydrochloric acid, a retarded hydrochloric acid, an organic acid solution, a chelant mixture, a hydrofluoric acid, a mud acid, a surfactant, or any combination thereof.

6. The method of claim 4, wherein the type of subsurface rock corresponds to a sandstone dominant formation, and wherein the composition of the reactive solution comprises a hydrofluoric acid, a hydrochloric acid, a chelant mixture, an organic acid component, a scale inhibitor component, or any combination thereof.

7. The method of claim 6, comprising generating the hydrofluoric acid using a hydrogen fluoride precursor.

8. The method of claim 6, wherein the scale inhibitor component is configured to block formation of one or more precipitates, wherein the one or more precipitates comprise calcium fluoride, magnesium fluoride, amorphous silica, fluorosilicates, or any combination thereof.

9. The method of claim 6, wherein the organic acid component comprises one or more chelants configured to balance a potential of hydrogen (pH) within the feature, block formation of precipitates, balance a dissolution capacity of the feature, or any combination thereof.

10. The method of claim 1, comprising simulating the intervention using the reactive solution and the injection rate before performing the intervention.

11. The method of claim 10, comprising: receiving real-time data from electrical telemetry cables extending along the production well, wherein the real-time data is indicative of changes to the feature based on injecting the reactive solution into the feature; and adjusting the injection rate of the reactive solution based on the real-time data.

12. The method of claim 1, comprising performing a second intervention at a second location in the production well that corresponds to a second measured depth of a second feature of the one or more features, wherein the second feature comprises characteristics different than the first feature, and wherein the second intervention comprises: determining a second injection rate of the reactive solution into the second feature, wherein the second injection rate is configured to penetrate the second feature according to the desired pattern; and injecting the reactive solution into the second feature at the second injection rate to generate the desired pattern within the second feature, wherein the second injection rate is different than the first injection rate based on the characteristics of the second feature being different than the characteristics of the first feature.

13. The method of claim 10, wherein the first feature corresponds to a natural fracture, and wherein the second feature corresponds to a rock matrix.

14. A method for increasing a heat transfer capacity of a geothermal reservoir, the method comprising: analyzing subsurface data to determine a measured depth of one or more features that intersect a geothermal well; running a downhole tool along the geothermal well to a position corresponding to the measured depth of a feature of the one or more features; and performing an intervention at the position using the downhole tool, wherein the intervention comprises injecting a reactive solution into the feature, wherein the reactive solution is configured to: penetrate the feature to a desired depth based on a reaction rate of the reactive solution with the subsurface rock of the geothermal reservoir; and penetrate the feature according to a desired pattern based on an injection rate of the reactive solution into the feature, wherein the desired pattern corresponds to a ramified wormhole.

15. The method of claim 14, comprising selecting a composition of the reactive solution based on a type of scale embedded within the feature.

16. The method of claim 15, comprising: selecting a hydrogen chloride acid-based solution, a hydrogen fluoride acid-based solution, an organic acid solution, a chelant mixture, a surfactant, a mud acid solution, or any combination thereof, for the reactive solution when the type of scale corresponds to carbonaceous scale; or selecting a mixture comprising a hydrofluoric acid component, a hydrochloric acid component, a scale inhibitor component, an organic acid component, or any combination thereof, for the reactive solution when the type of scale corresponds to siliceous scale.

17. The method of claim 14, comprising injecting the reactive solution into the geothermalreservoir to retrieve pressured geothermal fluid from the geothermal reservoir.

18. A system, comprising: a conveyance system configured to deploy a downhole tool within a geothermal well that intersects a geothermal reservoir; the downhole tool configured to perform an intervention at an intersection of the geothermal well with a feature of the geothermal reservoir; and a control system configured to: control operation of the conveyance system to run the downhole tool to a position of the intersection; and operate the downhole tool to inject a reactive fluid into the feature to generate a ramified wormhole within the geothermal reservoir.

19. The system of claim 18, wherein the geothermal reservoir corresponds to a volume of subsurface rock having the feature extending therethrough, and wherein a composition of the reactive fluid is selected based on a type of the subsurface rock.

20. The system of claim 18, comprising an additional geothermal well positioned a distance from the geothermal well, wherein the feature is positioned between the geothermal well and the additional geothermal well, and wherein the controller is configured to operate the downhole tool to inject the reactive fluid into the feature such that the reactive fluid penetrates the feature to a depth that corresponds to the distance between the geothermal well and the additional geothermal well.

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