Horizontal well staged fracturing simulation wellbore, its experimental device and experimental method

Abstract

The present invention relates to a horizontal well segmented fracturing simulation wellbore, an experimental device and an experimental method thereof, and relates to the technical field of oil and gas field production increase measures, and is used to realize the simulation of crack expansion under conditions of different fracturing segment numbers and segment spacings. The horizontal well segmented fracturing simulation wellbore of the present invention includes an external simulation wellbore, an internal sealing bridge plug, and an injection connection pipeline, and adopts modular assembly. Each wellbore is convenient and practical to assemble, and can perform crack expansion simulation under conditions of different fracturing segment numbers and segment spacings. Therefore, the simulation wellbore of the present invention is closer to the real simulation wellbore and fracturing process, and the perforation simulation of the fracturing wellbore can perform spiral perforation, directional perforation, and flow-limiting perforation simulation, and can conveniently perform various types of perforation parameter simulations.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field production increase measures, and in particular to a horizontal well staged fracturing simulation wellbore, an experimental device and an experimental method thereof. Background Art

[0002] With the continuous advancement of exploration and development technology, the development of unconventional oil and gas reservoirs is becoming more and more vigorous. For unconventional oil and gas reservoirs, horizontal well staged fracturing is an important means of increasing production and a major measure to achieve its economical and efficient development. During the design and construction of horizontal well staged fracturing, the horizontal well is divided into several fracturing sections according to the characteristics of the reservoir oil and gas content, fracturability and geostress around the horizontal wellbore trajectory, and strives to form multiple fracturing cracks during the fracturing process to increase the fracturing volume. During the horizontal well fracturing process, the fracturing crack morphology has an important influence on the fracturing effect. The fracturing crack expansion morphology is related to reservoir characteristics, natural fractures, the number of perforation sections and the interval between sections, and the scale of fracturing. Indoor experiments and numerical simulations are important means to study the expansion of hydraulic fracturing cracks. Among them, indoor experiments can intuitively observe the expansion characteristics of fracturing cracks. A large number of experimental instrument development and experimental test studies have been carried out for horizontal well fracturing at home and abroad, forming different types of experimental instruments, and studying the influence of lithology, geostress, construction parameters, perforation parameters, etc. on the expansion of fracturing cracks.

[0003] A large number of instrument research and experimental tests have been conducted at home and abroad on the physical simulation experiments of fracture expansion during fracturing transformation. After investigation, it was found that the existing experimental instruments and test methods have the following characteristics: (1) Perforation simulation is difficult. The experimental specimens of existing experimental instruments are generally 30-50cm cubes or cuboids. According to the similarity criterion, the size of the experimental wellbore is relatively small. Under the conditions of small-scale wellbore, the perforation holes are difficult to process. Therefore, it is difficult to consider the perforation in the experimental simulation wellbore, especially the spiral perforation method in the actual fracturing transformation process is difficult to simulate experimentally. (2) It is difficult to simulate segmented fracturing. The simulated wellbore of existing experimental instruments is mainly single-stage single cluster or single-stage multi-cluster experimental tests. Due to the size of the simulated wellbore and the cost of experimental testing, the sealing components of the simulated wellbore segmented fracturing are difficult to process. Most experimental instruments cannot consider segmented sealing in the simulated wellbore. Summary of the invention

[0004] The present invention provides a horizontal well staged fracturing simulation wellbore, an experimental device and an experimental method thereof, which are used to realize the simulation of crack expansion under the conditions of different fracturing stage numbers and stage spacings.

[0005] According to a first aspect of the present invention, the present invention provides a horizontal well staged fracturing simulation wellbore, comprising:

[0006] External simulated wellbore, which is used to simulate the casing used in fracturing stimulation and actual production;

[0007] an internal sealing bridge plug, which is disposed in the external simulated wellbore and is used to isolate at least a portion of the external simulated wellbore; and

[0008] An injection connection pipeline, which is inserted into the external simulated wellbore and connected to the internal sealing bridge plug, and is used to pump in experimental fluid;

[0009] The external simulated wellbore includes an upper simulated wellbore, a bottom perforated simulated wellbore and at least one intermediate perforated wellbore arranged between the upper simulated wellbore, and the diameter of the intermediate perforated wellbore is the same as that of the upper simulated wellbore to achieve modular assembly.

