CN114354683A - High/low temperature rock mass enhanced heat transfer and power disturbance test method under multi-field loading - Google Patents
High/low temperature rock mass enhanced heat transfer and power disturbance test method under multi-field loading Download PDFInfo
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- CN114354683A CN114354683A CN202210019202.5A CN202210019202A CN114354683A CN 114354683 A CN114354683 A CN 114354683A CN 202210019202 A CN202210019202 A CN 202210019202A CN 114354683 A CN114354683 A CN 114354683A
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Abstract
The invention discloses a method for testing the intensified heat transfer and power disturbance of a high/low temperature rock mass under multi-field loading, which mainly comprises the steps of heating a dry hot rock mass by a heating module to form a high-temperature rock mass, injecting a low-temperature fluid into the high-temperature rock mass, and changing the pore structure of the high-temperature rock mass under the action of low-temperature induced thermal stress and phase change of the injected fluid; the method comprises the steps of utilizing a refrigeration module to refrigerate natural gas hydrate to obtain low-temperature natural gas hydrate, then injecting high-temperature fluid into the low-temperature natural gas hydrate, enabling a cold rock body to be heated and expanded in the heat injection process, and enabling the hydrate to be heated and decomposed to cause pore structure change, so that the enhanced heat transfer and dynamic disturbance analysis and test of the rock body under the multi-field effect in the reservoir production increasing process are achieved. The method solves the problem of low interference loading of a heat source, a cold source and mechanical conditions, establishes the relation between a temperature field/chemical field → a stress field → a damage field under the loading of multiple physical fields, and realizes the technical effects of the phase change and the pore structure change on the rock mass enhanced heat exchange and dynamic disturbance test analysis.
Description
Technical Field
The invention relates to a reservoir transformation process under the loading conditions of temperature, stress and chemical reaction in unconventional geological energy, in particular to a test method for testing the enhanced heat transfer and dynamic disturbance of a high/low temperature rock mass under the loading condition of a multi-physical field.
Background
Under the influence of energy structure optimization, unconventional geological energy sources such as geothermal energy, natural gas hydrate and the like are more and more concerned. Although the hot dry rock reservoir has abundant geothermal resources, the high-temperature heat energy of the hot dry rock reservoir is difficult to extract to the ground due to large burial depth and low porosity and low permeability. The research shows that the injection of low-temperature fluid into high-temperature rock can promote the formation of a seam network of dry hot rock, thereby improving the development effect of a subsequent enhanced geothermal system. Similarly, natural gas hydrate reservoirs have low temperature and high pressure characteristics, and heat injection or depressurization methods are generally adopted if the natural gas production speed is to be accelerated. It can be seen that both hot dry rock and natural gas hydrate reservoirs involve reservoir stimulation modification under temperature acceleration.
Reservoir stimulation for hot dry rock and natural gas hydrate is mostly focused on damage fracture distribution (including fractures caused by thermal stress fracturing or hydraulic fracturing) of rock under a series of stimulation measures at present. But rarely pay attention to the heat exchange law and the dynamic response law of the rock before fracture damage.
However, in the reservoir production increasing process of high and low temperature rock mass under the acceleration of temperature, the rock mass is damaged and cracked by the direct influence of the heat exchange and the dynamic disturbance of the rock mass on the heat exchange and the dynamic disturbance of the rock mass (for example, the rock mass is heated to generate phase change in the process of injecting cold into the hot dry rock, the pore structure of the rock mass is changed under the action of low-temperature induced thermal cracking, the rock mass is heated to expand in the process of injecting heat into the low-temperature natural gas hydrate, and the pore structure is changed due to the temperature rise and decomposition of the hydrate). In view of the above, in order to promote the reservoir production of unconventional rock (specifically, high or low temperature rock) through temperature and to clarify the efficient transformation scheme and fracturing mechanism of high and low temperature rock, it is necessary to first explore the heat exchange and power disturbance law of high and low temperature rock under the action of multiple physical fields. At present, the research on the enhanced heat exchange and dynamic disturbance of the high and low temperature rock under the loading of multiple physical fields is rarely reported.
In addition, the prior art lacks low interference loading on a heat source, a cold source and mechanical conditions, and cannot effectively establish the relation between a temperature field/a chemical field (phase change) → a stress field → a damage field under the loading of multiple physical fields.
Disclosure of Invention
In order to explore the heat exchange and power disturbance rule of the high and low temperature rock mass under the action of multiple physical fields and provide basis for formulating a high-efficiency transformation scheme of the high and low temperature rock mass and defining a fracturing mechanism, the invention provides a high/low temperature rock mass enhanced heat transfer and power disturbance test method under multi-field loading, establishes the relation between a temperature field/a chemical field (phase change) → a stress field → a damage field under multi-physical field loading, solves the technical problem of low interference loading of high temperature, low temperature and mechanics, and realizes the technical effects of phase change, thermal stress, chemical reaction and pore structure change on rock mass enhanced heat exchange and power disturbance test analysis.
