A method for water pressure fracturing and proppant migration test under water injection hole filtration condition

Abstract

The application discloses a water pressure fracturing and proppant migration test method under the filtration condition of injection holes, and the test device comprises an injection assembly, a fracture assembly and a fixing assembly, the injection assembly is used for injecting liquid with proppants into the fracture assembly, a filtration fracture for realizing filtration before fracturing fluid is injected into the fracture assembly is arranged in the injection assembly, the filtration fracture realizes the change of the opening of the filtration fracture through filtration structures arranged on both sides of the filtration fracture, the fracture assembly is used for simulating the reaction of rock mass with fractures after liquid injection, and the fixing assembly is used for realizing the support and fixation of the fracture assembly and the application of load; the method further comprises the following steps: S1, test preparation; S2, load application; S3, fracturing; S4, completion of fracturing; and S5, repeated test. Under the existing proppant fracture seepage simulation test, liquid injection simulation with filtration can be realized, so that the hydraulic fracturing under the condition that the fractures of the injection water fracturing well or hole exist filtration can be researched, and a basis for actual production is provided.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of unconventional energy hydraulic fracturing mining, and particularly relates to a water pressure fracturing and proppant migration test method under the condition of water injection hole filtration. BACKGROUND

[0002] The porosity of unconventional oil and gas reservoirs in China is low, the permeability is poor, and the mining difficulty is relatively large, which seriously restricts the development of unconventional oil and gas resources in China. As an important means to improve the development of unconventional oil and gas resources in China, the hydraulic fracturing technology is an important means to improve the development of unconventional oil and gas resources in China. Due to the continuous injection of subsequent fracturing fluid, the fracture will expand into the reservoir, forming a certain length, height and width geometry. In order to keep the fracture in an open state, the sand-carrying fluid with proppant (mainly quartz sand) is then injected into the wellbore to prevent the fracture from closing again. At this time, one or more fracture channels with high conductivity are formed in the reservoir, so that the internal fluid can continuously seep from the fracture to the wellbore, thereby completing the development of unconventional oil and gas resources. However, since the formation is mostly fractured rock mass, part of the liquid flows in the formation fracture under the action of pressure difference, and the liquid is filtered into the rock wall, resulting in the loss of injection rate and injection pressure of the target reservoir. In the prior art, the research on this aspect is mostly to simply measure the filtration performance of the fracturing fluid by using the conventional similar Darcy seepage test, and the fracturing fluid filtration and sand-carrying fracturing cannot be effectively combined together. SUMMARY

[0003] The present application provides a water pressure fracturing and proppant migration test method under the condition of water injection hole filtration. Under the existing proppant fracture seepage simulation test, the injection simulation with filtration can be carried out, so as to study the hydraulic fracturing under the condition of formation water injection hole fracture filtration.

[0004] To this end, the technical scheme adopted by the present application is as follows: a water pressure fracturing and proppant migration test method under the condition of water injection hole filtration, comprising a test device, the test device comprises an injection assembly, a fracture assembly and a fixing assembly, the injection assembly is used for injecting liquid with proppant into the fracture assembly, the injection assembly is provided with a filtration fracture for realizing the filtration of the fracturing fluid before being injected into the fracture assembly, the filtration fracture realizes the change of the opening degree of the filtration fracture through the filtration structures arranged on both sides of the filtration fracture, the fracture assembly is used for simulating the reaction of the rock mass with fractures after the injection of liquid, and the fixing assembly is used for realizing the support and fixation of the fracture assembly and the application of load; the fracture assembly comprises upper and lower fracture plates arranged oppositely, the left end of the upper and lower fracture plates is provided with a notch for fracturing fluid injection, the upper fracture plate can move up and down, and a normal load from the fixing assembly is loaded on the upper fracture plate, and the lower fracture plate can move left and right, and a tangential load from the fixing assembly is loaded on the lower fracture plate.

