A method and system for evaluating the water conductivity of a hot dry rock enhanced geothermal system

Abstract

The application discloses a hot dry rock enhanced geothermal system water conductivity evaluation method and system. The method comprises the following steps: obtaining injection well liquid inflow data and production well liquid production data by using multiple optical fiber measuring points, calculating the cumulative injection well liquid inflow and the cumulative production well liquid production of the water conductivity evaluation section within a preset time, and then calculating the water conductivity efficiency; and performing water conductivity evaluation according to the water conductivity efficiency and in combination with fracturing design parameters and geological data. The system comprises a controller, a distributed optical fiber acoustic sensing device, a pipe sleeve and an optical cable; the distributed optical fiber acoustic sensing device is used for obtaining injection well liquid inflow data and production well liquid production data by using multiple optical fiber measuring points; and the controller is used for receiving the data obtained by the optical fiber measuring points to calculate the water conductivity efficiency and perform water conductivity evaluation. The method and system are simple and easy to implement, can efficiently obtain more accurate water conductivity efficiency, make the water conductivity evaluation more accurate, and are beneficial to efficient exploitation of geothermal energy.

Description

Technical Field

[0001] This invention relates to the fields of green, low-carbon new energy and geothermal field development technology, and in particular to a method and system for evaluating the water conductivity of a dry hot rock enhanced geothermal system. Background Technology

[0002] Multi-stage, multi-cluster horizontal well hydraulic fracturing is a key technology for the efficient development of enhanced geothermal systems. To improve the water conductivity of enhanced geothermal systems and ensure high conductivity between injection and production wells, low heat transfer fluid loss, and a high injection-to-production ratio, various downhole monitoring methods have been implemented in the field to help understand the water conductivity of enhanced geothermal systems, thereby enabling real-time monitoring and diagnosis of the water conductivity of enhanced geothermal systems.

[0003] However, since the heat exchange process of enhanced geothermal systems acts on deep dry hot rock reservoirs, it is difficult to accurately determine the communication between artificial fractures in the wells during the geothermal energy production process. It is even more difficult to achieve precise injection and production down to the cluster level. Therefore, the evaluation of the water conductivity of enhanced geothermal systems has always been a technical challenge in the industry and urgently needs to be tackled. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a method and system for evaluating the water conductivity of a dry hot rock-enhanced geothermal system that overcomes or at least partially solves the above problems.

[0005] In a first aspect, embodiments of the present invention provide a method for evaluating the water conductivity of a hot dry rock-enhanced geothermal system, comprising:

[0006] The injection well fluid inflow rate and production well fluid production rate data of multiple effective modified clusters in multiple water-conductivity evaluation sections of the production well were obtained at multiple times using multiple fiber optic measurement points.

[0007] Based on the injection well fluid inflow rate data and the production well fluid production rate data, the cumulative injection well fluid inflow rate and the cumulative production well fluid production rate of each of the multiple water conductivity evaluation sections within a preset time period are obtained.

[0008] Based on the obtained cumulative fluid inflow of the injection well and cumulative fluid production of the production well, the ratio of the cumulative fluid inflow of the injection well to the cumulative fluid production of the production well is calculated to obtain the water conduction efficiency within a preset time.

[0009] Based on the stated water conductivity efficiency, and in conjunction with fracturing design parameters and geological data, the water conductivity of the dry hot rock-enhanced geothermal system to be evaluated is assessed.

[0010] In one embodiment, the above-described method for evaluating the hydraulic conductivity of a hot dry rock-enhanced geothermal system, based on the injection well flow rate data, obtains the cumulative injection volume of the injection well in each of the plurality of hydraulic conductivity evaluation segments within a preset time period, including:

[0011] Based on the influent flow rate data, calculate the influent flow rate corresponding to the hydroconductivity evaluation section at multiple times;

[0012] Based on the inflow rate of the hydroconductivity evaluation section at multiple times, calculate the inflow rate of the hydroconductivity evaluation section in multiple time periods.

[0013] By calculating the sum of the influent flow rates corresponding to the multiple time periods, the cumulative influent volume of the injection well in the water conductivity evaluation section within the preset time period is obtained.

