Acid fracturing etching experimental device and experimental method

Acid pressure etching experimental device and experimental method technical field

[0001] The present invention relates to the field of oil and gas field development, and in particular to an acid pressure etching experimental device and experimental method.

Background technique

[0002] Acid fracturing, as a technical means to achieve efficient development of carbonate oil and gas reservoirs, has been widely used in the mining process of mines. The technical process of acid fracturing is to use fracturing hydraulic pressure to open oil and gas reservoirs to form artificial fractures, and then inject acid to etch the walls of the artificial fractures. After the acid fracturing is completed, the artificial cracks are closed and the unevenly etched grooves become high-speed oil and gas flow channels. Affected by the heterogeneity of the rock and mineral of the reservoir, this kind of etching is uneven, which in turn forms uneven etching grooves.

[0003] The uneven etching groove morphology formed by acid fracturing has an extremely important influence on the acid fracturing effect, and the acid fracturing effect of oil and gas reservoirs buried several kilometers underground cannot be directly observed. Therefore, indoor experiments are It has become an important method to study the etching effect of acid on the wall of artificial cracks.

[0004] During the acid fracturing construction process, supercritical carbon dioxide is generated after the acid solution reacts with the carbonate rock, and the generated supercritical carbon dioxide is mixed with the acid solution. The existing experimental methods or devices do not consider the influence of supercritical carbon dioxide on the etching effect, and the simulation of the acid-pressure etching process is not accurate enough, which further affects the accuracy of the etching result.

Summary of the invention

[0005] In order to solve the problem that the effect of supercritical carbon dioxide on the acid pressure etching effect is not reflected in the prior art, and the etching result is not accurate enough, one of the objectives of the present invention is to provide an acid pressure etching experimental device.

[0006] The present invention provides the following technical solutions:

[0007] An acid pressing etching experimental device, including an etching unit, an acid pressing unit, a back pressure unit and a heating unit;

[0008] The etching unit includes a first etching box, and a flat first cavity is provided inside the first etching box, and a first rock slab is provided in the first cavity;

[0009] The acid fracturing unit includes a first storage tank and a pressure component, the first storage tank is in communication with the first cavity, the first storage tank is used to store acid, the pressure component Used for hydraulic pressure of acid into the first cavity;

[0010] The back pressure unit includes a first back pressure tank and a first back pressure component, the first back pressure tank is in communication with the first cavity, and the first back pressure component is used to enter the The acid in the first back pressure tank exerts pressure;

[0011] The heating unit includes a first heating plate, and the first heating plate is disposed on the first etching box.

[0012] As a further alternative to the acid pressure etching experimental device, the first back pressure assembly includes a first nitrogen cylinder, and one end of the first back pressure tank facing away from the first cavity In communication with the first nitrogen cylinder, a first pressure guiding member is arranged inside the first back pressure tank, and the first pressure guiding member separates the first back pressure tank.

[0013] As a further alternative to the acid pressure etching experimental device, the first pressure guiding member is a first piston, and the first piston is slidably arranged in the first back pressure tank.

[0014] As a further alternative to the acid pressure etching experimental device, the first pressure guiding member is a first elastic membrane, and the edge of the first elastic membrane is connected to the first back pressure tank The inner wall is fixedly connected.

[0015] As a further alternative to the acid pressure etching experimental device, the first back pressure tank and the first

A first pressure regulating valve is arranged between the nitrogen cylinders.

[0016] As a further alternative to the acid pressure etching experimental device, the pressure component includes a second storage tank and a pump, the second storage tank is used to store pressure fluid, and the pump is used The pressure liquid is delivered into the first storage tank, and a pressure member is provided in the first storage tank, and the pressure member is used to separate the pressure liquid from the acid liquid and transfer pressure.

[0017] As a further alternative to the acid pressure etching experimental device, the etching unit further includes a second etching box, and a flat second cavity is provided inside the second etching box , The second cavity is in communication with the first cavity, and a second rock slab is provided in the second cavity;

[0018] The back pressure unit further includes a second back pressure tank and a second back pressure component, the second back pressure tank is in communication with the second cavity, and the second back pressure component is used to The acid liquid entering the second back pressure tank from the second cavity exerts pressure.