[0005] Further comprising the following test steps:

[0006] S1: test preparation; connect all parts of the test device completely, and after checking, load the predetermined proppant and fracturing fluid in the injection assembly;

[0007] S2: load application; apply a predetermined normal load to the upper fracture plate and a predetermined tangential load to the lower fracture plate through the fixed assembly, and make the filtration fracture opening reach a predetermined value;

[0008] S3: fracturing; start the injection assembly, and inject the fracturing fluid with proppant between the upper and lower fracture plates at a predetermined rate through the notch;

[0009] S4: complete fracturing; when the injection time of the fracturing fluid with proppant reaches the predetermined time, stop the injection, and record the distribution position of the proppant when the fracturing fluid with proppant stops moving between the upper and lower fracture plates, the flow rate of the fracturing fluid filtration during the test, the upward and downward displacement of the upper fracture plate, and the left and right displacement of the lower fracture plate;

[0010] S5: repeat the test; clean the fracturing fluid and proppant in the test device to restore the initial state of the test device, and then repeat steps S3-S4 after changing the filtration fracture opening to obtain the migration law of hydraulic fracturing and proppant under different filtration conditions.

[0011] As a preferred embodiment of the above-mentioned scheme, the fixed assembly comprises a lower pressure bearing plate arranged below the lower fracture plate, an upper pressure bearing plate arranged above the lower pressure bearing plate through support bolts, the upper pressure bearing plate being arranged above the upper fracture plate, and a plurality of normal load springs arranged between the upper pressure bearing plate and the upper fracture plate, a row of abutting bolts arranged on the right side of the lower pressure bearing plate and capable of abutting against the right side surface of the upper fracture plate, and a tangential load assembly arranged on the right side of the lower pressure bearing plate and used to simulate the tangential load when the lower fracture plate moves to the right.

[0012] Further preferably, the tangential load assembly comprises a tangential load spring, one end of the tangential load spring abutting against the right side surface of the lower fracture plate, and the other end of the tangential load spring being sleeved on a guide column arranged between the lower pressure bearing plate and the lower fracture plate, and a distance being left between the guide column and the lower fracture plate.

[0013] Further preferably, the lower pressure plate is provided with a height-adjustable support assembly below, which includes four support rods arranged in a rectangular distribution between the lower pressure plate and the ground, the support rods including a fixed sleeve, a telescopic rod movably arranged in the fixed sleeve, a fastening sleeve arranged outside the telescopic rod, an inner thread provided at the lower end of the fastening sleeve, an outer thread matching the inner thread provided at the outside of the upper end of the fixed sleeve, a rubber tube arranged between the fastening sleeve and the telescopic rod, and a gasket arranged between the upper end of the fastening sleeve and the upper end of the rubber tube, the length of the telescopic rod being fixed when the fastening sleeve is screwed on the fixed sleeve.

[0014] Further preferably, the injection assembly includes a fracturing fluid tank arranged on the ground through a support column, the fracturing fluid tank being provided with an injection pipe, the end of the injection pipe being arranged in parallel with the gap and provided with a plurality of liquid injection holes for injecting liquid into the gap, the injection pipe being provided with a water pump for driving the flow of liquid, the injection pipe being further provided with a proppant injection pipe for adding proppant into the injection pipe, the upper end of the proppant injection pipe being provided with a proppant adding assembly for quantitatively adding proppant into the liquid in the injection pipe, and the end of the injection pipe being provided with an injection fixing pipe which can be fixed at the left end of the fixing assembly and used to ensure that the liquid in the injection pipe is injected into the gap.

[0015] Further preferably, the filtration structure includes oppositely arranged filtration fixing plates and filtration adjusting plates, the filtration adjusting plates being arranged at the end of the injection pipe, the filtration fixing plates being provided with an injection section for connecting with the injection fixing pipe, the gap between the filtration fixing plates and the filtration adjusting plates being a filtration fracture, and the filtration fixing plates and the filtration adjusting plates being provided with filtration fracture opening bolts for adjusting the gap between the filtration fixing plates and the filtration adjusting plates.

[0016] Further preferably, the proppant adding assembly includes a proppant storage tank, the lower end of the proppant storage tank being provided with a proppant screw conveyor, one end of the proppant screw conveyor being in communication with the lower end of the proppant storage tank, and the other end of the proppant screw conveyor being in communication with the upper end of the proppant injection pipe.

