Experimental device and experimental method for segmented multi-cluster fracturing of horizontal wellbore

Abstract

The embodiment of the invention provides an experimental device for horizontal wellbore segmented multi-cluster fracturing and an experimental method thereof.The experimental device comprises a simulation wellbore, a plurality of perforation pieces and a plurality of connecting pipelines, the simulation wellbore is used for being arranged in a rock stratum sample, and a plurality of fracturing spaces are defined in the simulation wellbore in the length direction; the plurality of perforation pieces are arranged on the outer side of the simulation wellbore and are in one-to-one correspondence with the plurality of fracturing spaces, a plurality of perforation channels communicated with the corresponding fracturing spaces are formed in each perforation piece, and the plurality of connecting pipelines are connected with the plurality of fracturing spaces in a one-to-one correspondence manner and extend to the outside of the simulation wellbore. The experimental device is simpler in structure, the corresponding precision between the fracturing section of the segmented liquid injection tubular column and the annular cutting groove does not need to be considered when the experimental device is used, and operation is simpler.

Description

Technical Field

[0001] The present application relates to the technical field of shale fracturing physical simulation experiments, and in particular to an experimental device and an experimental method for horizontal wellbore segmented multi-cluster fracturing. Background Art

[0002] Multi-cluster temporary plugging fracturing in horizontal wellbore is one of the important means to develop unconventional oil and gas reservoirs. This technology involves two main processes: first, the initiation and synchronous expansion of multi-cluster fractures driven by fracturing fluid, i.e., primary fracturing; second, the temporary plugging agent is pumped to implement temporary plugging of fracture mouths and temporary plugging within fractures, and secondary fracturing is used to initiate new fractures to construct a complex fracture network, i.e., temporary plugging fracturing. Clarifying the morphology of the initiation and synchronous expansion of multi-cluster fractures in primary fracturing and revealing the expansion law of temporary plugging fracturing fractures will help optimize the multi-cluster temporary plugging fracturing process in horizontal wellbore and help the efficient development of oil and gas resources.

[0003] The prior art has provided an experimental device for simulating multi-cluster segmented fracturing of a horizontal wellbore on the ground, the experimental device comprising a casing, the casing being placed in the wellbore, and the annulus being filled with glue; the casing is annularly cut at multiple preset depths and cut into a rock sample to form multiple annular grooves to simulate a perforation cluster; a segmented injection string is inserted into the casing; a plurality of rubber sealing rings are sleeved on the outer surface of the string, and these sealing rings divide the wellbore into multiple fracturing sections, and the outlet of each injection pipeline is located between two annular grooves in each fracturing section; and the simulation of multi-cluster segmented fracturing of a horizontal wellbore is achieved by injecting liquid into the multiple injection pipelines respectively.

[0004] The experimental device in the prior art is not only complex in structure, but also the fracturing section of the segmented injection string must strictly correspond to the annular cutting groove, which requires the cutting groove depth to be accurate. However, the operation is difficult during the actual experiment, and it is easy for the annular cutting groove to be outside the fracturing section. Summary of the invention

[0005] The embodiment of the present application provides an experimental device for staged multi-cluster fracturing of horizontal wells. The experimental device does not require an additional injection string, has a simpler structure, and when in use, there is no need to consider the corresponding accuracy between the fracturing section of the staged injection string and the annular cutting groove, so the operation is simpler.

[0006] In a first aspect, an embodiment of the present application provides an experimental device for multi-cluster fracturing of horizontal wellbores, comprising: a simulated wellbore, which is used to be set in a rock formation sample, and the interior of the simulated wellbore defines a plurality of fracturing spaces along the length direction; a plurality of perforating members, which are set on the outside of the simulated wellbore and correspond one-to-one to the plurality of fracturing spaces, and each perforating member is formed with a plurality of perforating channels connected to the corresponding fracturing spaces; a plurality of connecting pipes, which are connected one-to-one to the plurality of fracturing spaces and extend to the outside of the simulated wellbore; the experimental device is configured to: introduce fracturing fluid into the fracturing space through the connecting pipes, so that the fracturing fluid flows to the rock formation sample through the perforating channels, so as to perform a primary fracturing on the rock formation sample; or, introduce a temporary plugging agent and a fracturing fluid into the fracturing space through the connecting pipes, so that the temporary plugging agent and the fracturing fluid flow to the rock formation sample through the perforating channels, so as to perform a temporary plugging and fracturing on the rock formation sample.

[0007] In a possible implementation, each perforating element includes: a plurality of spacer rings, the plurality of spacer rings are spaced apart along the length direction of the simulated wellbore, each spacer ring extends away from the simulated wellbore in the radial direction of the simulated wellbore, and a perforating channel is formed between two adjacent spacer rings.

