Indoor pulse fracturing sample hole sealing method

Abstract

The invention discloses an indoor pulsating fracturing sample hole sealing method which comprises the following steps: calibrating a plurality of positions on a fracturing pipe, and bonding a rubber sleeve on each calibrated position to form a plurality of rubber sleeve preliminary blocking layers; inserting the fracturing pipe with a plurality of rubber sleeve preliminary blocking layers into the rock sample drill hole, repeatedly drawing and inserting to detect the adhesion effect, and after the rubber sleeve is completely adhered; the space between every two adjacent rubber sleeve preliminary blocking layers and the space between the rubber sleeve preliminary blocking layer close to the input end of the fracturing pipe and the hole opening of the drill hole are filled with embedded steel bar glue, multiple embedded steel bar glue blocking layers are formed, a pulsating fracturing experiment is conducted after standing and fixing, and by means of the elasticity of the rubber sleeves, in the process that the fracturing pipe is inserted into the drill hole, the rubber sleeve blocking layers are separated from the drill hole through the embedded steel bar glue blocking layers. The fracturing pipe is helped to be straightened through rebounding of the rubber sleeve, the fracturing pipe is restrained to deviate up and down through friction between the rubber sleeve and the hole wall of the drill hole, and the problems of deviation and deflection of the fracturing pipe in the hole sealing process are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of mine hydraulic fracturing, and specifically to a method for sealing holes of indoor pulsating fracturing specimens. Background Art

[0002] Coal plays an important role in China's energy field. As a fracturing technical means, hydraulic fracturing is widely used in the coal mine field. With the development of hydraulic fracturing technology, pulsating fracturing technology has been proposed and gradually applied to the engineering site.

[0003] Currently, indoor research on pulsating fracturing technology usually adopts the means of similar simulation, and many valuable results have been obtained, which actively guide the design and construction of on-site pulsating fracturing. In the conventional fracturing method, a concrete block is poured, and a fracturing pipe is inserted when the concrete block is in a colloidal state. After it hardens, the fracturing pipe can be fixedly embedded in the concrete block. At this time, the concrete block is fractured through the fracturing pipe, and this method effectively solves the problem of inserting the fracturing pipe into the rock sample and sealing the hole.

[0004] Natural rock samples are real rock samples from the mine working face and can truly reflect the effect of pulsating fracturing. However, there are still certain property differences between natural rock samples and concrete blocks, and the natural rock samples cannot truly invert the fracturing failure process through the above method. When fracturing natural rock samples, generally a borehole needs to be drilled on the rock sample, and then the fracturing pipe is put in. Despite the fine design of the borehole, there is inevitably a certain spatial gap between the fracturing pipe and the borehole, resulting in the fracturing fluid flowing out along the hole wall from the fracturing pipe and failing to achieve the fracturing effect. Therefore, for the fracturing experiment of natural rock samples, it is necessary to seal the gap between the fracturing pipe and the borehole to form a sealed space between the borehole and the fracturing pipe to prevent the fracturing fluid from flowing away through the hole wall gap.

[0005] Currently, the sealing hole technology mainly inserts the fracturing pipe into the borehole of the rock sample and directly injects the sealing hole material, lacking a fixing device, and can only judge whether the fracturing pipe is offset and deflected through manual feeling. The offset and deflection of the fracturing pipe will cause the change of the rock sample cracking direction, especially when the rock sample is under load conditions, it is easy to affect the crack propagation direction. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for sealing holes of indoor pulsating fracturing specimens, which can avoid the problems of offset and deflection of the fracturing pipe caused by hole sealing.

[0007] The technical solution of the present invention is as follows:

[0008] A method for sealing holes of indoor pulsating fracturing specimens includes the following steps:

[0009] S1. Drill a hole in the center of the fracturing rock sample; drill the hole vertically, and the drilling depth is the middle height of the fracturing rock sample.

[0010] S2. Calibrate multiple positions along the axial direction of the fracturing pipe, and bond rubber sleeves at each calibrated position to form multiple preliminary rubber sleeve blocking layers.

[0011] S3. Insert the fracturing pipe with multiple preliminary rubber sleeve blocking layers into the rock sample borehole, and insert and extract it repeatedly to test the adhesion effect of the rubber sleeves on the fracturing pipe. If the rubber sleeves fall off, bond them again. If the adhesion effect of the rubber sleeves is good, proceed to the next step.

[0012] S4. Insert the fracturing pipe into the borehole for a certain distance so that the drill opening of the borehole is exactly in the interval of two preliminary rubber sleeve blocking layers near the output end of the fracturing pipe. Use a syringe to inject the rebar adhesive from the circumferential side of the fracturing pipe to fill the interval of the two preliminary rubber sleeve blocking layers near the output end of the fracturing pipe.

[0013] S5. Fill the rebar adhesive between the remaining adjacent two preliminary rubber sleeve blocking layers, and also between the preliminary rubber sleeve blocking layer near the input end of the fracturing pipe and the borehole opening to form multiple rebar adhesive blocking layers.

[0014] S6. Let the sealed fracturing rock sample stand until the rebar adhesive is firmly bonded, and then conduct a pulsating fracturing experiment.