[0014] In one embodiment, the above-described method for evaluating the hydraulic conductivity of a hot dry rock-enhanced geothermal system includes calculating the influent flow rate at multiple times for the hydraulic conductivity evaluation segment based on the influent flow rate data, comprising:

[0015] Based on the influent flow rate data of multiple effective modified clusters in each hydroconductivity evaluation section at each time point, the sum of the influent flow rates of the multiple effective modified clusters at the same time point is calculated to obtain the influent flow rates of the hydroconductivity evaluation section at multiple times.

[0016] In one embodiment, the above-described method for evaluating the hydraulic conductivity of a hot dry rock-enhanced geothermal system calculates the influent flow rate for the hydraulic conductivity evaluation segment across multiple time periods, including:

[0017] Based on the inflow rate at each of the multiple times corresponding to the water conductivity evaluation section, the product of the inflow rate at each time point and the duration of the corresponding time period is calculated to obtain the inflow rate for the time period.

[0018] In one embodiment, the above-described method for evaluating the hydraulic conductivity of a hot dry rock-enhanced geothermal system, based on the production flow rate data of the production wells, obtains the cumulative production volume of the production wells in each of the plurality of hydraulic conductivity evaluation segments within a preset time period, including:

[0019] Based on the production flow rate data of the production well, calculate the production flow rate of the water conductivity evaluation section at multiple times;

[0020] Based on the liquid production flow rate of the water conductivity evaluation section at multiple times, calculate the liquid production flow rate of the water conductivity evaluation section in multiple time periods.

[0021] The cumulative fluid production of the production well in the water conductivity evaluation section within a preset time period is obtained by summing the fluid production flow rates corresponding to the multiple time periods.

[0022] In one embodiment, the above-described method for evaluating the hydraulic conductivity of a hot dry rock-enhanced geothermal system, based on the production well flow rate data, calculates the production flow rate corresponding to the hydraulic conductivity evaluation segment at multiple time points, including:

[0023] Based on the production flow data of multiple effective modified clusters in each water conductivity evaluation section at each time point, the sum of the production flow of the multiple effective modified clusters at the same time point is calculated to obtain the production flow of the water conductivity evaluation section at multiple times.

[0024] In one embodiment, the above-described method for evaluating the hydraulic conductivity of a hot dry rock-enhanced geothermal system calculates the liquid production flow rate of the hydraulic conductivity evaluation segment in multiple time periods, including:

[0025] Based on the liquid flow rate corresponding to the liquid production rate at multiple times in the water conductivity evaluation section, the product of the liquid production rate and the duration of the corresponding time period is calculated to obtain the liquid production rate for the time period.

[0026] In one embodiment, the above-described method for evaluating the water conductivity of a hot dry rock-enhanced geothermal system includes at least one effective modified cluster in each water conductivity evaluation segment.

[0027] Secondly, embodiments of the present invention provide a water conductivity evaluation system for a dry hot rock-enhanced geothermal system, comprising:

[0028] Controller, distributed fiber optic acoustic sensing device, tubing and optical cable;

[0029] The controller is electrically connected to the distributed fiber optic acoustic sensing device.

[0030] The distributed fiber optic acoustic sensing device includes multiple fiber optic measurement points;

[0031] Both the injection well and the production well of the hot dry rock enhanced geothermal system are equipped with pipe sleeves, and the optical cable is installed in the pipe sleeves; the distributed optical fiber acoustic sensing device is connected to the optical cable.

[0032] The distributed fiber optic acoustic sensing device is used to acquire injection well fluid inflow data and production well fluid production flow data of multiple effective modification clusters in multiple water-conductivity evaluation sections of the production well at multiple times using multiple fiber optic measuring points.

[0033] The controller is used to receive the injection well fluid inflow data and production well fluid production data acquired by the distributed fiber optic acoustic sensing device, and based on the injection well fluid inflow data and production well fluid production data, to obtain the cumulative injection well fluid volume and cumulative production well fluid volume of each of the multiple water conductivity evaluation sections within a preset time; based on the obtained cumulative injection well fluid volume and cumulative production well fluid volume, to calculate the ratio of the cumulative injection well fluid volume to the cumulative production well fluid volume, to obtain the water conductivity efficiency within the preset time; based on the water conductivity efficiency, and in conjunction with fracturing design parameters and geological data, to evaluate the water conductivity of the dry hot rock enhanced geothermal system to be evaluated.

[0034] In one embodiment, the above-mentioned dry hot rock enhanced geothermal system water conductivity evaluation system further includes a downhole flow control device;

[0035] The controller is electrically connected to the downhole flow control device;

[0036] The downhole flow control device is installed at the fluid inlet of the injection well and is used to adjust the fluid inlet flow rate of the injection well according to the instructions sent by the controller.