[0008] In a possible implementation, a fluid outlet is opened between two adjacent separation rings in the simulated wellbore, and the fluid outlet is used to connect the perforation channel and the fracturing space.

[0009] In a possible implementation, the ratio of the radial length of the separation ring protruding from the simulated wellbore to the outer diameter of the simulated wellbore is set to be greater than or equal to 0.15 and less than or equal to 0.25.

[0010] In a possible implementation, among the multiple spacer rings in each perforating element, the spacer rings on both sides of the spacing direction are end spacer rings, and the spacer ring between the two end spacer rings is a middle spacer ring; the thickness of the end spacer ring is less than that of the middle spacer ring.

[0011] In a possible embodiment, the experimental device also includes: a plurality of connecting pipes, the plurality of connecting pipes corresponding one to one with the plurality of fracturing spaces, and each connecting pipe is passed through a plurality of separation rings along the length direction of the simulated wellbore, and each connecting pipe is an open structure at both ends; when the simulated wellbore is placed in the rock formation sample, the connecting pipe connects the annulus of the simulated wellbore between two adjacent perforating elements.

[0012] In a possible implementation, the outer surface of the simulated wellbore is configured as a concave-convex structure.

[0013] In a possible implementation manner, the diameter of the connecting pipe is set to be greater than or equal to 5 mm and less than or equal to 8 mm.

[0014] In a possible implementation, the experimental device further includes: a plurality of separators, the plurality of separators are arranged inside the simulated wellbore at intervals along the length direction, and two adjacent separators define a fracturing space.

[0015] In the second aspect, an embodiment of the present application provides an experimental method for staged multi-cluster fracturing of a horizontal wellbore, which adopts any of the experimental devices described above, and includes: providing a rock sample, and opening a horizontal wellbore in the rock sample; sealing and fixing a simulated wellbore in the horizontal wellbore; introducing fracturing fluid into the fracturing space through a connecting pipe to perform a primary fracturing of the rock sample; introducing a temporary plugging agent into the fracturing space through a connecting pipe, and introducing the fracturing fluid to flush the temporary plugging agent into the cracks formed by the primary fracturing for temporary plugging, and after the temporary plugging is completed, using the fracturing fluid to form a temporary plugging fracturing.

[0016] The experimental device for multi-cluster fracturing of horizontal wellbore provided in the embodiment of the present application defines multiple fracturing spaces along the length direction inside the simulated wellbore, and multiple perforating members are arranged on the outside of the simulated wellbore and correspond one-to-one with the multiple fracturing spaces. Multiple perforating channels connected to the corresponding fracturing spaces are formed on each perforating member, and multiple connecting pipes are connected one-to-one with the multiple fracturing spaces and extend to the outside of the simulated wellbore. When in use, the connecting pipe is used to directly transport the fracturing fluid and temporary plugging agent to the fracturing space in the simulated wellbore, and the perforating members on the simulated wellbore are used to complete the primary fracturing and temporary plugging fracturing, and the installation of the connecting pipe and the perforating members can be completed independently. Compared with the prior art, the experimental device in the embodiment of the present application does not require an additional injection string, and the structure is simpler. Moreover, when in use, there is no need to consider the corresponding accuracy between the fracturing section of the segmented injection string and the annular cutting groove, and the operation is simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0018] Figure 1 This is a schematic diagram of the structure of an experimental device in one embodiment of the present application;

[0019] Figure 2 This is a schematic diagram of the use scenario of the experimental device in one embodiment of the present application. Figure 1 ;

[0020] Figure 3 This is a schematic diagram of the use scenario of the experimental device in one embodiment of the present application. Figure 2 ;

[0021] Figure 4 This is a schematic diagram of the use scenario of the experimental device in one embodiment of the present application. Figure 3 ;

[0022] Figure 5 The schematic flow chart of the experimental method in one embodiment of the present application.

[0023] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0024] Horizontal well segmented multi-cluster fracturing means: using packers to separate several horizontal sections along the horizontal well, each horizontal section is a fracturing section, and each fracturing section contains multiple perforation clusters. For a certain fracturing section, the ground high-pressure pump truck group injects fluid into the section at high speed, and builds up high pressure in the section, thereby causing the perforation clusters in the section to fracture. Multiple perforation clusters fracture multiple cracks, and these cracks expand synchronously under the drive of the fracturing fluid. The above process is applied to each fracturing section in turn to complete the horizontal well segmented multi-cluster fracturing.

