Rock sample preparation methods, rock sample heat transfer performance testing methods and apparatus

Abstract

The present specification relates to the technical field of geothermal development, and particularly relates to a rock sample preparation method, a rock sample heat exchange performance testing method and device. The method comprises the following steps: printing a first fissure model by using a 3D printing technology to obtain a first fissure template; placing the first fissure template in a cavity of a pouring mold; the pouring mold comprises a shell, the shell is provided with a hole, a surface of the first fissure template on a side facing a first pouring space is provided with a first texture, and the first pouring space comprises a space remaining in the cavity except a space occupied by the first fissure template; after a temperature sensor is inserted into the first pouring space through the hole, a pouring material is filled in the first pouring space to form a first rock sample pouring piece; and the temperature sensor is arranged in an inside and / or a fissure surface of the first rock sample pouring piece. The embodiment of the present specification can embed the temperature sensor without changing the structure of the rock sample, so that the temperature of the inside and the fissure surface of the rock sample can be measured.

Description

Technical Field

[0001] This specification relates to the field of geothermal development technology, and in particular to a method for preparing rock samples, a method and apparatus for testing the heat transfer performance of rock samples. Background Technology

[0002] Hot dry rock, as a vast and widely distributed deep geothermal resource, possesses the outstanding advantages of being clean, pollution-free, and sustainable. The development of hot dry rock resources can effectively supplement the gap in traditional energy sources, optimize the energy structure, and provide stable, low-carbon energy support for heating, power generation, and other fields. It is of significant strategic importance for promoting energy transformation and ecological environmental protection.

[0003] The main technology for developing hot dry rock resources is the enhanced geothermal system. The operating principle of the enhanced geothermal system is to create an artificial fracture network in the underground hot dry rock reservoir through methods such as hydraulic fracturing. The working fluid flows and exchanges heat within the fractures, carrying the heat energy back to the surface. The flow and heat transfer characteristics of the working fluid within the fractures affect the development efficiency of hot dry rock resources. Therefore, experimental research on fracture flow heat transfer in rock samples is necessary. Currently, most rock samples used in experiments are natural rock samples. Temperature sensors are placed on the surface of the natural rock samples to form temperature measurement points. Because the sensors are usually located on the outer surface of the rock sample, the temperature measurement points are concentrated on the outer surface, making it impossible to measure the temperature inside the rock sample and at the fracture surface. Therefore, the temperature of the fracture surface and interior of the rock samples currently used in experiments cannot be measured, resulting in insufficient experimental data and difficulty in comprehensively and accurately reflecting the fracture flow heat transfer performance of the rock samples. Summary of the Invention

[0004] This specification provides a method for preparing a rock sample, a method and apparatus for testing the heat transfer performance of a rock sample, and an embodiment of the present invention, which embeds a temperature sensor without changing the structure of the rock sample, thereby enabling the measurement of the temperature inside the rock sample and the fracture surface.

[0005] This specification provides a method for preparing rock samples, including: Based on the first rock sample, construct the first fracture model; The first crack model was printed using 3D printing technology to obtain the first crack template; The first fissure template is located inside the cavity of the casting mold; the casting mold includes a shell, the shell surrounds the cavity, the shell is provided with holes, the surface of the first fissure template facing the first casting space has a first texture, and the first casting space includes the space remaining in the cavity excluding the space occupied by the first fissure template. After the temperature sensor is inserted into the first casting space through the hole, the first casting space is filled with casting material to form a first rock sample casting; the first rock sample casting has a fracture surface that matches the first texture, and the temperature sensor is provided inside the first rock sample casting and / or on the fracture surface.

[0006] In some embodiments, constructing the first fracture model includes: The morphological data of the first rock sample were obtained by extracting features from the first rock sample using a morphology scanner. Based on the morphological data of the first rock sample, a first fracture model was constructed.

[0007] In some embodiments, the housing encloses a cylindrical cavity, and the housing is provided with multiple sets of holes. The sets of holes are opened on the sidewalls of the cylindrical cavity. Each set of holes includes multiple holes arranged along the axial direction of the cylindrical cavity. The holes in different sets of holes have a corresponding relationship. The holes with the corresponding relationship in the multiple sets of holes are distributed radially along the cylindrical cavity and are located at the same axial height.

[0008] In some embodiments, the sensor assembly extends into the first casting space through holes in the hole set; the sensor assembly includes a plurality of temperature sensors and a fixing member for fixing the spacing of the plurality of temperature sensors; within the first casting space, each temperature sensor in the sensor assembly is located at a different radial depth.

[0009] In some embodiments, the casting material is a composite casting material; the composite casting material includes a matrix phase and a mixed phase, the matrix phase includes cement, and the mixed phase includes gravel and metal powder; the thermal conductivity of the composite casting material is [missing information]. ;λ eff λ represents the thermal conductivity of the composite casting material. M λ represents the thermal conductivity of the matrix phase. I This indicates the thermal conductivity of the mixed phase. I This indicates the volume fraction of the mixed phase.

[0010] In some embodiments, it also includes: Based on the second rock sample, a second fracture model was constructed; The second fracture model was printed using 3D printing technology to obtain the second fracture template; The second fissure template is placed inside the cavity of the casting mold; the surface of the second fissure template facing the second casting space has a second texture, and the second casting space includes the remaining space inside the cavity excluding the space occupied by the second fissure template; The temperature sensor is inserted into the second pouring space through the hole; The second casting space is filled with casting material to form a second rock sample casting; the second rock sample casting has a fracture surface that matches the second texture, and the interior and / or fracture surface of the second rock sample casting is provided with a temperature sensor.

[0011] In some embodiments, the first rock sample and the second rock sample are obtained by splitting a natural rock sample, the first rock sample having a first fracture surface and the second rock sample having a second fracture surface, the first fracture surface and the second fracture surface matching each other in morphology; The first rock sample casting and the second rock sample casting are used to splice together to form an experimental rock sample; the fracture surface of the first rock sample casting and the fracture surface of the second rock sample casting match in morphology, and the fracture surface of the first rock sample casting and the fracture surface of the second rock sample casting are used to form a fracture inside the experimental rock sample.

[0012] This specification also provides an embodiment of a method for testing the heat transfer performance of rock samples, including: A flow heat transfer experiment was conducted on the experimental rock sample, and the temperature data collected by the temperature sensor inside the experimental rock sample was obtained. The heat transfer performance of the experimental rock samples was calculated based on temperature data.

[0013] In some embodiments, calculating the heat transfer performance of the experimental rock sample includes: Calculate the heat transfer coefficient of the experimental rock sample. h represents the convective heat transfer coefficient of the fluid flowing in the experimental rock sample, subscript 1 indicates the inlet parameter of the experimental rock sample, subscript 2 indicates the outlet parameter of the experimental rock sample, u1 and u2 represent the fluid velocity, ρ1 and ρ2 represent the fluid density, A1 and A2 represent the flow cross-sectional area within a single fracture, and c p T1 and T2 represent the specific heat capacity at constant pressure, and A represents the fluid temperature. s T represents the effective heat transfer area of ​​a single crack. s T represents the temperature of the fracture surface of the experimental rock sample. s T1 and T2 are calculated based on temperature data collected by temperature sensors.

[0014] This specification also provides a rock sample preparation apparatus, comprising: A building module is used to construct the first fracture model based on the first rock sample; The printing module is used to print the first fracture model using 3D printing technology to obtain the first fracture template. A casting module is used to position a first fissure template within the cavity of a casting mold. The casting mold includes a shell that encloses the cavity and has a hole. The surface of the first fissure template facing the first casting space has a first texture. The first casting space includes the space remaining in the cavity excluding the space occupied by the first fissure template. After a temperature sensor is inserted into the first casting space through the hole, casting material is filled into the first casting space to form a first rock sample casting. The first rock sample casting has a fissure surface that matches the first texture, and a temperature sensor is provided inside the first rock sample casting and / or on the fissure surface.