In order to achieve the purpose, the invention adopts the technical scheme that:
a high/low temperature rock mass enhanced heat transfer and dynamic disturbance test method under multi-field loading is characterized by comprising two test methods of high temperature rock mass enhanced heat transfer and dynamic disturbance test and low temperature rock mass enhanced heat transfer and dynamic disturbance test; wherein:
the test method for the enhanced heat transfer and power disturbance test of the high-temperature rock mass comprises the following steps:
the first step is as follows: obtaining physical and mechanical parameters of a rock sample to be tested
1.1, cutting a plurality of cylindrical rock samples (such as granite) into two groups, wherein one group is used for determining basic physical parameters of rocks, and the other group is used as a rock sample to be tested;
1.2, determining basic physical property parameters of the rock through tests such as uniaxial compression, triaxial compression, permeability test and the like, wherein the tests comprise the following steps: permeability, porosity, thermal conductivity, tensile and compressive strength, Young's modulus, Poisson's ratio, and the like;
1.3, drilling the end face of the rock sample to be tested, fixing the drilling diameter and depth of the rock sample to be tested in order to control the injection position and the heat exchange area of the injected fluid, and carrying out CT scanning on the rock sample to be tested after drilling to obtain the imaging and porosity distribution results of the rock;
the second step is that: fabrication of test device modules
The test device module comprises a rock sample heating module and a low-temperature fluid injection module, wherein: the rock sample heating module is formed by sequentially overlapping an upper metal plate, a heat insulation material, a heating sheet and a lower metal plate from top to bottom; the low-temperature fluid injection module comprises a heat-insulation shell and a low-temperature fluid injection pipeline, wherein the low-temperature fluid injection pipeline penetrates through the heat-insulation shell, is exposed out of the upper part of the heat-insulation shell and then extends into a drill hole of a rock sample, and a pressure-resistant sealing measure is adopted;
the third step: preparation of the test
3.1, sequentially superposing and installing the rock sample heating module, the rock sample to be tested and the low-temperature fluid injection module between an upper pressure head and a lower pressure head of a uniaxial compression tester from top to bottom, wherein the rock sample heating module and the low-temperature fluid injection module provide pressure in the vertical direction by the uniaxial compression tester;
3.2: placing a thermal imager on one side of the rock sample; attaching stress strain gauges to different positions on the rock surface of the rock sample to be tested, and connecting the stress strain gauges with the stress strain gauges;
3.3: setting the heating temperature of the heating module of the rock sample, and selecting low-temperature injection fluid (water and liquid CO)2Liquid N2) And setting the temperature of the cryogenic fluid, opening the axial pressure control unit, and setting the loading axial pressure σV；
3.4: the heat insulation plate is buckled on the assembled heating module, the rock sample to be tested and the low-temperature fluid injection module, so that the combination of the three is insulated from the outside;
the fourth step: the test of the enhanced heat transfer and dynamic disturbance in the cold injection process of high-temperature rock (also called hot dry rock) is carried out
4:1: heating a rock sample to be tested by using a rock sample heating module, observing the surface temperature of a rock body by using a thermal imager until the surface temperature is uniformly distributed, and injecting low-temperature fluid into a drill hole of the rock sample to be tested;
due to the mechanical disturbance effect on the rock involved in the cryogenic fluid injection process of the multi-physical fields, the multi-physical fields include: thermal stress caused by the temperature difference between the low-temperature injection fluid and the high-temperature rock, phase change of the low-temperature fluid under the action of high temperature and chemical reaction of the low-temperature fluid and the high-temperature rock under the action of long time are required, so that in the process of injecting the low-temperature fluid, the following steps are required:
recording mechanical disturbance conditions of rock masses at different positions at different times through stress strain gauges arranged on the surface of the rock sample, and analyzing a power disturbance rule caused in the migration process of low-temperature injection fluid in the hot dry rock by combining stress evolution at different positions on the surface of the rock sample; recording the distribution of the temperature fields on the surface of the rock sample at different moments by a placed thermal imager, and analyzing the influence rule of the phase change of the low-temperature fluid and the change of the pore structure of the rock mass on the enhanced heat transfer by combining the distribution and the evolution of the temperature fields at different positions on the surface of the rock;
the fifth step: carrying out damage test after high-temperature rock (dry and hot rock) is injected and cooled
After the heat transfer enhancement and power disturbance test of the high-temperature dry and hot rock in the cooling injection process is finished, taking a rock sample out of the test device, carrying out CT scanning to obtain imaging and porosity distribution results after the permeability enhancement transformation, comparing the imaging and porosity distribution results with the CT scanning results obtained in the first step, and analyzing the distribution rule of cracks and pores after the dry and hot rock is cooled;
and a sixth step: and (3) replacing the rock sample to be tested, changing the axial pressure, the rock temperature, the type of the injected fluid, the temperature of the injected fluid, the injection flow rate and the type of the rock respectively, and repeating the steps from two to five so as to obtain rock mass enhanced heat transfer, stress-strain rules and fracture pore distribution rules in the processes of cold injection and yield increase of different axial pressure conditions, rock temperatures, injected fluids, injection temperatures, injection flow rates and rock types.
Further: in order to realize the tight fit of all components of the rock sample heating module, the upper metal plate, the heat insulation material, the heating sheet and the lower metal plate of the rock sample heating module are overlapped into a whole in an inserting mode. Specifically, the metal plate, the heat insulating material and the heating plate are all provided with jacks, the upper surface of the lower metal plate is provided with inserting strips corresponding to the jacks, and the inserting strips of the lower metal plate sequentially penetrate through the heating plate, the heat insulating material and the upper metal plate to stack all the components together.