[0025] Horizontal well segmented multi-cluster temporary plugging fracturing means: temporary plugging refers to the injection of plugging materials (temporary plugging powder, temporary plugging fiber or temporary plugging ball) into a certain fracturing section, thereby plugging a certain crack or some perforation holes. Field practice shows that horizontal well segmented multi-cluster fracturing generally cannot initiate fractures in all perforation clusters, that is, some perforation clusters can initiate fractures, while the remaining perforation clusters do not. In order to enable all perforation clusters to initiate fractures, the fractures that have been formed and the perforation clusters that have initiated fractures are temporarily plugged, and then the fluid is injected into the fracturing section at a high speed again, and high pressure is re-established in the section, forcing the perforation clusters that have not initiated fractures to initiate fractures. The above process is applied to each fracturing section in turn to complete the horizontal well segmented multi-cluster temporary plugging fracturing.

[0026] The prior art has developed an experimental device for simulating multi-cluster fracturing of horizontal wellbore segments on the ground. The experimental device has a casing, which is placed in the wellbore and filled with glue in the annulus; the casing is cut in circles at multiple preset depths and the rock sample is cut into to form multiple annular grooves to simulate the perforation clusters; the segmented injection string is inserted into the casing; the outer surface of the string is covered with multiple rubber sealing rings, which divide the wellbore into multiple fracturing segments, and the outlet of each injection line is located between two annular grooves in each fracturing segment; by injecting liquid into multiple injection lines respectively, the simulation of multi-cluster fracturing of horizontal wellbore segments is realized. This experimental device is not only complex in structure, but also the fracturing segment of the segmented injection string must strictly correspond to the annular cutting groove, which requires the cutting groove depth to be accurate, but the operation is difficult in the actual experiment, and it is easy to have the annular cutting groove not in the fracturing segment.

[0027] Based on this, the present application provides an experimental device for multi-cluster fracturing of horizontal wellbore segments, in which multiple fracturing spaces are defined inside the simulated wellbore along the length direction, multiple perforating members are arranged on the outside of the simulated wellbore and correspond to the multiple fracturing spaces one by one, and multiple perforating channels connected to the corresponding fracturing spaces are formed on each perforating member, and multiple connecting pipes are connected to the multiple fracturing spaces one by one and extend to the outside of the simulated wellbore. When in use, the connecting pipe is used to directly transport fracturing fluid and temporary plugging agent to the fracturing space in the simulated wellbore, and the perforating member on the simulated wellbore is used to complete the primary fracturing and temporary plugging fracturing, and the installation of the connecting pipe and the perforating member can be completed independently, the structure is simpler, and when in use, there is no need to consider the corresponding accuracy between the fracturing section of the segmented injection string and the annular cutting groove, and the operation is simpler.

[0028] See also Figure 1 , Figure 1 The schematic diagram of the structure of an experimental device in one embodiment of the present application is as follows: The present application provides an experimental device for staged multi-cluster fracturing of a horizontal wellbore, and the experimental device may include a simulated wellbore 100, a plurality of perforating elements 200, and a plurality of connecting pipes 300.

[0029] The simulated wellbore 100 is used to be set in the rock formation sample 10, and the interior of the simulated wellbore 100 defines a plurality of fracturing spaces 110 along the length direction. A plurality of perforating elements 200 are set outside the simulated wellbore 100 and correspond to the plurality of fracturing spaces 110 one by one, and each perforating element 200 is formed with a plurality of perforating channels 210 connected to the corresponding fracturing spaces 110. A plurality of connecting pipes 300 are connected to the plurality of fracturing spaces 110 one by one and extend to the outside of the simulated wellbore 100.

[0030] The experimental device is configured as follows: fracturing fluid is introduced into the fracturing space 110 through the connecting pipe 300, so that the fracturing fluid flows through the perforation channel 210 to the rock sample 10, so as to perform a primary fracturing on the rock sample 10; or, a temporary plugging agent and fracturing fluid are introduced into the fracturing space 110 through the connecting pipe 300, so that the temporary plugging agent and fracturing fluid flow through the perforation channel 210 to the rock sample 10, so as to temporarily plug and fracture the fractures formed by the fracturing.

[0031] In this embodiment, the simulated wellbore 100 can be horizontally arranged in the horizontal wellbore 12 of the rock sample 10 to simulate a horizontal well. The simulated wellbore 100 can be made of a casing made of steel. The interior of the simulated wellbore 100 defines a plurality of fracturing spaces 110 along the length direction, i.e., simulates the horizontal well staged fracturing technology (horizontal well staged fracturing technology: using packers or bridge plugs to separate the fracturing sections, and then fracturing each section by section, and opening multiple fractures in each fracturing section.)

[0032] In this embodiment, the outcrop (the part of rock, mineral vein and mineral deposit exposed on the ground) can be processed into a rock sample 10. In the prior art, there is also a scheme for using artificial cement samples to conduct experiments, but the physical properties of artificial cement (such as porosity, permeability, etc.) and rock mechanical properties (such as Young's modulus, compressive strength, etc.) are quite different from those of real rock samples, and it is difficult to accurately restore the structural weak surfaces of real rock samples such as lamination, bedding, and natural fractures. The obtained experimental fracture morphology cannot represent the reservoir fracturing fracture morphology; while the physical properties, rock mechanical properties and structural weak surface characteristics of the outcrop sample are similar to those of the reservoir. Therefore, the rock sample 10 processed from the outcrop is closer to the actual situation, the experimental conclusion is more accurate, and the reliability is higher.