[0015] The technical solution of this embodiment can construct a first fracture model based on a first rock sample; the first fracture model can be printed using 3D printing technology to obtain a first fracture template. Thus, this embodiment, through 3D printing technology, can create a fracture template with a specific texture on the surface of a rock sample to replicate the corresponding fracture morphology on the surface of a cast rock sample. Furthermore, the technical solution of this embodiment can place the first fracture template within the cavity of a casting mold; the casting mold includes a shell that encloses the cavity, and the shell has a hole; the surface of the first fracture template facing the first casting space has a first texture; the first casting space includes the space remaining within the cavity excluding the space occupied by the first fracture template; after inserting a temperature sensor through the hole into the first casting space, casting material can be filled into the first casting space to form a first rock sample; the first rock sample has a fracture surface matching the first texture, and a temperature sensor is provided inside the first rock sample and / or on the fracture surface. Therefore, the embodiments of this specification, based on a special casting mold and a special casting method, insert a temperature sensor into the casting space through a hole in the shell before casting. This allows the temperature sensor to be directly embedded inside the cast rock sample and / or on the fracture surface, without altering the structure of the rock sample. This enables the measurement of temperatures at different depths within the rock sample and on the fracture surface. When conducting fracture flow heat transfer experiments using the rock samples from these embodiments, temperature data from multiple locations inside the rock sample and on the fracture surface can be obtained, thus comprehensively and accurately reflecting the fracture flow heat transfer performance of the rock sample. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. The drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic flowchart of the rock sample preparation method in the embodiments of this specification; Figure 2 This is a schematic diagram of the first and second fracture models in the embodiments of this specification; Figure 3 This is a schematic diagram of the casting mold used in the embodiments of this specification; Figure 4 This is a schematic diagram of the bottom structure of the casting mold in the embodiments of this specification; Figure 5 This is a schematic diagram of the first rock sample casting in the embodiments of this specification; Figure 6 This is a flowchart illustrating the rock sample heat transfer performance testing method in the embodiments of this specification; Figure 7 This is a schematic diagram of the temperature sensor arrangement in the embodiments of this specification; Figure 8 This is a functional structural diagram of the rock sample preparation device in the embodiments of this specification; Figure 9 This is a schematic diagram of the rock sample fracture heat transfer performance testing system in the embodiments of this specification; Figure 10 This is a cross-sectional view of the rock sample holder in the embodiments of this specification; Figure 11 This is a three-dimensional structural diagram of the rock sample holder in the embodiments of this specification; Figure 12 This is a cross-sectional view of the sealing assembly in the embodiments of this specification; Figure 13 This is a three-dimensional structural diagram of the sealing assembly in the embodiments of this specification; Figure 14 This is a cross-sectional view of the tee component in the embodiments of this specification; Figure 15 This is a cross-sectional view of the sealing sleeve in the embodiments of this specification. Detailed Implementation

[0018] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. The specific embodiments described herein are only used to explain this disclosure, and not to limit this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure are within the scope of protection of this disclosure. In addition, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0019] The key technology for developing hot dry rock resources is the enhanced geothermal system. The operating principle of this system involves creating an artificial fracture network within the underground hot dry rock reservoir through hydraulic fracturing and chemical stimulation, forming sufficiently permeable heat exchange channels. A low-temperature working fluid is pressurized and pumped into the fractured reservoir via injection wells, where it exchanges heat thoroughly with the high-temperature rock mass during its flow. The heated high-temperature fluid is then extracted to the surface through production wells and enters the power plant's thermal cycle system for steam turbine power generation or direct heating. After heat exchange, the low-temperature working fluid is treated and reinjected underground, forming a sustainable circulating heat extraction model. This process does not rely on natural geothermal fluids, overcoming the geological limitations of traditional geothermal resource development and significantly expanding the scope of geothermal energy development. It is the main technological path for the large-scale utilization of hot dry rock resources. Therefore, efficient heat exchange of the working fluid within the fractures is the core objective of the enhanced geothermal system, and the flow and heat transfer characteristics of the working fluid within the fractures directly affect the success or failure of hot dry rock geothermal development.

[0020] Currently, rock sample fracture flow heat transfer experiments have the following problems: 1. The methods for obtaining rock sample fractures are relatively random, mostly based on natural rock samples artificially split to form fracture surfaces, making it impossible to obtain specific fracture shapes; 2. The composition of the experimental rock samples is random, while the flow heat transfer of the working fluid is affected by the combined effects of rock thermal conductivity and fracture convection heat transfer, making it impossible to investigate the effect of thermal conductivity on heat transfer performance by changing the rock sample composition alone; 3. The temperature measurement points in heat transfer experiments are limited, usually concentrated on the outer surface of the rock sample, with less measurement of the temperature inside the rock sample and the fracture surface, ignoring the influence of the thermal resistance of the rock sample; 4. Due to the limited number of temperature measurement points, most experiments can only calculate the local convection heat transfer coefficient to characterize the overall heat transfer coefficient, making it difficult to comprehensively reflect the changes in the heat transfer coefficient at different locations of the rock sample.

[0021] Please see Figure 1 This specification provides a method for preparing a rock sample, comprising the following steps.

[0022] Step 11: Construct the first fracture model based on the first rock sample.

[0023] Step 12: Print the first crack model using 3D printing technology to obtain the first crack template.

[0024] Step 13: Position the first crack template within the cavity of the casting mold; the casting mold includes a shell, which encloses the cavity, and the shell has holes; the surface of the first crack template facing the first casting space has a first texture, and the first casting space includes the remaining space within the cavity excluding the space occupied by the first crack template.

[0025] Step 14: After inserting the temperature sensor into the first casting space through the hole, the first casting space is filled with casting material to form a first rock sample casting; the first rock sample casting has a fracture surface that matches the first texture, and the interior and / or fracture surface of the first rock sample casting is provided with a temperature sensor.

[0026] The technical solution of this embodiment can construct a first fracture model based on a first rock sample; the first fracture model can be printed using 3D printing technology to obtain a first fracture template. Thus, this embodiment, through 3D printing technology, can create a fracture template with a specific texture on the surface of a rock sample to replicate the corresponding fracture morphology on the surface of a cast rock sample. Furthermore, the technical solution of this embodiment can place the first fracture template within the cavity of a casting mold; the casting mold includes a shell that encloses the cavity, and the shell has a hole; the surface of the first fracture template facing the first casting space has a first texture; the first casting space includes the space remaining within the cavity excluding the space occupied by the first fracture template; after inserting a temperature sensor through the hole into the first casting space, casting material can be filled into the first casting space to form a first rock sample; the first rock sample has a fracture surface matching the first texture, and a temperature sensor is provided inside the first rock sample and / or on the fracture surface. Therefore, the embodiments of this specification, based on a special casting mold and a special casting method, insert a temperature sensor into the casting space through a hole in the shell before casting. This allows the temperature sensor to be directly embedded inside the cast rock sample and / or on the fracture surface, without altering the structure of the rock sample. This enables the measurement of temperatures at different depths within the rock sample and on the fracture surface. When conducting fracture flow heat transfer experiments using the rock samples from these embodiments, temperature data from multiple locations inside the rock sample and on the fracture surface can be obtained, thus comprehensively and accurately reflecting the fracture flow heat transfer performance of the rock sample.

[0027] In some embodiments, a second fracture model can be constructed based on a second rock sample; the second fracture model can be printed using 3D printing technology to obtain a second fracture template; the second fracture template can be placed inside the cavity of a casting mold; the surface of the second fracture template facing the second casting space has a second texture, and the second casting space includes the space remaining in the cavity excluding the space occupied by the second fracture template; a temperature sensor can be inserted into the second casting space through the hole; casting material can be filled into the second casting space to form a second rock sample casting. The second rock sample casting has a fracture surface that matches the second texture. A temperature sensor is provided inside the second rock sample casting and / or on the fracture surface.

[0028] In some embodiments, the first and second rock samples can be obtained by splitting a natural rock sample. The first rock sample has a first fracture surface, and the second rock sample has a second fracture surface. The first and second fracture surfaces match in morphology. For example, the first and second fracture surfaces have matching shapes, consistent contours, and complementary concavities and convexities. Because the first and second fracture surfaces match, the natural rock sample can be restored by splicing the first and second rock samples. For example, the natural rock sample is a cylindrical natural rock sample. Splitting the cylindrical natural rock sample along a predetermined plane yields a first semi-cylindrical rock sample and a second semi-cylindrical rock sample. The first semi-cylindrical rock sample has a first fracture surface, and the second semi-cylindrical rock sample has a second fracture surface.