Further: in order to prevent the heating module, the rock sample to be tested and the low-temperature fluid injection module from being dislocated in the experimental process, the upper surface of an upper metal plate of the rock sample heating module is set to be in a U-shaped mode, and the bottom of the low-temperature fluid injection module is set to be in an inverted U-shaped mode.
Further: types of cryogenic fluids include water, liquid CO2Or liquid N2The injection temperature is-80 deg.C, -40 deg.C, -20 deg.C, 0 deg.C or 20 deg.C), and the injection flow rate is 2ml/min, 4ml/min, 6ml/min or 8 ml/min. The temperature injection temperature and the injection flow rate are only given a selection range and are not in one-to-one correspondence, and the same injection temperature can correspond to different injection flow rates and vice versa in the specific operation process.
For heat injection stimulation of a low temperature natural gas hydrate reservoir, the method comprising:
the first step is as follows: obtaining physical and mechanical parameters of a rock sample to be tested
1.1, synthesizing two groups of natural gas hydrate rock samples under the same condition at low temperature, prefabricating drill holes with certain diameter and depth in the synthesis process (fixing the diameter and the depth of the drill holes of the test rock sample for controlling the injection position of injection fluid and the heat exchange area), and carrying out CT scanning on the rock sample to be tested, which is prefabricated with the drill holes, to obtain the imaging and porosity distribution results of the rock; and the other group of the basic physical parameters of the rock are determined by tests such as uniaxial compression, triaxial compression, permeability test and the like, and the tests comprise the following steps: permeability, porosity, thermal conductivity, tensile and compressive strength, Young's modulus, Poisson's ratio, and the like;
the second step is that: fabrication of test device modules
The test device module include rock sample refrigeration module and high temperature fluid injection module, wherein: the rock sample refrigeration module consists of a shell and a coil pipe arranged in the shell, wherein the contact surface of the shell and the rock sample to be tested is a heat conduction surface, and the rest surfaces are heat preservation and heat insulation surfaces; the high-temperature fluid injection module consists of a heat insulation box body and a high-temperature fluid injection pipeline arranged in the heat insulation box body, wherein an outlet of the high-temperature fluid injection pipeline is exposed from the bottom of the heat insulation box body and extends into a drill hole of a rock sample to be tested and is sealed by heat insulation sealant;
the third step: preparation of the experiment
3.1: sequentially overlapping and installing the high-temperature fluid injection module, the rock sample to be tested and the rock sample refrigeration module between an upper pressure head and a lower pressure head of the uniaxial compression tester from top to bottom, wherein the rock sample refrigeration module and the connected rock sample-high-temperature fluid injection module are provided with pressure in the vertical direction by the uniaxial compression tester;
3.2: placing a thermal imager at one side of the rock sample, attaching stress strain gauges to different positions on the rock surface of the rock sample to be tested, and connecting the stress strain gauges with the thermal imager;
3.3: setting the refrigeration temperature of the rock sample refrigeration module, and selecting high-temperature injection fluid (water, supercritical CO)2Etc.), and setting the temperature of the high-temperature fluid, turning on the axial pressure control unit, and setting the loading axial pressure;
3.4: the insulation board is buckled on the assembled refrigeration module, the rock sample to be tested and the high-temperature fluid injection module, so that the combination of the refrigeration module, the rock sample to be tested and the high-temperature fluid injection module is insulated from the outside;
the fourth step: enhanced heat transfer and power disturbance test for low-temperature natural gas hydrate reservoir heat injection process
4.1: refrigerating a rock sample to be tested by utilizing heat conduction of a rock sample refrigerating module, observing the surface temperature of a rock body through a thermal imager until the surface temperature is uniformly distributed, and injecting high-temperature fluid into the rock sample to be tested;
due to the mechanical disturbance effect on the rock during the high-temperature fluid injection process involving multiple physical fields, the multiple physical fields include: thermal stress caused by the temperature difference between the high-temperature injection fluid and the low-temperature sample bedrock and natural gas hydrate decomposition caused by heat injection, so that in the high-temperature fluid injection process, the following requirements are met:
recording mechanical disturbance conditions of rock masses at different times and different positions through stress strain gauges arranged on the surface of the rock sample, and recording the distribution of temperature fields on the surface of the rock sample at different times through a placed thermal imager; analyzing the influence rule of the change of the pore structure caused by the decomposition of hydrate and thermal cracking in the heat injection process on the enhanced heat transfer by combining the distribution and the evolution of temperature fields at different positions on the surface of the rock; analyzing a power disturbance rule caused by the migration process of the high-temperature injection fluid in the low-temperature hydrate by combining the stress evolution of different positions on the surface of the rock sample;
the fifth step: carrying out damage test after low-temperature natural gas hydrate heat injection
After the heat injection process of the low-temperature natural gas hydrate is finished and the heat transfer enhancement and dynamic disturbance test are carried out, taking a sample out of the test device and carrying out CT scanning to obtain imaging and porosity distribution results after the permeation enhancement modification; comparing with the CT scanning result obtained in the first step, and analyzing the distribution rule of fractures and pores of the low-temperature natural gas hydrate reservoir after heat injection;
and a sixth step: and (3) replacing the rock sample to be tested, changing the axial pressure, the sample temperature, the injection fluid temperature and the injection flow rate respectively, and repeating the steps from two to five so as to obtain the rock mass enhanced heat transfer, stress-strain rule and fracture pore distribution rule in the natural gas hydrate heat injection production increasing process under different axial pressure conditions, sample temperatures, injection temperatures and injection flow rates.
