A method for fine characterization and characterization of weak structures in deep thermal reservoirs

Abstract

The present invention discloses a method for fine characterization and representation of the weak structure of deep heat reservoirs, and relates to the technical field of deep high-temperature geothermal resource exploration and development. The method comprises: a basic geological data analysis step, a structural surface morphology characterization step, a laboratory scale weak structure distribution characteristic characterization step, a well reservoir scale weak structure distribution characteristic characterization step, a field scale weak structure distribution characteristic characterization step, and a deep heat reservoir weakness evaluation step. The present invention constructs a multi-parameter model of deep heat reservoir characteristics of cross-scale common grid units with embedded weak structures, conducts research on the evolution law of deep heat reservoir characteristic parameters under high temperature and high pressure conditions and their characterization and characterization technology, comprehensively and quantitatively evaluates the degree of weakness and quality of heat reservoirs, effectively overcomes the scale effect problem, and provides important data support for research on target area optimization, well site demonstration, reservoir transformation, and quality and heat exchange.

Description

Technical Field

[0001] The present invention relates to the technical field of deep high-temperature geothermal resource exploration and development, and in particular to a method for finely characterizing and characterizing the weak structure of deep heat reservoirs. Background Art

[0002] Scientifically and effectively optimizing the development target area and accurately delineating the engineering site that can achieve large-scale fracturing under existing technical conditions are one of the most critical issues that determine the success or failure of deep geothermal resource development. The solution to this key issue requires the fine characterization and characterization of weak structures. A geological weak structure refers to a geological structure composed of multiple weak structural surfaces. The weak structural surface is the smallest unit that constitutes a weak structure. It is a structural surface in the rock mass whose mechanical strength is significantly lower than that of the surrounding rock and controls the stability of the rock mass. According to the cause of formation, it can generally be divided into three types: primary weak structural surface, tectonic weak structural surface and secondary weak structural surface. These weak structural surfaces mainly include faults, cracks, holes, karst troughs, weathering surfaces, broken zones, joint surfaces, etc. The rock is relatively broken, and a natural fracture system can usually be formed, and the primary weak structure is well developed. In this case, small-scale fracturing can produce twice the result with half the effort. However, a large number of deep thermal reservoir exploration and development practices have confirmed that if the original weak structure inside the deep thermal reservoir is not developed, it is difficult to obtain the ideal geothermal system EGS (Enhanced Geothermal Systems) fracture network structure through fracturing and reservoir creation. Only a well spacing of about 200 to 300 meters cannot achieve effective circulation heat extraction, let alone large-scale fracturing and mining. This is because large-volume and high-intensity fracturing has the risk of inducing earthquakes, which seriously restricts the strength and effect of reservoir transformation. Therefore, the characterization and representation of weak structures is particularly necessary.

[0003] Generally speaking, deep heat reservoirs have complex weak structures of different scales, which are not only complicated in their causes, but also have diverse controlling and influencing factors, and their formation and development are somewhat random, and their spatial distribution is highly heterogeneous. Therefore, its prediction, characterization and representation are a common problem in the geothermal geology community. In recent years, the geothermal academic community has paid more and more attention to the study of the changing laws and characterization methods of deep heat reservoir characteristics (geometry, physical properties, mechanics). Although certain results have been achieved, they are mainly based on the study of mechanical properties at the laboratory scale, lacking systematic research at a larger scale. Most of them use theoretical analysis, numerical simulation and indoor experiments to study the crack expansion law and morphological change characteristics of normal temperature samples under hydraulic stimulation. However, there are relatively few studies using in-situ testing and forward and inversion techniques to study the spatial distribution and changing laws of the macroscopic characteristics of deep heat reservoirs. The correlation and response mechanism between them and geophysical properties are not very clear, and the evolution law with temperature is basically blank, which has a large scale effect problem.