[0019] As a further alternative to the acid pressure etching experimental device, the etching unit further includes a third etching box, and a flat third cavity is provided inside the third etching box , The third cavity is in communication with the second cavity, and a third rock slab is provided in the third cavity;

[0020] The back pressure unit further includes a third back pressure tank and a third back pressure component, the third back pressure tank is in communication with the third cavity, and the third back pressure component is used to The acid liquid entering the third back pressure tank from the third cavity exerts pressure.

[0021] As a further alternative to the acid pressure etching experimental device, the heating unit further includes a second heating plate and a third heating plate, and the second heating plate is arranged on the second etching On the box, the third heating plate is arranged on the third etching box.

[0022] Another object of the present invention is to provide an experimental method.

[0023] The present invention provides the following technical solutions:

[0024] An experimental method using the above-mentioned acid pressure etching experimental device includes:

[0025] Load acid in the first storage tank;

[0026] Using the pressure component to hydraulic pressure the acid in the first storage tank into the first cavity, so that the acid and the first rock slab have a chemical reaction;

[0027] The first heating plate heats the first rock slab to a temperature above 31 °C to simulate the temperature in the formation. When the acid etches the first rock slab into the first back pressure tank, the The first back pressure component applies a pressure greater than 7.38 MPa to the acid to simulate the pressure in the formation to provide a pressure environment for the formation of supercritical carbon dioxide; and

[0028] Take out the first rock slab and observe the etching morphology.

[0029] The embodiments of the present invention have the following beneficial effects:

[0030] After the acid is filled into the first storage tank, the pressure component hydraulically presses the acid into the first cavity, and the acid etches the first rock slab and enters the first back pressure tank. At the same time, the first heating plate heats the first rock slab to above 31°C to simulate the temperature in the formation. The first back pressure component applies a pressure greater than 7.38 MPa to the acid in the first back pressure tank to simulate the pressure in the formation. , So that the carbon dioxide generated by the reaction between the acid and the first rock slab is in a supercritical state. After the acid solution is mixed with supercritical carbon dioxide, the first rock slab is continuously etched, which can more accurately simulate the acid fracturing etching process and obtain more accurate etching results.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, preferred embodiments are cited below in conjunction with accompanying drawings, which are described in detail as follows.

Description of the drawings

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings needed in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention. , Therefore should not be considered

For the limitation of the scope, those of ordinary skill in the art can also obtain other related drawings based on these drawings without creative work.

[0033] FIG. 1 shows a schematic diagram of the overall axonometric structure of the acid-pressure etching experimental device provided by Embodiment 1 of the present invention;

[0034] FIG. 2 shows a top view of the acid pressure etching experimental device provided by Embodiment 1 of the present invention;

[0035] FIG. 3 shows a schematic diagram of the internal structure of the first storage tank in the acid pressure etching experimental device provided by the embodiment 1 of the present invention;

[0036] FIG. 4 shows a schematic diagram of the structure of the first etching box in the acid pressure etching experimental device provided by the embodiment 1 of the present invention; [0037] FIG. 5 shows the acid pressure etching provided by the embodiment 1 of the present invention Schematic diagram of the internal structure of the first container in the experimental device;

[0038] FIG. 6 shows a schematic flow chart of the experimental method provided by Embodiment 2 of the present invention;

[0039] FIG. 7 shows a schematic diagram of the internal structure of the first container in the acid pressure etching experimental device provided in the third embodiment of the present invention.