[0029] In some embodiments, a topography scanner can be used to extract features from a first rock sample to obtain its topography data; a first fracture model can then be constructed based on this data. The topography scanner is a non-contact type. The scanner has an XY-axis automatic scanning range of 150mm × 150mm, a Z-axis automatic focusing stroke of 50mm, a maximum resolution of 0.1μm, and a scanning rate of 20mm / s. The scanner can use a line scan mode to scan the outer surface of the first rock sample to ensure high-precision data acquisition. After scanning, the scanner can extract the three-dimensional coordinate information of the outer surface of the first rock sample, which is then reconstructed using software to obtain the first fracture model. The first fracture model is a three-dimensional digital model. It represents the topography of the outer surface of the first rock sample. The first fracture model has fracture surfaces, and these surfaces have a first texture. The outer surface of the first rock sample includes a first fracture surface. The first texture can be determined based on the first fracture surface. Therefore, the morphology of the first rock sample, including the fractures, can be accurately converted into a digital model, providing an accurate morphological basis for subsequent 3D printing of the first fracture template. Optionally, the first fracture model can be constructed directly based on the morphological data of the outer surface of the first rock sample extracted by the morphology scanner. In this way, the first texture can be the same as the texture of the first fracture surface. Optionally, the morphological data of the outer surface of the first rock sample extracted by the morphology scanner can also be adjusted; the first fracture model can be constructed based on the adjusted morphological data. By adjusting, the morphological parameters such as the roughness, width, and orientation of the first fracture surface can be changed to obtain a first fracture model with a specific fracture morphology, replacing the random fracture acquisition method of artificial splitting of natural rock samples. This achieves on-demand design and precise control of fracture morphology, and then uses 3D printing technology to prepare a first fracture template with specific roughness, width, and orientation, improving the repeatability and comparability of the experiment. In this way, the first texture can be different from the texture of the first fracture surface. The first rock sample can be a semi-cylindrical rock sample, and the first fracture model can be a semi-cylindrical fracture model.

[0030] The process of constructing the second fracture model is similar to that of constructing the first fracture model, and will not be described in detail here.

[0031] Figure 2 The first and second fracture models are shown.

[0032] In some embodiments, multiple profile lines can be constructed on the first fracture surface based on the morphology data of the first fracture surface; the roughness of the first fracture surface can be calculated based on the contour height data of the multiple profile lines. N a M represents surface roughness, and L represents the number of profile lines. i R represents the length of the i-th profile line. i This represents the maximum fluctuation amplitude of the i-th profile line. Roughness is a major factor affecting convective heat transfer. By selecting rock samples with different roughnesses to construct fracture models, fracture templates with different roughnesses can be obtained through 3D printing, ensuring the subsequent investigation of the impact of different roughnesses on heat transfer performance.

[0033] In some embodiments, a first fracture model is imported into a 3D printer. Printing parameters are configured according to the characteristics of PLA (Polylactic Acid) filament. To compensate for the thermal shrinkage of PLA, proportional compensation is applied to each direction of the model to ensure the final dimensions match the design. For areas corresponding to the fracture surface texture in the model, a fine layer thickness and low printing speed are used to preserve microscopic roughness details. For the main body area, the layer thickness and printing speed are appropriately increased to improve overall forming efficiency. A small number of easily peelable support structures are added to the overhanging edges of the model to prevent damage to the surface texture. The nozzle and heated bed temperatures are set to the range suitable for PLA, and the cooling system is activated as needed to prevent edge warping and interlayer deformation. After parameter configuration, the nozzle and heated bed are reset to their origin and preheated to the required printing temperature. PLA filament is loaded, and printing is started. After printing, the support structures are removed to obtain the first fracture template. The first fracture template can be a semi-cylindrical fracture template. The first crack template is obtained by printing based on the first crack model. The crack surface of the first crack template replicates the crack surface of the first crack model, and the crack surface of the first crack template has a first texture. Printing the second crack model is similar to printing the first crack model. The second crack template can be a semi-cylindrical crack template. The second crack template is obtained by printing based on the second crack model. The crack surface of the second crack template replicates the crack surface of the second crack model, and the crack surface of the second crack template has a second texture.

[0034] In some embodiments, multiple temperature sensors can be obtained. These temperature sensors may include thermocouples. The thermocouples have conductors measuring 2 × Φ0.127 mm, a temperature range of -270°C to 400°C, and insulation layers with a temperature resistance greater than 260°C. The small-diameter flexible conductors of the thermocouples facilitate radial arrangement within the rock sample and also help reduce the size of the welding joints, minimizing interference with the local thermal conductivity of the rock sample. After obtaining multiple thermocouples, they can be pre-treated and welded. Specifically, the insulation layers at both ends of the thermocouples can be removed, exposing the conductor ends and maintaining good contact. Then, a thermocouple spot welder is used, controlling the welding power and pulse time within a low range, using a small current and short pulse to precisely connect and weld the two conductors at one end of the thermocouple. During welding, the weld joint size must be strictly controlled to ensure the weld joint volume is as small as possible to avoid distortion in the measurement of the local temperature field. After welding, a multimeter is used to check the continuity of each thermocouple to ensure the circuit is unobstructed; any unqualified weld joints are reprocessed. To achieve temperature measurement at different radial locations inside a rock sample, multiple welded thermocouples can be assembled into one or more sensor assemblies. Each sensor assembly includes multiple temperature sensors and fixing members for securing the multiple temperature sensors at intervals. The fixing members can be made of high-temperature heat shrink tubing. The thermocouples are sequentially bound according to a preset extension length, forming an assembly with the sensing ends arranged in sequence. During subsequent casting, after the sensor assembly is inserted into the cavity of the casting mold through holes in the mold shell, the sensing ends of each thermocouple are naturally distributed at different radial depths inside the rock sample.

[0035] Optionally, the temperature sensor can be calibrated. The soldered sensing end of the temperature sensor can be placed in a constant-temperature water tank, and the unsoldered end connected to a data acquisition unit. By controlling the constant-temperature water tank to heat to different preset temperatures, the thermoelectric potential output by the temperature sensor at different temperatures is measured. The standard temperature value corresponding to each temperature point is recorded one-to-one with the average thermoelectric potential obtained, forming a complete temperature and thermoelectric potential calibration dataset. Based on the calibration dataset and a preset calculation formula, a correction formula adapted to the experimental conditions is fitted. The correction formula is used to express the relationship between temperature and thermoelectric potential. The correction formula may include... . . Where T represents the measured temperature, E represents the potential difference of the temperature sensor, n represents the number of measurements, and i represents the measurement point number. The calibrated temperature sensor can then be used for subsequent rock sample casting and heat transfer experiments.

[0036] In some embodiments, the casting material can be a composite casting material; the composite casting material includes a matrix phase and a mixed phase, the matrix phase including cement, and the mixed phase including gravel and metal powder. The cement can be silicate PO.52.5 to ensure sufficient compressive strength and high-temperature resistance of the experimental rock sample. The gravel can be ISO standard sand to ensure uniform particle size. After cement hydration and hardening, the gravel forms a dense skeleton structure, significantly improving the compressive strength and high-temperature resistance of the rock sample, while limiting shrinkage deformation during cement setting, reducing the risk of rock sample cracking, and ensuring the stability of crack morphology. The metal powder is used to improve the thermal conductivity of the rock sample. By adjusting the volume fraction of metal powder in the mixed phase (ranging from 0% to 20%), quantitative control of the thermal conductivity of the rock sample can be achieved. Optionally, functional additives are also added to the composite casting material. Functional additives include polyether defoamers, polycarboxylate superplasticizers, and penetrating crystallizing waterproofing agents. Polyether defoamers are used to control the generation of bubbles inside and on the surface of the rock sample. Polycarboxylate superplasticizers are used to disperse cement particles, reduce water encapsulation, increase the fluidity of mixtures, and improve the density of cast samples. Penetrating crystallizing waterproofing agents are used to improve the impermeability of rock samples, ensuring that water flows only along fracture surfaces during experiments and does not leak from the rock sample matrix. For example, composite casting materials can be prepared as follows: Use 40% silicate cement, 40% standard sand, and 0% to 20% metal powder as base raw materials by volume ratio, then add 0.1% polyether defoamer, 0.5% polycarboxylate superplasticizer, and 1.0% penetrating crystallizing waterproofing agent by mass. First, dry mix all the above raw materials (i.e., cement, standard sand, metal powder, and three functional additives) to ensure thorough and uniform mixing. Then, add water at a water-cement ratio of 1:3 for wet mixing, stirring until uniform to obtain the casting slurry. This allows for the construction of complex rock sample systems with controllable composition, overcoming the technical bottleneck of random natural rock sample composition and the inability to independently investigate the impact of thermal conductivity on heat transfer. Meanwhile, the synergistic effect of functional additives can optimize the density and impermeability of the casting material, providing rock sample modules with preset thermal conductivity and fracture morphology for subsequent flow heat transfer experiments.