[0004] In addition, domestic and foreign research on the evolution mechanism of the physical and mechanical properties of thermal reservoirs under high temperatures is still very weak, and the existing research results are mostly concentrated on revealing the evolution characteristics of the physical and mechanical properties of rocks, and obtaining conclusions such as that with the increase of temperature, the wave velocity, density, strength, and elastic modulus of rocks gradually decrease, and the peak strain and permeability gradually increase. The above studies are mostly carried out on the change law of the physical and mechanical properties of rocks after high-temperature cooling. Although the research results can reflect the change characteristics of the physical and mechanical properties of deep thermal reservoirs with temperature to a certain extent, there are still certain differences from the evolution of characteristics under real-time high temperature and high pressure in-situ conditions. Therefore, it is more significant to carry out physical and mechanical property tests of deep thermal reservoirs under real-time high temperature and high pressure conditions (similar to in-situ conditions), which has more far-reaching guiding value for the design of fracturing development plans, the selection of fracturing layers, the stability evaluation of injection and production systems, and the formulation of reservoir protection plans.

[0005] Therefore, it is an urgent problem for those skilled in the art to propose a method for fine characterization and characterization of the weak structure of deep heat reservoirs to solve the difficulties existing in the prior art. Summary of the invention

[0006] In view of this, the present invention provides a method for fine characterization and representation of the weak structure of deep heat reservoirs, comprehensively utilizes the deep heat reservoir characteristic data obtained by different means at multiple scales, constructs a multi-parameter model of deep heat reservoir characteristics of cross-scale common grid units with embedded weak structures, conducts research on the evolution law of deep heat reservoir characteristic parameters under high temperature and high pressure conditions and their characterization and characterization technology, comprehensively and quantitatively evaluates the degree of weakness and quality of heat reservoirs, effectively overcomes the problem of scale effect, and provides important data support for research on target area optimization, well site demonstration, reservoir transformation, quality exchange and heat exchange.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for finely characterizing and characterizing the weak structure of deep thermal reservoirs comprises the following steps:

[0009] S1. Basic geological data analysis steps: obtain basic geological data, analyze the development characteristics and occurrence conditions of the weak structure inside the deep heat reservoir, and determine the main controlling factors affecting the development of the weak structure;

[0010] S2. Structural surface morphology characterization step: Based on the main controlling influencing factors determined in S1, experiments are conducted on natural weak structural surfaces of deep heat reservoirs of different sizes to obtain the evolution law of natural weak structural surfaces of deep heat reservoirs of different sizes with temperature;

[0011] S3, laboratory scale weak structure distribution characteristics characterization step: based on the evolution law of natural weak structure surfaces of deep heat reservoirs of different sizes obtained in S2 with temperature, the laboratory scale heat reservoir geometric characteristic distribution, laboratory scale heat reservoir physical characteristic distribution and laboratory scale heat reservoir mechanical characteristic distribution are obtained through different laboratory experiments;

[0012] S4, characterization step of weak structure distribution characteristics at well reservoir scale: based on the laboratory-scale deep heat reservoir characteristic distribution obtained in S3 and the field test data, a geological-geophysical model of the well reservoir medium is constructed to characterize and characterize the characteristic distribution of the well reservoir-scale heat reservoir;

[0013] S5. Characterization steps of weak structure distribution characteristics at site scale: Analyze the characteristic distribution of well-scale heat reservoirs to obtain the characteristic distribution information of deep heat reservoirs, establish a three-dimensional geological model of deep heat reservoirs at site scale, and characterize and represent the weak structure characteristic distribution of deep heat reservoirs at site scale, including: spatial distribution of geometric characteristics, physical characteristics and mechanical characteristics;

[0014] S6. Steps for evaluating the weakness of deep thermal reservoirs: Based on the characteristic distribution of weak structures in deep thermal reservoirs, the effective medium theory is used to establish a rock mechanics constitutive model of discontinuous thermal reservoir media at a set temperature; and the weak structural zones where large-scale fracturing can be implemented under existing technical conditions are delineated.

[0015] In the above method, optionally, the natural weak structural surfaces of deep heat reservoirs of different sizes in S2 include:

[0016] Micro-nano, micrometer-millimeter, millimeter-submeter, decimeter-tens of meters, and tens of meters and above scales.

[0017] The above method can be optionally tested on micro-nanoscale structure surfaces:

[0018] By setting the temperature atomic force microscope to observe and record the geometric physical parameters of the micro-nanoscale weak structural surfaces of heat reservoirs at different temperatures, a two-dimensional extension model of the micro-nanoscale fracture network of heat reservoirs was constructed based on the physical data of the weak structural surfaces. The distribution morphology and change characteristics of the weak structural surfaces were analyzed, and the evolution law of the micro-nanoscale weak structural surfaces of deep heat reservoirs at the set temperature was obtained.

