CN108760515B - Experimental system and method for testing crack height expansion by loading stress - Google Patents
Experimental system and method for testing crack height expansion by loading stress Download PDFInfo
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- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
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- G01N2203/0058—Kind of property studied
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Abstract
The invention discloses an experimental system and a method for testing crack height expansion by loading stress, wherein the experimental system comprises: the loading frame is used for loading an experimental sample, and a square loading cavity is formed inside the loading frame; a true triaxial ground stress loading unit for loading a pressure to the test sample, comprising: an inflatable loading plate having a hollow structure, a pressure pump in communication with said inflatable loading plate for providing pressure thereto, said inflatable loading plate comprising: the loading device comprises a first loading plate and a second loading plate, wherein the first loading plate is positioned between the loading cavity and an experimental sample, and the second loading plate is positioned at one end of the experimental sample; the pressure sensor is connected with the pressure pump; and the controller is electrically connected with the pressure pump and the pressure sensor. The invention can independently load a plurality of layers of horizontal stress fields on the vertical direction of an experimental sample, and provides favorable technical support for the optimal design of the crack control high-pressure cracking process.
Description
Technical Field
The invention relates to the technical field of hydraulic fracturing physical simulation experiments in oil and gas field development, in particular to an experiment system and method for testing fracture height expansion by loading stress.
Background
Hydraulic fracturing has been widely used in the modern petroleum industry as one of the primary measures for oil and gas stimulation. With the large development of low permeability, complex hydrocarbon reservoirs (e.g., natural fracture reservoirs), hydraulic fracturing techniques face new challenges. The objects faced in reservoir transformation are more and more complex, wherein factors including structural stress abnormity, natural fractures, horizontal bedding development, deep large-scale horizontal well type and the like restrict the understanding of the initiation and extension mechanism of hydraulic fractures.
In order to correctly recognize the hydraulic fracturing fracture-setting and extending mechanism of a complex reservoir stratum, in recent years, an indoor hydraulic fracturing physical simulation experiment technology is deeply researched and widely applied. The method has the advantages that the law of crack propagation is known through physical simulation of hydraulic fracturing, so that the research level of natural fractured reservoirs such as compact oil and the like, hydraulic fracturing of highly deviated wells and horizontal wells under complex conditions is improved, and the method has the decisive effects of improving the current hydraulic fracturing level, improving the yield increasing effect and improving the oil and gas yield.
The Chinese patent No. CN106640016A provides a multi-scale true triaxial horizontal well hydraulic fracturing pressure bearing cylinder and a using method thereof, and the Chinese patent No. CN105332682A provides an experimental method for the influence of a high-pressure fracture body in a carbonate reservoir on the expansion of a hydraulic fracture, wherein the hydraulic fracturing pressure bearing cylinder and the using method can realize the physical simulation of fracture cracking and extension under indoor conditions, and meanwhile, the independent loading of three-dimensional main stress of a sample is realized in a hydraulic rigid loading mode in the experimental process.
However, the problems generally existing in the prior art are as follows: at present, a jack is usually used for rigid loading during stress loading, and due to the limitation of the experimental loading mode, loading of 3 ground stress values of vertical and single-layer bidirectional horizontal main stress can only be performed, simulation cannot be performed on the difference of vertical horizontal stress, and a seam height extension experiment under the condition of an interlayer stress difference cannot be performed.
Therefore, it is very necessary to provide a new technique for realizing independent loading of the vertical multi-layer horizontal stress field of the experimental sample, which can overcome the defects in the prior art.
Disclosure of Invention
The invention aims to provide an experimental system and method for testing crack height expansion by loading stress, which can overcome the defects in the prior art and can independently load a multi-layer horizontal stress field on an experimental sample in the vertical direction, thereby providing favorable technical support for the optimal design of a crack control high-pressure cracking process.