[0010] In one embodiment, the upper simulated wellbore, the middle perforated wellbore and the bottom perforated simulated wellbore are all provided with holes along their respective radial directions.

[0011] In one embodiment, a thin-walled tube is sealingly bonded in the hole to form a perforation hole, and a cross groove is arranged on the thin-walled tube along its length direction, and the depth of the cross groove is at least 60% of the thin-walled tube.

[0012] In one embodiment, the perforations are arranged in one or more distribution modes including spiral perforation, directional perforation or flow-limiting perforation.

[0013] In one embodiment, at least a first annular groove is disposed on the outer walls of the upper simulated wellbore, the middle perforated wellbore and the bottom perforated simulated wellbore.

[0014] In one embodiment, the upper end of the upper simulated wellbore is provided with a sealing connector for fixedly connecting the injection connecting pipeline, the lower end of the upper simulated wellbore is connected to the upper end of the middle perforation wellbore by a thread, and the lower end of the middle perforation wellbore is connected to the upper end of the bottom perforation simulated wellbore by a thread.

[0015] In one embodiment, the internal sealing bridge plug comprises a bridge plug tube, the upper end of which is connected to the injection connection line.

[0016] At least one second annular groove for installing a sealing ring is respectively arranged at the upper and lower ends of the outer wall of the bridge plug tube, and at least one sealing bridge plug hole is arranged along its radial direction at the middle part of the bridge plug tube.

[0017] According to a second aspect of the present invention, the present invention provides an experimental device including the above-mentioned horizontal well staged fracturing simulation wellbore, further comprising:

[0018] The horizontal well is subjected to staged fracturing to simulate the experimental specimen including the wellbore cementation;

[0019] A loading device for performing principal stress loading on the test specimen; and

[0020] An injection device for pumping a test fluid into the injection connection pipeline;

[0021] Wherein, the loading device comprises loading baffles for loading along three directions of the experimental specimen respectively.

[0022] In one embodiment, the loading device further includes a control system and a three-way principal stress loading injection pump electrically connected to the control system, and the three-way principal stress loading injection pump is respectively connected to the loading baffles.

[0023] In one embodiment, an acoustic emission probe for acoustic emission monitoring is provided on the loading baffle.

[0024] In one embodiment, the injection device comprises an experimental fluid injection pump and a liquid injection pipeline connecting the experimental fluid injection pump and the injection connecting pipeline, and an intermediate container is also arranged on the liquid injection pipeline.

[0025] According to a third aspect of the present invention, the present invention provides an experimental method for simulating a wellbore by staged fracturing of a horizontal well, comprising the following steps:

[0026] Step 1: Determine the fracturing sequence during the experiment;

[0027] Step 2: according to the fracturing sequence, moving the internal sealing bridge plug to a corresponding position in the external simulated wellbore;

[0028] Step 3: pumping the experimental fluid into the injection connection pipeline until the fracturing cracks extend to the boundary of the experimental specimen or extend into the cracks of other fracturing sections;

[0029] Step 3: After the single-stage experiment is completed, the internal sealing bridge plug is moved to the position of the next perforation stage, and step 3 is repeated until all the fracturing stages have completed the experimental test;

[0030] Step 4: Observe the crack extension on the end face of the test specimen, perform CT scanning of crack extension to clarify the crack extension inside the specimen, and observe the crack extension law and extension of the test specimen.

[0031] Compared with the prior art, the advantages of the present invention are that it adopts modular assembly, each wellbore is easy and practical to assemble, and can simulate the fracture extension under different fracturing stage numbers and stage spacing conditions. Therefore, the simulated wellbore of the present invention is closer to the real simulated wellbore and fracturing process, and the perforation simulation of the fracturing wellbore can perform spiral perforation, directional perforation and flow-limiting perforation simulation, and can conveniently perform various types of perforation parameter simulations, thereby providing basic parameters and technical support for hydraulic fracturing perforation parameters, clustering parameters, construction parameters and fracturing material optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Hereinafter, the present invention will be described in more detail based on embodiments and with reference to the accompanying drawings.