[0019] The above method can be optionally tested on micron-millimeter scale structures:

[0020] Based on the high-energy CT real-time scanning set temperature, set pressure triaxial experimental system, the three-dimensional information of the micron-millimeter scale weak structural surface of the heat reservoir under different set temperature and set pressure conditions is obtained. The refined 3D visualization model is established through the three-dimensional reconstruction technology, and the morphological characteristics and expansion path of the micron-millimeter scale weak structural surface of the deep heat reservoir at the set temperature are extracted, and the evolution law of the micron-millimeter scale weak structural surface of the deep heat reservoir with temperature is obtained.

[0021] The above method can be optionally tested on millimeter-submeter scale structural surfaces:

[0022] Based on the soft structure of the structural surface and the microscopic flow characteristics of the pore fluid, a seismic wave propagation model was constructed. The geophysical data processing method was used to invert the morphological characteristics of the millimeter-submeter scale soft structure of the thermal reservoir at different temperatures, and the evolution law of the millimeter-submeter scale soft structure surface of the deep thermal reservoir under high temperature was obtained.

[0023] The above method can be optionally used for testing structural surfaces at a scale of decimeter to tens of meters:

[0024] Collect imaging logging, surface and borehole microseismic data, and use comprehensive logging evaluation technology and source positioning and imaging theory based on seismic rays and wave equations to analyze the collected imaging logging, surface and borehole microseismic data to obtain formation anisotropy, jointly invert stress distribution, development mechanism of weak structural surfaces, and size and trend of weak structural surfaces, determine the main stress direction of deep heat reservoirs, and predict the development direction and evolution law of weak structural surfaces at the decimeter to tens of meters scale.

[0025] The above method can be optionally tested on structural surfaces with a scale of tens of meters or more:

[0026] Use seismic data to predict weak structural surfaces and ground stress directions;

[0027] Based on the correlation between weak structural surfaces and ground stress, the spatial distribution of weak structural surfaces is obtained through regional tectonic stress field simulation, and the evolution law of weak structural surfaces at the current scale of deep heat reservoirs is portrayed and characterized.

[0028] In the above method, optionally, the specific contents in S3 include:

[0029] Through high-energy CT real-time scanning and triaxial experiments, a three-dimensional reconstruction technology is used to build a visualization numerical model of deep heat storage. Combined with high-temperature and high-pressure servo permeability experiments, the three-dimensional reconstruction model is optimized, and a deep heat storage porosity and permeability evolution model containing temperature and pressure parameters is constructed to characterize and characterize the distribution of laboratory-scale heat storage physical properties.

[0030] Through cross-band rock physics experiments, the changes of longitudinal and transverse wave velocities, resistivity, magnetism, polarizability, density and elastic parameters of heat reservoirs in different frequency bands with temperature and pressure are studied, and a geological model of the physical characteristics of deep heat reservoirs at high temperatures is established to characterize and characterize the distribution of physical characteristics of heat reservoirs at laboratory scale at high temperatures.

[0031] Through triaxial compression experiments under different temperature and pressure conditions, acoustic emission, wave velocity and deformation are monitored simultaneously to study the changes in the mechanical properties of heat reservoirs at high temperatures, establish a mathematical and physical model of the evolution of the mechanical properties of deep heat reservoirs with temperature, study the correlation and constitutive relationship between the mechanical properties of heat reservoirs, and characterize and represent the distribution of mechanical characteristics of deep heat reservoirs at laboratory scale under high temperatures.

[0032] In the above method, optionally, the specific contents of S4 include:

[0033] Based on indoor test analysis, integrated outcrop, drilling, logging and field test data, the structure of the well storage medium is identified and interpreted, and a geological-geophysical model of the well storage medium is constructed based on the obtained geological information. Using logging evaluation and constrained inversion technology, the anisotropy of the well storage medium is analyzed, the principal stress direction of the deep heat reservoir is determined, and the distribution characteristics of the heat reservoir at the well storage scale are portrayed and characterized.

[0034] In the above method, optionally, the specific contents of S6 include:

[0035] Aiming at the complex weak structural characteristics of deep heat reservoirs, a rock mechanics thermal constitutive model of discontinuous heat storage media at high temperature is established based on effective medium theory.