The above object of the present invention can be achieved by the following technical solutions:
an experimental system for loading stress testing crack height propagation, comprising:
the loading frame is used for loading an experimental sample, and a square loading cavity is formed inside the loading frame;
a true triaxial ground stress loading unit for loading a pressure to the test sample, comprising: an inflatable load plate in a hollow configuration, a pressure pump in communication with the inflatable load plate for providing pressure to the inflatable load plate, wherein the inflatable load plate comprises: the loading device comprises a first loading plate and a second loading plate, wherein the first loading plate is positioned between the loading cavity and an experimental sample, and the second loading plate is positioned at one end of the experimental sample;
the pressure sensor is connected with the pressure pump;
and the controller is electrically connected with the pressure pump and the pressure sensor.
In a preferred embodiment, each set of the first loading plates comprises a pair of maximum horizontal stress loading plates oppositely arranged along a first direction and a pair of minimum horizontal stress loading plates oppositely arranged along a second direction perpendicular to the first direction, wherein the pressure applied to the loading plates in the pair of maximum horizontal stress loading plates is the maximum horizontal stress, and the pressure applied to the loading plates in the pair of minimum horizontal stress loading plates is the minimum horizontal stress.
In a preferred embodiment, the controller is provided with a storage unit, the storage unit stores loading stress data corresponding to each loading plate, and the controller can store pressure data collected by the pressure sensor and adjust the output pressure of the pressure pump.
In a preferred embodiment, the hollow portion of the inflatable loading plate is adapted to contain a working medium, and the inflatable loading plate has a maximum loading pressure of at least 69 mpa.
In a preferred embodiment, the material of the inflatable loading plate is a titanium-nickel alloy.
In a preferred embodiment, the working medium is water.
In a preferred embodiment, the experimental sample is a cuboid, and the length, width and height thereof are respectively as follows: 762mm x 914mm, the middle part of the experimental sample is drilled with a borehole, the bottom part is provided with an open hole section, and the top part is used for cementing.
In a preferred embodiment, the loading frame comprises opposing base and top covers and a securing mechanism disposed between the base and top covers, wherein the top cover is provided with a through hole for simulating a wellbore.
In a preferred embodiment, the first loading plates are divided into three groups, and the three groups of first loading plates are matched with the pressure pump to form three layers of 6 horizontal pressure channels with maximum horizontal stress and three layers of minimum horizontal stress which are vertically distributed from top to bottom; the second loading plate and the pressure pump are matched to form a vertical pressure channel.
An experiment method of the experiment system for testing the crack height expansion based on the loading stress comprises the following steps:
connecting the inflatable loading plates with the pressure pumps, and sequentially installing pressure sensors between each group of the inflatable loading plates and the pressure pumps;
opening an evacuation line of the inflatable loading plate, injecting a working medium into the inflatable loading plate, and completing evacuation operation after the inflatable loading plate is filled until the working medium is discharged;
activating a pressure pump, regulating the pressure within the pressure channel such that the pressure in the inflatable load plate is increased to a predetermined confining pressure;
injecting a fracturing sample with preset pressure into the through hole of the loading frame; stopping the injection after the crack has propagated to the end of the loaded sample; and unloading the pressure of the fracturing sample to 0, and unloading the pressure of the working medium in the expandable loading plate to 0.
The invention has the characteristics and advantages that: the application provides an experimental system and a method for testing crack height extension by loading stress, through being located set up first load plate and being located between loading chamber and the experimental sample the experimental sample tip sets up the second load plate, wherein, first load plate is provided with two sets ofly at least along the depth direction in loading chamber, can cooperate with the force pump, realizes loading different horizontal stress along the vertical to the experimental sample to realized really simulating the three-dimensional ground stress loading environment of rock sample in the reservoir under indoor condition, especially realized the independent loading of multilayer horizontal stress field on the vertical, can show the vertical extension form of crack more clearly, help scientific research personnel deepen the understanding of storing up the high extension mechanism of interlayer stress shielding crack.
Furthermore, the expandable loading plate adopts a high-strength titanium-nickel alloy thin plate as a confining pressure loading plate, has the advantages of small volume, light weight, high bearing pressure, simple structure and simple processing, manufacturing and maintenance, and effectively overcomes the defects of uneven rigid loading, small loading capacity and incapability of layered loading of the traditional hydraulic jack.