Further: in order to prevent the experimental process, the dislocation takes place for rock specimen refrigeration module, the rock specimen of waiting to test and high temperature fluid injection module, the bottom of rock specimen refrigeration module establish into the type of falling U, the top of high temperature fluid injection module establish into the type of U mode.
The invention has the advantages that:
the heating module is utilized to heat the dry hot rock to form the high-temperature rock mass, the low-temperature fluid is injected into the high-temperature rock mass, and the pore structure of the high-temperature rock mass is changed under the action of low-temperature induced thermal stress and phase state change of the injected fluid; the method comprises the steps of utilizing a refrigeration module to refrigerate natural gas hydrate to obtain low-temperature natural gas hydrate, then injecting high-temperature fluid into the low-temperature natural gas hydrate, enabling a cold rock body to be heated and expanded in a heat injection process, enabling the hydrate to be heated and decomposed to cause pore structure change, and achieving the enhanced heat transfer and dynamic disturbance analysis test of the rock body under the action of multiple physical fields in the reservoir production increasing process, wherein the multiple physical fields comprise: ground stress, thermal stress, phase change, and chemical reaction.
The invention solves the problem of low interference loading of a heat source, a cold source and mechanical conditions, establishes the relation between a temperature field/a chemical field (phase change) → a stress field → a damage field under the loading of multiple physical fields, and realizes the technical effects of heat stress, phase change, chemical reaction and pore structure change on rock mass enhanced heat exchange and dynamic disturbance test analysis.
The invention not only provides an effective method for teaching and scientific research of novel unconventional geological energy hot dry rock and natural gas hydrate, but also provides powerful guarantee for guiding the efficient development of the hot dry rock and natural gas hydrate reservoir.
Drawings
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 diagram of a device for testing the heat transfer and dynamics of a rock mass under the action of multiple physical fields, which is used in the test method of the invention;
figure 2 is a schematic view of a cryogenic fluid injection module;
FIG. 3 is a schematic view of a rock sample refrigeration module;
FIG. 4 is a schematic view of a rock sample heating module;
fig. 5 is a schematic view of a high temperature fluid injection module.
In the figure: 1-axial pressure control interface, 2-axial pressure oil cylinder, 3-upper pressure head, 4-rock sample heating module or high-temperature fluid injection module, 5-rock sample to be tested, 6-low-temperature fluid injection module or rock sample refrigeration module, 7-lower pressure head, 8-assembled thermal insulation plate, 9-thermal imager, 10-stress strain gauge, 11-low-temperature fluid injection pipeline, 12-coil pipe, 13-lower metal plate, 14-heating plate, 15-thermal insulation material, 16-upper metal plate, 17-high-temperature fluid injection pipeline, 18-jack, 19-plug strip, 20-low-temperature fluid thermal insulation shell, 21-high-temperature fluid thermal insulation shell and 22-heat conduction contact surface.
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.
The first embodiment is as follows:
the embodiment relates to cold injection fluid permeation enhancement modification on high-temperature rock, namely a rock sample heating module shown in a figure 4 is installed at a position 4 in the figure 1, a low-temperature fluid injection module shown in a figure 2 is installed at a position 6 in the figure 1, and then rock heat exchange rules, dynamic response and cracking tests caused by multi-physical field action in the hot dry rock cold injection permeation enhancement modification process are further performed, and the concrete steps are as follows:
the first step is as follows: obtaining physical and mechanical parameters of a rock sample to be tested
Cutting a group of cylindrical rock samples, wherein the size of the rock samples is phi 50mm multiplied by 100mm, the rock samples can be granite, sandstone, carbonate rock and the like, the rock samples are divided into two groups, one group is used for carrying out tests such as uniaxial compression, triaxial compression, permeability test and the like to determine basic physical property parameters of the rock, the other group is used as a rock sample 5 to be tested, drilling is carried out on the end face of the rock sample 5 to be tested, the drilling diameter and the drilling depth of the test rock sample are fixed for controlling the injection position of an injection fluid and the heat exchange area, CT scanning is carried out on the rock sample 5 to be tested, and imaging and porosity distribution results of the rock are obtained;
the second step is that: test device module installation
The test device module comprises a rock sample heating module 4 shown in figure 4 and a cryogenic fluid injection module 6 shown in figure 2.