[0036] Based on the rock mechanics thermal constitutive model of discontinuous heat storage media under high temperature, the parallel superposition calculation method of pore and matrix strain is adopted to calculate and analyze the obtained heat storage parameters, and a nonlinear evaluation method for deep heat storage is obtained to evaluate the quality and weakness of the heat storage, and to identify the weak structural zones where large-scale fracturing can be implemented under existing technical conditions.

[0037] It can be seen from the above technical solution that, compared with the prior art, the method for fine characterization and characterization of the weak structure of deep heat storage in the present invention has the following beneficial effects:

[0038] (1) Comprehensively utilize the deep heat reservoir characteristic data obtained by different means at multiple scales to construct a multi-parameter model of deep heat reservoir characteristic distribution in cross-scale common grid units with embedded weak structures, conduct research on the evolution law of deep heat reservoir characteristic parameters under high temperature and high pressure conditions and their characterization and representation technology, comprehensively and quantitatively evaluate the weakness and quality of the heat reservoir, and delineate the weak structure zone, which can effectively overcome the scale effect problem;

[0039] (2) Integrate the fracture data obtained by different means at multiple scales to construct a discrete fracture network of deep heat reservoirs in cross-scale common grid units, and conduct research on the evolution law and fine characterization and characterization technology of multi-scale pores / fractures in deep heat reservoirs under high temperature and high pressure conditions. This is of great significance for guiding the fracturing transformation of heat reservoirs and improving heat extraction efficiency. It can also provide reliable data support for the numerical simulation of fracture network structure under multi-field coupling.

[0040] (3) It is of greater significance to conduct physical and mechanical property tests of deep thermal reservoirs under real-time high temperature and high pressure conditions (similar to in-situ conditions), which has more precise guiding significance for the design of fracturing schemes, the selection of fracturing layers, the stability evaluation of injection-production systems, and the formulation of reservoir protection plans. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0042] Figure 1 A flow chart of a method for fine characterization and characterization of weak structures of deep thermal reservoirs provided by the present invention. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] In this application, relational terms such as first and second, etc. are used only 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. The terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, the elements defined by the sentence "comprise one..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0045] The present invention can be used in many general or special computing device environments or configurations, such as personal computers, server computers, handheld or portable devices, tablet devices, multi-processor devices, distributed computing environments including any of the above devices or devices, etc.

[0046] Reference Figure 1 As shown, the present invention discloses a method for fine characterization and characterization of the weak structure of deep thermal reservoir, comprising the following steps:

[0047] S1. Basic geological data analysis steps: obtain basic geological data, analyze the development characteristics and occurrence conditions of the weak structure inside the deep heat reservoir, and determine the main controlling factors affecting the development of the weak structure;

[0048] S2. Structural surface morphology characterization step: Based on the main controlling influencing factors determined in S1, experiments are conducted on natural weak structural surfaces of deep heat reservoirs of different sizes to obtain the evolution law of natural weak structural surfaces of deep heat reservoirs of different sizes with temperature;

[0049] S3, laboratory scale weak structure distribution characteristics characterization step: based on the evolution law of natural weak structure surfaces of deep heat reservoirs of different sizes obtained in S2 with temperature, the laboratory scale heat reservoir geometric characteristic distribution, laboratory scale heat reservoir physical characteristic distribution and laboratory scale heat reservoir mechanical characteristic distribution are obtained through different laboratory experiments;

[0050] S4, characterization step of weak structure distribution characteristics at well reservoir scale: based on the laboratory-scale deep heat reservoir characteristic distribution obtained in S3 and the field test data, a geological-geophysical model of the well reservoir medium is constructed to characterize and characterize the characteristic distribution of the well reservoir-scale heat reservoir;

[0051] S5. Characterization steps of weak structure distribution characteristics at site scale: Analyze the characteristic distribution of well-scale heat reservoirs to obtain the characteristic distribution information of deep heat reservoirs, establish a three-dimensional geological model of deep heat reservoirs at site scale, and characterize and represent the weak structure characteristic distribution of deep heat reservoirs at site scale, including: spatial distribution of geometric characteristics, physical characteristics and mechanical characteristics;

[0052] S6. Steps for evaluating the weakness of deep thermal reservoirs: Based on the characteristic distribution of weak structures in deep thermal reservoirs, the effective medium theory is used to establish a rock mechanics constitutive model of discontinuous thermal reservoir media at a set temperature; and the weak structural zones where large-scale fracturing can be implemented under existing technical conditions are delineated.