[0037] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0038] The method for evaluating the hydraulic conductivity of a hot dry rock-enhanced geothermal system provided in this invention is based on distributed optical fiber sensing monitoring technology. It acquires influent and production flow data of the effective modified cluster at multiple times through multiple optical fiber measuring points. Then, it calculates the cumulative influent and production volume of each hydraulic conductivity evaluation segment within a preset time period, thereby obtaining the hydraulic conductivity efficiency of each evaluation segment within the preset time period. This allows for the acquisition of hydraulic conductivity efficiency of the hot dry rock-enhanced geothermal system by monitoring injection and production data down to the segment / cluster level, thus enabling the evaluation of hydraulic conductivity. Therefore, the method for evaluating the hydraulic conductivity of a hot dry rock-enhanced geothermal system provided in this invention can efficiently obtain more accurate hydraulic conductivity efficiency, making the evaluation of the hydraulic conductivity of the hot dry rock-enhanced geothermal system more accurate and beneficial for the efficient exploitation of geothermal energy.

[0039] Furthermore, the hot dry rock enhanced geothermal system water conductivity evaluation system provided in this embodiment of the invention utilizes distributed optical fiber sensing monitoring technology to accurately monitor the acoustic / vibration signals of the entire well section of the injection and production wells of the hot dry rock enhanced geothermal system in real time. The water conductivity of the hot dry rock enhanced geothermal system can be effectively evaluated by analyzing the optical fiber monitoring signals. This system is simple to operate and suitable for engineering personnel. It has good application value for evaluating the water conductivity of hot dry rock enhanced geothermal systems based on distributed optical fiber acoustic sensing monitoring technology, providing technical support for real-time on-site guidance of geothermal energy production, and has strong promotion and practical value.

[0040] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0041] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0042] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0043] Figure 1 This is a schematic diagram of the process for evaluating the water conductivity of a hot dry rock-enhanced geothermal system in an embodiment of the present invention.

[0044] Figure 2 This is a schematic diagram of the calculation process for the cumulative liquid inflow of the injection well in the water conductivity evaluation section within a preset time in an embodiment of the present invention;

[0045] Figure 3 This is a schematic diagram illustrating the calculation process of the cumulative fluid production of the production well within a preset time in the water conductivity evaluation section of this invention.

[0046] Figure 4 This is a schematic diagram of the structure of the water conductivity evaluation system for the dry hot rock enhanced geothermal system in an embodiment of the present invention. Detailed Implementation

[0047] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0048] The inventors of this invention have discovered that segmented multi-cluster hydraulic fracturing in horizontal wells is a core technology for the development of hot dry rock enhanced geothermal systems. Effective real-time diagnosis of the water conductivity of hot dry rock enhanced geothermal systems helps optimize geothermal energy extraction. During geothermal energy extraction, if the water conductivity of the hot dry rock enhanced geothermal system is not clearly determined, especially if the water conductivity of different completion sections of the system cannot be accurately assessed, it will directly restrict the efficient extraction of geothermal energy. Therefore, it is necessary to conduct research and development on methods for diagnosing the water conductivity of hot dry rock enhanced geothermal systems in horizontal wells.

[0049] Hot dry rock enhanced geothermal systems are typically divided into several modified sections, each containing several modified clusters. Artificial fractures are created using hydraulic fracturing to connect the injection well and the production well. During the production process of a hot dry rock enhanced geothermal system, cryogenic fluid is injected through the injection well. This cryogenic fluid flows through the high-temperature hot dry rock reservoir for sufficient heat exchange before being extracted from the production well. Therefore, the water conductivity of the artificial fractures between the injection and production wells in a hot dry rock enhanced geothermal system is crucial and directly determines the efficiency of thermal energy extraction.

[0050] Therefore, accurately determining the communication status of artificial fractures between wells during the geothermal energy production process, and monitoring the injection and production volumes down to the cluster level to obtain water conductivity, are urgent problems to be solved in the evaluation of the water conductivity of enhanced geothermal systems.

[0051] To address the aforementioned issues, this invention provides a method and system for evaluating the water conductivity of a hot dry rock-enhanced geothermal system.