[0033] Figure 1 is an axial cross-sectional view of a simulated wellbore for staged fracturing of a horizontal well in an embodiment of the present invention;

[0034] Figure 2 It is a schematic diagram of the structure of an experimental device for simulating a wellbore by staged fracturing of a horizontal well in an embodiment of the present invention.

[0035] Reference numerals:

[0036] 1-injection connection pipeline; 2-sealing connection; 3-upper simulated wellbore;

[0037] 4,7,9,13,15,23-first annular groove;

[0038] 5,10,18-eyelets;

[0039] 6,11,19 - perforation holes;

[0040] 8,14-Turnbuckle;

[0041] 12-middle perforation simulated wellbore; 16, 22-seal ring; 17-sealed bridge plug hole; 20-internal sealed bridge plug;

[0042] 21-bottom perforation simulation wellbore; 24-sealing plate; 25-experimental specimen; 26-horizontal well staged fracturing simulation wellbore; 27-vertical stress loading baffle; 28-horizontal maximum principal stress loading baffle; 29-horizontal minimum principal stress loading baffle; 30-vertical principal stress loading pipeline; 31-horizontal minimum principal stress loading pipeline; 32-horizontal maximum principal stress loading pipeline; 33-experimental fluid injection pipeline; 34-pressure gauge; 35-intermediate container; 36-fracturing fluid injection pump; 37-three-way principal stress loading injection pump; 38-control system. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the accompanying drawings.

[0044] Example 1

[0045] like Figure 1 As shown, according to the first aspect of the present invention, the present invention provides a horizontal well staged fracturing simulation wellbore, including an external simulation wellbore 100, an internal sealing bridge plug 20 and an injection connection pipeline 1. The external simulation wellbore 100 is used to simulate the casing used in actual production. The internal sealing bridge plug 20 is arranged in the external simulation wellbore 100, and is used to isolate at least part of the external simulation wellbore 100. The injection connection pipeline 1 is inserted into the external simulation wellbore 100 and is connected to the internal sealing bridge plug 20, and is used to pump in the experimental fluid.

[0046] In combination with the "multi-stage clustering" fracturing process and experimental level, the external simulated wellbore 100 uses different types of wellbores for modular assembly design. For example, the external simulated wellbore 100 includes an upper simulated wellbore 3, a bottom perforated simulated wellbore 21, and at least one intermediate perforated simulated wellbore 12 disposed between the upper simulated wellbore 3. The number of sections of the intermediate perforated simulated wellbore 12 can be designed as needed. The diameter of the intermediate perforated simulated wellbore 12 is the same as the diameter (e.g., outer diameter and inner diameter) of the upper simulated wellbore 3, thereby achieving modular assembly.

[0047] First, the upper simulated wellbore 3 is described in detail. The upper simulated wellbore 3 is mainly used to connect the middle simulated wellbore 12, form a perforation fracturing section, and fix the injection connection pipeline 1. The upper simulated wellbore 3 is both a fracturing simulation well section and a fracturing wellhead.

[0048] In addition, a sealing connector 2 for fixing and connecting the injection connection pipeline 1 is provided at the upper end of the upper simulated wellbore 3, and the lower end of the upper simulated wellbore 3 is connected to the upper end of the middle perforation simulated wellbore 12 by threads. For example, a screw button 8 can be provided at the lower port of the upper simulated wellbore 3 to connect with the middle perforation simulated wellbore 12.

[0049] The length of the upper simulated wellbore 3 is 100 mm to 150 mm, the outer diameter of the upper simulated wellbore 3 is 20 mm, and the inner diameter is 15.0 mm. It can be understood that the length and diameter of the upper simulated wellbore 3 can be adjusted as needed.

[0050] The intermediate perforated simulation wellbore 12 is mainly used to isolate the experimental specimen 25, connect the perforated holes 6, 11, 19 described below to form a fracturing section, etc. The single section length of the intermediate perforated simulation wellbore 12 is 50 mm to 150 mm, which can be processed according to actual needs. The upper and lower ends of the intermediate perforated simulation wellbore 12 are both provided with threads to be connected to the upper simulation wellbore 3 and the bottom perforated simulation wellbore 21 respectively, thereby realizing the modular assembly of the simulation wellbore. According to the experimental requirements, a simulation wellbore may be equipped with multiple intermediate perforated simulation wellbores 12 to simulate multiple fracturing sections.