[0053] Specifically, S1 analyzes the development characteristics and occurrence conditions of weak structures inside deep heat reservoirs, studies the impact of regional geological processes such as magma, tectonics, metamorphism, dissolution, remelting and weathering on the development of weak structures, determines their main controlling factors, and reveals their formation mechanism.

[0054] Different weights are assigned to different influencing factors. The weight coefficients of influencing factors such as magma, structure, metamorphism, dissolution, remelting and weathering are calculated for specific regions. According to the size of the weight coefficient, one or several factors are determined as the main controlling factors. Different research areas have strong individual differences and cannot be generalized. Based on the basic geological research of the "three histories" and "two fields" of thermal reservoirs, weak structure simulation and prediction research is carried out to provide support for the refined characterization of weak structural surfaces in deep thermal reservoirs at high temperatures.

[0055] S5 uses geophysical structure interpretation, attribute analysis, dip scanning, spectral decomposition, P-wave anisotropy, stress field simulation and other technologies to carry out joint inversion, data fusion, inter-well interpolation and extrapolation research, obtain fine structural characteristic information of deep heat reservoirs, establish a three-dimensional geological model of deep heat reservoirs at the site scale, analyze and interpret the precise information of weak structures of different types and scales (spatial distribution, geometric shape, development density, scale, burial depth, superposition and contact relationship, etc.), and finely depict and characterize the spatial distribution of geometric, physical and mechanical properties of weak structures of deep heat reservoirs at the site scale.

[0056] Furthermore, the natural weak structural surfaces of deep thermal reservoirs of different sizes in S2 include:

[0057] Micro-nano, micrometer-millimeter, millimeter-submeter, decimeter-tens of meters, and tens of meters and above scales.

[0058] Furthermore, the micro-nanoscale structure surface test:

[0059] By setting the temperature atomic force microscope to observe and record the geometric physical parameters of the micro-nanoscale weak structural surfaces of heat reservoirs at different temperatures, a two-dimensional extension model of the micro-nanoscale fracture network of heat reservoirs was constructed based on the physical data of the weak structural surfaces. The distribution morphology and change characteristics of the weak structural surfaces were analyzed, and the evolution law of the micro-nanoscale weak structural surfaces of deep heat reservoirs at the set temperature was obtained.

[0060] Specifically, the geometric physical parameters of weak structural surfaces such as micro-nano-scale pores and cracks in heat reservoirs at different temperatures were observed and recorded through high-temperature atomic force microscopy. Based on the data of width, length, geometry, density, connectivity and other weak structural surfaces, a two-dimensional expansion model of the micro-nano-scale fracture network of heat reservoirs was constructed by combining image processing technology, topology, data mining and other technologies and theories. The distribution morphology and change characteristics of the weak structural surfaces were analyzed, revealing the evolution law of micro-nano-scale weak structural surfaces in deep heat reservoirs under high temperature.

[0061] Furthermore, the micron-millimeter scale structure surface test:

[0062] Based on the high-energy CT real-time scanning set temperature, set pressure triaxial experimental system, the three-dimensional information of the micron-millimeter scale weak structural surface of the heat reservoir under different set temperature and set pressure conditions is obtained. The refined 3D visualization model is established through the three-dimensional reconstruction technology, and the morphological characteristics and expansion path of the micron-millimeter scale weak structural surface of the deep heat reservoir at the set temperature are extracted, and the evolution law of the micron-millimeter scale weak structural surface of the deep heat reservoir with temperature is obtained.

[0063] Specifically, a refined 3D visualization model is established through three-dimensional reconstruction technology to extract the spatial distribution, geometric shape, density, width, length and other morphological characteristics of weak structural surfaces such as micron-millimeter pores and cracks in deep heat reservoirs under high temperature and their expansion paths, revealing the evolution law of micron-millimeter weak structural surfaces in deep heat reservoirs with temperature.

[0064] Furthermore, the millimeter-submeter scale structural surface test:

[0065] Based on the soft structure of the structural surface and the microscopic flow characteristics of the pore fluid, a seismic wave propagation model was constructed. The geophysical data processing method was used to invert the morphological characteristics of the millimeter-submeter scale soft structure of the thermal reservoir at different temperatures, and the evolution law of the millimeter-submeter scale soft structure surface of the deep thermal reservoir under high temperature was obtained.

