CN110658077B - Enhanced geothermal system crack communication evaluation and heat extraction test method - Google Patents
Enhanced geothermal system crack communication evaluation and heat extraction test method Download PDFInfo
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Abstract
The invention discloses a test method for crack communication evaluation and heat extraction test of an enhanced geothermal system. The experimental method can be used for analyzing the communication condition of the fractures or fracture networks formed under different fracturing modes to the injection well and the production well. By adopting the experimental method, heat extraction test experiments can be continuously carried out on the pressed rock sample after fracturing modification, including the liquid production rate, the liquid production temperature and the heat collection rate of the enhanced geothermal system. In addition, influences of different stress conditions, rock temperature, fracturing fluid, fracturing discharge capacity, rock sample lithology and the like on fracturing transformation effects and communication and heat extraction performance of the fractures on an injection and production system can be discussed.
Description
Technical Field
The invention relates to a fracturing modification and heat extraction process of an enhanced geothermal system, in particular to a communication evaluation and post-fracturing heat extraction testing device and method for a fracturing fracture of the enhanced geothermal system to an injection and production system.
Background
Abundant geothermal energy sources are stored in the hot dry rock reservoir, but the high-temperature energy sources are difficult to be effectively utilized due to the characteristics of low porosity and low permeability. The method provides possibility for the efficient development of the hot dry rock by forming cracks in a thermal reservoir or reopening original natural cracks in the thermal reservoir through an artificial fracturing technology so as to form an enhanced geothermal system. However, not only does the efficient extraction of energy from hot dry rock require the creation of fractures or a network of fractures in the reservoir, the efficient communication of the injection system and the production system through the fractures in the hot reservoir is still a necessary condition for thermal energy extraction.
Because the research is still in the starting and exploring stages of enhanced geothermal system research at present, the research on the dry hot rock hydraulic fracturing mainly focuses on the fracture morphology possibly formed by the hydraulic fracturing and the influence of a high-temperature and high-pressure environment on the fracture initiation and expansion process. Whether the cracks formed by artificial fracturing can communicate with an injection-production system so as to provide an effective channel for the flow of heat-carrying fluid is not reported.
Disclosure of Invention
The invention aims to provide a test method for enhanced geothermal system crack communication evaluation and heat extraction test, which solves the technical problem that cracks formed in different fracturing modes perform injection-production system communication evaluation and heat extraction test, and realizes the integrated technical effect of crack form monitoring, injection-production system communication evaluation and heat extraction performance test in different fracturing modes.
In order to solve the above technical problems, the present invention provides an enhanced geothermal system crack communication evaluation and heat extraction test method, including:
the first step is as follows: preparing a rock sample to be tested
Cutting a plurality of same physical and mechanical performance parametersThe method comprises the steps of (1) drilling holes at two ends of the cut cuboid rock sample to simulate a fracturing shaft, wherein the diameter of each drilled hole is dwellThe depth of the drilling hole is hwellThen carrying out full-size CT scanning on the processed rock sample to obtain an imaging result;
the second step is that: preparation of the test
Pack into an inclosed cavity with a cuboid rock specimen, be equipped with in the cavity with the thermocouple of rock specimen contact be used for heating the rock specimen, the cavity both ends seted up respectively with the communicating fracturing fluid entry of cavity, be called first fracturing fluid entry and second fracturing fluid entry respectively, three kinds of fracturing modes are realized to two entries, are respectively:
in the first mode: fracturing from one of the fracturing fluid inlets, and observing fracture morphology generated by fracturing from the fracturing fluid inlet;
in the second mode: firstly fracturing from one fracturing fluid inlet, then fracturing from the other fracturing fluid inlet, and observing the fracture morphology;
the third mode: simultaneously fracturing from two fracturing fluid inlets, and observing the fracture form;
the third step: three-dimensional axial pressure sigma for rock sample loadingV、σH、σhTo simulate the actual ground stress condition, and after the pressure is stabilized, the heating temperature T of the thermocouple is setrockLoading the initial temperature of the rock sample until the temperature of the rock sample rises to the set temperature TrockThen keeping the temperature for 12 hours;
the fourth step: fracturing test of rock sample by selecting fracturing mode
The following three cases are classified according to the fracturing mode;
first fracturing mode: after the temperature is kept for 12 hours, injecting the fracturing fluid from the inlet of the fracturing fluid to keep the constant temperature TinjThe fracturing fluid is continuously loaded at constant temperature in the injection process, the injection pressure change is recorded, the fracturing transformation is stopped when the injection pressure is suddenly reduced and tends to be stable, and the frequency of acoustic emission events is recorded and recorded as AEASo as to obtain the first fracturing mode and the set temperature T of the samplerockThe fracture formed by the fracturing modification is carried out at the time due to the entering of the fracturing fluidThe temperature field distribution of the rock sample is disturbed.