[0033] When making the experimental device of this embodiment, firstly, a steel casing can be selected as the simulated wellbore 100, and a plurality of fracturing spaces 110 can be separated in the simulated wellbore 100 by using a separator 140. Then, a plurality of liquid outlets 120 are opened at positions corresponding to each fracturing space 110 on the simulated wellbore 100. Finally, a perforating member 200 with a plurality of perforating channels 210 is welded to the outside of the simulated wellbore 100, so that the plurality of perforating channels 210 are connected to the plurality of liquid outlets 120 in a one-to-one correspondence, and the manufacturing is completed.

[0034] See also Figure 2 , Figure 2 This is a schematic diagram of the use scenario of the experimental device in one embodiment of the present application. Figure 1 When using the experimental device to prepare for the experiment, firstly, a horizontal wellbore 12 is processed on the rock sample 10. Specifically, the rock sample 10 can be processed into an outcrop sample (the part of the rock, ore vein and ore bed exposed on the ground). Then, the experimental device is placed in the horizontal wellbore 12 as a whole and sealed and fixed. Finally, the connecting pipe 300 is connected to the pump, and all the preparations before the experiment are completed.

[0035] See also Figure 3 , Figure 3 This is a schematic diagram of the use scenario of the experimental device in one embodiment of the present application. Figure 2 , Figure 3 The line with a solid arrow in the middle represents the fracturing fluid, and A represents the crack formed by one fracturing. During the experiment, when one fracturing is performed, the fracturing fluid is introduced into the fracturing space 110 through the connecting pipe 300, so that the fracturing fluid passes through the fracturing space 110 and enters any one or more perforation channels 210, and the energy of the fracturing fluid is concentrated in the narrow and long perforation channels 210. The fracturing fluid passing through the perforation channels 210 promotes the rapid formation of stress concentration points in the rock formation sample 10 near the perforation channels 210, and finally the rock formation sample 10 is fractured by hydraulic action.

[0036] In some specific embodiments, the primary fracturing process is performed as follows: inject fracturing fluid into one of the fracturing spaces 110 through the connecting pipe 300 at a displacement of 10 mL / min to 20 mL / min, so that the fracturing fluid fills the fracturing space 110, and creates high pressure in the fracturing space 110 to initiate cracks, thereby achieving primary fracturing of the fracturing segment corresponding to the fracturing space 110. Stop the pump after 200 mL of fracturing fluid has been pumped.

[0037] See also Figure 4 , Figure 4 This is a schematic diagram of the use scenario of the experimental device in one embodiment of the present application. Figure 3 , Figure 4 The line with a solid arrow in the middle represents the fracturing fluid, the solid circle represents the temporary plugging agent, A represents the crack formed by the first fracturing, and B represents the crack formed by the temporary plugging fracturing. During the experiment, when the temporary plugging fracturing is performed, the temporary plugging agent is introduced into the fracturing space 110 through the connecting pipe 300, and the temporary plugging agent passes through the perforation channel 210, thereby temporarily plugging the crack formed by the fracturing, so as to further perform the temporary plugging fracturing.

[0038] In some specific embodiments, the temporary plugging and fracturing process is carried out according to the following steps: first, 200 / 300 mesh, 15 cm 3 The quartz sand is placed into the fracturing space 110 through the connecting pipe 300 to ensure that there is enough quartz sand temporary plugging agent near the crack mouth, which is convenient for temporary plugging of the crack mouth. Then, a quartz sand-containing fracturing fluid with a viscosity of 200mPa·s and a sand concentration of 60g / 100mL is pumped at a displacement of 20mL / min, and the quartz sand is carried into the crack by the viscous resistance of the high-viscosity fluid to temporarily plug the crack. With the continuous injection of fracturing fluid, the temporary plugging agent gradually blocks the crack and the crack mouth, and the amount of fracturing fluid flowing into the first fractured crack begins to decrease, so that the fracturing space 110 is again high-pressure, thereby starting a new fracture crack and achieving temporary plugging fracturing.

[0039] It should be noted that quartz sand can be used as a temporary plugging agent for simulation experiments. When conducting fracturing operations on site, it is necessary to select appropriate on-site temporary plugging agents according to actual conditions, such as acid-soluble temporary plugging agents, oil-soluble temporary plugging agents, water-soluble temporary plugging agents, one-way pressure temporary plugging agents, etc.