[0017] Further preferably, the right end of the injection fixing pipe is provided with a rectangular slot for the upper fracture plate and the lower fracture plate to extend into, and the upper fracture plate is movable up and down in the rectangular slot, the left end of the upper fracture plate being inserted with a front-and-back extending sealing protruding strip, the upper end of the sealing protruding strip being provided with a ring of upper-and-lower sealing rings, the upper wall of the rectangular slot being provided with a sealing strip groove for the sealing protruding strip to insert into and move up and down, and the upper-and-lower sealing rings being located in the sealing strip groove, the front-and-rear side walls of the rectangular slot being provided with clamping strips for ensuring that the lower fracture plate is in close contact with the lower wall of the rectangular slot, the lower end of the clamping strips being in contact with the upper end of the lower fracture plate, and the upper end of the clamping strips being abutted against the upper fracture plate through a micro spring.

[0018] Further preferably, the lower fissure plate top surface is provided with left and right extending protrusions on both front and back sides, the protrusions are provided with left and right sealing rings on upper ends, the lower fissure plate bottom surface is provided with sealing grooves corresponding to the positions of the protrusions.

[0019] Further preferably, the lower fissure plate is provided with a bottom plate in the fixing assembly, the bottom plate is provided with several front and back extending rollers at intervals.

[0020] The present application has the following advantages: in the existing proppant fissure seepage simulation test, liquid injection simulation with filtration can be carried out, so that the hydraulic fracturing of the formation injection fracturing well or hole under the condition of fissure filtration can be studied, and the basis for actual production is provided. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Flow chart of the present application.

[0022] Figure 2 Stereoscopic diagram of the test device in the present application Figure 1 .

[0023] Figure 3 Stereoscopic diagram of the test device in the present application Figure 2 .

[0024] Figure 4 Structural diagram of the test device in the present application.

[0025] Figure 5 Left view of Figure 4 .

[0026] Figure 6 Schematic diagram of the support rod in the present application.

[0027] Figure 7 Schematic diagram of the liquid injection fixing pipe in the present application.

[0028] Figure 8 Enlarged view of N in Figure 4 .

[0029] Figure 9 Enlarged view of M in Figure 2 .

[0030] Figure 10 Schematic diagram of the filtration structure in the present application. DETAILED DESCRIPTION

[0031] The present application will be further described below by examples and in conjunction with the drawings:

[0032] As Figures 1-10As shown, a variable fracturing fluid density-controlled proppant directional movement test device mainly consists of an injection component A, a fracture component B, and a fixing component C. The injection component A is used to inject liquid containing proppant into the fracture component B. The injection component A is provided with a filtration fracture to allow the fracturing fluid to be filtered out before being injected into the fracture component. The filtration fracture opening is changed by filtration structures set on both sides of the filtration fracture. The fracture component B is used to simulate the reaction of rock mass with fractures after liquid injection. The fixing component C is used to support and fix the fracture component and apply load.

[0033] This device is equipped with a filtration structure, enabling it to simulate filtration during fluid injection, thereby mimicking filtration through injection holes in hydraulic fracturing. Simultaneously, the device can apply normal loads to the upper fracture plate and tangential loads to the lower fracture plate. This causes the upper and lower fracture plates to move during fracturing fluid seepage, resulting in changes in the stress on the plates. Therefore, this application not only simulates the initial stress field during seepage but also the stress changes during the seepage process, allowing for a realistic simulation of proppant-supported fracturing fluid seeping through fractures.

[0034] The specific structure of fracture assembly B includes an upper fracture plate 1 and a lower fracture plate 2 arranged opposite each other. Both the upper fracture plate 1 and the lower fracture plate 2 have notches for fracturing fluid injection extending forward and backward at their left ends. The upper fracture plate 1 can move up and down and is loaded with a normal load from the fixed assembly. The lower fracture plate 2 can move left and right and is loaded with a tangential load from the fixed assembly.

[0035] The specific structure of the fixing component C includes a lower bearing plate 3 disposed below the lower split plate 2, and an upper bearing plate 4 disposed above the lower bearing plate 3 by support bolts 5, with the upper bearing plate 4 located above the upper split plate 1. To achieve the loading of normal loads on the upper split plate, a number of normal load springs 6 are disposed between the upper bearing plate 4 and the upper split plate 1. The number of normal load springs and the selection of springs of different specifications can be set as needed. In this embodiment, 18 normal load springs are evenly disposed between the upper bearing plate 4 and the upper split plate 1. To prevent the upper split plate from moving left and right, a row of clamping bolts 7 is disposed on the right side of the lower bearing plate 3 to abut against the right side of the upper split plate 1.