In the second mode: after the heat preservation is carried out for 12 hours, the constant temperature is T after the injection from a fracturing fluid inletinjThe fracturing fluid is continuously loaded at constant temperature in the injection process, and when the injection pressure is suddenly reduced and tends to be stable, the fracturing modification is stopped, and the frequency of acoustic emission events is recorded; then injecting fracturing fluid with the same constant temperature from another fracturing fluid inlet, continuously loading at constant temperature in the injection process, stopping fracturing reformation after the injection pressure is suddenly reduced and tends to be stable, and recording the times of acoustic emission events so as to obtain the second fracturing mode and the set temperature T of the samplerockCarrying out fracture reconstruction to form a fracture;
third fracturing mode: after the heat preservation is carried out for 12 hours, the constant temperature is T by simultaneously injecting from two fracturing fluid inletsinjThe fracturing fluid is continuously loaded at constant temperature in the injection process, and when the injection pressure is suddenly reduced and tends to be stable, the fracturing modification is stopped, and the frequency of acoustic emission events is recorded; thereby obtaining a third fracturing mode and a set temperature T of the samplerockCarrying out fracture transformation on the formed fracture;
the fifth step: opening a fracturing fluid inlet of the rock sample after the fracturing transformation under the condition of keeping temperature loading, so that fracturing fluid entering the rock sample is quickly volatilized or gasified (influenced by heating temperature), and the fractured rock sample is recovered to the initial set temperature TrockThe method specifically comprises the following steps of:
step 5.1: the rock sample is restored to the initial set temperature T after fracturingrockAfter 2h, injecting a constant-temperature and constant-pressure heat-carrying fluid from one fracturing fluid inlet, enabling the heat-carrying fluid to flow out from the other fracturing fluid inlet after passing through a fractured rock sample, and respectively recording the inlet temperature T of the heat-carrying fluid flowing in and out in the heat extraction process under the condition that the pressure difference exists between the outlet and the inletⅠInlet pressure PⅠInlet flow rate QⅠAnd the outlet temperature TⅡOutlet pressure PⅡOutlet flow rate QⅡCalculating the flow impedance I of the measured rock sampleAAnd miningHeat rate WA；
Step 5.2: stopping temperature loading after the outlet temperature is stable, opening the cover plate to take out the fractured rock sample after the temperature of the rock sample is reduced to the room temperature, and carrying out full-size CT scanning on the rock sample to obtain an imaging result CTA；
And a sixth step: and (3) replacing the rock sample, respectively changing the ground stress condition, the rock temperature, the fracturing fluid, the fracturing discharge capacity, the lithology of the rock sample or the drilling depth, and repeating the steps from two to five so as to obtain the fracture form of the enhanced geothermal system, the communication condition of the fracture to the injection and extraction system and the heat extraction performance of the fracture form of all the rock samples under different stress conditions, rock temperatures, fracturing fluids, fracturing discharge capacities, lithology of the rock sample and drilling depth and fracturing transformation under the same physical and mechanical parameters.
The seventh step: and (4) preparing a rock sample with another physical mechanical parameter again, and repeating the steps from one step to six steps, so as to obtain the fracture morphology of the enhanced geothermal system, the communication condition of the fracture to the injection and production system and the heat extraction performance of the fracture morphology of the rock sample under different physical mechanical parameters under different stress conditions, rock temperatures, fracturing fluids, fracturing discharge capacity, rock sample lithology and drilling depth fracturing transformation.