Referring to fig. 4, the rock sample heating module 4 is formed by sequentially stacking an upper metal plate 16, a heat insulation material 15, a heating sheet 14 and a lower metal plate 13 from top to bottom; the upper metal plate 16, the heat insulation material 15 and the heating sheet 14 are all provided with jacks 18, the upper surface of the lower metal plate 13 is provided with inserting strips 19 corresponding to the jacks, and the inserting strips 19 of the lower metal plate 13 sequentially penetrate through the jacks 18 of the heating sheet, the heat insulation material and the upper metal plate to stack all components together; as can be seen from the figure, the top surface of the upper metal plate 16 is formed in a U-shape in order to facilitate the mounting of the rock sample heating module on the axial upper ram 3 of the uniaxial compression tester
Referring to fig. 2, the cryogenic fluid injection module comprises a cryogenic fluid insulation shell 20 and a cryogenic fluid injection pipeline 11, wherein an outlet of the cryogenic fluid injection pipeline 11 is exposed from the upper part of the cryogenic fluid insulation shell 20 and then extends into a drilled hole of the rock sample 5 to be tested, and pressure-resistant sealing measures are taken;
during assembly, a rock sample heating module 4 and a rock sample 5-low-temperature fluid injection module 6 of a rock sample to be tested which are connected are arranged between an upper pressure head 3 and a lower pressure head 7 of a uniaxial compression tester from top to bottom, the uniaxial compression tester provides loading force by a shaft pressure oil cylinder 2, the shaft pressure oil cylinder 2 is connected with an axial pressure control unit (not shown in the figure) through a shaft pressure control interface 1, and the rock sample heating module 4 is connected with a temperature control unit (not shown in the figure);
the third step: preparation of the experiment
Placing a thermal imager 9 on one side of the rock sample;
attaching stress strain gauges to different positions on the surface of the rock sample 5 to be tested, wherein all the stress strain gauges are connected with a stress strain gauge 10;
opening a temperature control unit of the rock sample heating module 4, and setting a heating temperature;
selection of low temperature injection fluids (water, liquid CO)2Liquid N2) And setting the temperature of the cryogenic fluid;
opening an axial pressure control unit of the uniaxial compression tester, and setting loading axial pressure;
finally, the assembled heat-insulation plate 8 with the opening is buckled on the assembled rock sample heating module 4, the rock sample 5 to be tested and the low-temperature fluid injection module 6, so that the combined body of the three is heat-insulated from the outside;
adjusting the angle of the thermal imager 9 to enable the thermal imager to observe the rock through the hole of the insulation board 8;
the fourth step: test for carrying out enhanced heat transfer and dynamic disturbance in high-temperature rock (hot dry rock) injection cooling process
Heating a rock sample 5 to be tested by using a rock sample heating module 4 (in order to prevent thermal cracking caused in the heating process, the heating rate is controlled within 5 ℃/min), observing the surface temperature of a rock body to be uniformly distributed (approximately requiring heat preservation for 12h) by using a thermal imager 9, and injecting a low-temperature fluid into a drill hole of the rock sample 5 to be tested through a low-temperature fluid injection pipeline 11; the mechanical disturbance effect on the rock during the cryogenic fluid injection process involving multiple physical fields, the multiple physical fields comprising: thermal stress caused by the temperature difference between low-temperature injection fluid and high-temperature rock, phase change of low-temperature fluid under the action of high temperature and chemical reaction of low-temperature fluid and high-temperature rock under the action of long time are recorded by stress strain gauges arranged on the surface of the rock sample 5 to be tested, and the distribution of the surface temperature field of the rock sample at different times is recorded by a thermal imager 9;
analyzing the influence rule of the phase change of the low-temperature fluid and the change of the pore structure of the rock mass on the enhanced heat transfer in the cold injection process by combining the distribution and the evolution of temperature fields at different positions on the surface of the rock; analyzing a power disturbance rule caused by the migration process of the low-temperature injection fluid in the hot dry rock by combining the stress evolution of different positions on the surface of the rock sample;
the fifth step: carrying out damage test after high-temperature rock (dry and hot rock) is injected and cooled
After the enhanced heat transfer and dynamic disturbance test of the injection cooling process of the high-temperature dry hot rock is finished, taking a rock sample out of the test device and carrying out CT scanning to obtain imaging and porosity distribution results after the infiltration enhancement modification;
comparing with the CT scanning result obtained in the first step, and analyzing the distribution rule of cracks and pores after the hot dry rock is subjected to injection cooling;
and a sixth step: and (3) replacing the rock sample 5 to be tested, changing the axial pressure, the rock temperature, the type of the injected fluid, the temperature of the injected fluid, the injection flow velocity and the type of the rock, and repeating the steps from two to five for multiple times, thereby obtaining the heat exchange rule, the stress-strain rule and the fracture pore distribution rule of the rock under different axial pressure conditions, rock temperatures, injected fluids, injection temperatures, injection flow velocities and the rock type cold injection yield increase process (accompanied by multi-physical field disturbance).
Example two:
the second embodiment is to perform heat injection fluid permeation enhancement modification on a low-temperature natural gas hydrate reservoir, that is, a rock sample refrigeration module shown in fig. 3 is installed at a position 6 in fig. 1, and a high-temperature fluid injection module shown in fig. 5 is installed at a position 4 in fig. 1, so that a rock heat exchange rule, a dynamic response and a fracturing test caused by multi-physical field action in the process of heat injection and permeation enhancement modification of the low-temperature natural gas hydrate reservoir are performed.