Specific embodiments of the present application are disclosed in detail with reference to the following description and drawings, indicating the manner in which the principles of the application may be employed. It should be understood that the embodiments of the present application are not so limited in scope. The embodiments of the application include many variations, modifications and equivalents within the spirit and scope of the appended claims.
Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments, in combination with or instead of the features of the other embodiments.
It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps or components.
Drawings
FIG. 1 is a schematic diagram of stress loading in an experimental system for testing crack height propagation by loading stress according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of an experimental system for testing crack height propagation by loading stress according to an embodiment of the present disclosure;
FIG. 3 is a schematic structural diagram of a loading frame in an experimental system for testing crack height propagation by loading stress according to an embodiment of the present disclosure;
FIG. 4 is a flowchart illustrating the steps of an experiment for testing crack height propagation under loading stress in an embodiment of the present application.
Description of reference numerals:
10-test sample; 1-loading a frame; 11-inflatable loading plate; 12-a pressure pump; 2-true triaxial ground stress loading unit; 3-a controller; x-a first direction; y-a second direction; z-vertical; 41-top cover; 410-a through hole; 42-a base plate; 43-ring-shaped steel ring; 44-bolt; 45-screw cap; 46-half moon shaped steel block.
Detailed Description
The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, it should be understood that these embodiments are merely illustrative of the present invention and are not intended to limit the scope of the present invention, and various equivalent modifications of the present invention by those skilled in the art after reading the present invention fall within the scope of the appended claims.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.
The invention provides an experimental system and method for testing crack height expansion by loading stress, which can overcome the defects in the prior art, and provide favorable technical support for the optimization design of a crack control high-pressure cracking process by independently loading multiple layers of horizontal stress fields on an experimental sample in the vertical direction.
Referring to fig. 1 to 3, an experimental system for testing crack height propagation by loading stress according to an embodiment of the present disclosure may include: the loading frame 1 is used for loading an experimental sample 10, and a loading cavity in a square shape is formed inside the loading frame 1; a true triaxial ground stress loading unit 2 for loading a test specimen 10 with pressure, comprising: an inflatable load plate 11 having a hollow structure, a pressure pump 12 in communication with said inflatable load plate 11 for providing pressure to said inflatable load plate 11, wherein said inflatable load plate 11 comprises: a first loading plate positioned between the loading cavity and the experimental sample 10 and a second loading plate positioned at one end of the experimental sample 10, wherein at least two groups of the first loading plates are arranged along the depth direction of the loading cavity; a pressure sensor used for being connected with the pressure pump 12, and a controller 3 electrically connected with the pressure pump 12 and the pressure sensor.
The embodiment of the invention provides an experimental system for testing the crack height expansion by loading stress, which comprises: the device comprises a loading frame 1, a true triaxial ground stress loading unit 2 and a pressure data acquisition and control mechanism.
In this embodiment, the loading frame 1 of the experimental sample 10 may be a cylindrical steel container, and the sample loading space formed inside may be a square loading chamber. Accordingly, the cross-sectional area of the test specimen 10 disposed in the loading chamber is also square.
Specifically, the present application provides a test specimen 10 having a size larger than that of the existing test specimen 10, thereby facilitating the arrangement of a sufficient number of first loading plates along the depth direction of the loading chamber. In one specific embodiment, the experimental sample 10 is a rectangular parallelepiped, and has a width and a height: 762mm (mm) × 762mm × 914 mm. The experimental sample 10 may be a natural outcrop sample of different geological reservoirs or an artificial sample poured by a specific cement formula, and the like, and the application is not limited specifically herein. The middle part of the experimental sample 10 is drilled with a borehole, the bottom part is provided with an open hole section, and the top part is used for well cementation. Specifically, the depth of the borehole may be about 500 mm. The open hole section of the bottom can be about 100 mm. The top of the test specimen 10 was used for cementing.