Further, the flow impedance I of the rock sample measured in step 5.1AThe calculation formula of (2) is as follows:
wherein the content of the first and second substances,
PⅠis the inlet pressure, PⅡIs the outlet pressure in MPa;
q is the flow of the heat-carrying fluid, and the unit is ml/min;
because the heat-carrying fluid is injected in a constant pressure mode during the flow impedance test and the established heat storage transformation chamber is a closed chamber, the inlet flow Q is measured at the momentⅠEqual to the outlet flow QⅡThat is, the flow rate Q of the heat-carrying fluid is equal to the inlet flow rate QⅠOutlet flow QⅡ。
Further, the heat collecting rate W of the rock sample measured in the step 5.1AThe calculation formula of (2) is as follows:
wherein:
w (t) is the enhanced geothermal system heat collecting rate at the time t, and the unit is W;
q (t) is the flow rate of the heat-carrying fluid at the moment t, and the unit is ml/min;
TⅠis the heat-carrying fluid inlet temperature in units;
t is the total heat extraction time from the beginning of the injection of the heat-carrying fluid to the end of the heat extraction experiment, in min;
Cpthe specific heat capacity is constant pressure, unit J/(Kg. K).
The invention has the advantages that:
the experimental method can simulate the communication condition of the cracks or crack networks formed under different fracturing modes (only fracturing of the injection well and fracturing of both the injection well and the extraction well) to the injection well and the extraction well, and can also continue to carry out heat extraction test experiments aiming at the rock samples after fracturing modification, including the liquid production rate, the liquid production temperature and the heat extraction rate of the enhanced geothermal system. In addition, the influences of different stress conditions, rock temperature, fracturing fluid, fracturing discharge capacity, rock sample lithology and the like on the fracturing transformation effect and the communication and heat extraction performance of the fractures on an injection and production system can be analyzed. The method not only provides an effective method for teaching research of the enhanced geothermal system, but also provides a basis for guiding the efficient development of the hot dry rock.
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In order to illustrate the embodiments of the invention more clearly, the drawings that are needed in the description of the embodiments will be briefly described below, it being apparent that the drawings in the following description are only some embodiments of the invention, and that other drawings may be derived from those drawings by a person skilled in the art without inventive effort.
FIG. 1 is a schematic view of a sealed chamber used in the test method of the present invention.
In the figure: 1-a closed cavity, 2-a rock sample, 3-a thermocouple, 4-a first fracturing fluid inlet, 5-a second fracturing fluid inlet and 6-an end cover.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, and the scope of the present invention will be more clearly and clearly defined.
Before the test, firstly A, B, C three groups of cuboid rock samples with the same rock physical and mechanical properties are prepared, the size of the rock sample is 0.3m multiplied by 0.1m, the rock sample can be granite, sandstone, carbonate rock, shale, coal rock and the like, and two ends of the cuboid rock sample are drilled to simulate a fractured shaft, the diameter of the drilled hole is dwellDepth of drilling hole is hwellAnd then carrying out full-size CT scanning on the processed rock sample to obtain imaging results of the rock sample A, the rock sample B and the rock sample C before fracturing.
The first embodiment is as follows:
example one fracturing is performed in a first mode, that is, from one of the first fracturing fluid inlet 4 and the second fracturing fluid inlet 5, the fracture morphology generated from the fracturing of the fracturing fluid inlet is observed, and for the sake of simplifying the description, the fracturing from the first fracturing fluid inlet 4 is described as an example; the method comprises the following specific steps:
the first step is as follows: preparation of the test
A rock sample 2 of the group A rock samples is taken and loaded into a closed cavity 1 shown in figure 1, a thermocouple 3 which is in contact with the rock sample 2 is arranged in the cavity 1 and is used for heating the rock sample, and the left end and the right end of the cavity 1 are respectively provided with a fracturing fluid inlet which is communicated with the cavity and is respectively called as a first fracturing fluid inlet 4 and a second fracturing fluid inlet 5; the inner ring of the cavity 1 is provided with a sealing gasket to realize a sealing test, and the end cover 6 at the left end of the cavity is detachable to facilitate the taking and placing of rock samples;
the second step is that: three-dimensional axial pressure sigma for loading rock sample 2V、σH、σhTo simulate the actual stress conditions, after the pressure has stabilized, the tube is openedThe heating temperature T of the thermocouple 3 is initially setrockThe rock sample 2 is loaded at the starting temperature until the temperature of the rock sample 2 rises to the set temperature TrockThen keeping the temperature for 12 hours;
the third step: selecting a fracturing mode from a first fracturing fluid inlet 4 to perform a fracturing test on the rock sample 2
When the temperature of the rock sample 2 rises to the set temperature TrockThen keeping the temperature for 12h, injecting the constant temperature T from the first fracturing fluid inlet 4injThe distilled water is used as fracturing fluid, the constant temperature loading is continuously carried out in the injection process, the pressure change is recorded, the fracturing transformation is stopped when the injection pressure is suddenly reduced and tends to be stable, the frequency of the acoustic emission event is recorded through the acoustic generation probe and is recorded as AEASo as to obtain a sample 2 only at the first fracturing fluid inlet 4 and at the set temperature TrockAnd (3) carrying out fracturing modification on the formed crack, wherein the temperature field distribution of the fracturing fluid entering the rock sample is disturbed.