[0037] The thermal conductivity of the composite casting material is ;λ eff λ represents the thermal conductivity of the composite casting material. M λ represents the thermal conductivity of the matrix phase. I This indicates the thermal conductivity of the mixed phase. I This indicates the volume fraction of the mixed phase.

[0038] In some embodiments, the casting mold includes a shell. The shell encloses a cavity. The cavity may be a cylindrical cavity. The shell has holes. Specifically, the shell has multiple sets of holes, which are formed on the sidewalls of the cylindrical cavity. Each set of holes includes multiple holes arranged along the axial direction of the cylindrical cavity. The arrangement may be evenly spaced along the axial direction of the cylindrical cavity. The holes in different sets of holes have a corresponding relationship, and the corresponding holes in the multiple sets of holes are radially distributed along the cylindrical cavity and located at the same axial height. The distribution may be evenly spaced radially along the cylindrical cavity. Here, axial direction refers to the direction of the central axis of the cylindrical cavity, radial direction refers to the direction perpendicular to the central axis, and sidewall refers to the circumferential cylindrical surface of the cylindrical cavity. The holes are used to allow temperature sensors or sensor assemblies to extend into the casting space. Within the casting space, the temperature sensors in the sensor assembly are located at different radial depths.

[0039] Please see Figure 3 The housing is provided with a first set of holes and a second set of holes. The first set of holes includes holes 31, 32, and 33. Holes 31, 32, and 33 are arranged axially along the cylindrical cavity. The second set of holes includes holes 21, 22, and 23. Holes 21 and 31 correspond to each other. Holes 21 and 31 are radially distributed along the cylindrical cavity and are located at the same axial height. Holes 22 and 32 correspond to each other. Holes 22 and 32 are radially distributed along the cylindrical cavity and are located at the same axial height. Holes 23 and 33 correspond to each other. Holes 23 and 33 are radially distributed along the cylindrical cavity and are located at the same axial height. The housing includes a first housing and a second housing. The first housing and the second housing are fixedly connected by side fixing nuts 1, together enclosing the cavity. The casting mold also includes a bottom baffle 5, which is tightly connected to the housing by bottom wall fixing nuts.

[0040] The first crack template 4 can be placed inside the cavity. The first crack template 4 is tightly connected to the bottom baffle 5 by a mold fixing nut and is located between the first shell and the second shell. After the first crack template 4 is placed inside the cavity, the surface of the first crack template 4 facing the first casting space has a first texture. The first casting space refers to the remaining space inside the cavity excluding the space occupied by the first crack template 4.

[0041] Please see Figure 4 The bottom baffle 5 is tightly connected to the housing via a bottom wall fixing nut 6. The first slit template 4 is tightly connected to the bottom baffle 5 via a mold fixing nut 7.

[0042] Before casting, a release agent is sprayed onto the inner surface of the casting mold and the surface of the first fissure template. Casting is performed after the release agent dries to prevent adhesion during demolding. Then, the first fissure template is connected to the bottom baffle with nuts, and the position of the first fissure template is adjusted so that it is positioned between the first and second shells. Next, the bottom baffle is connected to the shell with nuts, and finally, the first and second shells are connected to each other with nuts. After mold assembly, temperature sensors or sensor assemblies are inserted into the first casting space through holes in the shell, and the positions of each temperature sensor are adjusted to ensure measurement accuracy. Subsequently, the prepared composite casting material is poured into the first casting space, and the mold is thoroughly shaken to remove air bubbles. The entire mold is then placed in a cement curing chamber for one day of curing. After curing, demolding is performed, and the first rock sample casting is continued to be cured for 15 to 30 days until its compressive strength reaches 20 MPa or higher. The first rock sample casting has a fissure surface matching the first texture, and temperature sensors are installed inside the first rock sample casting and / or on the fissure surface. This allows for the embedding of temperature sensors without altering the rock sample structure, facilitating the measurement of temperatures inside the rock sample and at fracture surfaces.

[0043] Figure 5 The first rock sample casting is shown.

[0044] The process of filling the second casting space with casting material to form the second rock sample casting is similar to the process of filling the first casting space with casting material to form the first rock sample casting, and will not be described in detail here.

[0045] In some embodiments, the first and second rock sample castings are used to assemble an experimental rock sample. The fracture surface of the first rock sample casting matches a first texture on the surface of a first fracture template, the first texture being determined based on a first fracture surface. The fracture surface of the second rock sample casting matches a second texture on the surface of a second fracture template, the second texture being determined based on a second fracture surface. The fracture surfaces of the first and second rock sample castings are morphologically matched, and these surfaces are used to form fractures within the experimental rock sample.

[0046] For example, the first rock sample casting and the second rock sample casting are both semi-cylindrical. By splicing the first rock sample casting and the second rock sample casting, a cylindrical experimental rock sample can be obtained.

[0047] In some embodiments, multiple experimental rock samples can be obtained through the above-described embodiments. Each experimental rock sample includes a first rock sample casting and a second rock sample casting. Within the same experimental rock sample, the first rock sample casting and the second rock sample casting are cast using the same casting material. Different experimental rock samples can be cast using the same or different casting materials. The fracture surfaces of different experimental rock samples can have the same or different roughness.

[0048] For example, multiple natural rock samples can be obtained. For each natural rock sample, it can be split to obtain a first rock sample and a second rock sample. A first fracture model can be constructed based on the first rock sample. This first fracture model can be printed using 3D printing technology to obtain a first fracture template. The first fracture template can be placed inside the cavity of the casting mold. The surface of the first fracture template facing the first casting space has a first texture. The first casting space includes the space remaining inside the cavity excluding the space occupied by the first fracture template. A temperature sensor can be inserted into the first casting space through the hole. Casting material can be filled into the first casting space to form the first rock sample casting. The second rock sample can be used to construct a second fracture model. The second fracture model can be printed using 3D printing technology to obtain a second fracture template. The second fracture template can be placed in the cavity of the casting mold. The surface of the second fracture template facing the second casting space has a second texture. The second casting space includes the space remaining in the cavity excluding the space occupied by the second fracture template. A temperature sensor can be inserted into the second casting space through the hole. Casting material can be filled into the second casting space to form a second rock sample casting. The first rock sample casting and the second rock sample casting can be spliced ​​together to form an experimental rock sample.

[0049] This allows multiple experimental rock samples to be obtained from multiple natural rock samples.

[0050] For example, a natural rock sample can be obtained and split to obtain a first rock sample and a second rock sample. Multiple first fracture models can be constructed based on the first rock sample, and these models can be printed using 3D printing technology to obtain multiple first fracture templates. Similarly, multiple second fracture models can be constructed based on the second rock sample, and these models can be printed using 3D printing technology to obtain multiple second fracture templates. Each first fracture model can correspond to one second fracture model. This correspondence can be understood as: the first texture of the fracture surface of the first fracture model matches the second texture of the fracture surface of the second fracture model. Each first fracture template can correspond to one second fracture template. This correspondence can be understood as: the first texture of the fracture surface of the first fracture template matches the second texture of the fracture surface of the second fracture template.

[0051] For each first fissure template, it can be placed inside the cavity of the casting mold. The surface of the first fissure template facing the first casting space has a first texture. The first casting space includes the space remaining in the cavity excluding the space occupied by the first fissure template. A temperature sensor can be inserted into the first casting space through the hole. Casting material can be filled into the first casting space to form a first rock sample casting. Multiple first rock sample castings can be obtained in this way.