[0052] First, the method for evaluating the water conductivity of a dry hot rock-enhanced geothermal system provided in the embodiments of the present invention will be described, referring to... Figure 1 As shown, the method may specifically include:

[0053] S11. Utilize multiple fiber optic measuring points to acquire injection well fluid inflow data and production well fluid production flow data of multiple effective modified clusters in multiple water-conductivity evaluation sections of the production well at multiple times.

[0054] S12. Based on the influent flow rate data and the production flow rate data, obtain the cumulative influent volume of the injection well and the cumulative production volume of the production well for each of the plurality of water conductivity evaluation sections within a preset time.

[0055] S13. Based on the obtained cumulative liquid inflow of the injection well and cumulative liquid production of the production well, calculate the ratio of the cumulative liquid inflow of the injection well to the cumulative liquid production of the production well to obtain the water conduction efficiency within a preset time.

[0056] S14. Based on the water conductivity efficiency and in conjunction with the fracturing design parameters and geological data, evaluate the water conductivity of the injection well to be evaluated.

[0057] The method for evaluating the hydraulic conductivity of a hot dry rock-enhanced geothermal system provided in this invention is based on distributed optical fiber sensing monitoring technology. It acquires influent and production flow data of the effective modified cluster at multiple times through multiple optical fiber measuring points. Then, it calculates the cumulative influent and production volume of each hydraulic conductivity evaluation segment within a preset time period, thereby obtaining the hydraulic conductivity efficiency of each evaluation segment within the preset time period. This allows for the acquisition of hydraulic conductivity efficiency of the hot dry rock-enhanced geothermal system by monitoring injection and production data down to the segment / cluster level, thus enabling the evaluation of hydraulic conductivity. Therefore, the method for evaluating the hydraulic conductivity of a hot dry rock-enhanced geothermal system provided in this invention can efficiently obtain more accurate hydraulic conductivity efficiency, making the evaluation of the hydraulic conductivity of the hot dry rock-enhanced geothermal system more accurate and beneficial for the efficient exploitation of geothermal energy.

[0058] Furthermore, in one embodiment, in step S11 above, the injection well influent flow rate data and production well production flow rate data are obtained using multiple optical fiber measuring points. In this embodiment of the invention, high-frequency distributed acoustic sensing optical fiber monitoring technology can be used to perform real-time quantitative monitoring of the influent flow rate of each completed well of the injection well and the production flow rate of each completed well of the production well during the production process of the hot dry rock enhanced geothermal system, thereby evaluating the water conductivity of the hot dry rock enhanced geothermal system.

[0059] In this embodiment of the invention, it should be noted that the aforementioned effective modified clusters are artificially created fractures with good connectivity. Specifically, this refers to areas or groups within a modified section of a hot dry rock-enhanced geothermal system that, after effective modification, significantly impact water conductivity. Effective modification means that through artificial intervention, the original geological structure, rock properties, or other related factors are altered, thereby positively affecting water conductivity. This may include increased porosity and permeability, and the formation of channels more conducive to water flow.

[0060] Clusters indicate that these alterations are not isolated points, but rather relatively concentrated areas or groups with a certain spatial distribution. These clusters may be spatially connected or have similar geological features and alteration mechanisms, collectively affecting the overall hydraulic conductivity of the evaluation section.

[0061] Further, in one embodiment, in step S12 above, based on the injection well flow rate data, the cumulative injection volume of each of the plurality of hydraulic conductivity evaluation sections within a preset time period is obtained, referring to... Figure 2 As shown, the specific process includes the following:

[0062] S21. Based on the above injection well flow rate data, calculate the flow rate corresponding to the above water conductivity evaluation section at multiple times.

[0063] S22. Based on the inflow rate of the hydroconductivity evaluation section at multiple times, calculate the inflow rate of the hydroconductivity evaluation section in multiple time periods.

[0064] S23. By calculating the sum of the influent flow rates corresponding to multiple time periods, the cumulative influent volume of the injection well in the water conductivity evaluation section within the preset time period is obtained.

[0065] In one embodiment, step S21 above, calculating the influent flow rate of the hydroconductivity evaluation section at multiple times based on the influent flow rate data, may specifically include:

[0066] Based on the influent flow rate data of multiple effective modified clusters in each hydroconductivity evaluation section at each time point, the sum of the influent flow rates of the multiple effective modified clusters at the same time point is calculated to obtain the influent flow rates of the hydroconductivity evaluation section at multiple times.