[0051] The length of the bottom perforated simulation wellbore 21 is 50 mm to 150 mm, and one end of the bottom perforated simulation wellbore 21 is sealed and welded through a sealing plate 24. A screw button 14 is provided at the upper end of the bottom perforated simulation wellbore 21 to facilitate assembly with the middle perforated simulation wellbore 12.

[0052] Therefore, through one upper simulated wellbore 3, one or more middle perforated simulated wellbores 12 and one bottom perforated simulated wellbore 21, a staged fracturing simulated wellbore required for different types of experiments can be assembled.

[0053] Furthermore, the upper simulated wellbore 3 , the middle perforated simulated wellbore 12 and the bottom perforated simulated wellbore 21 are all provided with holes 5 , 10 , 18 along their respective radial directions.

[0054] Specifically, the upper simulated wellbore eyelet 5 of the upper simulated wellbore 3 can be arranged according to the experimental plan, and the inner diameter of the eyelet 5 is 1.5mm-3.0mm, which is the fracturing section of the experimental test during the experimental test. The inner diameter of the middle perforated simulated wellbore eyelet 10 of the middle perforated simulated wellbore 12 is a 1.5mm-3.0mm eyelet, which is used to form the simulated perforated eyelet. The bottom perforated simulated wellbore eyelet 18 of the bottom perforated simulated wellbore 21 can be arranged in the same manner as the middle perforated simulated wellbore eyelet 10, so as to form the perforated eyelet.

[0055] Furthermore, each of the holes 5, 10, 18 is sealed with a thin-walled tube to form a perforation hole 6, 11, 19, and a cross groove is provided on the thin-walled tube along its length, and the depth of the cross groove is at least 60% of the thin-walled tube. Figure 1 As shown, a hard plastic thin-walled pipe is sealed and bonded in the upper simulated wellbore hole 5 to form an upper simulated wellbore perforation hole 6, a hard plastic thin-walled pipe is sealed and bonded in the middle perforation simulated wellbore hole 10 to form an middle perforation simulated wellbore perforation hole 11, and a hard plastic thin-walled pipe is sealed and bonded in the bottom perforation simulated wellbore hole 18 to form a bottom perforation simulated wellbore perforation hole 19. The arrangement mode and perforation hole length of the middle perforation simulated wellbore perforation hole 11 can be adjusted as required.

[0056] Each hole 5 is sealed and fixed to the thin-walled tube by epoxy resin. According to the size of the hole 5, the inner diameter of the thin-walled tube can be 1mm to 3mm, and the length can be 10mm to 50mm. The thin-walled tube can be used to simulate the perforation holes with an inner diameter of 1mm to 3mm and a length of 10mm to 50mm, which can be determined according to needs. Therefore, using the holes and thin-walled tubes of each wellbore, different phase angles, azimuths, hole densities, perforation inner diameters, perforation hole lengths, etc. can be formed, thereby simulating the effects of different perforation parameters on the expansion of staged fracturing cracks.

[0057] The perforations 6, 11, 19 mentioned above can be arranged in one or more of the following ways: spiral perforation, directional perforation or flow-limiting perforation in the actual fracturing process.

[0058] At least first annular grooves 4, 7, 9, 13, 15, 23 are provided on the outer walls of the upper simulated wellbore 3, the middle perforated simulated wellbore 12 and the bottom perforated simulated wellbore 21, which are used to strengthen the anchoring force between each wellbore and the experimental specimen during the casting process of the experimental specimen, thereby enhancing the sealing performance of each wellbore and the experimental specimen 25.

[0059] For example, one or more upper simulated wellbore upper annular grooves 4 and one or more upper simulated wellbore lower annular grooves 7 are respectively provided at the upper end and the lower end of the upper simulated wellbore 3, and the inner diameters of the upper simulated wellbore upper annular grooves 4 and the upper simulated wellbore lower annular grooves 7 are 2.0 mm. In addition, a first annular groove may be provided in the middle of the upper simulated wellbore 3.