[0040] Description of main component symbols:

[0041] 100-etching unit; 110-first etching box; 111-first box body; 112-first cover plate; 120-second etching box;

121-second box body; 122-second cover plate; 130-third etching box; 131-third box body; 132-third cover plate; 200-acid pressure unit; 210-first storage tank; 211 -Pressure component; 220-Pressure component; 221-Second storage tank; 222-Pump; 300-Back pressure unit; 310 First container; 311-First pressure guide component; 320-First back pressure component; 321 -The first nitrogen bottle; 322-the first pressure regulating valve; 330-the second container; 340-the second back pressure assembly; 341-the second nitrogen bottle; 342-the second pressure regulating valve; 350-the third container; 360 -The third back pressure component; 361-the third nitrogen cylinder; 362-the third pressure regulating valve; 400-the heating unit.

Detailed ways

[0042] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the drawings are exemplary, and are only used to explain the present invention, but should not be construed as limiting the present invention.

[0043] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or a central element may also be present. When an element is considered to be "connected" to another element, it can be directly connected to the other element or an intermediate element may be present at the same time. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0044] In the present invention, unless otherwise clearly defined and defined, the terms "installed", "connected", "connected", "fixed" and other terms should be understood in a broad sense, for example, it may be a fixed connection or It can be detachably connected or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meaning of the above-mentioned terms in the present invention can be understood according to specific circumstances.

[0045] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, "plurality" means two or more than two, unless specifically defined otherwise.

[0046] Unless otherwise defined, all technical and scientific terms used herein are the same as those belonging to the technical field of this application.

The technical personnel usually understand the same meaning. The terminology used in the template herein is only for the purpose of describing specific embodiments, and is not intended to limit the present invention. The term "and/or" as used herein includes any and all combinations of one or more related listed items.

Example 1

[0048] Please refer to FIGS. 1 to 5 together. This embodiment provides an acid-fracturing etching experimental device for simulating the etching effect of acid on the walls of artificial cracks during the acid-fracturing process, so that the experimenter can obtain the results according to the experiment. The uneven etched trench morphology is used to evaluate the effect of acid fracturing.

[0049] Such an acid pressing etching experimental device includes an acid pressing unit 200, an etching unit 100, a back pressure unit 300, and a heating unit 400. The acid fracturing unit 200 injects acid liquid into the etching unit 100 at a certain pressure, and the etching process is simulated in the etching unit 100. The back pressure unit 300 provides back pressure to simulate the pressure in the formation, and the heating unit 400 heats the etching unit 100 to simulate the temperature in the formation to provide a pressure environment for the formation of supercritical carbon dioxide.

[0050] The acid fracturing unit 200 includes a first storage tank 210 and a pressure component 220. The first storage tank 210 is arranged in a vertical direction for storing acid liquid, and the bottom end of the first storage tank 210 is in communication with the etching unit 100, and the acid liquid can flow into the etching unit 100 from the first storage tank 210. The pressure component 220 applies pressure to the acid liquid in the first storage tank 210 to hydraulically press the acid into the etching unit 100.

[0051] In this embodiment, the pressure component 220 is composed of a second storage tank 221 and a pump 222. Wherein, the second storage tank 221 is arranged in a vertical direction for storing pressure liquid, and the second storage tank 221 is in communication with the top end of the first storage tank 210 through a pump 222. When the pump 222 is turned on, the pressure liquid in the second storage tank 221 can be delivered to the first storage tank 210.

[0052] Correspondingly, a pressure member 211 is provided in the first storage tank 210, and the pressure member 211 separates the pressure liquid from the acid liquid to prevent the pressure liquid from mixing with the acid liquid. When the pressure liquid in the second storage tank 221 is delivered to the first storage tank 210, the pressure liquid pushes the pressure applying member 211 to move downward, transfers the pressure to the acid liquid, and then hydraulics the acid into the etching unit 100.

[0053] With this structure, it is possible to prevent the pump 222 from directly contacting the acid liquid, thereby preventing the pump 222 from being corroded by the acid liquid.

[0054] Specifically, the pump 222 is an advection pump 222, and the pressure member 211 is a fourth piston. The pressing member 211 is slidably arranged in the first storage tank 210 in a vertical direction, and the side wall of the pressing member 211 is closely attached to the inner side wall of the first storage tank 210.