[0040] It can be seen that the experimental device of the embodiment of the present application uses the connecting pipe 300 to directly deliver the fracturing fluid and temporary plugging agent to the fracturing space 110 in the simulated wellbore 100, and uses the perforating member 200 on the simulated wellbore 100 to complete the primary fracturing and temporary plugging fracturing, and the installation of the connecting pipe 300 and the perforating member 200 can be completed independently. Compared with the prior art, the experimental device of the embodiment of the present application does not require an additional injection string, and the structure is simpler. In addition, when using it, there is no need to consider the corresponding accuracy between the fracturing section of the segmented injection string and the annular cutting groove, and the operation is simpler.

[0041] In some embodiments, each perforating element 200 includes a plurality of spacer rings 220 , which are spaced apart along the length direction of the simulated wellbore 100 , each spacer ring 220 extends in a radial direction away from the simulated wellbore 100 , and a perforating channel 210 is formed between two adjacent spacer rings 220 .

[0042] In this embodiment, the separator ring 220 can be made of high-strength steel. Each separator ring 220 is sleeved on the outside of the simulated wellbore 100 and fixedly connected to the outer wall of the simulated wellbore 100 by welding. The narrow and long channel formed between two adjacent separator rings 220 is the perforation channel 210. This type of perforating element 200 has a simple and firm structure and high reliability.

[0043] In some specific embodiments, the spacing between two adjacent spacer rings 220 may also be set to be between 2 mm and 5 mm, such as 2 mm, 3 mm, 4 mm, 5 mm, etc. This is conducive to simulating primary fracturing and temporary plugging fracturing under different perforation cluster spacings.

[0044] In some specific embodiments, the radial heights of the plurality of perforating elements 200 are consistent, that is, the radial heights of the separation rings 220 of the plurality of perforating elements 200 are consistent, so as to reduce experimental errors.

[0045] In some specific embodiments, the radial height of each separator ring 220 can be set to be between 5 mm and 10 mm, such as 5 mm, 6 mm, 7.5 mm, 8 mm, 10 mm, etc. The radial height of the separator ring 220 is set within the above range, which ensures that the height of the perforation channel 210 is not too small, so that the fracturing fluid can achieve energy concentration in the perforation channel 210, and the separator ring 220 does not protrude too much from the simulated wellbore 100, thereby reducing the difficulty of sealing the simulated wellbore 100.

[0046] In some embodiments, the outer diameter of the separator ring 220 can also be set according to the length of the simulated wellbore 100. When the length of the simulated wellbore 100 is longer, the outer diameter of the separator ring 220 is also larger, and the separator ring 220 protrudes more from the simulated wellbore 100. When the simulated wellbore 100 is embedded in the horizontal wellbore 12 of the rock formation sample 10, since the annulus between the simulated wellbore 100 and the horizontal wellbore 12 is larger, it is conducive to injecting thicker sealant to fix the simulated wellbore 100.

[0047] Further, the ratio of the radial length of the separator ring 220 protruding from the simulated wellbore 100 to the outer diameter of the simulated wellbore 100 is set to be greater than or equal to 0.15 and less than or equal to 0.25, such as 0.15, 0.2, 0.25, etc. In some specific embodiments, the outer diameter of the simulated wellbore 100 is 35 mm, the radial length of the separator ring 220 protruding from the simulated wellbore 100 is 7.5 mm, and the outer diameter of the separator ring 220 is 50 mm.

[0048] In some embodiments, the simulated wellbore 100 is further provided with a liquid outlet 120 between two adjacent separation rings 220 , and the liquid outlet 120 is used to connect the perforation channel 210 with the fracturing space 110 .

[0049] For the same fracturing space 110, the direction of the liquid outlet 120 thereon can be set according to actual conditions. For example, multiple liquid outlets 120 on the same fracturing space 110 can be set to be the same and can be arranged at any angle.

[0050] In some embodiments, among the multiple spacer rings 220 in each perforating element 200, the spacer rings 220 on both sides of the spacing direction are end spacer rings 222, and the spacer ring 220 between the two end spacer rings 222 is a middle spacer ring 224. The thickness of the end spacer ring 222 is less than that of the middle spacer ring 224.

[0051] As can be seen from the above, when using the experimental device, a high-pressure fracturing fluid needs to pass through the perforation channel 210, which places certain requirements on the fixing strength of the separator ring 220. For the end separator ring 222, after it is fixed to the simulated wellbore 100, it can also be fixed with the sealing glue 14 on one side for a secondary time, so the fixing effect of the end separator ring 222 is good, and the thickness of the end separator ring 222 can be appropriately reduced to save materials. As for the middle separator ring 224, it is only fixed to the simulated wellbore 100 without secondary fixation, so the thickness of the middle separator ring 224 should be appropriately increased, and the contact area between the middle separator ring 224 and the simulated wellbore 100 should be increased to ensure the fixing effect of the middle separator ring 224.