[0036] At the same time, in order to facilitate the left and right movement of the lower fissure plate, an initial tangential load is provided, and a tangential load assembly is further provided on the right side of the lower pressure plate 3 to simulate the tangential load when the lower fissure plate 2 moves to the right. The specific structure of the tangential load assembly includes a tangential load spring 8, one end of which abuts against the right side of the lower fissure plate 2, and the other end of which is sleeved on a guide column 9 between the lower pressure plate 3 and the lower fissure plate 2. In order to ensure that the lower fissure plate can move left and right, a distance is left between the guide column 9 and the lower fissure plate 2. In order to facilitate the change of the distance between the guide column and the lower fissure plate, the guide column is provided with a bolt extending leftward from the right end of the lower pressure plate, and in order to realize the compression of the tangential load spring, a nut for adjusting the compression amount of the tangential load spring can be further provided on the bolt.

[0037] In order to facilitate the adjustment of the inclination and inclination of the fissure assembly, a height-adjustable support assembly is provided below the lower pressure plate 3, and the specific structure of the support assembly includes four support rods 10 arranged in a rectangular shape between the lower pressure plate 3 and the ground, and the distance between the lower ends of the four support rods is greater than the distance between the upper ends, i.e. the support rods are inclined inwardly to support the lower pressure plate. By adjusting the heights of the four support rods, the fissure assembly can be adjusted to any angle between 0 and 90° relative to the ground. In order to realize the telescopic adjustment of the support rods, the support rod 10 includes a fixed sleeve 10a, and a telescopic rod 10b is arranged in the fixed sleeve 10a and can move up and down in the fixed sleeve 10a. In order to fix the telescopic rod after telescoping, a fastening sleeve 10c is sleeved outside the telescopic rod 10b, an internal thread is arranged at the lower end of the fastening sleeve 10c, and an external thread corresponding to the internal thread is arranged outside the upper end of the fixed sleeve 10a. A rubber tube 10d is arranged between the fastening sleeve 10c and the telescopic rod 10b, and when the fastening sleeve 10c is tightened on the fixed sleeve 10a, the rubber tube 10d is squeezed, thereby fixing the length of the telescopic rod 10b. In order to prevent the upper end of the fastening sleeve from directly rubbing against the rubber tube, a gasket 10e is arranged between the upper end of the rubber tube 10d and the upper end of the fastening sleeve 10c.

[0038] In the embodiment, the lower pressure plate 3 is a rectangular plate, and the supporting rods 10 are arranged at the four corners of the lower pressure plate 3. In order to realize the installation of the supporting rods, two opposite clamps 11 are arranged at the upper and lower ends of the supporting rods 10, and the clamps at the upper and lower ends are arranged in staggered mode. A spherical groove 11a is arranged in the clamp 11, and a ball head bolt 12 fixed on the ground is clamped in the two spherical grooves 11a at the lower end. Two ball head clamping members 13 capable of being fixed at the corners of the lower pressure plate 3 are clamped in the two spherical grooves 11a at the upper end. The ball head clamping member 13 comprises two clamping supporting members 13a, the two clamping supporting members 13a are respectively fixed on either side of the corner of the lower pressure plate 3, and the two clamping supporting members 13a are fixed to each other. In order to realize the function of the clamping supporting member, the clamping supporting member 13a comprises a ball head arranged in the spherical groove and a fixed part fixed on the lower pressure plate, and the fixed part and the ball head are connected through a connecting part, the connecting part comprises a first connecting part for realizing the mutual fixation of the two clamping supporting members 13a and a second connecting part extending along the first connecting part, and the ball head is arranged at the end of the second connecting part.