[0067] In practice, the formula for calculating the influent flow rate at a certain moment in the water conductivity evaluation section of the hot dry rock enhanced geothermal system is as follows:

[0068]

[0069] in,

[0070] Let m be the injection flow rate at time t in the Nth water conductivity evaluation section of the injection well. 3 / min;

[0071] n represents the nth effective modification cluster in the Nth water conductivity evaluation section, and is dimensionless.

[0072] In one embodiment, calculating the influent flow rate of the hydroconductivity evaluation section in multiple time periods in step S22 above may specifically include:

[0073] Based on the inflow rate at multiple times corresponding to the water conductivity evaluation section, the product of the inflow rate at each time point and the duration of the corresponding time period is calculated to obtain the inflow rate for the time period.

[0074] In practical implementation, the formula for calculating the influent flow rate over the aforementioned time period is as follows:

[0075]

[0076] in,

[0077] Q NLet m be the influent flow rate of the Nth hydroconductivity evaluation segment in the mth time period. 3 ;

[0078] t m Let m be the time at time m, min.

[0079] In one embodiment, the formula for calculating the cumulative fluid injection volume of the injection well in the water conductivity evaluation section in step S23 above is as follows:

[0080]

[0081] in, The cumulative fluid injection volume (m) of the injection well during time period T, the Nth water conductivity evaluation segment of the injection well. 3 .

[0082] Further, in one embodiment, in step S12 above, based on the produced fluid flow rate data, the cumulative produced fluid volume of the production well in each of the multiple hydraulic conductivity evaluation sections within a preset time period is obtained, referring to... Figure 3 As shown, the process may include the following:

[0083] S31. Based on the production flow rate data of the production well, calculate the production flow rate corresponding to the water conductivity evaluation section at multiple times.

[0084] S32. Based on the liquid production flow rate corresponding to the liquid production flow rate of the liquid production flow rate at multiple times, calculate the liquid production flow rate of the liquid production flow rate of the liquid production flow rate at multiple time periods.

[0085] S33. By calculating the sum of the production flow rates corresponding to the multiple time periods, the cumulative production volume of the production well in the water conductivity evaluation section within the preset time period is obtained.

[0086] In one embodiment, step S31 above, calculating the production flow rate of the hydraulic conductivity evaluation section at multiple times based on the production well's fluid flow rate data, may specifically include:

[0087] Based on the liquid production flow data of multiple effective modified clusters in each hydroconductivity evaluation section at each time, the sum of the liquid production flow of the multiple effective modified clusters at the same time is calculated to obtain the liquid production flow of the hydroconductivity evaluation section at multiple times.

[0088] In practical implementation, the formula for calculating the liquid production flow rate of the hydroconductivity evaluation section of the hot dry rock enhanced geothermal system at a certain moment is as follows:

[0089]

[0090] in,

[0091] Let m be the production flow rate at time t in the Nth hydroconductivity evaluation section of the injection well. 3 / min;

[0092] n is the nth corresponding effective modification rate cluster of the Nth hydraulic conductivity evaluation section, which is dimensionless;

[0093] In one embodiment, the calculation of the liquid production flow rate corresponding to the hydroconductivity evaluation segment in step S32 above for multiple time periods may specifically include:

[0094] Based on the liquid production flow rate at multiple times corresponding to the water conductivity evaluation section, the product of the liquid production flow rate and the corresponding time period is calculated to obtain the liquid production flow rate for the time period.

[0095] In practical implementation, the formula for calculating the product flow rate during the aforementioned time period is as follows:

[0096]

[0097] in,

[0098] Q PN Let m be the influent flow rate of the Nth hydroconductivity evaluation segment in the mth time period. 3 ;

[0099] t m Let m be the time at time m, min.

[0100] In one embodiment, the formula for calculating the cumulative fluid production of the injection well in the hydraulic conductivity evaluation section in step S33 above is as follows:

[0101]

[0102] in, The cumulative fluid production of the injection well during time period T of the Nth water conductivity evaluation segment is expressed in m. 3 .

[0103] Further, in one embodiment, in step S13 above, the ratio of the cumulative fluid inflow of the injection well to the cumulative fluid production of the production well is calculated, and the formula for the water conductivity within a preset time period is:

[0104]

[0105] in,

[0106] Let be the water conductivity efficiency of the Nth water conductivity evaluation segment within the time period T, which is dimensionless.