The first step is as follows: generating a group of natural gas hydrate rock samples under a low temperature condition, wherein one part of the natural gas hydrate rock samples is prefabricated with drill holes with certain diameter and depth in the sample generation process, then performing CT scanning on the drilled samples in a heat-preservation and pressure-maintaining environment to obtain an imaging and porosity distribution result, and the other part of the natural gas hydrate rock samples is not prefabricated with the drill holes and is used for performing tests such as uniaxial compression, triaxial compression, permeability test and the like to determine basic physical property parameters of the rock;
the second step is that: test device module installation
The testing device module comprises a rock sample refrigeration module 6 shown in figure 3 and a high-temperature fluid injection module 4 shown in figure 5.
Referring to fig. 3, the rock sample refrigeration module 6 is composed of a casing with an inverted U-shaped bottom and a coil pipe 12 arranged in the casing, the contact surface of the casing and the rock sample refrigeration module 6 is a heat conduction contact surface 22, and the rest surfaces are heat preservation and insulation surfaces, that is, the contact surface of the casing and the rock sample refrigeration module 6 is made of heat conduction materials, and the rest surfaces of the casing are made of heat preservation and insulation materials. When the device is used, the refrigeration liquid is introduced into the coil 12 to keep the rock sample refrigeration module at a set temperature, and the temperature of the refrigeration liquid is controlled by a temperature control unit (not shown in the figure).
Referring to fig. 5, the high-temperature fluid injection module comprises a high-temperature fluid heat-insulating casing 21 with a U-shaped top and a high-temperature fluid injection pipeline 17 arranged in the high-temperature fluid heat-insulating casing 21, wherein an outlet of the high-temperature fluid injection pipeline 17 is exposed from the bottom of the high-temperature fluid heat-insulating casing 21 and extends into a prefabricated hole of the rock sample 5 to be tested and is sealed by heat-insulating sealant; when in use, the inlet of the high-temperature fluid injection pipeline 17 is connected with a high-temperature fluid injection system.
During the equipment, with rock specimen refrigeration module 6 and the rock specimen 5-high temperature fluid injection module 4 of treating after connecting from supreme installation on the unipolar compression tester between last pressure head 3 and the pressure head 7 down (as shown in figure 1), provide vertical pressure by unipolar compression device, unipolar compression tester is by the axial compression hydro-cylinder 2 provide the loading force.
The third step: preparation of the experiment
Placing a thermal imager 9 at one side of the rock sample 5 to be tested;
attaching stress strain gauges to different positions on the surface of the rock sample 5 to be tested, wherein all the stress strain gauges are connected with a stress strain gauge 10;
opening a temperature control unit of the rock sample refrigeration module 6 to maintain the temperature of the rock sample refrigeration module 6 at a set refrigeration temperature;
opening a temperature control unit in the high-temperature fluid injection system to keep the temperature of the high-temperature fluid at a set temperature;
opening an axial pressure control unit of the uniaxial compression tester, and setting loading axial pressure;
finally, the assembled heat-insulation plate 8 with the opening is buckled on the assembled rock sample refrigerating module 6, the rock sample 5 to be tested and the high-temperature fluid injection module 4, so that the combination of the three is heat-insulated from the outside;
the angle of the thermal imaging camera 9 is adjusted, so that the rock sample 5 to be tested can be observed through the open hole of the heat insulation plate 8.
The fourth step: mechanical disturbance test for low-temperature natural gas hydrate heat injection process
Refrigerating the rock sample 5 to be tested by using a rock sample refrigerating module 6, observing the surface temperature of the rock mass to be uniformly distributed by using a thermal imager 9, and injecting high-temperature fluid into a drill hole of the rock sample 5 to be tested through a high-temperature fluid injection pipeline 17 after heat preservation is needed for 12 hours;
the mechanical disturbance effect of multiple physical fields on the rock is involved in the high-temperature fluid injection process, and the multiple physical fields comprise: thermal stress caused by the temperature difference between high-temperature injection fluid and low-temperature sample bedrock and natural gas hydrate decomposition caused by heat injection, recording the mechanical disturbance conditions of rock masses at different positions at different moments through stress strain gauges arranged on the surface of the rock sample, and recording the distribution of the surface temperature field of the rock sample at different moments through a placed thermal imager;
analyzing the influence rule of the change of the pore structure caused by the decomposition of hydrate and thermal cracking in the heat injection process on the enhanced heat transfer by combining the distribution and the evolution of temperature fields at different positions on the surface of the rock; analyzing a power disturbance rule caused by the migration process of the high-temperature injection fluid in the low-temperature hydrate by combining the stress evolution of different positions on the surface of the rock sample;
the fifth step: carrying out damage test after low-temperature natural gas hydrate heat injection
After the heat injection process of the low-temperature natural gas hydrate is finished and the heat transfer enhancement and dynamic disturbance test are carried out, taking a sample out of the test device and carrying out CT scanning to obtain imaging and porosity distribution results after the permeation enhancement modification; comparing with the CT scanning result obtained in the first step, and analyzing the distribution rule of fractures and pores of the low-temperature natural gas hydrate reservoir after heat injection;
and a sixth step: and (3) replacing the rock sample 5 to be tested, changing the axial pressure, the sample temperature, the injection fluid temperature and the injection flow velocity respectively, and repeating the steps from two to five for multiple times, so as to obtain rock mass enhanced heat transfer, stress-strain rule and fracture pore distribution rule in the natural gas hydrate heat injection production increasing process under different axial pressure conditions, sample temperatures, injection temperatures and injection flow velocities.