[0052] Therefore, the thickness of the end separation ring 222 is set to be smaller than the thickness of the middle separation ring 224, which can ensure the fixing effect of the separation ring 220 and save materials.

[0053] In some specific embodiments, the thickness of the end separation ring 222 can be set between 1.5 mm and 3 mm, such as 1.5 mm, 2 mm, 3 mm, etc. The thickness of the middle separation ring 224 can be set between 4 mm and 6 mm, such as 4 mm, 5 mm, 6 mm, etc.

[0054] In some embodiments, the experimental device may also include a plurality of connecting pipes 400, each of which corresponds to a plurality of fracturing spaces 110 one by one, and each connecting pipe 400 is passed through a plurality of separation rings 220 along the length direction of the simulated wellbore 100, and each connecting pipe 400 is an open-ended structure at both ends, so that when the simulated wellbore 100 is placed in the rock sample 10, the connecting pipe 400 connects to the annulus between two adjacent perforating elements 200.

[0055] When the simulated wellbore 100 is placed and fixed in the horizontal wellbore 12, a sealant 14 (such as epoxy resin glue) is required to seal the annulus of the simulated wellbore 100 between two adjacent perforating members 200. However, since multiple separation rings 220 protrude from the outer periphery of the simulated wellbore 100, the separation rings 220 form a barrier to the flow of the sealant 14 along the annulus, which is not conducive to the full flow of the sealant 14 along the length direction of the simulated wellbore 100, and is not conducive to the formation of a uniform sealing layer, and the sealing and fixing effect cannot be guaranteed.

[0056] In the present embodiment, each connecting tube 400 is penetrated through a plurality of separation rings 220 of each perforating element 200 along the length direction of the simulated wellbore 100, and both ends are open, that is, the connecting tube 400 is used to guide the sealant liquid 14 on one side of the perforating element 200 to the other side, so that the sealant liquid 14 can fully flow between two adjacent perforating elements 200 in the simulated wellbore 100, effectively isolating the fracturing section (the section with the perforating element 200) and the non-fracturing section (the section without the perforating element 200), so that the fracturing fluid will not flow to the non-fracturing section, thereby ensuring the reliability of the experiment.

[0057] In some specific embodiments, the inner diameter of the connecting tube 400 may be set to be between 2 mm and 4 mm, and the length of the connecting tube 400 may be set according to the thickness of the perforating element 200 to ensure that the connecting tube 400 completely penetrates the perforating element 200 .

[0058] In some embodiments, the outer surface of the simulated wellbore 100 is configured to have an uneven structure to increase the sealing strength when sealing the annulus between the simulated wellbore 100 and the formation sample 10 .

[0059] Specifically, the outer surface of the simulated wellbore 100 is processed with densely distributed grooves 130 with a width of 4 mm and a depth of 1 mm to perform roughening, thereby increasing the bonding strength between the outer surface of the wellbore and the well wall.

[0060] In some embodiments, the diameter of the connecting pipe 300 is set to be greater than or equal to 5 mm and less than or equal to 8 mm, such as 5 mm, 6 mm, 8 mm, etc. The diameter of the connecting pipe 300 in the above range is larger than the diameter of the injection channel of the existing design, so that the temporary plugging agent can be injected without blocking the pipeline.

[0061] In some embodiments, the experimental device may further include a plurality of separators 140 , which are spaced apart along the length direction inside the simulated wellbore 100 , and two adjacent separators 140 define a fracturing space 110 .

[0062] The separator 140 may be welded inside the simulated wellbore 100 , and two adjacent separators 140 and the inner wall of the simulated wellbore 100 form a fracturing space 110 .

[0063] The working principle of the experimental device of this application is described below based on a specific experimental process:

[0064] 1. Make an experimental device.

[0065] Step 1: Select a casing with a length of 360 mm, an outer diameter of 35 mm, and an inner diameter of 25 mm as the simulated wellbore 100. The outer surface of the simulated wellbore 100 is processed with densely distributed grooves 130 with a width of 4 mm and a depth of 1 mm to perform roughening, thereby increasing the bonding strength between the outer surface of the wellbore and the well wall.

[0066] Step 2: Weld three groups of separators 140 inside the simulated wellbore 100 , the portion between two separators 140 is the fracturing space 110 , and the portion outside the two separators 140 is the non-fracturing space. The three groups of separators 140 form three fracturing spaces 110 .

[0067] Step 3: Open multiple holes at each corresponding fracturing space 110 on the simulated wellbore 100 to form multiple liquid outlets 120. Three perforating elements 200 are welded and installed at each corresponding fracturing space 110. The multiple perforating channels 210 on each perforating element 200 correspond to the multiple liquid outlets 120. The outer diameter of the separator ring 220 of the perforating element 200 is 50 mm, the thickness of the end separator ring 222 is 2 mm, and the thickness of the middle separator ring 224 is 5 mm.