[0060] The upper and lower ends of the intermediate perforation simulation wellbore 12 are respectively provided with one or more intermediate perforation simulation wellbore annular grooves 9 and one or more intermediate perforation simulation wellbore lower end annular grooves 13, and the inner diameters of the intermediate perforation simulation wellbore annular grooves 9 and the intermediate perforation simulation wellbore lower end annular grooves 13 are 2.0 mm. In addition, a first annular groove may be provided in the middle portion of the intermediate perforation simulation wellbore 12.

[0061] The upper and lower ends of the bottom perforation simulation wellbore 21 are respectively provided with an upper annular groove 15 and one or more lower annular grooves 23, and the inner diameters of the upper annular groove 15 and the lower annular groove 23 are 2.0 mm. In addition, a first annular groove can be provided in the middle of the bottom perforation simulation wellbore 21.

[0062] The internal sealing bridge plug 20 includes a bridge plug tube (sealed bridge plug tube), which is mainly used to isolate part of the simulated wellbore, so that the experimental fluid is injected into the experimental specimens of different perforation and fracturing sections through the bridge plug tube and perforation holes to form fracturing cracks.

[0063] The upper end of the bridge plug tube is provided with a screw hole with an inner diameter of 5 mm for connecting with the injection connecting pipeline 1, and the lower part thereof is completely sealed.

[0064] Preferably, the bridge plug tube has an outer diameter of 13.5 mm, an inner diameter of 9.0 mm, and a length of 100 mm.

[0065] At least one second annular groove for installing the sealing ring 16, 22 is provided at each of the upper and lower ends of the outer wall of the bridge plug tube. Figure 1As shown, the number of the second annular grooves at the upper end of the bridge plug tube can be two, and each second annular groove is provided with a sealing ring 16; the number of the second annular grooves at the lower end of the bridge plug tube can also be two, and each second annular groove is provided with a sealing ring 22. The diameter of the second annular groove can be 1.5 mm, and the sealing rings 16 and 22 can be annular rubber sealing rings with a diameter of 2.0 mm.

[0066] The middle portion of the bridge plug tube is provided with at least one sealing bridge plug hole 17 extending in its radial direction. Figure 1 As shown, four sealed bridge plug holes 17 with a diameter of 2 mm are arranged on the bridge plug tube, so that the experimental fluid entering the bridge plug tube flows toward the perforated holes to form fracturing cracks.

[0067] The horizontal well segmented fracturing simulation wellbore of the present invention adopts modular assembly, and each wellbore is easy and practical to assemble, and can simulate the fracture expansion under different fracturing segment numbers and segment spacing conditions. Therefore, the simulated wellbore of the present invention is closer to the real simulated wellbore and fracturing process, and the perforation simulation of the fracturing wellbore can perform spiral perforation, directional perforation and flow-limiting perforation simulation, and can conveniently perform various types of perforation parameter simulations. In addition, the simulated wellbore of the present invention utilizes the internal sealing bridge plug 20 and the external simulated wellbore 100 to realize the simulation of fracturing fracture expansion in any order, including the simulation order from top to bottom, from bottom to top, first in the middle and then at both ends, or first at both ends and then in the middle.

[0068] Since each wellbore can consider not only conditions such as the number of fracturing stages, stage spacing, and perforation parameters, it is also possible to consider well types such as vertical wells and horizontal wells in combination with the fracturing technology.

[0069] Example 2

[0070] like Figure 2 As shown, according to the second aspect of the present invention, the present invention provides an experimental device including the above-mentioned horizontal well segmented fracturing simulation wellbore 26, and the experimental device also includes an experimental specimen 25 that cements the horizontal well segmented fracturing simulation wellbore 26, a loading device for performing principal stress loading on the experimental specimen 25, and an injection device for pumping experimental fluid into the injection connecting pipeline 1.

[0071] The loading device includes loading baffles for loading along three directions of the test specimen 25. Figure 2 As shown, the loading device includes a vertical stress loading baffle 27 and a horizontal maximum principal stress loading baffle 28 arranged on the side of the experimental specimen 25 and a horizontal minimum principal stress loading baffle 29 arranged at the bottom of the experimental specimen 25 .