The fourth step: opening a first fracturing fluid inlet 4 and a second fracturing fluid inlet 5 of the fractured and transformed rock sample 2 under the condition of keeping the temperature loading, so that the fracturing fluid entering the rock sample 2 is quickly volatilized or gasified, and the fractured rock sample 2 is recovered to the initial temperature TrockAnd then carrying out fracture communication evaluation and heat extraction test of the post-fracturing enhanced geothermal system, and specifically comprising the following steps of:
step 4.1: restoration of the fractured rock sample 2 to the initial temperature TrockAfter 2h, the first fracturing fluid inlet 4 is used as a heat-carrying fluid inlet, the second fracturing fluid inlet 5 is used as a heat-carrying fluid outlet, namely, the heat-carrying fluid with constant temperature and constant pressure is injected from the first fracturing fluid inlet 4, the heat-carrying fluid flows out from the second fracturing fluid inlet 5 after passing through a fractured rock sample, namely, in the process, the inlet temperature T of the heat-carrying fluid flowing in and out in the heat extraction process under the condition that the pressure difference exists between the outlet and the inlet is recorded respectivelyⅠInlet pressure PⅠInlet flow rate QⅠAnd the outlet temperature TⅡOutlet pressure PⅡOutlet flow rate QⅡCalculating the flow impedance I of the measured rock sampleAAnd the heat collecting rate WAThe calculation formula is shown in the technical scheme, and the calculation formula is not shown in the technical schemeRestateing;
step 4.2: stopping temperature loading after the outlet temperature is stable, opening the cover plate to take out the fractured rock sample after the temperature of the rock sample 2 is reduced to the room temperature, and carrying out full-size CT scanning on the rock sample 2 to obtain an imaging result CT after fracturing modification of the rock sample 2A；
The fifth step: another rock sample in the group A is taken, and the steps 1-4 are repeated, so that test results of all rock samples in the group A are obtained; analyzing all rock sample acoustic emission events of the group A and damage of full-size CT scanning results before and after fracturing on cuboid rock samples, thereby obtaining fracture forms of the group A rock samples which are fractured from only one fracturing fluid inlet; judging the communication condition of the fracture to an injection-production system in a fracturing mode only from one fracturing fluid inlet according to the flow impedance of the fluid after reservoir modification and by combining the acoustic emission event with the CT scanning image result; and according to the heat extraction rate, obtaining the heat extraction performance of the fracture form in the first fracturing mode.
Example two
Taking the rock samples of the group B to carry out the test of the second embodiment, wherein the second embodiment adopts a second fracturing mode, namely, firstly fracturing from one fracturing fluid inlet, then fracturing from the other fracturing fluid inlet, and observing the fracture form; for simplicity of description, the example of fracturing first from the first fracturing fluid inlet 4 and then from the second fracturing fluid inlet 5 is described. The specific steps are different from the first embodiment only in the fracturing mode, and are reflected in the third step.
The third step: when the temperature of the rock sample rises to the set temperature TrockThen keeping the temperature for 12h, injecting the constant temperature T from the first fracturing fluid inlet 4injThe fracturing fluid is continuously loaded at constant temperature in the injection process, and when the injection pressure is suddenly reduced and tends to be stable, the fracturing modification is stopped, and the frequency of acoustic emission events is recorded; then injecting fracturing fluid with the same constant temperature from a second fracturing fluid inlet 5, continuously loading at constant temperature in the injection process, stopping fracturing transformation after the injection pressure is suddenly reduced and tends to be stable, and recording the times of acoustic emission events so as to obtain the second fracturing mode and the set temperature T of the samplerockCarrying out fracture reconstruction to form a fracture;
EXAMPLE III
Taking C group rock samples to carry out the third test of the embodiment, wherein the third fracturing mode is adopted in the third test of the embodiment, namely, the first fracturing fluid inlet 4 and the second fracturing fluid inlet 5 are fractured simultaneously, the fracture morphology is observed, the specific steps are basically the same as the first test of the embodiment, and the difference is in the fracturing mode of the third step, and the specific steps are as follows:
after the heat preservation is carried out for 12 hours, the constant temperature T is injected from the first fracturing fluid inlet 4 and the second fracturing fluid inlet 5 simultaneouslyinjThe fracturing fluid is continuously loaded at constant temperature in the injection process, and when the injection pressure is suddenly reduced and tends to be stable, the fracturing modification is stopped, and the frequency of acoustic emission events is recorded; thus obtaining sample 2 in the third fracturing mode and the set temperature TrockAnd carrying out fracture reconstruction on the formed fracture.