[0107] In one embodiment, the above-described method for evaluating the water conductivity of a hot dry rock-enhanced geothermal system includes at least one effective modified cluster in each water conductivity evaluation segment.

[0108] Furthermore, in one embodiment, in step S14 above, the water conductivity of the dry hot rock enhanced geothermal system to be evaluated is assessed based on the water conductivity efficiency, combined with fracturing design parameters and geological data. Based on the evaluation results, the thermal energy production strategy of the dry hot rock enhanced geothermal system is adjusted to guide subsequent repeated fracturing and stimulation designs.

[0109] This invention also provides a system for evaluating the water conductivity of a hot dry rock-enhanced geothermal system, which may specifically include: a controller, a distributed fiber optic acoustic sensing device, a pipe sleeve, and an optical cable;

[0110] The controller is electrically connected to the distributed fiber optic acoustic sensing device.

[0111] The distributed fiber optic acoustic sensing device includes multiple fiber optic measurement points;

[0112] Both the injection well and the production well of the hot dry rock enhanced geothermal system are equipped with pipe sleeves, and the optical cable is installed in the pipe sleeves; the distributed optical fiber acoustic sensing device is connected to the optical cable.

[0113] The distributed fiber optic acoustic sensing device is used to acquire injection well fluid inflow data and production well fluid production flow data of multiple effective modification clusters in multiple water-conductivity evaluation sections of the production well at multiple times using multiple fiber optic measuring points.

[0114] The controller is used to receive the injection well fluid inflow data and production well fluid production data acquired by the distributed fiber optic acoustic sensing device, and based on the injection well fluid inflow data and production well fluid production data, to obtain the cumulative injection well fluid volume and cumulative production well fluid volume of each of the multiple water conductivity evaluation sections within a preset time; based on the obtained cumulative injection well fluid volume and cumulative production well fluid volume, to calculate the ratio of the cumulative injection well fluid volume to the cumulative production well fluid volume, to obtain the water conductivity efficiency within the preset time; based on the water conductivity efficiency, and in conjunction with fracturing design parameters and geological data, to evaluate the water conductivity of the dry hot rock enhanced geothermal system to be evaluated.

[0115] The hot dry rock enhanced geothermal system water conductivity evaluation system provided in this invention utilizes distributed optical fiber sensing monitoring technology to accurately monitor the acoustic / vibration signals of the entire well section of the injection and production wells of the hot dry rock enhanced geothermal system in real time. The system can effectively evaluate the water conductivity of the hot dry rock enhanced geothermal system by analyzing the optical fiber monitoring signals. This system is simple to operate and suitable for engineering applications. It has good application value for evaluating the water conductivity of hot dry rock enhanced geothermal systems based on distributed optical fiber acoustic sensing monitoring technology, providing technical support for real-time on-site guidance of geothermal energy production, and has strong promotion and practical value.

[0116] In one embodiment, the optical cable may be, for example, an armored optical cable; in a specific implementation, refer to... Figure 4 As shown, armored optical cables are lowered into geothermal deep wells along with casings for high-frequency distributed optical fiber acoustic sensing (DAS) monitoring. The armored optical cables include injection well optical cables and production well optical cables. The injection well optical cables are installed in the casings of the injection wells, and the production well optical cables are installed in the casings of the production wells.

[0117] In one embodiment, a distributed optical fiber sensing device is used to send laser signals from multiple optical fiber measuring points on the ground to an optical cable, and receive optical signals carrying sound / vibration information returned by the optical cable. The returned optical signals are analyzed and the acoustic energy information is displayed to locate the water conductivity evaluation section, and then the water conductivity efficiency of the dry hot rock enhanced geothermal system to be evaluated is calculated.

[0118] It should be noted that, in specific implementation, the water conductivity evaluation section should be divided into one or more fracturing sections based on the actual situation, including but not limited to fracturing design parameters, geological data, and fiber optic settings (the water conductivity evaluation section can also be adjusted during production based on monitoring results).

[0119] Currently, for downhole monitoring of fluid injection rates in multi-stage, multi-cluster hydraulic fracturing of horizontal wells in hot dry rock enhanced geothermal systems, Distributed Acoustic Sensing (DAS) technology, representing the latest generation of downhole monitoring technology, is being widely applied in industry. The most common fiber optic deployment method is permanent external casing installation, where the fiber is fixed to the completion cement sheath outside the geothermal well. This near-wellbore approach monitors the fluid injection and production rates of each completion cluster, typically using high-frequency (200Hz-2000Hz) fiber optic monitoring signals for interpretation and analysis.