[0055] In another embodiment of the present application, the pressure component 220 may also be a cylinder. The oil cylinder is erected on the top end surface of the first storage tank 210, and its piston rod vertically penetrates into the first storage tank 210 and is fixedly connected with the pressure member 211. When the piston rod of the oil cylinder extends, the acid can be hydraulically injected into the etching unit 100.

[0056] The etching unit 100 includes a first etching box 110, a second etching box 120, and a third etching box 130, respectively simulating a first-level seam, a second-level seam, and a third-level seam. Among them, the second-level seam is the branch seam of the first-level seam, and the third-level seam is the branch seam of the second-level seam.

[0057] Specifically, the first etching box 110 has a flat rectangular parallelepiped shape and is composed of a first box body 111 and a first cover 112. The first box body 111 and the first cover plate 112 are arranged along the thickness direction of the first etching box 110, and the first box body 111 and the first cover plate 112 are fixed together by a plurality of screws.

[0058] The first box body 111 is provided with a groove toward one side of the first cover plate 112. After the first cover plate 112 is closed on the first box body 111, the groove is closed to form a flat first cavity. , The first rock slab used to simulate the etching process of the first-level fracture wall is placed in the first cavity.

[0059] Along the length direction of the first etching box 110, one end of the first cavity is in communication with the first storage tank 210. The acid in the first storage tank 210 is pressed into the first cavity and reacts with the first rock slab.

[0060] In addition, a transparent observation window is provided on the first cover 112. Through the observation window, the experimenter can grasp the situation inside the first etching box 110 in time during the experiment.

[0061] Similarly, the second etching box 120 is also in the shape of a flat rectangular parallelepiped, and is composed of a second box body 121 and a second cover 122.

The thickness direction of the second etch box 120 is perpendicular to the thickness direction of the first etch box 110. The second box body 121 and the second cover plate 122 are arranged along the thickness direction of the second etching box 120, and the second box body 121 and the second cover plate 122 are fixed together by a plurality of screws.

[0062] The side of the second box body 121 facing the second cover plate 122 is also provided with a groove. After the second cover plate 122 is closed on the second box body 121, the groove is closed to form a flat second space. Cavity, the second rock slab used to simulate the etching process of the secondary fracture wall is placed in the second cavity.

[0063] Along the length direction of the second etching box 120, one end of the second etching box 120 is connected to the side of the first box body 111 facing away from the first cover 112, and the second cavity is connected to the first cavity. The cavity is connected. The acid in the first cavity is filtered off into the second cavity and reacts with the second rock slab.

[0064] A transparent observation window is also provided on the second cover 122. Through the observation window, the experimenter can grasp the situation inside the second etching box 120 in time during the experiment.

[0065] Similarly, the third etching box 130 is also in the shape of a flat rectangular parallelepiped, composed of a third box body 131 and a third cover 132, and the thickness direction of the third etching box 130 is the same as that of the first etching box 110 The thickness direction is parallel. The third box body 131 and the third cover plate 132 are arranged along the thickness direction of the third etching box 130, and the third box body 131 and the third cover plate 132 are fixed together by a plurality of screws.

[0066] The side of the third box body 131 facing the third cover plate 132 is also provided with a groove. After the third cover plate 132 is closed on the third box body 131, the groove is closed to form a flat third cavity. Cavity, the third rock slab used to simulate the etching process of the tertiary fracture wall is placed in the third cavity.

[0067] Along the length direction of the third etching box 130, one end of the third etching box 130 is connected to the side of the second box body 121 facing away from the second cover 122, and the third cavity is connected to the second cavity. The cavity is connected. The acid in the second cavity is filtered off into the third cavity and reacts with the third rock slab.

[0068] A transparent observation window is also provided on the third cover 132. Through the observation window, the experimenter can grasp the situation inside the third etching box 130 in time during the experiment.

[0069] The back pressure unit 300 includes a first container 310, a first back pressure component 320, a second container 330, a second back pressure component 340, a third container 350, and a third back pressure component 360.