[0052] For each second fissure template, it can be placed inside the cavity of the casting mold. The surface of the second fissure template facing the second casting space has a second texture. The second casting space includes the space remaining in the cavity excluding the space occupied by the second fissure template. A temperature sensor can be inserted into the second casting space through the hole. Casting material can be filled into the second casting space to form a second rock sample casting. Multiple second rock sample castings can thus be obtained.

[0053] Each first rock sample casting can correspond to one second rock sample casting. Each first rock sample casting can be joined with a second rock sample casting to form an experimental rock sample. Thus, multiple experimental rock samples can be obtained from a single natural rock sample.

[0054] Please see Figure 6 This specification provides an embodiment of a method for testing the heat transfer performance of a rock sample, including the following steps.

[0055] Step 61: Conduct a flow heat transfer experiment on the experimental rock sample to obtain the temperature data collected by the temperature sensor inside the experimental rock sample.

[0056] Step 62: Calculate the heat transfer performance of the experimental rock sample based on the temperature data.

[0057] The experimental rock sample is obtained by splicing a first rock sample casting and a second rock sample casting. A temperature sensor is embedded inside the experimental rock sample to measure the temperature inside the sample and at the fracture surface. This allows for the acquisition of temperature data at multiple locations inside the experimental rock sample and at the fracture surface, thus comprehensively and accurately reflecting the heat transfer performance of the fracture flow.

[0058] In some embodiments, the first and second rock sample castings can be joined together and proppant added to form a complete cylindrical experimental rock sample with a certain opening and a rough fracture surface. The experimental rock sample is then completely fitted into a heat-shrink tubing. After installing three temperature sensors at equal intervals on the outer surface of the rock sample, the heat-shrink tubing is fixed to the outer surface of the rock sample, ensuring that it covers the entire outer surface and the edges of both ends. A hot air gun is used to heat the heat-shrink tubing at a uniform speed along the axial direction of the rock sample, causing the tubing to tightly adhere to the surface of the rock sample, achieving a comprehensive seal. This process prevents seepage fluid from leaking from the joined edges of the rock sample during the experiment, ensuring that the fluid flows only along the pre-set fracture channels. Additionally, it fixes the rock sample structure, enhancing its overall stability and preventing cracking or misalignment during experimental clamping. It also protects the outer surface of the rock sample, preventing mechanical damage from the experimental apparatus. After the heat-shrink tubing is applied, the sealing edges at both ends of the rock sample must be inspected to ensure there are no wrinkles or looseness defects. Then, high-temperature resistant sealant is applied to strengthen the sealing effect. The experimental rock sample was placed in the sample holder for flow heat transfer experiments, and the data from each temperature sensor was recorded. The temperature sensors were arranged as follows. Figure 7 As shown. The experimental rock sample is equipped with fracture surface temperature sensors, internal temperature sensors, and external surface temperature sensors. The fracture surface temperature sensors, including sensors Ts1, Ts2, Ts3, Ts4, Ts5, Ts6, Ts7, Ts8, and Ts9, are located on the fracture surface of the experimental rock sample. The internal temperature sensors, including sensors Ts10, Ts11, and Ts12, are located inside the experimental rock sample (e.g., inside the first and second rock sample castings). The external surface temperature sensors, including sensors Tf1, Tf2, and Tf3, are located on the outer surface of the experimental rock sample. The fracture surface temperature sensors and internal temperature sensors are installed within the experimental rock sample through casting.

[0059] In some embodiments, temperature parameters of the experimental rock sample can be calculated based on temperature data. Temperature parameters include at least one of the following: the distribution of outer surface temperature along the axis, the distribution of fracture surface temperature along the axis, the distribution of fracture surface temperature along the radial direction, and the distribution of internal temperature along the radial direction.

[0060] It can calculate the temperature distribution along the axis of the outer surface of the experimental rock sample. . The following formula can be used to calculate the temperature data collected by temperature sensors Tf1, Tf2, and Tf3.

[0061] . , , These represent the temperature data collected by temperature sensors Tf1, Tf2, and Tf3, respectively. l Indicates the arrangement interval. xThis indicates the length from the inlet end face.

[0062] In some embodiments, the temperature distribution along the axis of the fracture surface of the experimental rock sample can be calculated. . The following formula can be used to calculate the temperature data collected by temperature sensors Ts4, Ts5, and Ts6.

[0063] . , , These represent the temperature data collected by temperature sensors Ts4, Ts5, and Ts6, respectively. l Indicates the arrangement interval. x This indicates the length from the inlet end face.

[0064] In some embodiments, the radial distribution of temperature along the fracture surface of the experimental rock sample can be calculated. . The following formula can be used to calculate the temperature data collected by temperature sensors Ts1, Ts4, and Ts7.

[0065] . , , These represent the temperature data collected by temperature sensors Ts1, Ts4, and Ts7, respectively. l Indicates the arrangement interval. x This indicates the length from the inlet end face.

[0066] In some embodiments, the temperature distribution along the radial line inside the experimental rock sample can be calculated. . The following formula can be used to calculate the temperature data collected by temperature sensors Ts4, Ts10, and Tf1.

[0067] . , , These represent the temperature data collected by temperature sensors Ts4, Ts10, and Tf1, respectively. l Indicates the arrangement interval. x This indicates the length from the inlet end face.

[0068] During the flow heat transfer experiment on the experimental rock sample, the fluid flows along the axial direction of the rock sample from one section to another. The inlet end face is the end face of the experimental rock sample from which the fluid flows in.

[0069] In some embodiments, the heat transfer coefficient of the experimental rock sample can be calculated based on temperature parameters. For example, the heat transfer coefficient of the experimental rock sample can be calculated. .

[0070] h represents the convective heat transfer coefficient of the fluid flowing within the experimental rock sample; subscript 1 indicates the inlet parameter of the experimental rock sample; subscript 2 indicates the outlet parameter of the experimental rock sample; u1 and u2 represent the fluid velocity; ρ1 and ρ2 represent the fluid density; A1 and A2 represent the flow cross-sectional area within a single fracture; c p T1 and T2 represent the specific heat capacity at constant pressure, and A represents the fluid temperature. s T represents the effective heat transfer area of ​​a single crack. s T represents the temperature of the fracture surface of the experimental rock sample. s T1 and T2 are calculated based on temperature data collected by temperature sensors. s According to or The calculation is as follows. For example, substituting the length x from the inlet end face into the calculation... or Then the temperature of the fracture surface at point x can be calculated.

[0071] In some embodiments, multiple experimental rock samples can be obtained using the rock sample preparation method described in this specification. The heat transfer performance of each experimental rock sample can be tested separately using the rock sample heat transfer performance testing method described in this specification.

[0072] Different experimental rock samples can be cast using different casting materials. Therefore, the correlation between heat transfer performance and thermal conductivity can be determined based on the heat transfer performance and thermal conductivity of each of the multiple experimental rock samples. For example, a function representing the relationship between heat transfer performance and thermal conductivity can be constructed using fitting or other methods based on the heat transfer performance and thermal conductivity of each of the multiple experimental rock samples. Furthermore, the fracture surfaces of different experimental rock samples can have different roughnesses. Therefore, the correlation between roughness and thermal conductivity can also be determined based on the roughness and thermal conductivity of each of the multiple experimental rock samples. For example, a function representing the relationship between roughness and thermal conductivity can be constructed using fitting or other methods based on the roughness and thermal conductivity of each of the multiple experimental rock samples.

[0073] Please see Figure 8 This specification provides an embodiment of a rock sample preparation apparatus, comprising the following units.

[0074] Module 81 is used to construct the first fracture model based on the first rock sample; Printing module 82 is used to print the first crack model using 3D printing technology to obtain the first crack template; A casting module 83 is used to position the first fissure template within the cavity of a casting mold. The casting mold includes a shell that encloses the cavity and has a hole. The surface of the first fissure template facing the first casting space has a first texture. The first casting space includes the space remaining in the cavity excluding the space occupied by the first fissure template. After a temperature sensor is inserted into the first casting space through the hole, casting material is filled into the first casting space to form a first rock sample casting. The first rock sample casting has a fissure surface that matches the first texture, and a temperature sensor is provided inside the first rock sample casting and / or on the fissure surface.