[0120] In one embodiment, the aforementioned hot dry rock enhanced geothermal system water conductivity evaluation system further includes a downhole flow control device; the controller is electrically connected to the downhole flow control device; the downhole flow control device is installed at the fluid inlet of the injection well and is used to adjust the injection well flow rate according to instructions sent by the controller. During the production process of the hot dry rock enhanced geothermal system, the loss of injected fluid should be minimized to ensure the injection-to-production ratio as much as possible. This downhole flow control device can precisely adjust the injection well flow rate, effectively preventing the loss of injected fluid.

[0121] The following is a specific example illustrating the water conductivity evaluation method and system for dry hot rock enhanced geothermal systems provided in this invention.

[0122] Reference Figure 4 As shown, both the injection well and the production well of the hot dry rock enhanced geothermal system are equipped with casings. In this example, armored optical cables are used. The armored optical cables are lowered into the hot dry rock enhanced geothermal system of the geothermal deep well to be evaluated along with the casings for high-frequency DAS monitoring.

[0123] The distributed fiber optic acoustic sensing device sends laser signals from the ground to multiple measuring points on the armored optical cable, receives optical signals carrying sound / vibration information returned from multiple measuring points in the armored optical cable, analyzes the returned optical signals, and displays the acoustic energy information.

[0124] During geothermal energy production, distributed fiber optic acoustic sensing devices continuously receive and analyze acoustic / vibration information from the entire well section of the injection and production wells. First, qualitative observation is conducted using fiber optic DAS waterfall plots to identify multiple water conductivity evaluation sections. Specifically, well-connected and unconnected artificial fractures are identified within these water conductivity evaluation sections. Since unconnected fractures contribute zero to water conductivity, they often require repeated modification and connection. Well-connected artificial fractures are then considered as effective modification clusters and subjected to water conductivity evaluation analysis.

[0125] The aforementioned distributed fiber optic acoustic sensor device uses multiple fiber optic measuring points to acquire injection well fluid inflow data and production well fluid production flow data of multiple effective modified clusters in multiple water-conductivity evaluation sections of the production well at multiple times.

[0126] The controller receives the injection well fluid flow rate data and the production well fluid flow rate data mentioned above, and calculates the water conductivity efficiency of the dry hot rock enhanced geothermal system of the deep geothermal well within a preset time. Based on the water conductivity efficiency, and in combination with the fracturing design parameters and geological data, the controller evaluates the water conductivity of the dry hot rock enhanced geothermal system to be evaluated.

[0127] Based on the evaluation results of the water conductivity of the hot dry rock-enhanced geothermal system to be evaluated, the thermal energy production strategy of the hot dry rock-enhanced geothermal system in this case was adjusted, and the subsequent repeated fracturing stimulation design was guided.

[0128] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for evaluating the water conductivity of a hot dry rock-enhanced geothermal system, characterized in that, include: The injection well fluid inflow rate and production well fluid production rate data of multiple effective modified clusters in multiple water-conductivity evaluation sections of the production well were obtained at multiple times using multiple fiber optic measurement points. Based on the injection well fluid inflow rate data and the production well fluid production rate data, the cumulative injection well fluid inflow rate and the cumulative production well fluid production rate of each of the multiple water conductivity evaluation sections within a preset time period are obtained. Based on the obtained cumulative fluid inflow of the injection well and cumulative fluid production of the production well, the ratio of the cumulative fluid inflow of the injection well to the cumulative fluid production of the production well is calculated to obtain the water conduction efficiency within a preset time. Based on the stated water conductivity efficiency, and in conjunction with fracturing design parameters and geological data, the water conductivity of the dry hot rock-enhanced geothermal system to be evaluated is assessed.

2. The method as described in claim 1, characterized in that, Based on the injection well flow rate data, the cumulative injection volume of each of the plurality of hydraulic conductivity evaluation sections within a preset time period is obtained, including: Based on the influent flow rate data, calculate the influent flow rate corresponding to the hydroconductivity evaluation section at multiple times; Based on the inflow rate of the hydroconductivity evaluation section at multiple times, calculate the inflow rate of the hydroconductivity evaluation section in multiple time periods. By calculating the sum of the influent flow rates corresponding to the multiple time periods, the cumulative influent volume of the injection well in the water conductivity evaluation section within the preset time period is obtained.