[0039] The specific structure of the injection assembly A comprises a fracturing fluid tank 15 arranged on the ground through a supporting column 14, and an injection pipe 16 is arranged on the fracturing fluid tank 15, the end of the injection pipe 16 is arranged in parallel with the gap, and a plurality of liquid outlet holes for injecting liquid into the gap are arranged. In order to facilitate the flow of liquid in the injection pipe 16, a water pump 17 is arranged on the injection pipe 16. In order to realize the addition of the proppant, a proppant injection pipe 18 is further arranged on the injection pipe 16, and a proppant adding assembly for adding the proppant into the liquid in the injection pipe in a certain amount is arranged at the upper end of the proppant injection pipe 18. In order to ensure that the liquid in the injection pipe 16 can be accurately injected into the gap, an injection fixing pipe 19 fixed at the left end of the fixed assembly is arranged at the end of the injection pipe 16, preferably, the upper end of the injection fixing pipe is fixed on the upper pressure plate through a bolt, and the lower end of the injection fixing pipe is fixed on the lower pressure plate through a bolt.

[0040] The specific structure of the filtration loss structure comprises oppositely arranged filtration loss fixing plates 25 and filtration loss adjusting plates 26, and the filtration loss fixing plates 25 and the filtration loss adjusting plates 26 are both provided with through holes for the fracturing fluid to pass through, and the gap between the filtration loss fixing plates 25 and the filtration loss adjusting plates 26 is a filtration loss fracture. The filtration loss adjusting plate 26 is arranged at the end of the injection pipe 16, and the filtration loss adjusting plate 26 can be integrally arranged with the injection pipe 16. An injection section for connecting with the injection fixing pipe 19 is arranged on the filtration loss fixing plate 25, and a filtration loss fracture opening bolt 27 for adjusting the gap between the filtration loss fixing plate and the filtration loss adjusting plate is arranged on the filtration loss fixing plate 25 and the filtration loss adjusting plate 26. In order to facilitate the measurement of the filtration loss fracturing fluid, a collection tank for collecting the filtration loss fracturing fluid is arranged below the filtration loss fracture, and a liquid level meter is arranged in the collection tank.

[0041] The support agent adding assembly comprises a support agent storage tank 20, a support agent screw conveyor 21 is arranged at the lower end of the support agent storage tank 20, one end of the support agent screw conveyor 21 is communicated with the lower end of the support agent storage tank 20, and the other end is communicated with the upper end of the support agent injection pipe 18; a fixed amount of support agent is added into a certain amount of liquid by the support agent screw conveyor.

[0042] Since the liquid injection fixing pipe 19 is arranged at the end of the liquid injection pipe, in order to ensure the sealing during liquid injection, a rectangular groove 19a for the upper fracture plate 1 and the lower fracture plate 2 to extend into is arranged at the right end of the liquid injection fixing pipe 19, and the upper fracture plate 1 can move up and down in the rectangular groove 19a. In order to ensure the sealing between the upper end of the upper fracture plate and the rectangular groove during the up-and-down movement of the upper fracture plate, a front-and-back extending sealing protrusion 1a is inserted above the left end of the upper fracture plate 1, the upper end of the sealing protrusion 1a is sleeved with a circle of upper-and-lower sealing rings, meanwhile, a sealing strip groove 19b for the sealing protrusion 1a to insert into and move up and down is arranged on the upper wall of the rectangular groove 19a, and the upper-and-lower sealing rings are always located in the sealing strip groove 19b. In this embodiment, a position-to-protrusion 1c is arranged at the position close to the left end of the upper fracture plate, after installation, the left side surface of the position-to-protrusion just abuts against the right side surface of the liquid injection fixing pipe, so that the abutting bolt can be prevented from being excessively pressed to compress the upper-and-lower sealing rings during installation, so that the upper fracture plate cannot move up and down normally.

[0043] In order to ensure the sealing between the lower end of the lower fracture plate and the rectangular groove, a clamping strip 22 for ensuring the lower fracture plate 2 to tightly contact with the lower wall of the rectangular groove 19a is arranged on the front-and-back side walls of the rectangular groove 19a, the lower end of the clamping strip 22 contacts with the upper end of the lower fracture plate, the upper end of the clamping strip 22 abuts against the upper fracture plate 1 through a micro spring 23, and the lower end of the lower fracture plate is always contacted with the lower inner wall of the rectangular groove through the compressed micro spring.