Claims (7)
1. A test method for the intensified heat transfer and the dynamic disturbance of a high-temperature rock mass under multi-field loading is characterized by comprising the following steps:
the first step is as follows: obtaining physical and mechanical parameters of a rock sample to be tested
1.1, cutting a plurality of cylindrical rock samples into two groups, wherein one group is used for determining basic physical property parameters of rocks, and the other group is used as a rock sample to be tested;
1.2, determining basic physical property parameters of the rock through uniaxial compression, triaxial compression and permeability tests;
1.3, drilling the end face of the rock sample to be tested, wherein the diameter and the depth of all the rock samples are the same, and carrying out CT scanning on the rock sample to be tested after drilling to obtain the imaging and porosity distribution result of the rock;
the second step is that: fabrication of test device modules
The test device module comprises a rock sample heating module and a low-temperature fluid injection module, wherein: the rock sample heating module is formed by sequentially overlapping an upper metal plate, a heat insulation material, a heating sheet and a lower metal plate from top to bottom; the low-temperature fluid injection module comprises a heat-insulation shell and a low-temperature fluid injection pipeline, wherein the low-temperature fluid injection pipeline penetrates through the heat-insulation shell, is exposed out of the upper part of the heat-insulation shell and then extends into a drill hole of a rock sample, and a pressure-resistant sealing measure is adopted;
the third step: preparation of the test
3.1, sequentially superposing and installing the rock sample heating module, the rock sample to be tested and the low-temperature fluid injection module between an upper pressure head and a lower pressure head of a uniaxial compression tester from top to bottom, wherein the rock sample heating module and the low-temperature fluid injection module provide pressure in the vertical direction by the uniaxial compression tester;
3.2: placing a thermal imager on one side of the rock sample; attaching stress strain gauges to different positions on the rock surface of the rock sample to be tested, and connecting the stress strain gauges with the stress strain gauges;
3.3: setting the heating temperature of the rock sample heating module, selecting low-temperature injection fluid, setting the temperature of the low-temperature fluid, opening an axial pressure control unit, and setting loading axial pressure;
3.4: the heat insulation plate is buckled on the assembled heating module, the rock sample to be tested and the low-temperature fluid injection module, so that the combination of the three is insulated from the outside;
the fourth step: enhanced heat transfer and dynamic disturbance test in high-temperature rock injection cooling process
4:1: heating a rock sample to be tested by using a rock sample heating module, observing the surface temperature of a rock body by using a thermal imager until the surface temperature is uniformly distributed, and injecting low-temperature fluid into a drill hole of the rock sample to be tested;
recording mechanical disturbance conditions of rock masses at different positions at different times through stress strain gauges arranged on the surface of the rock sample, and analyzing a power disturbance rule caused in the migration process of low-temperature injection fluid in the hot dry rock by combining stress evolution at different positions on the surface of the rock sample; recording the distribution of the temperature fields on the surface of the rock sample at different moments by a placed thermal imager, and analyzing the influence rule of the phase change of the low-temperature fluid and the change of the pore structure of the rock mass on the enhanced heat transfer by combining the distribution and the evolution of the temperature fields at different positions on the surface of the rock;
the fifth step: carrying out damage test after high-temperature rock injection cooling
After the heat transfer enhancement and power disturbance test of the high-temperature dry and hot rock in the cooling injection process is finished, taking a rock sample out of the test device, carrying out CT scanning to obtain imaging and porosity distribution results after the permeability enhancement transformation, comparing the imaging and porosity distribution results with the CT scanning results obtained in the first step, and analyzing the distribution rule of cracks and pores after the dry and hot rock is cooled;
and a sixth step: and (3) replacing the rock sample to be tested, changing the axial pressure, the rock temperature, the type of the injected fluid, the temperature of the injected fluid, the injection flow rate and the type of the rock respectively, and repeating the steps from two to five so as to obtain rock mass enhanced heat transfer, stress-strain rules and fracture pore distribution rules in the processes of cold injection and yield increase of different axial pressure conditions, rock temperatures, injected fluids, injection temperatures, injection flow rates and rock types.
2. The method for testing the enhanced heat transfer and the dynamic disturbance of the high-temperature rock mass under the multi-field loading as claimed in claim 1, wherein the upper metal plate, the heat insulation material, the heating plate and the lower metal plate of the rock sample heating module are overlapped into a whole in an inserting manner.
3. The method for testing the enhanced heat transfer and dynamic disturbance of the high-temperature rock mass under the multi-field loading as claimed in claim 2, wherein the metal plate, the heat insulating material and the heating plate are all provided with the insertion holes, the upper surface of the lower metal plate is provided with the insertion strips corresponding to the insertion holes, and the insertion strips of the lower metal plate sequentially penetrate through the heating plate, the heat insulating material and the upper metal plate to stack all the components together.
4. The method for testing the enhanced heat transfer and dynamic disturbance of the high-temperature rock under the multi-field loading as claimed in claim 1, wherein the upper surface of the upper metal plate of the rock sample heating module is set to be in a U-shaped mode, and the bottom of the low-temperature fluid injection module is set to be in an inverted U-shaped mode.