[0075] In some embodiments, the construction module 81 is further configured to construct a second fracture model based on the second rock sample; The printing module 82 is also used to print the second fracture model using 3D printing technology to obtain the second fracture template; The casting module 83 is also used to position the second fissure template within the cavity of the casting mold; the surface of the second fissure template facing the second casting space has a second texture, the second casting space including the space remaining in the cavity excluding the space occupied by the second fissure template; after inserting a temperature sensor through the hole into the second casting space, casting material is filled into the second casting space to form a second rock sample casting; the second rock sample casting has a fissure surface matching the second texture, and a temperature sensor is provided inside the second rock sample casting and / or on the fissure surface.

[0076] The following describes a rock sample fracture heat transfer performance testing system, which is used to implement the above-mentioned rock sample heat transfer performance testing method.

[0077] Please refer to the following: Figures 9 to 15As shown, this application provides a rock sample fracture heat transfer performance testing system. The system includes a rock sample holder 100, an injection module 200, a confining pressure module 300, a back pressure module 400, a collection module 500, a heating module 600, a monitoring component 700, and a data acquisition module 800. The rock sample holder 100 includes an experimental chamber for holding a rock sample 10 with pre-existing fractures, and a confining pressure chamber located outside the experimental chamber. The injection module 200 is connected to the inlet of the experimental chamber and is used to drive fluid into the rock sample 10 with pre-existing fractures. The confining pressure module 300 is connected to the confining pressure chamber and is used to pressurize the rock sample with pre-existing fractures. 10. Apply confining pressure; back pressure module 400 is connected to the outlet of the experimental chamber, and back pressure module 400 is used to cooperate with injection module 200 to control fluid pressure difference; collection module 500 is connected to the outlet of the experimental chamber, and collection module 500 is used to collect the seepage test fluid; heating module 600 is installed on rock sample holder 100, and heating module 600 is used to heat rock sample 10 with pre-set cracks; monitoring component 700 is used to monitor at least one of injection flow rate, pressure, temperature, confining pressure, and fluid seepage quality data; data acquisition module 800 is electrically connected to monitoring component 700, and data acquisition module 800 is used to collect and store injection flow rate, pressure, temperature, confining pressure, and fluid seepage quality data in real time.

[0078] Overall, this rock sample fracture heat transfer performance testing system, through the coordinated operation of multiple modules, achieves high-precision, full-process monitoring of the heat transfer characteristics of fractured rock sample 10 under complex stress and thermal field conditions. It significantly improves the measurement accuracy and experimental repeatability of the convective heat transfer coefficient, thereby solving key technical problems in existing dry hot rock single fracture flow heat transfer experiments, such as inaccurate injection temperature control, large measurement errors due to the temperature measurement position being far from the rock sample 10, ignoring the thermal resistance effect of rock surface temperature, inability to directly measure the temperature near the fracture, and severe structural damage caused by the preparation process of rock sample 10.

[0079] Specifically, the injection module 200 in this application can precisely heat or cool the injected fluid through the constant temperature water tank 221, ensuring the consistency of the injection temperature under different experimental conditions. By effectively controlling variables, heat transfer deviations caused by initial temperature fluctuations are avoided. Furthermore, by setting the injection tee component 214 and the outflow tee component 511, the temperature sensor can be directly placed on the inlet and outlet end faces of the rock sample 10 without damaging the pipeline, greatly shortening the temperature measurement path, reducing the impact of environmental heat dissipation, and improving the accuracy of inlet and outlet fluid temperature acquisition. Moreover, by improving the sealing component 130 on the rock sample holder 100, the opening channel 136 on the sealing component 130 can be used to arrange the outer surface temperature sensor 781 and the crack temperature sensor 782 on the rock sample 10 while ensuring the sealing effect. This achieves accurate temperature acquisition and in-situ, continuous monitoring of the temperature field of the rock sample 10, avoiding the destruction of the integrity of the rock sample 10 and the interference of interface contact thermal resistance caused by subsequent drilling and installation, and providing reliable data support for obtaining the true convective heat transfer coefficient.

[0080] The rock sample fracture heat transfer performance testing system of this application not only achieves precise control of fluid injection temperature, high-fidelity acquisition of temperature at key locations, and stable seepage control under the combined effect of confining pressure and back pressure, but also significantly reduces the interference of uncertain factors during the experiment through structural innovation. This application can be used to conduct single-fracture convective heat transfer experiments under various geological conditions, providing basic data support for the study of fracture network heat transfer mechanisms in enhanced geothermal systems (EGS). It has advantages such as high measurement accuracy, good operational stability, and wide applicability, and possesses significant scientific research value and engineering application prospects.

[0081] In the embodiments of this application, the designer can adjust the specific size and shape of the rock sample 10 according to the needs of use, and no specific limitations are made here. Preferably, the rock sample 10 is constructed as a cylinder. For example, in a specific embodiment, the rock sample holder 100 is suitable for cylindrical rock samples 10 with a diameter of 50 mm and a length of 80 mm-120 mm. The rock sample 10 can be prepared by the rock sample preparation method of the embodiments of this specification. For example, a first rock sample casting and a second rock sample casting can be obtained by the rock sample preparation method of the embodiments of this specification. The first rock sample casting and the second rock sample casting can be joined together and a proppant can be added to form a complete cylindrical experimental rock sample 10 with a certain opening and a rough fracture surface.

[0082] More preferably, the rock sample 10 is formed by casting. Specifically, cement, gravel, and water are mixed in a certain proportion by casting, and the required sensors can be embedded in the rock sample 10 during the casting process, thereby reducing damage to the structure of the rock sample 10 in subsequent experiments.

[0083] In the embodiments of this application, such as Figure 9 In the embodiment shown, the injection module 200 includes an injection pipe 210 for connecting to the inlet of the experimental chamber and a fluid supply pipe 220. The injection pipe 210 is sequentially provided with an injection pump 211, a piston-type intermediate container 212 and an injection control valve 213. The fluid supply pipe 220 is connected to the liquid inlet of the piston-type intermediate container 212. The fluid supply is sequentially provided with a constant temperature water tank 221, an injection flow meter 222 and a medium control valve 223.

[0084] Specifically, the fluid in the constant temperature water tank 221 is injected into the rock sample holder 100 according to the flow operation state set by the control component via the injection pump 211. Furthermore, the fluid injection parameters can be recorded by the monitoring component 700 and the data acquisition module 800. By using the constant temperature water tank 221, temperature control can be achieved to ensure that the experimental temperature meets the injection temperature requirements in actual engineering applications.

[0085] Furthermore, the injection pump 211 can be driven by a high-pressure dual pump, ensuring both the continuity of the experiment and the constant injection flow rate and injection pressure. The control components include at least a flow regulation module, which can precisely adjust the frequency of the injection pump 211. By adjusting the frequency of the injection pump 211, the injection flow rate can be controlled. Additionally, one end of the injection pump 211 is connected to the constant temperature water tank 221, and an injection flow meter 222 is installed between the two for measuring the flow rate.

[0086] In the embodiments of this application, such as Figure 9 In the embodiment shown, the confining pressure module 300 includes a confining pressure pipeline 310, a confining pressure supply water tank 311, a confining pressure control valve 312, a confining pressure pump 313, and a communicating vessel 314 disposed on the confining pressure pipeline 310. The communicating vessel 314 is used to connect the confining pressure chamber.

[0087] Specifically, one end of the confining pressure pump 313 is connected to the confining pressure supply water tank 311, and the other end of the confining pressure pump 313 is connected to the rock sample holder 100 via a connector 314. The connector 314 ensures that all the pumped water enters the confining pressure chamber to provide confining pressure. The confining pressure control valve 312 can be used to adjust the confining pressure to ensure its stability and prevent changes in the confining pressure due to temperature increases during heating. Furthermore, the connector 314 is detachable, facilitating the connection between the confining pressure module 300 and the rock sample holder 100.

[0088] In the embodiments of this application, such as Figure 9In the embodiment shown, the back pressure module 400 includes a back pressure pipeline 410 for connecting to the outlet of the experimental chamber and a back pressure supply pipeline 420. A hand-cranked pump 411 and an outlet back pressure valve 412 are sequentially provided on the back pressure pipeline 410. The back pressure supply pipeline 420 is connected to the back pressure pipeline 410. A back pressure tank 421 and a back pressure regulating control valve 422 are sequentially provided on the back pressure supply pipeline 420.