In the present embodiment, the true triaxial ground stress loading unit 2 is used for loading pressure to the test sample 10, and is capable of loading at least one vertical stress and two horizontal stresses with different magnitudes to the test sample 10. The true triaxial ground stress loading unit 2 may include: an inflatable loading plate 11 having a hollow structure, and a pressure pump 12 communicating with the inflatable loading plate 11 and for providing pressure to the inflatable loading plate 11. Wherein said expandable loading plate 11 comprises: a first load plate located between the loading chamber and the test specimen 10 and a second load plate located at one end of the test specimen 10. Wherein the first loading plate is provided with at least two groups along the depth direction of the loading cavity. When at least two groups of the first loading plates are arranged along the depth direction of the loading cavity (namely the simulated vertical direction z), different horizontal stresses can be loaded along the vertical direction z, and therefore a real formation stress environment is simulated. The second loading plate may be loaded on the top end of the test specimen 10, and of course, may also be loaded on the bottom end of the test specimen 10.
Specifically, each set of the first loading plates comprises a pair of maximum horizontal stress loading plates oppositely arranged along a first direction x and a pair of minimum horizontal stress loading plates oppositely arranged along a second direction y perpendicular to the first direction x, wherein the pressure applied to the loading plates in the pair of maximum horizontal stress loading plates is the maximum horizontal stress, and the pressure applied to the loading plates in the pair of minimum horizontal stress loading plates is the minimum horizontal stress.
In the present embodiment, the first direction x and the second direction y may correspond to a geographical east-west direction and a north-south direction, respectively. In general, when the horizontal stress is the greatest in a first direction x, the corresponding horizontal stress is the least in a second direction y perpendicular to that direction.
Specifically, the present application provides an inflatable loading plate 11 having a hollow portion for containing a working medium, wherein the inflatable loading plate 11 has a maximum loading pressure of at least 69 mpa. The material of the expandable loading plate 11 is a high-strength titanium-nickel alloy material, so that the expandable loading plate has better pressure resistance. The working medium can be water, on one hand, flexible loading of stress can be preferably realized, and on the other hand, the experiment cost can be reduced. Of course, the working medium may be other fluids, and the specific application is not limited thereto.
In this embodiment, a pressure data acquisition and control mechanism is further provided, which may include a pressure sensor connected to the pressure pump 12 and a controller 3 electrically connected to the pressure pump 12 and the pressure sensor. Wherein the pressure sensors may be provided between each set of expandable load plates 11 and pressure pump 12 for acquiring stress data of the actual load.
The controller 3 may be provided with a storage unit, the storage unit stores loading stress data corresponding to each loading plate, and the controller 3 may store pressure data collected by the pressure sensor and adjust the output pressure of the pressure pump 12. Specifically, for example, when the pressure data collected by the pressure sensor does not reach the pre-stored pressure data, the parameters of the pressure pump 12 may be adjusted until it reaches. In particular, the controller 3 may be in the form of a computer. In addition, the experimental system for testing the crack height expansion by loading stress can be further provided with a parameter input unit. The predetermined pressure to be applied can be input by the parameter input unit. The pressure data of the subsequent input parameter input unit can be stored in said memory unit, so that the controller 3 adjusts the actual output of the pressure pump 12 on the basis of the pressure data.
In this embodiment, a first loading plate is disposed between the loading cavity and the experimental sample 10, and a second loading plate is disposed at an end of the experimental sample 10, wherein at least two groups of the first loading plates are disposed along a depth direction of the loading cavity, and can be matched with the pressure pump 12 to load different horizontal stresses on the experimental sample 10 along a vertical direction z, so that a three-dimensional ground stress loading environment of the rock sample in the reservoir is truly simulated under an indoor condition, in particular, independent loading of a multilayer horizontal stress field on the vertical direction z is realized, a vertical crack extension form can be more clearly displayed, and a researcher can deeply know a high extension mechanism of a storage interlayer stress shielding crack.
Furthermore, the expandable loading plate 11 adopts a high-strength titanium-nickel alloy thin plate as a confining pressure loading plate, has the advantages of small volume, light weight, high bearing pressure, simple structure and simple processing, manufacturing and maintenance, and effectively overcomes the defects of uneven rigid loading, small loading capacity and incapability of layered loading of the traditional hydraulic jack.