[0044] In order to ensure the sealing between the front-and-back sides of the upper fracture plate and the lower fracture plate, protrusions 2a extending left-and-right are arranged on the front-and-back sides of the top surface of the lower fracture plate 2, meanwhile, sealing grooves 1b corresponding to the protrusions 2a are arranged on the bottom surface of the upper fracture plate 1, left-and-right sealing rings are sleeved on the upper ends of the protrusions 2a, and the left-and-right sealing rings are always located in the sealing grooves.

[0045] In the embodiment, the card strip is arranged in a door type, and a small pit is arranged at the position corresponding to the installation position of the micro spring at the upper end of the card strip. Since the lower fissure plate can move to the right, in order to facilitate the fixation of the card strip, a card strip groove into which the card strip is inserted is vertically arranged on the left and right side walls of the rectangular groove, and any one of the two ends of the card strip is horizontally arranged with an extension section which can be clamped into the card strip groove. In order to facilitate the processing of the sealing strip groove and the two card strip grooves, a circle of grooves is arranged in the rectangular groove, wherein the sealing strip groove is arranged on the inner wall of the rectangular groove, and the card strip grooves are arranged on the front and rear inner walls of the rectangular groove. In order to ensure sealing, sealing strips are filled in the card strip grooves and the grooves on the lower inner wall of the rectangular groove, and the cross section of the sealing strip is circular.

[0046] In order to reduce the friction when the lower fissure plate moves to the right, a bottom plate 24 is arranged below the lower fissure plate 2 in the fixing assembly, and a plurality of front and rear extending rollers 24a are arranged on the bottom plate 24 at intervals.

[0047] In order to better observe the movement of the fracturing fluid with the proppant, the upper and lower pressure bearing plates are made of transparent materials such as organic glass, and the device is preferably equipped with a high-speed camera. In order to facilitate the recovery of the fracturing fluid, a fracturing groove 3a is arranged in the lower pressure bearing plate, and the upper and lower fissure plates are arranged in the fracturing groove, and a collection tank 3b is arranged at the right end of the fracturing groove, and the collection tank is communicated with the outside through a collection pipe. A pressure gauge and a flow meter are arranged at the position close to the end of the liquid injection pipe, and a strain sensor for measuring stress is arranged between each spring and the fissure plate.

[0048] Based on the above test device, a water pressure fracturing and proppant migration test method under the filtration condition of the water injection hole includes the following test steps:

[0049] Step 1: Test preparation; connect all parts of the test device completely, and after checking, fill the predetermined proppant in the proppant storage tank in the injection assembly, and fill the fracturing fluid in the fracturing tank.

[0050] Second step: load application; the predetermined normal load is applied to the upper fracture plate and the predetermined tangential load is applied to the lower fracture plate by the fixing assembly, and the fracture assembly reaches the predetermined dip angle and inclination. Specifically, the compression of the normal load spring is achieved by screwing the support bolt, so that the normal load on the upper fracture plate reaches the predetermined value, and the normal load is the elastic force of all normal load springs. By changing the distance between the fixing column and the diameter of the lower fracture plate, the compression amount of the tangential load spring is changed, so that the tangential load on the lower fracture plate reaches the predetermined value, and the normal load is the elastic force of all tangential load springs. By screwing the filtration fracture opening bolt, the opening of the filtration fracture is changed to reach the predetermined value. By adjusting the height of the four support rods, the fracture assembly can reach the predetermined dip angle and inclination, that is, the fracture surface between the upper fracture plate and the lower fracture plate reaches the predetermined dip angle and inclination.

[0051] Third step: fracturing; start the water pump and the proppant screw conveyor, mix the fracturing fluid and the proppant, and then inject them into the space between the upper fracture plate and the lower fracture plate at the predetermined rate.

[0052] Fourth step: completion of fracturing; when the injection time of the fracturing fluid with proppant reaches the predetermined time, stop the injection, that is, stop the water pump and the proppant screw conveyor, and record the distribution position of the proppant when the fracturing fluid with proppant stops moving between the upper fracture plate and the lower fracture plate, the flow rate of the fracturing fluid filtration during the test, the displacement of the upper fracture plate and the displacement of the lower fracture plate, so as to obtain the sliding rule of the lower fracture plate under the action of the tangential load spring and the non-uniform deformation rule of the upper fracture plate, and analyze the distribution rule of the proppant in the fracture.