[0068] Step 4: Drill holes on the multiple separation rings 220 of each perforating element 200, insert and fix the connecting pipe 400.

[0069] 2. Experimental process:

[0070] Step 5: Process the natural outcrop into a rock sample 10 of 400 mm×400 mm×400 mm, and drill a horizontal wellbore 12 with an inner diameter of 51 mm and a depth of 360 mm in the center of the rock sample 10.

[0071] Step 6: Tightly wind the raw tape in the perforation channel 210 of each perforating element 200 until the perforation channel 210 is filled. The purpose of this method is to prevent the sealant 14 from penetrating into the fracturing space 110 and avoid clogging the fracturing space 110.

[0072] Step 7, pour 10mL of epoxy resin glue into the horizontal wellbore 12, insert the experimental device into the horizontal wellbore 12, and the sealant 14 gradually returns to the annulus between the simulated wellbore 100 and the well wall through the connecting pipe 400, filling the annulus between the simulated wellbore 100 and the well wall, and the sealant 14 finally returns to the wellhead. For the annulus near the wellhead that has not been filled with the sealant 14, a small amount of sealant 14 is dripped from the wellhead to complete the filling of the remaining part. This process is similar to the on-site cementing process, which aims to tightly bond the simulated wellbore 100 to the well wall, complete the effective isolation between the fracturing sections, and prevent the fluid from flowing along the outer wall of the wellbore during the fracturing experiment.

[0073] Step 8: For one of the fracturing spaces 110, connect the corresponding connecting pipe 300 to the pump. Inject fracturing fluid into the fracturing space 110 through the connecting pipe 300 at a displacement of 10 mL / min to 20 mL / min, so that the fracturing fluid fills the fracturing space 110, and builds up high pressure in the fracturing space 110 to initiate cracks, thereby achieving a primary fracturing of the fracturing segment corresponding to the fracturing space 110. Stop the pump after 200 mL of fracturing fluid has been injected.

[0074] Step 9: 200 / 300 mesh, 15cm 3 Quartz sand is placed in the above-mentioned fracturing space 110 to ensure that there is enough temporary plugging agent near the crack mouth, which is convenient for temporary plugging of the crack mouth; then, a fracturing fluid containing quartz sand with a viscosity of 200mPa·s and a sand concentration of 60g / 100mL is pumped at a displacement of 20mL / min, and the viscous resistance of the high-viscosity fluid is used to carry the quartz sand in the fracturing section into the crack, which is convenient for temporary plugging in the crack. As the temporary plugging agent is continuously injected, the temporary plugging agent gradually blocks the crack and the crack mouth; the amount of temporary plugging agent flowing into the first fractured crack is reduced, so that the fracturing space 110 is again high-pressure, thereby starting a new fracture crack and achieving temporary plugging fracturing.

[0075] Step 10: Repeat steps 8 and 9 for the remaining two fracturing spaces 110 .

[0076] See also Figure 5 , Figure 5 The following is a schematic flow chart of an experimental method in one embodiment of the present application. In addition, the present application also provides an experimental method for staged multi-cluster fracturing of a horizontal wellbore, which can use the experimental device in any of the above embodiments, and can be implemented by the following steps:

[0077] Step S510 , providing a rock formation sample 10 , and opening a horizontal wellbore 12 in the rock formation sample 10 .

[0078] Step S520 , sealing and fixing the simulated wellbore 100 in the horizontal wellbore 12 .

[0079] Step S530 , introducing fracturing fluid into the fracturing space 110 through the connecting pipe 300 , so that the fracturing fluid is ejected toward the rock formation sample 10 through the perforation channel 210 , so as to perform a primary fracturing on the rock formation sample 10 .

[0080] Step S540, introduce a temporary plugging agent into the fracturing space 110 through the connecting pipe 300, and introduce fracturing fluid to flush the temporary plugging agent into the cracks formed by the primary fracturing to perform temporary plugging, and after the temporary plugging is completed, use the fracturing fluid to temporarily plug and fracture the rock sample 10.

[0081] Step S520 may also include: pouring sealant liquid into the horizontal wellbore 12; placing the simulated wellbore 100 in the horizontal wellbore 12, so that the sealant liquid fills the annulus between two adjacent perforating elements 200 of the simulated wellbore 100 through the connecting pipe 400 to fix the simulated wellbore 100.

[0082] The fracturing process of step S530 and step S540 can refer to the above description, which will not be repeated here.