In a specific embodiment, the first loading plates are three groups, three groups of the first loading plates cooperate with the pressure pump 12 to form three layers of 6 horizontal pressure channels with maximum horizontal stress and minimum horizontal stress distributed up and down along the vertical direction z, and the second loading plates cooperate with the pressure pump 12 to form one vertical pressure channel. 7 pressure channels capable of independently loading stress are formed integrally.
Taking the above example of forming 7 pressure channels, correspondingly, the loading frame 1 mainly includes: bottom plate 42, top cap 41, 7 annular steel rings 43, 28 half-moon shaped steel blocks 46, 12 bolts 44 and 12 nuts 45. Of course, the number of the above-mentioned components can be adjusted adaptively according to the size of the actual experimental sample 10 and the specific structure of the loading frame 1, and the application is not limited herein.
Wherein the base plate 42 may be threaded for attachment to a bolt 44 during assembly. The bolt 44 sequentially penetrates through the half-moon-shaped steel block 46 and the top cover 41 from bottom to top, the top of the bolt 44 is provided with threads, and the top cover 41 is fixed through a nut 45. The half-moon-shaped steel blocks 46 are respectively arranged on the side walls of the annular steel ring 43 in four directions, namely south, east and west. 7 annular steel rings 43 are directly stacked on the bottom plate 42. A through circular hole is formed in the middle of the top cover 41 so as to form a simulated shaft in a fracturing experiment.
The true triaxial ground stress loading unit 2 may include: 7 inflatable load plates 11 and corresponding servo-controlled pressure pumps 12. Wherein, the expandable loading plate 11 is respectively clung to the side walls of the half-moon-shaped steel block 46 in four directions of southeast, northwest and the bottom of the top cover 41, and the other side is clung to the loaded sample; the corresponding 7 servo control pressure pumps 12 are respectively connected with the expandable loading plate 11 through pipelines, high-pressure fluid is injected through the expandable loading plate 11, and maximum horizontal stress, minimum horizontal stress and vertical stress are applied to the experimental sample so as to simulate the real formation stress state.
Referring to fig. 4, in view of the experimental system for testing crack height propagation by loading stress provided in the above embodiment, an experimental method is correspondingly provided in the embodiments of the present application, and the method may include the following steps:
step S10: connecting the inflatable loading plates 11 with the pressure pump 12, and simultaneously sequentially installing pressure sensors between each group of inflatable loading plates 11 and the pressure pump 12;
step S12: opening an evacuation line of inflatable loading plate 11, injecting a working medium into inflatable loading plate 11, and completing an evacuation operation after inflatable loading plate 11 is filled until the working medium is discharged;
step S14: starting the pressure pump 12, and adjusting the pressure in the pressure channel so that the pressure in the inflatable loading plate 11 is increased to a predetermined confining pressure;
step S16: injecting a fracturing sample of a predetermined pressure into the through-hole 410 of the loading frame 1; stopping the injection after the crack has propagated to the end of the loaded sample; and unloading the pressure of the fracturing sample to 0, and unloading the pressure of the working medium in the expandable loading plate to 0.
In a specific application scenario, preparation before experiment is first performed: according to the experimental requirements, the natural or artificial experimental sample 10 is prepared by using a linear cutting and cement pouring mode.
The experimental sample 10 placement was then performed: an experimental sample is hung in a loading cavity of the loading frame 1, 7 groups of expandable loading plates 11 are sequentially placed to be tightly attached to the surface of the sample, the top cover 41 is covered, and the top cover 41 is fixed through a screw cap 45.