[0089] The backpressure module 400 works in conjunction with the injection module 200 to maintain the pressure within the rock sample holder 100 at a preset level, ensuring the stability of fluid flow in the fracture and preventing vaporization or cavitation, thereby improving the accuracy of flow rate, temperature, pressure, and flow data acquisition. Specifically, the hand-cranked pump 411 can manually control the outlet pressure of the backpressure pipeline 410 to prevent the high-temperature liquid from vaporizing. Furthermore, the backpressure regulating control valve 422 ensures backpressure stability.

[0090] In the embodiments of this application, such as Figure 9 In the embodiment shown, the collection module 500 includes an outflow pipe 510 and a collection container 520. The monitoring component 700 includes a flow measurement balance 710. The collection container 520 is disposed on the flow measurement balance 710. The outflow pipe 510 connects the outlet of the experimental chamber to the collection container 520.

[0091] The fluid seeping from the outlet of the rock sample holder 100 is guided to the collection container 520 via the outflow pipe 510. The collection container 520 is mounted on the flow measurement balance 710, which enables high-precision weighing and measurement of the seeping fluid. Furthermore, the flow measurement balance 710 is electrically connected to the data acquisition module 800, which continuously records the mass change of the outflowing fluid per unit time. Combined with time parameters, the instantaneous flow rate and cumulative flow rate can be accurately calculated.

[0092] In embodiments of the invention, such as Figure 9 , Figure 10 and Figure 11 In the embodiment shown, the heating module 600 includes a heating component 610 sleeved on the rock sample holder 100 and a heating control console 620 electrically connected to the heating component 610.

[0093] Specifically, the heating component 610 includes a heating coil. When energized, the heating coil rapidly generates a uniform heat field that covers the outer wall of the rock sample holder 100, ensuring effective heat transfer to the entire rock sample 10. Furthermore, the temperature can be manually controlled, and under the action of a temperature controller, constant temperature or constant heat heating can be achieved to ensure that the experimental temperature truly simulates the formation temperature.

[0094] In the embodiments of this application, such as Figure 10 , Figure 11 , Figure 12 , Figure 13 In the embodiment shown, the rock sample holder 100 includes a holder housing 110, a sealing sleeve 120, and two sealing components 130. Both ends of the sealing sleeve 120 are provided with stepped structures. The sealing sleeve 120 is disposed inside the holder housing 110. The inner cavity of the sealing sleeve 120 constitutes an experimental chamber. The space between the sealing sleeve 120 and the holder housing 110 constitutes a confining pressure chamber.

[0095] Two sealing assemblies 130 are respectively disposed at both ends of the clamp housing 110. Each sealing assembly 130 includes an external threaded sleeve 131 threadedly connected to the clamp housing 110, an internal threaded sleeve 132 inserted into and threadedly connected to the external threaded sleeve 131, a cylindrical smooth sealing device 133 coaxially disposed with the internal threaded sleeve 132, a stepped smooth sealing device 134 sleeved on the outside of the cylindrical smooth sealing device 133 and abutting against the external threaded sleeve 131, and a sealing ring 135 disposed on the outer wall of the stepped smooth sealing device 134. The sealing ring 135 can seal against the outer wall of the clamp housing 110. The stepped smooth sealing device 134 can match and connect with the stepped structure of the sealing sleeve 120. The cylindrical smooth sealing device 133 is provided with a pipeline channel extending along the axis.

[0096] During the experiment, such as Figure 10 In the embodiment shown, rock sample 10 is filled into sealing sleeve 120 at a specified pressure and position.

[0097] like Figure 15 In the illustrated embodiment, the sealing sleeve 120 has stepped structures at both ends, forming a stepped cylindrical sealing sleeve 120. In a specific embodiment, the sealing sleeve 120 is made of high-temperature and high-pressure resistant fluororubber.

[0098] The stepped structures at both ends of the sealing sleeve 120 can be matched and connected with the stepped smooth sealing device 134, ensuring a sealing effect. The middle part of the sealing sleeve 120 can wrap around the experimental rock sample 10.

[0099] Furthermore, the injection pipe 210 can be connected to the experimental chamber through the pipe channel on a cylindrical smooth sealing device 133, and the outflow pipe 510 can be connected to the experimental chamber through the pipe channel on another cylindrical smooth sealing device 133.

[0100] The external threaded sleeve 131 and the internal threaded sleeve 132 can form an adjustable structure, which facilitates thread adjustment along the axial direction of the clamp housing 110, thereby adjusting the axial dimension and better adapting to the clamping requirements of rock samples 10 of different sizes.

[0101] Furthermore, the stepped smooth sealing device 134 can be limited by the external threaded sleeve 131 and matched with the stepped structure of the sealing sleeve 120. The cylindrical smooth sealing device 133 can be limited by the internal threaded sleeve 132 and abut against the end face of the rock sample 10. The end of the cylindrical smooth sealing device 133 can be inserted into the sealing sleeve 120, thereby ensuring the clamping stability of the sealing sleeve 120 and the rock sample 10 at the same time.

[0102] In the embodiments of this application, such as Figure 12 In the embodiment shown, one of the cylindrical smooth sealing devices 133 is also provided with an opening channel 136, which connects the experimental chamber with the inner cavity of the internal threaded sleeve 132, and is used for the lead wire of the temperature sensor to pass through.

[0103] Specifically, such as Figure 12 In the illustrated embodiment, the opening channel 136 is inclinedly disposed within the cylindrical smooth sealing device 133. A stepped smooth sealing device 134 is fitted onto the cylindrical smooth sealing device 133 and covers the port of the opening channel 136, thereby sealing the opening channel 136 and ensuring a good seal after the lead wire is installed, preventing pressure relief or leakage problems in the rock sample holder 100.

[0104] In the embodiments of this application, such as Figure 9 and Figure 7 In the embodiment shown, the monitoring component 700 includes an inlet temperature sensor 720, an inlet pressure sensor 730, a back pressure sensor 740, an outlet temperature sensor 750, an outlet pressure sensor 760, a confining pressure sensor 770, and at least one rock sample temperature sensor 780 for being disposed on the outer surface of the rock sample 10 and / or embedded in the cracks of the rock sample 10.

[0105] An inlet pressure sensor 730 is installed on the injection line 210, a back pressure sensor 740 and an outlet pressure sensor 760 are installed on the outflow line 510, and a confining pressure sensor 770 is installed on the confining pressure line 310.

[0106] The injection pipeline 210 is equipped with an injection tee component 214, through which the inlet pressure sensor 730 and the inlet temperature sensor 720 can directly contact the inlet end face of the rock sample 10 and be electrically connected to the data acquisition module 800. The outflow pipeline 510 is equipped with an outflow tee component 511, through which the outlet pressure sensor 760 and the outlet temperature sensor 750 can directly contact the outlet end face of the rock sample 10 and be electrically connected to the data acquisition module 800. The rock sample temperature sensor 780 can be electrically connected to the data acquisition module 800 through the opening channel 136.

[0107] Specifically, such as Figure 7 In the embodiment shown, the rock sample temperature sensor 780 is provided in multiple sets, including at least one outer surface temperature sensor 781 for being disposed on the outer surface of the rock sample 10, and at least one crack temperature sensor 782 for being embedded in the cracks of the rock sample 10.

[0108] like Figure 14 In the illustrated embodiment, the first and second ports of the injection tee component 214 are used to connect to the injection pipeline 210. The third port of the injection tee component 214 is provided with a retractable hollow plug 2141. The inlet pressure sensor 730 and the inlet temperature sensor 720 can pass through the retractable hollow plug 2141 and enter the rock sample holder 100 along the injection pipeline 210, allowing the inlet pressure sensor 730 and the inlet temperature sensor 720 to be positioned on the inlet end face of the rock sample 10, thus improving measurement accuracy. The retractable hollow plug 2141 is used to fix the sensors and ensure a seal. Furthermore, both the inlet pressure sensor 730 and the inlet temperature sensor 720 are electrically connected to the data acquisition module 800.