[0083] In step S530 and step S540, dye tracers with different colors can be added to the fracturing fluid. In this way, after the fracturing is completed, the formation process and the morphology of hydraulic fractures of the primary fracturing and temporary plugging fracturing can be distinguished by color, and the turning characteristics of the primary fracturing and temporary plugging fracturing fractures can be analyzed, and the pump pressure curve characteristics of the primary fracturing and temporary plugging fracturing can be analyzed at the same time. Finally, support is provided for the design of process parameters for shale reservoir fracturing wells.

[0084] Finally, it should be noted that those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include common knowledge or customary technical means in the art not disclosed by the present invention, are not limited to the precise structure described above and shown in the drawings, and may be modified and changed in various ways without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. An experimental device for staged multi-cluster fracturing of horizontal wells, characterized in that: include: A simulated wellbore (100) is used to be arranged in a rock formation sample (10), wherein a plurality of fracturing spaces (110) are defined inside the simulated wellbore (100) along a length direction; a plurality of perforating elements (200), the plurality of perforating elements (200) being arranged outside the simulated wellbore (100) and corresponding one-to-one to the plurality of fracturing spaces (110), and each of the perforating elements (200) being formed with a plurality of perforating channels (210) connected to the corresponding fracturing space (110); A plurality of connecting pipes (300) connected to the plurality of fracturing spaces (110) in a one-to-one correspondence and extending to the outside of the simulated wellbore (100); The experimental device is configured as follows: A fracturing fluid is introduced into the fracturing space (110) through the connecting pipe (300), so that the fracturing fluid flows toward the rock formation sample (10) through the perforation channel (210), so as to perform a primary fracturing on the rock formation sample (10); or, A temporary plugging agent and a fracturing fluid are introduced into the fracturing space (110) through the connecting pipe (300), so that the temporary plugging agent and the fracturing fluid flow toward the rock formation sample (10) through the perforation channel (210), thereby temporarily plugging and fracturing the rock formation sample (10).

2. The experimental device according to claim 1, characterized in that: Each of the perforating elements (200) comprises: A plurality of separator rings (220) are arranged at intervals along the length direction of the simulated wellbore (100), each separator ring (220) extends in a radial direction of the simulated wellbore (100) away from the simulated wellbore (100), and the perforation channel (210) is formed between two adjacent separator rings (220).

3. The experimental device according to claim 2, characterized in that: The simulated wellbore (100) is provided with a liquid outlet (120) between two adjacent separation rings (220), and the liquid outlet (120) is used to connect the perforation channel (210) and the fracturing space (110).

4. The experimental device according to claim 2, characterized in that: The ratio of the radial length of the separation ring (220) protruding from the simulated wellbore (100) to the outer diameter of the simulated wellbore (100) is set to be greater than or equal to 0.15 and less than or equal to 0.

25.

5. The experimental device according to claim 2, characterized in that: Among the plurality of separation rings (220) in each perforating element (200), the separation rings (220) located at both sides of the spacing direction are end separation rings (222), and the separation ring (220) located between the two end separation rings (222) is an intermediate separation ring (224); The thickness of the end separation ring (222) is smaller than the thickness of the middle separation ring (224).

6. The experimental device according to claim 2, characterized in that: Also includes: A plurality of connecting pipes (400), wherein the plurality of connecting pipes (400) correspond one-to-one to the plurality of fracturing spaces (110); Each of the connecting pipes (400) is arranged through the plurality of separating rings (220) along the length direction of the simulated wellbore (100), and each of the connecting pipes (400) is an open-ended structure at both ends; When the simulated wellbore (100) is placed in the rock formation sample (10), the connecting pipe (400) connects the annulus between two adjacent perforating elements (200) of the simulated wellbore (100).

7. The experimental device according to any one of claims 1 to 6, characterized in that: include: The outer surface of the simulated wellbore (100) is arranged to have an uneven structure.

8. The experimental device according to any one of claims 1 to 6, characterized in that: The diameter of the connecting pipe (300) is set to be greater than or equal to 5 mm and less than or equal to 8 mm.

9. The experimental device according to any one of claims 1 to 6, characterized in that: Also includes: A plurality of separators (140) are provided inside the simulated wellbore (100) at intervals along the length direction, and two adjacent separators (140) define one fracturing space (110).

10. An experimental method for staged multi-cluster fracturing of a horizontal wellbore, the experimental method using the experimental device according to any one of claims 1 to 9, characterized in that: The experimental method includes: Providing a rock formation sample and opening a horizontal wellbore in the rock formation sample; sealing and fixing a simulated wellbore in the horizontal wellbore; Introducing fracturing fluid into the fracturing space through a connecting pipeline to perform a primary fracturing on the rock formation sample; A temporary plugging agent is introduced into the fracturing space through the connecting pipe, and the fracturing fluid is introduced to flush the temporary plugging agent into the cracks formed by the primary fracturing to perform temporary plugging. After the temporary plugging is completed, the fracturing fluid is used to form a temporary plugging fracturing.

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