Then connecting a true triaxial ground stress loading unit 2: the expandable loading plate 11 and the servo control pressure pump 12 are respectively connected by a high-pressure pipeline; meanwhile, each pressure sensor is sequentially arranged between each group of the expandable loading plates 11 and the servo control pressure pump 12 and is respectively connected with the acquisition system and the pressure pump 12 through network cables;
the data acquisition system is prepared next: starting a pressure sensor and parameter input and acquisition software;
and then applying confining pressure: opening a loading plate emptying pipeline, filling the loading plate with injected fluid, then discharging the fluid, and closing an emptying valve after emptying; respectively inputting 7 channel confining pressure values in a software system, starting a servo control pressure pump 12, and respectively adjusting 7 groups of expandable loading plates 11 to preset confining pressures;
then injecting a high-pressure fluid fracturing sample into the shaft;
after the fracture propagates to the end of the sample, stopping injection and unloading the pressure of the well bore fluid to 0; respectively inputting parameters in a software system, and unloading the fluid pressure in 7 inflatable loading plates 11 to 0; opening an evacuation line;
the top cover 41 is subsequently removed, and the test specimen 10 is taken out and cut to observe the form of the crack.
When the specific experiment is carried out, the rock sample needs to be processed into a hexahedral block according to the experimental requirements, and the length, the width and the height are 762mm multiplied by 914mm respectively. A borehole is drilled in the center of the rock sample, the depth of the borehole is 500mm, a 100mm open hole section is reserved at the bottom, and the upper part is well-fixed.
When the specific experiment is implemented, the loaded sample adopts natural outcrop samples of different geological reservoirs or artificial samples poured by a specific cement formula.
In the implementation of specific experiments, the pressure of the wellbore fluid can be loaded to 82MPa at most.
When a specific experiment is carried out, the expandable loading plate 11 is of a hollow structure, is formed by integrally butt-welding two high-strength titanium-nickel alloy sheets, and has the characteristics of large loading area, uniform pressure loading and high bearing pressure, and the highest loading pressure can reach 69 MPa.
When a specific experiment is carried out, the working medium inside the expandable loading plate 11 is clear water.
During specific experiment implementation, at most 3 expandable loading plates 11 can be placed on a single rock sample loading surface in the longitudinal direction, and independent loading of 7 pressure channels with maximum horizontal layer, minimum horizontal main stress and vertical stress of at most three layers can be realized.
Any numerical value recited herein includes all values from the lower value to the upper value that are incremented by one unit, provided that there is a separation of at least two units between any lower value and any higher value. For example, if it is stated that the number of a component or a value of a process variable (e.g., temperature, pressure, time, etc.) is from 1 to 90, preferably from 20 to 80, and more preferably from 30 to 70, it is intended that equivalents such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 are also expressly enumerated in this specification. For values less than 1, one unit is suitably considered to be 0.0001, 0.001, 0.01, 0.1. These are only examples of what is intended to be explicitly recited, and all possible combinations of numerical values between the lowest value and the highest value that are explicitly recited in the specification in a similar manner are to be considered.
Unless otherwise indicated, all ranges include the endpoints and all numbers between the endpoints. The use of "about" or "approximately" with a range applies to both endpoints of the range. Thus, "about 20 to about 30" is intended to cover "about 20 to about 30", including at least the endpoints specified.
All articles and references, including patent applications and publications, disclosed herein are hereby incorporated by reference for all purposes. The term "consisting essentially of …" describing a combination shall include the identified element, ingredient, component or step as well as other elements, ingredients, components or steps that do not materially affect the basic novel characteristics of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, components, or steps herein also contemplates embodiments that consist essentially of such elements, components, or steps. By using the term "may" herein, it is intended to indicate that any of the described attributes that "may" include are optional.
A plurality of elements, components, parts or steps can be provided by a single integrated element, component, part or step. Alternatively, a single integrated element, component, part or step may be divided into separate plural elements, components, parts or steps. The disclosure of "a" or "an" to describe an element, ingredient, component or step is not intended to foreclose other elements, ingredients, components or steps.
The above embodiments in the present specification are all described in a progressive manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment is described with emphasis on being different from other embodiments.
The above description is only a few embodiments of the present invention, and although the embodiments of the present invention are described above, the above description is only for the convenience of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. An experimental system for testing crack height propagation by loading stress, which is characterized by comprising:
the loading frame is used for loading an experimental sample, and a square loading cavity is formed inside the loading frame;
a true triaxial ground stress loading unit for loading a pressure to the test sample, comprising: an inflatable load plate in a hollow configuration, a pressure pump in communication with the inflatable load plate for providing pressure to the inflatable load plate, wherein the inflatable load plate comprises: the loading device comprises a first loading plate and a second loading plate, wherein the first loading plate is positioned between the loading cavity and an experimental sample, and the second loading plate is positioned at one end of the experimental sample;
the pressure sensor is connected with the pressure pump;
and the controller is electrically connected with the pressure pump and the pressure sensor.