[0070] The first container 310 is arranged in a vertical direction, and its top end is connected to an end of the first cavity facing away from the first storage tank 210. As the etching process in the first etching box 110 progresses, part of the acid solution gradually passes through the entire first etching box 110 and enters the first container 310. At this time, the first back pressure component 320 applies pressure to this part of the acid liquid to simulate the pressure in the formation to provide a pressure environment for the formation of supercritical carbon dioxide.

[0071] In this embodiment, the first back pressure component 320 is composed of a first nitrogen cylinder 321 and a first pressure regulating valve 322. The first nitrogen cylinder 321 is in communication with the bottom end of the first container 310, and the first pressure regulating valve 322 is connected between the first nitrogen cylinder 321 and the first container 310.

[0072] Correspondingly, a first pressure guiding member 311 is provided inside the first container 310. The acid liquid entering the inside of the first container 310 is always located above the first pressure guiding member 311, and the nitrogen entering the inside of the first container 310 is always located below the first pressure guiding member 311.

[0073] The first pressure regulating valve 322 is opened, the nitrogen in the first nitrogen cylinder 321 enters the first container 310, and the pressure is transferred to the acid liquid through the first pressure guiding member 311, thereby simulating the pressure in the formation, and the pressure is The size can be adjusted by the first pressure regulating valve 322.

[0074] Specifically, the first pressure guiding member 311 adopts a first piston, which is slidably arranged in the first container 310 in a vertical direction, and the side wall of the first piston closely fits with the inner side wall of the first container 310 . The nitrogen in the first nitrogen cylinder 321 enters the

When there is a container 310, there is a tendency to push the first piston upward, and the first piston squeezes the acid liquid above, thereby exerting pressure on the acid liquid.

[0075] Similarly, the second container 330 is also arranged in a vertical direction, and its top end is connected with an end of the second cavity facing away from the first etching box 110. As the etching process in the second etching box 120 progresses, part of the acid solution gradually passes through the entire second etching box 120 and enters the second container 330. At this time, the second back pressure component 340 applies pressure to this part of the acid liquid to simulate the pressure in the formation to provide a pressure environment for the formation of supercritical carbon dioxide.

[0076] In this embodiment, the second back pressure assembly 340 is composed of a second nitrogen cylinder 341 and a second pressure regulating valve 342. The second nitrogen cylinder 341 is in communication with the bottom end of the second container 330, and the second pressure regulating valve 342 is connected between the second nitrogen cylinder 341 and the second container 330.

[0077] Correspondingly, a second pressure guiding member is provided inside the second container 330. The acid liquid entering the second container 330 is always located above the second pressure guiding member, and the nitrogen entering the second container 330 is always located below the second pressure guiding member.

[0078] The second pressure regulating valve 342 is opened, the nitrogen in the second nitrogen cylinder 341 enters the second container 330, and the pressure is transmitted to the acid liquid through the second pressure guiding member, thereby simulating the pressure in the formation and the magnitude of the pressure It can be adjusted by the second pressure regulating valve 342.

[0079] Specifically, the second pressure guiding member adopts a second piston, which is slidably arranged in the second container 330 in a vertical direction, and the side wall of the second piston is closely attached to the inner side wall of the second container 330. When the nitrogen in the second nitrogen cylinder 341 enters the second container 330, there is a tendency to push the second piston upward, and the second piston squeezes the acid liquid above, thereby exerting pressure on the acid liquid.

[0080] Similarly, the third container 350 is also arranged in a vertical direction, and its top end is connected with an end of the third cavity facing away from the second etching box 120. As the etching process in the third etching box 130 progresses, part of the acid solution gradually passes through the entire third etching box 130 and enters the third container 350. At this time, the third back pressure component 360 applies pressure to this part of the acid liquid to simulate the pressure in the formation to provide a pressure environment for the formation of supercritical carbon dioxide.

[0081] In this embodiment, the third back pressure component 360 is composed of a third nitrogen cylinder 361 and a third pressure regulating valve 362. The third nitrogen cylinder 361 is in communication with the bottom end of the third container 350, and the third pressure regulating valve 362 is connected between the third nitrogen cylinder 361 and the third container 350.