[0053] Fifth step: repeat the test; clean the fracturing fluid and the proppant in the test device, restore the test device to the initial state, then change the filtration opening by screwing the filtration fracture opening bolt, and repeat the steps from the third step to the fourth step, so as to obtain the migration rule of hydraulic fracturing and proppant under different filtration conditions. When repeating the test, the injection rate of the fracturing fluid, the mixing concentration of the proppant, the normal load and the tangential load should be kept unchanged.

Claims

1. A test method for hydraulic fracturing and proppant migration under conditions of water injection hole filtration loss, characterized in that: The test apparatus includes an injection component (A), a fracture component (B), and a fixing component (C). The injection component (A) is used to inject fracturing fluid with proppant into the fracture component (B). The injection component (A) is provided with filtration fractures to allow the fracturing fluid to be filtered out before being injected into the fracture component. The filtration fractures have their openings changed by filtration structures on both sides. The fracture component (B) is used to simulate the reaction of fractured rock mass after fluid injection. The fixing component... Component (C) is used to support and fix the fracture assembly and apply load; the fracture assembly (B) includes an upper fracture plate (1) and a lower fracture plate (2) arranged opposite each other. The left ends of the upper fracture plate (1) and the lower fracture plate (2) are provided with notches for fracturing fluid injection. The upper fracture plate (1) can move up and down and is loaded with a normal load from the fixing component. The lower fracture plate (2) can move left and right and is loaded with a tangential load from the fixing component. The injection assembly (A) includes a fracturing fluid tank (15) installed on the ground via a support column (14). The fracturing fluid tank (15) is provided with an injection pipe (16). The end of the injection pipe (16) is parallel to the notch and is provided with multiple liquid outlet holes for injecting liquid into the notch. The injection pipe (16) is provided with a water pump (17) that can drive the liquid flow. The injection pipe (16) is also provided with a proppant injection pipe (18) for adding proppant into the injection pipe. The upper end of the proppant injection pipe (18) is provided with a proppant addition assembly for quantitatively adding proppant to the liquid in the injection pipe. The end of the injection pipe (16) is provided with an injection fixing pipe (19) that can be fixed to the left end of the fixing assembly and is used to ensure that the liquid in the injection pipe (16) is injected into the notch. The filtration structure includes a filtration fixing plate (25) and a filtration adjusting plate (26) arranged opposite to each other. The filtration adjusting plate (26) is located at the end of the injection tube (16). The filtration fixing plate (25) is provided with an injection section for connecting to the injection fixing tube (19). The gap between the filtration fixing plate (25) and the filtration adjusting plate (26) is a filtration slit. The filtration fixing plate (25) and the filtration adjusting plate (26) are provided with filtration slit opening bolts (27) for adjusting the gap between the filtration fixing plate and the filtration adjusting plate. It also includes the following test steps: S1: Experiment preparation; After connecting all the components of the test device and verifying that everything is correct, fill the injection assembly with the predetermined proppant and fracturing fluid. S2: Load applied; A predetermined normal load is applied to the upper fracture plate by fixing the components, and a predetermined tangential load is applied to the lower fracture plate, while the filtration fracture aperture reaches a predetermined value. S3: Perform hydraulic fracturing; Start the injection assembly to inject fracturing fluid with proppant into the space between the upper and lower fracture plates at a predetermined rate through the notch; S4: Fracturing complete; When the proppant-supported fracturing fluid injection time reaches the predetermined time, the injection is stopped, and the distribution position of the proppant, the flow rate of fracturing fluid lost during the test, the vertical displacement of the upper fracture plate and the horizontal displacement of the lower fracture plate are recorded when the proppant-supported fracturing fluid stops moving between the upper and lower fracture plates. S5: Repeat the experiment; Clean the fracturing fluid and proppant inside the test device to restore the test device to its initial state. Then, after changing the filtration fracture opening, repeat steps S3-S4 to obtain the migration law of hydraulic fracturing and proppant under different filtration conditions.