5. The method for testing the enhanced heat transfer and dynamic disturbance of the high-temperature rock body under the multi-field loading according to any one of claims 1 to 4, wherein the types of the low-temperature fluid comprise water and liquid CO2Or liquid N2The injection temperature is-80 deg.C, -40 deg.C, -20 deg.C, 0 deg.C or 20 deg.C, and the injection flow rate is 2ml/min, 4ml/min, 6ml/min or 8 ml/min.
6. A method for testing the intensified heat transfer and the dynamic disturbance of a low-temperature rock mass under multi-field loading is characterized by comprising the following steps:
the first step is as follows: obtaining physical and mechanical parameters of a rock sample to be tested
1.1, synthesizing two groups of natural gas hydrate rock samples under the same low temperature condition, prefabricating drill holes with the same diameter and the same depth in the synthesis process, and carrying out CT scanning on the rock sample to be tested, which is prefabricated with the drill holes, to obtain the imaging and porosity distribution results of the rock; the other group determines the basic physical property parameters of the rock through uniaxial compression, triaxial compression and permeability test;
the second step is that: fabrication of test device modules
The test device module include rock sample refrigeration module and high temperature fluid injection module, wherein: the rock sample refrigeration module consists of a shell and a coil pipe arranged in the shell, wherein the contact surface of the shell and the rock sample to be tested is a heat conduction surface, and the rest surfaces are heat preservation and heat insulation surfaces; the high-temperature fluid injection module consists of a heat insulation box body and a high-temperature fluid injection pipeline arranged in the heat insulation box body, wherein an outlet of the high-temperature fluid injection pipeline is exposed from the bottom of the heat insulation box body and extends into a drill hole of a rock sample to be tested and is sealed by heat insulation sealant;
the third step: preparation of the experiment
3.1: sequentially overlapping and installing the high-temperature fluid injection module, the rock sample to be tested and the rock sample refrigeration module between an upper pressure head and a lower pressure head of the uniaxial compression tester from top to bottom, wherein the rock sample refrigeration module and the connected rock sample-high-temperature fluid injection module are provided with pressure in the vertical direction by the uniaxial compression tester;
3.2: placing a thermal imager at one side of the rock sample, attaching stress strain gauges to different positions on the rock surface of the rock sample to be tested, and connecting the stress strain gauges with the thermal imager;
3.3: setting the refrigeration temperature of a rock sample refrigeration module, selecting high-temperature injection fluid, setting the temperature of the high-temperature fluid, opening an axial pressure control unit, and setting loading axial pressure;
3.4: the insulation board is buckled on the assembled refrigeration module, the rock sample to be tested and the high-temperature fluid injection module, so that the combination of the refrigeration module, the rock sample to be tested and the high-temperature fluid injection module is insulated from the outside;
the fourth step: enhanced heat transfer and power disturbance test for low-temperature natural gas hydrate reservoir heat injection process
4.1: refrigerating a rock sample to be tested through heat conduction by utilizing a heat conduction contact surface arranged in a rock sample refrigerating module, observing the surface temperature of a rock body through a thermal imager until the temperature is uniformly distributed, and injecting high-temperature fluid into the rock sample to be tested;
recording mechanical disturbance conditions of rock masses at different times and different positions through stress strain gauges arranged on the surface of the rock sample, and recording the distribution of temperature fields on the surface of the rock sample at different times through a placed thermal imager; analyzing the influence rule of the change of the pore structure caused by the decomposition of hydrate and thermal cracking in the heat injection process on the enhanced heat transfer by combining the distribution and the evolution of temperature fields at different positions on the surface of the rock; analyzing a power disturbance rule caused by the migration process of the high-temperature injection fluid in the low-temperature hydrate by combining the stress evolution of different positions on the surface of the rock sample;
the fifth step: carrying out damage test after low-temperature natural gas hydrate heat injection
After the heat injection process of the low-temperature natural gas hydrate is finished and the heat transfer enhancement and dynamic disturbance test are carried out, taking a sample out of the test device and carrying out CT scanning to obtain imaging and porosity distribution results after the permeation enhancement modification; comparing with the CT scanning result obtained in the first step, and analyzing the distribution rule of fractures and pores of the low-temperature natural gas hydrate reservoir after heat injection;
and a sixth step: and (3) replacing the rock sample to be tested, changing the axial pressure, the sample temperature, the injection fluid temperature and the injection flow rate respectively, and repeating the steps from two to five so as to obtain the rock mass enhanced heat transfer, stress-strain rule and fracture pore distribution rule in the natural gas hydrate heat injection production increasing process under different axial pressure conditions, sample temperatures, injection temperatures and injection flow rates.
7. The method for testing the enhanced heat transfer and dynamic disturbance of the low-temperature rock mass under the multi-field loading as claimed in claim 6, wherein the bottom of the rock sample refrigeration module is set in an inverted U-shaped mode, and the top of the high-temperature fluid injection module is set in a U-shaped mode.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117129355A (en) * | 2023-10-23 | 2023-11-28 | 北京大学 | High-temperature visual micrometer indentation test device and method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117129355A (en) * | 2023-10-23 | 2023-11-28 | 北京大学 | High-temperature visual micrometer indentation test device and method |
| CN117129355B (en) * | 2023-10-23 | 2024-02-13 | 北京大学 | High-temperature visual micrometer indentation test device and method |
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