2. The system of claim 1, wherein each set of the first load plates comprises a pair of maximum horizontal stress load plates disposed opposite each other along a first direction and a pair of minimum horizontal stress load plates disposed opposite each other along a second direction perpendicular to the first direction, wherein the pressure applied to the load plates in the pair of maximum horizontal stress load plates is the maximum horizontal stress and the pressure applied to the load plates in the pair of minimum horizontal stress load plates is the minimum horizontal stress.
3. The system for testing crack height propagation according to claim 2, wherein the controller is provided with a storage unit, the storage unit stores loading stress data corresponding to each loading plate, and the controller can store pressure data collected by the pressure sensor and adjust the output pressure of the pressure pump.
4. The loading stress test fracture height propagation assay system of claim 3, wherein the expandable loading plate has a hollow portion for containing a working medium and the expandable loading plate has a maximum loading pressure of at least 69 megapascals.
5. The loading stress test fracture height propagation experimental system of claim 4, wherein the material of the expandable loading plate is a titanium-nickel alloy.
6. The system for testing crack height propagation under load stress of claim 5, wherein the working medium is water.
7. The system for testing crack height propagation under loading stress of claim 5, wherein the test sample is a cuboid, and the length, width and height of the cuboid are respectively as follows: 762mm x 914mm, the middle part of the experimental sample is drilled with a borehole, the bottom part is provided with an open hole section, and the top part is used for cementing.
8. The system of claim 7, wherein the loading frame comprises opposing base and top plates and a securing mechanism disposed between the base and top plates, wherein the top plate has a through hole disposed therein for simulating a well bore.
9. The system for testing crack height propagation according to claim 8, wherein the first loading plates are divided into three groups, and the three groups of the first loading plates cooperate with the pressure pump to form three layers of 6 horizontal pressure channels with maximum horizontal stress and minimum horizontal stress, which are vertically distributed from top to bottom; the second loading plate and the pressure pump are matched to form a vertical pressure channel.
10. An experimental method for the experimental system for testing the crack height propagation based on the loading stress of claim 9, is characterized by comprising the following steps:
connecting the inflatable loading plates with the pressure pumps, and sequentially installing pressure sensors between each group of the inflatable loading plates and the pressure pumps;
opening an evacuation line of the inflatable loading plate, injecting a working medium into the inflatable loading plate, and completing evacuation operation after the inflatable loading plate is filled until the working medium is discharged;
activating a pressure pump, regulating the pressure within the pressure channel such that the pressure in the inflatable load plate is increased to a predetermined confining pressure;
injecting a fracturing sample with preset pressure into the through hole of the loading frame; stopping the injection after the crack has propagated to the end of the loaded sample; and unloading the pressure of the fracturing sample to 0, and unloading the pressure of the working medium in the expandable loading plate to 0.
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| CN109612841B (en) * | 2019-01-25 | 2023-10-24 | 中国人民解放军军事科学院国防工程研究院 | Target plate three-way confining press for deep penetration test of projectile body |
| CN112145149A (en) * | 2020-08-21 | 2020-12-29 | 中国地质大学（武汉） | Multiphase multi-field coupling transportation process simulation device for geothermal reservoir |
| CN113432975B (en) * | 2021-06-11 | 2022-09-27 | 中国石油大学(北京) | Detection device and detection system for rock sample pressurization test |
| CN113790971A (en) * | 2021-09-02 | 2021-12-14 | 新疆斐德莱布能源科技有限公司 | Three-dimensional stress loading device and method for large-size true triaxial hydraulic fracturing simulation experiment |
| CN115372156B (en) * | 2022-08-26 | 2024-07-09 | 中国矿业大学 | Device for applying heterogeneous stress and hydraulic fracturing implementation method |
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