[0072] The loading device also includes a control system 38 and a three-way principal stress loading injection pump 37 electrically connected to the control system 38. The three-way principal stress loading injection pump 37 is connected to the vertical stress loading baffle 27 through a vertical principal stress loading pipeline 30, is connected to the horizontal maximum principal stress loading baffle 28 through a horizontal maximum principal stress loading pipeline 32, and is connected to the horizontal minimum principal stress loading baffle 29 through a horizontal minimum principal stress loading pipeline 31.

[0073] In addition, if acoustic emission monitoring is required, an acoustic emission probe for acoustic emission monitoring may be provided on each loading plate.

[0074] The injection device includes an experimental fluid injection pump 36 and an experimental fluid injection pipeline 33 connecting the experimental fluid injection pump 36 and the injection connection pipeline 1. An intermediate container 35 for storing the experimental fluid is also provided on the experimental fluid injection pipeline 33. In addition, a pressure gauge 34 is also provided on the experimental fluid injection pipeline 33 to indicate the pipeline pressure.

[0075] According to the above-mentioned horizontal well staged fracturing simulation wellbore 26, not only the horizontal well staged simulation can be performed, but also the layered fracture extension simulation of different types of lithology or reservoirs in the vertical well can be realized.

[0076] In addition, the "multi-stage clustering" fracturing fracture propagation simulation of horizontal wells can be carried out to study the influence of the number of fracturing stages, stage spacing, hole parameters, construction parameters, lithology, etc. on fracture propagation. At the same time, the vertical well layered fracturing fracture propagation simulation can also be carried out to study the fracturing fracture propagation under different lithology, reservoir thickness, interlayer properties and other conditions.

[0077] Therefore, the experimental device of the present invention is combined with the horizontal well staged fracturing simulation wellbore 26 in the above-mentioned embodiment 1, which can simulate the fracturing initiation and crack propagation morphology during the vertical well layered fracturing and horizontal well staged fracturing. The simulated wellbore and experimental method of the present invention belong to the field of oil and gas field production increase measures, and can provide theoretical support for the optimization of fracturing transformation process, construction parameter optimization and liquid performance.

[0078] Example 3

[0079] According to the third aspect of the present invention, the present invention provides an experimental method for the above-mentioned horizontal well segmented fracturing simulation wellbore 26, which needs to construct experimental method steps matching the simulated wellbore based on the characteristics of the simulated wellbore and combined with the conditions of the fracturing transformation physical simulation experimental system.

[0080] First, carry out experimental preparation work.

[0081] Specifically, the experimental scheme needs to be specified. According to the fracturing process and reservoir conditions in the study area, the experimental fracturing method is clarified, and the parameters such as the size of the experimental specimen, the perforation scheme (such as the size and distribution of the perforation holes, etc.), the number of fracturing stages (such as the number of intermediate perforation simulation wellbores 12, etc.), and the interval between stages are determined. Then, the overall length of the external simulation wellbore 100 and the length of each component are determined, and the perforation scheme, hole length, injection displacement, ground stress and other parameters are clarified. According to the various parameters, the corresponding experimental scheme and experimental process are compiled, and the experimental results description and record table are compiled.

[0082] Then the processing of the experimental specimen 25 was carried out.

[0083] Since the experimental specimen 25 is a horizontal well staged fracturing simulation wellbore 26 cemented therein, it is necessary to first form the above-mentioned horizontal well staged fracturing simulation wellbore 26. The simulation wellbore is processed according to the wellbore parameters determined in the above-mentioned experimental scheme to form the various parts of the simulation wellbore required by the experimental scheme. Holes are drilled on each simulation wellbore according to the experimental scheme, and then each simulation wellbore is assembled. After the simulation wellbore is assembled, the perforation holes are processed and installed, and the thin-walled pipe is fixed to the holes of each external simulation wellbore with epoxy resin to form the perforation holes.

[0084] After the horizontal well staged fracturing simulation wellbore 26 is processed and assembled, it is cast to form an experimental specimen 25. First, the experimental material of the experimental specimen 25 is determined. The experimental material mainly includes concrete mixed with cement and fine sand or materials that are reprocessed after the reservoir outcrop in the target area is crushed. Concrete with mechanical properties similar to the research target is prepared by using cement and fine sand, or the outcrop in the target area is crushed and processed for the experimental specimen 25.