The invention can optimize the optimal fracturing mode by comparing the fracture form obtained by adopting different fracturing modes, the communication condition of the fracture to an injection-production system and the heat extraction performance under the obtained fracture form, and plays a guiding role in the high-efficiency development of the dry-hot rock.
The three embodiments only list the fracture forms of the rock samples with the same physical and mechanical parameters under different fracture test modes, the communication conditions of the fractures to an injection and production system and the heat extraction performance of the obtained fracture forms. In practice, one fracturing mode can be fixed, and the physical mechanical parameters, the ground stress condition, the rock temperature, the fracturing fluid, the fracturing discharge capacity, the lithology of the rock sample or/and the drilling depth of the rock sample are changed, or other one or more conditions are fixed, so that the rock samples with different physical mechanical parameters can be tested under different stress conditions, fracturing modes, fracture forms of an enhanced system formed by fracturing transformation of the rock temperature, the fracturing fluid, the fracturing discharge capacity, the lithology of the rock sample and the drilling depth, the communication condition of the fracture to the injection and extraction system, and the heat extraction performance of the fracture form. Therefore, the scope of the present invention is not limited to the embodiments, and any changes or substitutions which are not thought of through the inventive work should be included in the scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.
Claims (3)
1. An enhanced geothermal system crack communication evaluation and heat extraction test testing method is characterized by comprising the following steps of:
the first step is as follows: preparing a rock sample to be tested
Cutting a plurality of cuboid rock samples with the same physical and mechanical property parameters, and drilling holes at two ends of the cut cuboid rock samples to simulate a fracturing shaft, wherein the diameter of each hole is dwellThe depth of the drilling hole is hwellThen carrying out full-size CT scanning on the processed rock sample to obtain an imaging result;
the second step is that: preparation of the test
Pack into an inclosed cavity with a cuboid rock specimen, be equipped with in the cavity with the thermocouple of rock specimen contact be used for heating the rock specimen, the cavity both ends seted up respectively with the communicating fracturing fluid entry of cavity, be called first fracturing fluid entry and second fracturing fluid entry respectively, three kinds of fracturing modes are realized to two entries, are respectively:
in the first mode: fracturing from one of the fracturing fluid inlets, and observing fracture morphology generated by fracturing from the fracturing fluid inlet;
in the second mode: firstly fracturing from one fracturing fluid inlet, then fracturing from the other fracturing fluid inlet, and observing the fracture morphology;
the third mode: simultaneously fracturing from two fracturing fluid inlets, and observing the fracture form;
the third step: three-dimensional axial pressure sigma for rock sample loadingV、σH、σhTo simulate the actual ground stress condition, and after the pressure is stabilized, the heating temperature T of the thermocouple is setrockLoading the initial temperature of the rock sample until the temperature of the rock sample rises to the set temperature TrockThen keeping the temperature for 12 hours;
the fourth step: fracturing test of rock sample by selecting fracturing mode
The following three cases are classified according to the fracturing mode;
first fracturing mode: after the temperature is kept for 12 hours, injecting the fracturing fluid from the inlet of the fracturing fluid to keep the constant temperature TinjIs fracturedContinuously loading fluid at constant temperature in the injection process, recording the change of injection pressure, stopping fracturing transformation when the injection pressure is suddenly reduced and tends to be stable, recording the times of acoustic emission events, and recording as AEASo as to obtain the first fracturing mode and the set temperature T of the samplerockThen, carrying out fracturing modification on the formed crack, wherein the distribution of the temperature field of the fracturing fluid entering the rock sample is disturbed;