[0066] Specifically, based on weak structures such as pores and cracks and the microscopic flow characteristics of pore fluids, a seismic wave propagation model was constructed. Using well logging, near-well seismic data, and other data, and adopting geophysical data processing methods such as offset imaging and attenuation imaging, the spatial distribution, geometric characteristics, density, width, length and other morphological characteristics of millimeter-sub-meter scale weak structures in heat reservoirs at different temperatures were inverted, and the evolution law of millimeter-sub-meter scale weak structural surfaces in deep heat reservoirs under high temperature was obtained.

[0067] Furthermore, for the structural surface test on the scale of decimeter to tens of meters:

[0068] By using acoustic and imaging logging, surface and borehole microseismic data, and adopting comprehensive logging evaluation technology and source positioning and imaging theory based on seismic rays and wave equations, the collected imaging logging, surface and borehole microseismic data are analyzed to obtain the anisotropy of the formation, and jointly invert the stress distribution, the development mechanism of the weak structural surface, and the size and trend of the weak structural surface, determine the principal stress direction of the deep heat reservoir, and predict the development direction and evolution law of the weak structural surface at the decimeter to tens of meters scale.

[0069] Furthermore, for structural surface tests of tens of meters and above:

[0070] Use seismic data to predict weak structural surfaces and ground stress directions;

[0071] Based on the correlation between weak structural surfaces and ground stress, the spatial distribution of weak structural surfaces is obtained through regional tectonic stress field simulation, and the evolution law of weak structural surfaces at the current scale of deep heat reservoirs is portrayed and characterized.

[0072] Specifically, seismic data are used to predict weak structural surfaces and geostress directions using techniques such as ant bodies, correlation bodies, curvature bodies, dip scanning, spectral decomposition, and P-wave anisotropy. Based on the correlation between weak structural surfaces such as faults and cracks and geostress (weak structural surfaces are the macroscopic manifestation of stress), the spatial distribution of weak structural surfaces is obtained through regional tectonic stress field simulation, and the evolution law of weak structural surfaces at this scale of deep heat reservoirs is portrayed and characterized.

[0073] Furthermore, the specific contents of S3 include:

[0074] Through high-energy CT real-time scanning and triaxial experiments, a three-dimensional reconstruction technology is used to build a visualization numerical model of deep heat storage. Combined with high-temperature and high-pressure servo permeability experiments, the three-dimensional reconstruction model is optimized, and a deep heat storage porosity and permeability evolution model containing temperature and pressure parameters is constructed to characterize and characterize the distribution of laboratory-scale heat storage physical properties.

[0075] Through cross-band rock physics experiments, the changes of longitudinal and transverse wave velocities, resistivity, magnetism, polarizability, density and elastic parameters of heat reservoirs in different frequency bands with temperature and pressure (axial and circumferential) are studied, and a geological model of the physical characteristics of deep heat reservoirs at high temperatures is established to characterize and characterize the distribution of physical characteristics of heat reservoirs at laboratory scale at high temperatures.

[0076] Through triaxial compression experiments under different temperature and pressure conditions, acoustic emission, wave velocity and deformation are monitored simultaneously to study the changes in the mechanical properties of heat reservoirs at high temperatures, establish a mathematical and physical model of the evolution of the mechanical properties of deep heat reservoirs with temperature, study the correlation and constitutive relationship between the mechanical properties of heat reservoirs, and characterize and represent the distribution of mechanical characteristics of deep heat reservoirs at laboratory scale under high temperatures.

[0077] Furthermore, the specific contents of S4 include:

[0078] Based on indoor test analysis, integrated outcrop, drilling, logging and field test data, the structure of the well storage medium is identified and interpreted, and a geological-geophysical model of the well storage medium is constructed based on the obtained geological information. Using logging evaluation and constrained inversion technology, the anisotropy of the well storage medium is analyzed, the principal stress direction of the deep heat reservoir is determined, and the distribution characteristics of the heat reservoir at the well storage scale are portrayed and characterized.

[0079] Specifically, based on indoor test analysis, integrated outcrop, drilling, logging and field test data, the structure of the well storage medium is identified and interpreted. According to the obtained geological information (porosity, permeability, fracture geometry, etc.) and physical laws such as conservation of mass and momentum, Lagrangian mechanics is used to construct a geological-geophysical model of the well storage medium. Using logging evaluation and constrained inversion technology, the anisotropy of the well storage medium is analyzed, the principal stress direction of the deep heat reservoir is determined, the development characteristics and evolution laws of the weak structure of the well storage medium are revealed, and the distribution characteristics of heat reservoirs at the well storage scale are portrayed and characterized.