[0082] Correspondingly, a third pressure guiding member is provided inside the third container 350. The acid liquid entering the third container 350 is always above the third pressure guiding member, and the nitrogen entering the third container 350 is always located below the third pressure guiding member.

[0083] The third pressure regulating valve 362 is opened, the nitrogen in the third nitrogen cylinder 361 enters the third container 350, and the pressure is transmitted to the acid liquid through the third pressure guide member, thereby simulating the pressure in the formation and the magnitude of the pressure It can be adjusted by the third pressure regulating valve 362.

[0084] Specifically, the third pressure guiding member adopts a third piston, and the third piston is slidably arranged in the third container 350 in a vertical direction, and the side wall of the third piston is closely attached to the inner side wall of the third container 350. When the nitrogen in the third nitrogen cylinder 361 enters the third container 350, there is a tendency to push the third piston upward, and the third piston squeezes the acid liquid above, thereby exerting pressure on the acid liquid.

[0085] The heating unit 400 includes a first heating plate, a second heating plate, and a third heating plate.

[0086] Specifically, the first heating plate is arranged on the side of the first box body 111 facing away from the first cover plate 112, and the heat is transferred to the first rock slab through the first box body 111, simulating the acid pressing etching process Temperature environment.

[0087] In this embodiment, the first heating plate is an electric heating plate, and a resistance wire is encapsulated inside the first heating plate, and the resistance wire converts electrical energy into internal energy after being energized.

[0088] In another embodiment of the present application, a heat exchange pipe may also be provided inside the first heating plate, and a high-temperature fluid (such as steam, water, etc.) is passed into the heat exchange pipe to transfer the heat of the high-temperature fluid. Give the first rock board.

[0089] Similarly, the second heating plate is arranged on the side of the second box body 121 facing away from the second cover plate 122, and the heat is transferred to the second rock slab through the second box body 121, simulating the acid pressing etching process Temperature environment.

[0090] Similarly, the third heating plate is arranged on the side of the third box body 131 facing away from the third cover plate 132, and passes through the third box body.

131 transfers heat to the third rock slab to simulate the temperature environment in the acid fracturing etching process.

Example 2

[0092] Please refer to FIG. 6, this embodiment provides an experimental method using the above-mentioned acid pressure etching experimental device, and the specific steps are as follows:

[0093] S1, check the back pressure unit 300. Confirm that the first pressure regulating valve 322, the second pressure regulating valve 342, and the third pressure regulating valve 362 are closed, and the first piston is in the middle of the first container 310, the second piston is in the middle of the second container 330, and the third piston is in the third. The middle of the container 350.

[0094] S2, assembling the etching unit 100. Open the first cover 112, the second cover 122 and the third cover 132, install the corresponding first, second, and third rock plates, and then reinstall the first cover 112 and the second cover. The board 122 and the third cover 132.

[0095] S3, configuring an acid solution. Open the first storage tank 210, take out the fourth piston, fill the first storage tank 210 with acid to the required amount for the experiment, and then put back the fourth piston.

[0096] S4, prepare back pressure. The first pressure regulating valve 322, the second pressure regulating valve 342, and the third pressure regulating valve 362 are opened, and the pressures of the first nitrogen cylinder 321, the second nitrogen cylinder 341, and the third nitrogen cylinder 361 are adjusted to above 7.38 MPa.

[0097] S5, simulate a temperature environment. Turn on the first heating plate, the second heating plate and the third heating plate, and heat the first rock slab, the second rock slab and the third rock slab to a temperature above 31°C.

[0098] S6, simulating the first stage etching. The pressure component 220 is used to hydraulically press the acid in the first storage tank 210 into the first cavity, the second cavity and the third cavity, so that the acid liquid and the first rock slab, the second rock slab, and the third rock slab are generated. chemical reaction.