2. The test method for water pressure fracturing and proppant migration under the condition of water injection hole filtration loss as described in claim 1, characterized in that: The fixing component (C) includes a lower bearing plate (3) disposed below the lower crack plate (2), an upper bearing plate (4) disposed above the lower bearing plate (3) by support bolts (5), the upper bearing plate (4) is located above the upper crack plate (1), and a number of normal load springs (6) are disposed between the upper bearing plate (4) and the upper crack plate (1), a row of clamping bolts (7) that can abut against the right side of the upper crack plate (1) are disposed on the right side of the lower bearing plate (3), and a tangential load component for simulating the tangential load when the lower crack plate (2) moves to the right is also disposed on the right side of the lower bearing plate (3).

3. The test method for water pressure fracturing and proppant migration under the condition of water injection hole filtration loss as described in claim 2, characterized in that: The tangential load assembly includes a tangential load spring (8), one end of which rests against the right side of the lower slit plate (2), and the other end of which is sleeved on a guide post (9) located between the lower pressure plate (3) and the lower slit plate (2), with a distance between the guide post (9) and the lower slit plate (2).

4. The test method for water pressure fracturing and proppant migration under the condition of water injection hole filtration loss as described in claim 2, characterized in that: A height-adjustable support assembly is provided below the lower pressure plate (3). The support assembly includes four support rods (10) arranged in a rectangular pattern between the lower pressure plate (3) and the ground. Each support rod (10) includes a fixed sleeve (10a). A telescopic rod (10b) that can move up and down inside the fixed sleeve (10a) is provided. A fastening sleeve (10c) is provided outside the telescopic rod (10b). The lower end of the fastening sleeve (10c) The fixed sleeve (10a) is provided with an internal thread, and the upper outer side of the fixed sleeve (10a) is provided with an external thread that matches the internal thread. A rubber tube (10d) is provided between the fastening sleeve (10c) and the telescopic rod (10b). A gasket (10e) is provided between the upper end of the rubber tube (10d) and the upper end of the fastening sleeve (10c). When the fastening sleeve (10c) is tightened on the fixed sleeve (10a), the rubber tube (10d) will be squeezed, thereby fixing the length of the telescopic rod (10b).

5. The test method for water pressure fracturing and proppant migration under the condition of water injection hole filtration loss as described in claim 1, characterized in that: The proppant addition assembly includes a proppant storage tank (20), and a proppant screw conveyor (21) is provided at the lower end of the proppant storage tank (20). One end of the proppant screw conveyor (21) is connected to the lower end of the proppant storage tank (20), and the other end is connected to the upper end of the proppant injection pipe (18).

6. The test method for water pressure fracturing and proppant migration under the condition of water injection hole filtration loss as described in claim 1, characterized in that: The right end of the injection fixing tube (19) is provided with a rectangular groove (19a) into which the upper slit plate (1) and the lower slit plate (2) extend. The upper slit plate (1) can move up and down within the rectangular groove (19a). A sealing protrusion (1a) extending forward and backward is inserted above the left end of the upper slit plate (1). The upper end of the sealing protrusion (1a) is fitted with an upper and lower sealing ring. The upper wall of the rectangular groove (19a) is provided with a sealing protrusion (1a) extending forward and backward. 1a) A sealing strip groove (19b) that can be inserted and moved up and down, and the upper and lower sealing rings are located in the sealing strip groove (19b). The front and rear side walls of the rectangular groove (19a) are provided with a retaining strip (22) to ensure that the lower slit plate (2) and the lower wall of the rectangular groove (19a) are in close contact. The lower end of the retaining strip (22) is in contact with the upper end of the lower slit plate, and the upper end of the retaining strip (22) is pressed against the upper slit plate (1) by a micro spring (23).

7. The test method for water pressure fracturing and proppant migration under the condition of water injection hole filtration loss as described in claim 1, characterized in that: The lower slit plate (2) has protrusions (2a) extending to the left and right on both the front and rear sides of its top surface. The upper end of the protrusion (2a) is fitted with left and right sealing rings. The bottom surface of the upper slit plate (1) is provided with a sealing groove (1b) corresponding to the position of the protrusion (2a). The left and right sealing rings are located in the sealing groove.

8. The test method for water pressure fracturing and proppant migration under the condition of water injection hole filtration loss as described in claim 1, characterized in that: Below the lower slit plate (2) is a base plate (24) located within the fixing assembly, and several rollers (24a) extending forward and backward are arranged on the base plate (24) at intervals on the left and right.

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