[0085] During the processing of the experimental specimen 25, the prepared material is poured into a mold, and the horizontal well staged fracturing simulation wellbore 26 is pre-buried in the mold during the pouring process. After the processing is completed, the mold is removed and the experimental specimen 25 is obtained after it is naturally dried for about one month.

[0086] Next, the experimental device in the above-mentioned Example 2 was assembled.

[0087] After the experimental specimen 25 meets the experimental requirements, the experimental specimen 25 is loaded into the experimental frame, the corresponding loading baffles are installed, and the main stress loading pipelines and the experimental fluid injection pipeline 33 are connected. If acoustic emission monitoring is required, during the loading process of the experimental specimen 25, the acoustic emission probe is installed in each loading baffle and the corresponding lines are connected.

[0088] Third, implement the fracturing test experimental process.

[0089] The experimental fracturing fluid is prepared according to the experimental requirements, and the experimental fluid required for the experiment, that is, the viscosity of the fracturing fluid, is prepared. A certain amount of tracer is added to the experimental fluid, and the experimental fluid is placed in the intermediate container 35 after the experimental fluid is prepared.

[0090] According to the experimental plan, the three-dimensional principal stress is loaded to the designed value. After loading, the fracturing injection sealing test is carried out. After the wellbore injection pressure is about 5.0MPa and stabilized for 3-5min, the stability of the three-dimensional principal stress and liquid injection pressure is observed. Under the condition of good sealing of the initial test pressure, the fracturing test is carried out. During the fracturing test, the vertical well stratified fracturing or the horizontal well "multi-stage clustered" fracturing is mainly considered, and multi-stage testing is required.

[0091] The fracturing test experiment includes the following steps:

[0092] Step 1: Determine the fracturing sequence during the experiment. The experiment can start fracturing from the bottom perforated simulated wellbore 21, the upper simulated wellbore 3, or the middle perforated simulated wellbore 12.

[0093] Step 2: According to the fracturing sequence, adjust the internal sealing bridge plug 20 to a corresponding position in the external simulated wellbore.

[0094] Step 3: Pump the experimental fluid into the injection connection pipeline 1 until the fracturing cracks extend to the boundary of the experimental specimen 25 or extend into the cracks of other fracturing sections.

[0095] Step 3: After the single-stage test is completed, the internal sealing bridge plug 20 is adjusted again to be located at the position of the next perforation stage, and step 3 is repeated until all the fracturing stages have completed the experimental test.

[0096] Step 4: After the experiment is completed, the pressure of the experimental fluid injection pipeline 33 is unloaded, and then the three-dimensional principal stress is unloaded, all pressures are unloaded to atmospheric pressure, and then the experimental specimen 25 is taken out to observe the crack expansion on the end face of the experimental specimen 25.

[0097] First, a preliminary observation of the crack expansion is made. A large-scale CT scanning instrument can also be used to perform a CT scan of the crack expansion to clarify the crack expansion situation inside the specimen.

[0098] In addition, the test specimen 25 can be knocked open to observe the crack expansion law and extension of the test specimen 25.

[0099] By using the simulated wellbore in Example 1 and the experimental method in Example 3, the "multi-stage clustering" fracturing crack expansion simulation of horizontal wells can be carried out, and the influence of the number of fracturing stages, stage spacing, hole parameters, construction parameters, lithology, etc. on the crack expansion can be studied. At the same time, vertical well layered fracturing crack expansion simulation can also be carried out to study the crack expansion under different lithology, reservoir thickness, interlayer properties, etc. Therefore, the present invention can study the influence of fracturing stage spacing, fracturing stage number, ground stress and construction parameters on the crack expansion law of staged fracturing, and the research results can provide theoretical support for fracturing transformation segmentation, construction parameter optimization, etc.