[0099] Specifically, the pump 222 is turned on, the pressure liquid is injected into the first storage tank 210 with a preset displacement and pressure value, and the fourth piston in the first storage tank 210 is pushed, and then the acid liquid is pushed. Inject into the first cavity. Part of the acid liquid in the first cavity is filtered off into the second cavity, and part of the acid liquid in the second cavity is filtered off into the third cavity.

[0100] S7, simulating the second stage etching.

[0101] When the acid in the first cavity etches the first rock slab and enters the first container 310, the first back pressure component 320 applies pressure to the acid to simulate the pressure in the formation to provide the pressure to form supercritical carbon dioxide surroundings. The carbon dioxide generated by the reaction between the acid liquid and the first rock slab is in a supercritical state and mixed with the acid liquid in an environment greater than 31°C and higher than 7.38 MPa.

[0102] When the acid in the second cavity etches the second rock slab and enters the second container 330, the second back pressure component 340 applies pressure to the acid to simulate the pressure in the formation to provide the pressure to form supercritical carbon dioxide surroundings. The carbon dioxide generated by the reaction between the acid liquid and the second rock slab is in a supercritical state and mixed with the acid liquid in an environment greater than 31°C and higher than 7.38 MPa.

[0103] When the acid in the third cavity etches the third rock slab and enters the third container 350, the third back pressure component 360 applies pressure to the acid to simulate the pressure in the formation to provide the pressure to form supercritical carbon dioxide surroundings. The carbon dioxide generated by the reaction between the acid liquid and the third rock slab is in a supercritical state and mixed with the acid liquid in an environment greater than 31°C and higher than 7.38MPa.

[0104] S8, observe the results. Take out the first rock slab, the second rock slab and the third rock slab, and observe the etching morphology.

[0105] On the whole, the less smooth the etching form, the more complicated the oil and gas flow channel formed after the acid fracturing is over and the fracture is closed, that is, the better the acid effect. From a local perspective, the greater the depth of the etched trench, the end of acid fracturing and the closure of the crack

Later, the larger the cross-sectional area of the formed oil and gas flow channel, the better the acid fracturing effect.

[0106] In the above-mentioned test process, the first heating plate, the second heating plate and the third heating plate were used to heat the first rock slab, the second rock slab and the third rock slab, respectively, to provide the formation of supercritical carbon dioxide. Temperature environment. At the same time, the back pressure unit 300 is used to apply back pressure to the acid liquid to simulate the pressure in the formation to provide a pressure environment for the formation of supercritical carbon dioxide. In this environment, the acid liquid reacts with the first rock slab, the second rock slab and the third rock slab to generate supercritical carbon dioxide, and the carbon dioxide is mixed with the acid liquid, which can more accurately simulate the acid pressure in the branch joints under the high temperature and high pressure environment During the etching process, more accurate etching results are obtained.

Example 3

[0108] Please refer to FIG. 7, the difference from Embodiment 1 is that the structure of the first pressure guiding member 311 is different.

[0109] Specifically, a horizontal flange is welded on the inner side wall of the first container 310, and the first pressure guiding member 311 uses a first elastic membrane. The first elastic membrane is arranged in the horizontal direction and fixed on the flange plate by bolts.

[0110] The first elastic membrane separates the acid liquid from the nitrogen. When the nitrogen in the first nitrogen cylinder 321 enters the first container 310, the first elastic membrane is squeezed, so that the middle of the first elastic membrane has an upward convex deformation. Trend, and then transfer pressure to the acid above the first elastic membrane.

[0111] Similarly, the second pressure guiding member may also be a second elastic membrane, and the third pressure guiding member may also be a third elastic membrane.

[0112] In all the examples shown and described herein, any specific value should be interpreted as merely exemplary rather than limiting, and therefore, other examples of the exemplary embodiment may have different values.

[0113] It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined in subsequent drawings. And explanation.

[0114] The above-mentioned embodiments only express several embodiments of the present invention, and their description is more specific and detailed, but they should not be interpreted as limiting the scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all fall within the protection scope of the present invention.