3. The method as described in claim 2, characterized in that, Based on the influent flow rate data, calculate the influent flow rate corresponding to the hydrodynamic evaluation section at multiple time points, including: Based on the influent flow rate data of multiple effective modified clusters in each hydroconductivity evaluation section at each time point, the sum of the influent flow rates of the multiple effective modified clusters at the same time point is calculated to obtain the influent flow rates of the hydroconductivity evaluation section at multiple times.

4. The method as described in claim 2, characterized in that, Calculate the influent flow rate of the hydroconductivity evaluation section for each of the multiple time periods, including: Based on the inflow rate at each of the multiple times corresponding to the water conductivity evaluation section, the product of the inflow rate at each time point and the duration of the corresponding time period is calculated to obtain the inflow rate for the time period.

5. The method as described in claim 1, characterized in that, Based on the production well fluid production flow data, the cumulative fluid production of each of the multiple hydraulic conductivity evaluation sections within a preset time period is obtained, including: Based on the production flow rate data of the production well, calculate the production flow rate of the water conductivity evaluation section at multiple times; Based on the liquid production flow rate of the water conductivity evaluation section at multiple times, calculate the liquid production flow rate of the water conductivity evaluation section in multiple time periods. The cumulative fluid production of the production well in the water conductivity evaluation section within a preset time period is obtained by summing the fluid production flow rates corresponding to the multiple time periods.

6. The method as described in claim 5, characterized in that, Based on the production well fluid flow rate data, calculate the corresponding fluid flow rate at multiple times for the hydraulic conductivity evaluation section, including: Based on the production flow data of multiple effective modified clusters in each water conductivity evaluation section at each time point, the sum of the production flow of the multiple effective modified clusters at the same time point is calculated to obtain the production flow of the water conductivity evaluation section at multiple times.

7. The method as described in claim 5, characterized in that, Calculate the liquid production flow rate of the hydroconductivity evaluation section for each of the multiple time periods, including: Based on the liquid flow rate corresponding to the liquid production rate at multiple times in the water conductivity evaluation section, the product of the liquid production rate and the duration of the corresponding time period is calculated to obtain the liquid production rate for the time period.

8. The method for evaluating the water conductivity of a hot dry rock-enhanced geothermal system as described in any one of claims 1-7, characterized in that, Each water conductivity evaluation section includes at least one effective modification cluster.

9. A system for evaluating the water conductivity of a hot dry rock-enhanced geothermal system, characterized in that, include: Controller, distributed fiber optic acoustic sensing device, tubing and optical cable; The controller is electrically connected to the distributed fiber optic acoustic sensing device. The distributed fiber optic acoustic sensing device includes multiple fiber optic measurement points; Both the injection well and the production well of the hot dry rock enhanced geothermal system are equipped with pipe sleeves, and the optical cable is installed in the pipe sleeves; the distributed optical fiber acoustic sensing device is connected to the optical cable. The distributed fiber optic acoustic sensing device is used to acquire injection well fluid inflow data and production well fluid production flow data of multiple effective modification clusters in multiple water-conductivity evaluation sections of the production well at multiple times using multiple fiber optic measuring points. The controller is used to receive the injection well fluid inflow data and production well fluid production data obtained by the distributed fiber optic acoustic sensing device, and to obtain the cumulative injection well fluid inflow and cumulative production well fluid production of each of the multiple water conductivity evaluation sections within a preset time based on the injection well fluid inflow data and production well fluid production data. Based on the obtained cumulative fluid inflow of the injection well and cumulative fluid production of the production well, the ratio of the cumulative fluid inflow of the injection well to the cumulative fluid production of the production well is calculated to obtain the water conduction efficiency within a preset time. Based on the stated water conductivity efficiency, and in conjunction with fracturing design parameters and geological data, the water conductivity of the dry hot rock-enhanced geothermal system to be evaluated is assessed.

10. The water conductivity evaluation system for dry hot rock enhanced geothermal systems as described in claim 9, characterized in that, It also includes downhole flow control devices; The controller is electrically connected to the downhole flow control device; The downhole flow control device is installed at the fluid inlet of the injection well and is used to adjust the fluid inlet flow rate of the injection well according to the instructions sent by the controller.

Images