[0100] Although the present invention has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A horizontal well staged fracturing simulation wellbore, characterized in that: include: External simulated wellbore, which is used to simulate the casing used in fracturing stimulation and actual production; an internal sealing bridge plug, which is disposed in the external simulated wellbore and is used to isolate at least a portion of the external simulated wellbore; and An injection connection pipeline, which is inserted into the external simulated wellbore and connected to the internal sealing bridge plug, and is used to pump in experimental fluid; The external simulated wellbore includes an upper simulated wellbore, a bottom perforated simulated wellbore, and a plurality of intermediate perforated wellbores arranged between the upper simulated wellbore, and the diameter of the intermediate perforated wellbore is the same as that of the upper simulated wellbore to achieve modular assembly; the outer diameter of the simulated wellbore is 20 mm, and the inner diameter is 15.0 mm; The internal sealing bridge plug comprises a bridge plug tube, the outer diameter of the bridge plug tube is 13.5 mm, the inner diameter is 9.0 mm, the upper end of the bridge plug tube is connected to the injection connection pipeline, the upper and lower ends of the outer wall of the bridge plug tube are respectively provided with at least one second annular groove for installing a sealing ring, and the middle part of the bridge plug tube is provided with at least one sealing bridge plug hole arranged along its radial direction; the internal sealing bridge plug and the external simulated wellbore can realize the simulation sequence from top to bottom, from bottom to top, first the middle and then the two ends, or first the two ends and then the middle; the upper simulated wellbore, the middle perforated wellbore and the bottom perforated simulated wellbore are all provided with holes along their respective radial directions; A thin-walled tube is sealed and bonded in the hole to form a perforation hole. A cross groove is arranged on the thin-walled tube along its length direction. The depth of the cross groove is at least 60% of the thin-walled tube. By using the holes and thin-walled tubes of each wellbore, different phase angles, azimuth angles, hole densities, perforation inner diameters and perforation hole lengths can be formed, thereby simulating the influence of different perforation parameters on the expansion of staged fracturing cracks.

2. The horizontal well staged fracturing simulation wellbore according to claim 1, characterized in that: The perforation holes are made in accordance with one or more perforation modes including spiral perforation, directional perforation or flow-limiting perforation.

3. The horizontal well staged fracturing simulation wellbore according to claim 1 or 2, characterized in that: At least a first annular groove is disposed on the outer walls of the upper simulated wellbore, the middle perforated wellbore and the bottom perforated simulated wellbore.

4. The horizontal well staged fracturing simulation wellbore according to claim 1 or 2, characterized in that: The upper end of the upper simulated wellbore is provided with a sealing connector for fixedly connecting the injection connecting pipeline, the lower end of the upper simulated wellbore is connected to the upper end of the middle perforation wellbore by a thread, and the lower end of the middle perforation wellbore is connected to the upper end of the bottom perforation simulated wellbore by a thread.

5. An experimental device for simulating a horizontal well staged fracturing wellbore according to any one of claims 1 to 4, characterized in that: Also includes: The horizontal well is subjected to staged fracturing to simulate the experimental specimen including the wellbore cementation; A loading device for applying principal stress to the experimental specimen; as well as An injection device for pumping experimental fluid into the injection connection pipeline; Wherein, the loading device comprises loading baffles for loading along three directions of the experimental specimen respectively.

6. The horizontal well staged fracturing simulation wellbore according to claim 5, characterized in that: The loading device also includes a control system and a three-way principal stress loading injection pump electrically connected to the control system, and the three-way principal stress loading injection pump is respectively connected to the loading baffles.

7. The horizontal well staged fracturing simulation wellbore according to claim 5 or 6, characterized in that: The loading baffle is provided with an acoustic emission probe for acoustic emission monitoring.

8. The horizontal well staged fracturing simulation wellbore according to claim 5 or 6, characterized in that: The injection device comprises an experimental fluid injection pump and a liquid injection pipeline connecting the experimental fluid injection pump and the injection connecting pipeline, and an intermediate container is also arranged on the liquid injection pipeline.

9. An experimental method for simulating a wellbore by staged fracturing of a horizontal well according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Determine the fracturing sequence during the experiment; Step 2: according to the fracturing sequence, moving the internal sealing bridge plug to a corresponding position in the external simulated wellbore; Step 3: pumping the experimental fluid into the injection connection pipeline until the fracturing cracks extend to the boundary of the experimental specimen or extend into the cracks of other fracturing sections; Step 3: After the single-stage experiment is completed, the internal sealing bridge plug is moved to the position of the next perforation stage, and step 3 is repeated until all the fracturing stages have completed the experimental test; Step 4: Observe the crack propagation on the end face of the test specimen, perform a CT scan of the crack propagation to clarify the crack propagation inside the specimen, and observe the crack propagation law and extension of the crack of the test specimen.

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