[0080] Furthermore, the specific contents of S6 include:

[0081] Aiming at the complex weak structural characteristics of deep heat reservoirs, a rock mechanics thermal constitutive model of discontinuous heat storage media at high temperature is established based on effective medium theory.

[0082] Based on the rock mechanics thermal constitutive model of discontinuous heat storage media under high temperature, the parallel superposition calculation method of pore and matrix strain is adopted to calculate and analyze the obtained heat storage parameters, and a nonlinear evaluation method for deep heat storage is obtained to evaluate the quality and weakness of the heat storage, and to identify the weak structural zones where large-scale fracturing can be implemented under existing technical conditions.

[0083] Specifically, the complex weak structural characteristics of deep heat reservoirs include: fault type, crack-pore type, pore type, cave type, broken type, joint type, etc.

[0084] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can refer to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment. The system and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without creative work.

[0085] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for fine characterization and characterization of the weak structure of deep thermal reservoirs, characterized in that: The following steps are involved: S1. Basic geological data analysis steps: obtain basic geological data, analyze the development characteristics and occurrence conditions of the weak structure inside the deep heat reservoir, and determine the main controlling factors affecting the development of the weak structure; S2. Structural surface morphology characterization step: Based on the main controlling influencing factors determined in S1, experiments are conducted on natural weak structural surfaces of deep heat reservoirs of different sizes to obtain the evolution law of natural weak structural surfaces of deep heat reservoirs of different sizes with temperature; S3, laboratory scale weak structure distribution characteristics characterization step: based on the evolution law of natural weak structure surfaces of deep heat reservoirs of different sizes obtained in S2 with temperature, the laboratory scale heat reservoir geometric characteristic distribution, laboratory scale heat reservoir physical characteristic distribution and laboratory scale heat reservoir mechanical characteristic distribution are obtained through different laboratory experiments; S4, characterization step of weak structure distribution characteristics at well reservoir scale: based on the laboratory-scale deep heat reservoir characteristic distribution obtained in S3 and the field test data, a geological-geophysical model of the well reservoir medium is constructed to characterize and characterize the characteristic distribution of the well reservoir-scale heat reservoir; S5. Characterization steps of weak structure distribution characteristics at site scale: Analyze the characteristic distribution of well-scale heat reservoirs to obtain the characteristic distribution information of deep heat reservoirs, establish a three-dimensional geological model of deep heat reservoirs at site scale, and characterize and represent the weak structure characteristic distribution of deep heat reservoirs at site scale, including: spatial distribution of geometric characteristics, physical characteristics and mechanical characteristics; S6. Evaluation steps for the weakness of deep thermal reservoirs: Based on the characteristic distribution of weak structures of deep thermal reservoirs, the rock mechanics constitutive model of discontinuous thermal reservoir media at a set temperature is established using effective medium theory; weak structural zones where large-scale fracturing can be implemented under existing technical conditions are delineated; The specific contents of S3 include: through high-energy CT real-time scanning and triaxial experiments, using three-dimensional reconstruction technology to build a deep heat reservoir visualization numerical model, combined with high-temperature and high-pressure servo permeability experiments, optimize the three-dimensional reconstruction model, build a deep heat reservoir porosity evolution model containing temperature and pressure parameters, and characterize and represent the distribution of laboratory-scale heat reservoir physical properties; through cross-band rock physics experiments, study the changes of longitudinal and transverse wave velocities, resistivity, magnetism, polarizability, density and elastic parameters of heat reservoirs in different frequency bands with temperature and pressure, establish a geological model of deep heat reservoir physical properties at a set temperature, and characterize and represent the distribution of laboratory-scale heat reservoir physical characteristics at a set temperature; through triaxial compression experiments under different temperature and pressure conditions, synchronously monitor acoustic emission, wave velocity and deformation, study the changes of heat reservoir mechanical properties at a set temperature, establish a mathematical and physical model of the evolution of deep heat reservoir mechanical properties with temperature, study the correlation and constitutive relationship between heat reservoir mechanical properties, and characterize and represent the distribution of laboratory-scale deep heat reservoir mechanical characteristics at a set temperature; The specific contents of S4 include: based on the analysis of indoor tests, integrating outcrop, drilling, logging and field test data, identifying and interpreting the structure of well storage media, constructing a geological-geophysical model of well storage media based on the obtained geological information, using logging evaluation and constrained inversion technology to analyze the anisotropy of well storage media, determine the principal stress direction of deep heat reservoirs, and characterize and characterize the distribution characteristics of heat reservoirs at the well storage scale; The specific contents of S6 include: Aiming at the complex weak structural characteristics of deep heat reservoirs, a rock mechanics thermal constitutive model of discontinuous heat storage media at a set temperature is established based on the effective medium theory; Based on the rock mechanics thermal constitutive model of discontinuous heat storage media at a set temperature, the parallel superposition calculation method of pore and matrix strain is adopted to calculate and analyze the obtained heat storage parameters, and a nonlinear evaluation method for deep heat storage is obtained to evaluate the quality and weakness of the heat storage, and to identify the weak structural zones where large-scale fracturing can be implemented under existing technical conditions.