in the second mode: after the heat preservation is carried out for 12 hours, the constant temperature is T after the injection from a fracturing fluid inletinjThe fracturing fluid is continuously loaded at constant temperature in the injection process, and when the injection pressure is suddenly reduced and tends to be stable, the fracturing modification is stopped, and the frequency of acoustic emission events is recorded; then injecting fracturing fluid with the same constant temperature from another fracturing fluid inlet, continuously loading at constant temperature in the injection process, stopping fracturing reformation after the injection pressure is suddenly reduced and tends to be stable, and recording the times of acoustic emission events so as to obtain the second fracturing mode and the set temperature T of the samplerockCarrying out fracture reconstruction to form a fracture;
third fracturing mode: after the heat preservation is carried out for 12 hours, the constant temperature is T by simultaneously injecting from two fracturing fluid inletsinjThe fracturing fluid is continuously loaded at constant temperature in the injection process, and when the injection pressure is suddenly reduced and tends to be stable, the fracturing modification is stopped, and the frequency of acoustic emission events is recorded; thereby obtaining a third fracturing mode and a set temperature T of the samplerockCarrying out fracture transformation on the formed fracture;
the fifth step: opening a fracturing fluid inlet of the rock sample after the fracturing transformation under the condition of keeping temperature loading, so that fracturing fluid entering the rock sampleIs influenced by heating temperatureQuickly volatilizes or gasifies to make the fractured rock sample recover to the initial set temperature TrockThe method specifically comprises the following steps of:
step 5.1: the rock sample is restored to the initial set temperature T after fracturingrockAfter 2h, injecting a constant-temperature and constant-pressure heat-carrying fluid from one fracturing fluid inlet, and allowing the heat-carrying fluid to flow out from the other fracturing fluid inlet after the heat-carrying fluid passes through the fractured rock sampleRecording the inlet temperature T of the heat-carrying fluid flowing in and out of the heat extraction process in the presence of a pressure difference between the outlet and the inletⅠInlet pressure PⅠInlet flow rate QⅠAnd the outlet temperature TⅡOutlet pressure PⅡOutlet flow rate QⅡCalculating the flow impedance I of the measured rock sampleAAnd the heat collecting rate WA；
Step 5.2: stopping temperature loading after the outlet temperature is stable, opening the cover plate to take out the fractured rock sample after the temperature of the rock sample is reduced to the room temperature, and carrying out full-size CT scanning on the rock sample to obtain an imaging result CTA；
And a sixth step: changing the rock sample, respectively changing the ground stress condition, the rock temperature, the fracturing fluid, the fracturing discharge capacity, the lithology of the rock sample or the drilling depth, and repeating the steps from two to five so as to obtain the fracture form of the enhanced geothermal system, the communication condition of the fracture to the injection and extraction system and the heat extraction performance of the fracture form of all the rock samples under different stress conditions, rock temperatures, the fracturing fluid, the fracturing discharge capacity, the lithology of the rock sample and the drilling depth under the same physical and mechanical parameters;
the seventh step: and (4) preparing a rock sample with another physical mechanical parameter again, and repeating the steps from one step to six steps, so as to obtain the fracture morphology of the enhanced geothermal system, the communication condition of the fracture to the injection and production system and the heat extraction performance of the fracture morphology of the rock sample under different physical mechanical parameters under different stress conditions, rock temperatures, fracturing fluids, fracturing discharge capacity, rock sample lithology and drilling depth fracturing transformation.
2. The method of claim 1, wherein the flow impedance I of the rock sample measured in step 5.1 isAThe calculation formula of (2) is as follows:
in the formula:
PⅠis the inlet pressure, PⅡIs the outlet pressure in MPa;
q is the flow rate of the heat-carrying fluid in ml/min.
3. The method for testing enhanced geothermal system fracture communication evaluation and heat extraction test of claim 1 or claim 2, wherein the heat extraction rate W of the rock sample measured in step 5.1AThe calculation formula of (2) is as follows:
wherein:
w (t) is the enhanced geothermal system heat collecting rate at the time t, and the unit is W;
q (t) is the flow rate of the heat-carrying fluid at the moment t, and the unit is ml/min;
TⅠis the heat-carrying fluid inlet temperature in units;
t is the total heat extraction time from the beginning of the injection of the heat-carrying fluid to the end of the heat extraction experiment, in min;
Cpthe specific heat capacity is constant pressure, unit J/(Kg. K).
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