[0109] Similarly, the first and second ports of the outflow tee component 511 are used to connect to the outflow pipe 510, and the third port of the outflow tee component 511 is also equipped with a retractable hollow plug. The outlet pressure sensor 760 and the outlet temperature sensor 750 can pass through the retractable hollow plug and enter the rock sample holder 100 along the outflow pipe 510, allowing the outlet pressure sensor 760 and the outlet temperature sensor 750 to be positioned on the outlet end face of the rock sample 10, thus improving measurement accuracy. The retractable hollow plug is used to fix the sensors and ensure a seal. Furthermore, both the outlet pressure sensor 760 and the outlet temperature sensor 750 are electrically connected to the data acquisition module 800.

[0110] Furthermore, such as Figure 7 In the illustrated embodiment, three sets of external surface temperature sensors 781 are provided. These three sets of external surface temperature sensors 781 are arranged equidistantly along the axial direction on the outer wall surface of the experimental rock sample 10 to record the external surface temperature of the rock sample 10. The external surface temperature sensors 781 can be fixed to the outer surface of the rock sample 10 using heat shrink tubing. Before fixing with heat shrink tubing, spacers can be added between the cracks to ensure the cracks have a certain opening.

[0111] Furthermore, three sets of crack temperature sensors 782 are provided. These three sets of crack temperature sensors 782 are embedded axially at equal intervals in the cracks within the rock sample 10 during the preparation of the rock sample 10 to record the crack temperature. The leads of the outer surface temperature sensor 781 and the crack temperature sensor 782 can be electrically connected to the data acquisition module 800 through the opening channel 136.

[0112] A confining pressure sensor 770 is positioned at the connection between the rock sample holder 100 and the confining pressure pump 313 to measure the confining pressure and can cooperate with the confining pressure control valve 312 to regulate the confining pressure. A back pressure sensor 740 is installed on the back pressure line 410 to measure the back pressure and can cooperate with the back pressure control valve to regulate the back pressure.

[0113] Those skilled in the art will understand that this specification can be provided as a method, system, or computer program product. Therefore, this specification may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware. Furthermore, this specification may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0114] This specification is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments thereof. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. The computer may be a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email device, game console, tablet computer, wearable device, or any combination of these devices.

[0115] The functional units in the embodiments of this specification can be integrated into one processing unit, or each functional unit can exist physically separately, or two or more functional units can be integrated into one processing unit.

[0116] Those skilled in the art will understand that the descriptions of the various embodiments in this specification have different focuses, and parts not described in detail in a certain embodiment can be referred to in the relevant descriptions of other embodiments. Furthermore, it is understood that those skilled in the art, after reading this specification, can conceive of any combination of some or all of the embodiments listed in this specification without creative effort, and such combinations are also within the scope of disclosure and protection of this specification.

[0117] Although this specification has been described through embodiments, those skilled in the art will understand that the above embodiments are merely illustrative of the core ideas of this specification. Those skilled in the art will appreciate that many variations and modifications are possible with this specification. It is intended that the appended claims encompass these variations and modifications without departing from the spirit of this specification.

Claims

1. A method for preparing a rock sample, characterized in that, include: Based on the first rock sample, construct the first fracture model; The first crack model was printed using 3D printing technology to obtain the first crack template; The first fissure template is located inside the cavity of the casting mold; the casting mold includes a shell, the shell surrounds the cavity, the shell is provided with holes, the surface of the first fissure template facing the first casting space has a first texture, and the first casting space includes the space remaining in the cavity excluding the space occupied by the first fissure template. After the temperature sensor is inserted into the first casting space through the hole, the first casting space is filled with casting material to form a first rock sample casting; the first rock sample casting has a fracture surface that matches the first texture, and the temperature sensor is provided inside the first rock sample casting and / or on the fracture surface.

2. The method according to claim 1, characterized in that, The construction of the first fracture model includes: The morphological data of the first rock sample were obtained by extracting features from the first rock sample using a morphology scanner. Based on the morphological data of the first rock sample, a first fracture model was constructed.

3. The method according to claim 1, characterized in that, The shell encloses and forms a cylindrical cavity; The housing is provided with multiple sets of holes, which are opened on the side wall of the cylindrical cavity. Each set of holes includes multiple holes arranged along the axial direction of the cylindrical cavity. The holes in different sets of holes have a corresponding relationship. The holes with the corresponding relationship in the multiple sets of holes are distributed radially along the cylindrical cavity and are located at the same axial height.

4. The method according to claim 3, characterized in that, The sensor assembly extends into the first casting space through the holes in the hole set; the sensor assembly includes multiple temperature sensors and fasteners for fixing the spacing of the multiple temperature sensors; within the first casting space, each temperature sensor in the sensor assembly is located at a different radial depth.

5. The method according to claim 1, characterized in that, The casting material is a composite casting material; the composite casting material includes a matrix phase and a mixed phase, the matrix phase includes cement, and the mixed phase includes gravel and metal powder; the thermal conductivity of the composite casting material is [missing information]. ; λ eff λ represents the thermal conductivity of the composite casting material. M λ represents the thermal conductivity of the matrix phase. I This indicates the thermal conductivity of the mixed phase. I This indicates the volume fraction of the mixed phase.

6. The method according to claim 1, characterized in that, Also includes: Based on the second rock sample, a second fracture model was constructed; The second fracture model was printed using 3D printing technology to obtain the second fracture template; The second fissure template is placed inside the cavity of the casting mold; the surface of the second fissure template facing the second casting space has a second texture, and the second casting space includes the remaining space inside the cavity excluding the space occupied by the second fissure template; The temperature sensor is inserted into the second pouring space through the hole; The second casting space is filled with casting material to form a second rock sample casting; the second rock sample casting has a fracture surface that matches the second texture, and the interior and / or fracture surface of the second rock sample casting is provided with a temperature sensor.

7. The method according to claim 6, characterized in that, The first rock sample and the second rock sample are obtained by splitting a natural rock sample. The first rock sample has a first fracture surface, and the second rock sample has a second fracture surface. The first fracture surface and the second fracture surface match each other in morphology. The first rock sample casting and the second rock sample casting are used to splice together to form an experimental rock sample; the fracture surface of the first rock sample casting and the fracture surface of the second rock sample casting match in morphology, and the fracture surface of the first rock sample casting and the fracture surface of the second rock sample casting are used to form a fracture inside the experimental rock sample.

8. A method for testing the heat transfer performance of rock samples, characterized in that, include: A flow heat transfer experiment was conducted on the experimental rock sample to obtain temperature data collected by a temperature sensor inside the experimental rock sample. The experimental rock sample was obtained by the rock sample preparation method described in claim 7. The heat transfer performance of the experimental rock samples was calculated based on temperature data.

9. The method according to claim 8, characterized in that, The calculation of the heat transfer performance of the experimental rock sample includes: Calculate the heat transfer coefficient of the experimental rock sample. h represents the convective heat transfer coefficient of the fluid flowing in the experimental rock sample, subscript 1 indicates the inlet parameter of the experimental rock sample, subscript 2 indicates the outlet parameter of the experimental rock sample, u1 and u2 represent the fluid velocity, ρ1 and ρ2 represent the fluid density, A1 and A2 represent the flow cross-sectional area within a single fracture, and c p T1 and T2 represent the specific heat capacity at constant pressure, and A represents the fluid temperature. s T represents the effective heat transfer area of ​​a single crack. s T represents the temperature of the fracture surface of the experimental rock sample. f T represents the internal temperature of the experimental rock sample. s T1 and T2 are calculated based on temperature data collected by temperature sensors.

10. A rock sample preparation apparatus, characterized in that, include: A building module is used to construct the first fracture model based on the first rock sample; The printing module is used to print the first fracture model using 3D printing technology to obtain the first fracture template. A casting module is used to position a first fissure template within the cavity of a casting mold. The casting mold includes a shell that encloses the cavity and has a hole. The surface of the first fissure template facing the first casting space has a first texture. The first casting space includes the space remaining in the cavity excluding the space occupied by the first fissure template. After a temperature sensor is inserted into the first casting space through the hole, casting material is filled into the first casting space to form a first rock sample casting. The first rock sample casting has a fissure surface that matches the first texture, and a temperature sensor is provided inside the first rock sample casting and / or on the fissure surface.

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