2. A method for fine characterization and characterization of weak structures of deep heat reservoirs according to claim 1, characterized in that: The natural weak structural surfaces of deep heat reservoirs in S2 of different sizes include: micro-nano, micron-millimeter, millimeter-submeter, decimeter-tens of meters, and tens of meters and above.

3. A method for fine characterization and characterization of weak structures of deep heat reservoirs according to claim 2, characterized in that: Tests on micro-nano scale structures: By setting the temperature atomic force microscope to observe and record the geometric physical parameters of the micro-nanoscale weak structural surfaces of heat reservoirs at different temperatures, a two-dimensional extension model of the micro-nanoscale fracture network of heat reservoirs was constructed based on the physical data of the weak structural surfaces. The distribution morphology and change characteristics of the weak structural surfaces were analyzed, and the evolution law of the micro-nanoscale weak structural surfaces of deep heat reservoirs at the set temperature was obtained.

4. A method for fine characterization and characterization of weak structures of deep heat reservoirs according to claim 2, characterized in that: Experiments on micron-millimeter scale structural surfaces: Based on a high-energy CT real-time scanning set temperature, set pressure triaxial experimental system, the three-dimensional information of the micron-millimeter scale weak structural surface of the heat reservoir under different set temperature and set pressure conditions is obtained. A refined 3D visualization model is established through three-dimensional reconstruction technology to extract the morphological characteristics and expansion path of the micron-millimeter scale weak structural surface of the deep heat reservoir at the set temperature, and the evolution law of the micron-millimeter scale weak structural surface of the deep heat reservoir with temperature is obtained.

5. A method for fine characterization and characterization of weak structures of deep heat reservoirs according to claim 2, characterized in that: For millimeter-submeter scale structural surface tests: Based on the soft structure of the structural surface and the microscopic flow characteristics of the pore fluid, a seismic wave propagation model was constructed. The geophysical data processing method was used to invert the morphological characteristics of the millimeter-submeter soft structure of the thermal reservoir at different temperatures, and the evolution law of the millimeter-submeter soft structure surface of the deep thermal reservoir at the set temperature was obtained.

6. A method for fine characterization and characterization of weak structures of deep heat reservoirs according to claim 2, characterized in that: For the decimeter-to-tens-of-meter scale structural surface test: collect imaging logging, surface and well microseismic data, use comprehensive logging evaluation technology and source positioning and imaging theory based on seismic rays and wave equations to analyze the collected imaging logging, surface and well microseismic data, obtain formation anisotropy, jointly invert stress distribution, development mechanism of weak structural surfaces, and size and trend of weak structural surfaces, determine the main stress direction of deep heat reservoirs, and predict the development direction and evolution law of weak structural surfaces at decimeter-to-tens-of-meter scales.

7. A method for fine characterization and characterization of weak structures of deep heat reservoirs according to claim 2, characterized in that: Tests on structural surfaces of tens of meters or more: Use seismic data to predict weak structural surfaces and ground stress directions; Based on the correlation between weak structural surfaces and ground stress, the spatial distribution of weak structural surfaces is obtained through regional tectonic stress field simulation, and the evolution law of weak structural surfaces at the current scale of deep heat reservoirs is portrayed and characterized.

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