[0015] Furthermore, the interval distance between adjacent rubber sleeves is greater than the wire diameter of the rubber sleeve.

[0016] Furthermore, twice the wire diameter of the rubber sleeve plus the diameter of the fracturing pipe is 0.5 mm - 1 mm greater than the borehole diameter. Since the rubber sleeve has a certain elasticity, when inserted into the borehole, the rubber sleeve is in a compressed state. At this time, the rubber sleeve will squeeze against the borehole wall. After inserting to the specified depth, use the elasticity of the rubber sleeve to straighten the fracturing pipe. The thickness of the rubber sleeve is the wire diameter of the rubber sleeve. For different experiments, different sizes of specimens and different diameters of the fracturing pipe, the appropriate borehole diameter and rubber sleeve can be selected.

[0017] Furthermore, the rubber sleeve is a fitting made of rubber, with functions such as sealing, waterproofing, and fixing, and does not react with the rebar adhesive.

[0018] Furthermore, in S4, insert and extract the fracturing pipe in the rock sample borehole repeatedly to check the filling effect of the rebar adhesive. If it is found that there is an unfilled space, supplement the rebar adhesive in a timely manner, and repeat the inspection multiple times to make the rebar adhesive completely fill the interval and ensure the sealing of the blocking layer.

[0019] Furthermore, the multiple rubber sleeves are produced in the same batch.

[0020] Furthermore, before curing, the anchor glue is in the form of a paste with fluidity and slow flow rate, which is convenient for controllable injection into the rock sample borehole. And the curing speed of the anchor glue is relatively slow to ensure that the anchor glue does not solidify during the hole sealing process. After curing, the anchor glue forms a solid with high strength and corrosion resistance, which can be tightly combined with the rock sample and does not chemically react with water.

[0021] Furthermore, after the fracturing experiment is completed, the anchor glue is knocked off from the fracturing pipe wall by a hammer to realize the recycling of the fracturing pipe.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. The hole sealing method of the present invention utilizes an active deviation correction hole sealing structure with dynamic constraint. By bonding a rubber sleeve on the fracturing pipe, according to Hooke's law, using the elasticity of the rubber sleeve, during the process of inserting the fracturing pipe into the borehole, the rubber sleeve rebounds to help straighten the fracturing pipe, and the friction between the rubber sleeve and the borehole wall is used to restrict the up and down offset of the fracturing pipe, effectively solving the problems of offset and deflection of the fracturing pipe during the hole sealing process. And the fracturing pipe is inserted and pulled out in the borehole to check the adhesion effect of the rubber sleeve on the fracturing pipe, thereby ensuring the sealing effect of the hole sealing.

[0024] 2. The hole sealing method of the present invention effectively prevents the seepage and overflow of the anchor glue through the rubber sleeve preliminary blocking layer formed by the well - adhered rubber sleeve, avoiding the cracking difficulty and the change of cracking direction caused by the blockage of the hole sealing material at the fracturing pipe orifice. The rubber sleeve preliminary blocking layer, combined with the multi - layer anchor glue group fault layer, constitutes a multi - layer high - strength elastic gluing and sealing structure to achieve a better hole sealing effect and avoid the influence of the fracturing fluid leakage and escape on the fracturing effect due to poor hole sealing effect.

[0025] 3. For the hole sealing method of the present invention, after the pulsating fracturing experiment, the hole sealing material only adheres to the outer wall of the fracturing pipe. By knocking it off with a hammer, the recycling of the fracturing pipe can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a sectional view of the schematic diagram of the rock sample structure prepared by the hole sealing method of the present invention.

[0027] Figure 2 It is a top view of the schematic diagram of the rock sample structure prepared by the hole sealing method of the present invention.

[0028] Among them, 1. Fractured rock sample, 2. Fracturing pipe, 3. Anchor glue blocking layer, 4. Rubber sleeve preliminary blocking layer. SPECIFIC EMBODIMENTS

[0029] The following is combined with Figures 1 to 2, a detailed description of the specific embodiments of the present invention is provided. In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0030] The terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features; in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0031] It should be noted that the circuit connections involved in the present invention all adopt conventional circuit connection methods and do not involve any innovation.

[0032] Embodiment

[0033] As Figures 1 to 2 shown, an indoor pulsating fracturing sample sealing method, applicable to rocks of any size, specifically includes the following steps:

[0034] S1. Drill a hole in the center of the fracturing rock sample 1. Select a large piece of hard rock, cut and polish it to form a cylindrical sample with a diameter of 68 mm and a height of 136 mm. Select any circular surface and drill a circular hole with a diameter of 10 mm and a depth of 80 mm in its central area.

[0035] For the convenience of sealing the hole, the diameter of the drill hole in this embodiment is slightly larger than the diameter of the fracturing pipe 2. The depth of the drill hole is half of the height of the rock sample, so that the fracturing fluid starts to fracture from the geometric center of the whole rock sample, which is convenient for studying the crack propagation. The drill hole is drilled by a bench drill, and the inner wall of the drill hole is ensured to be smooth and stable. The drill hole angle is perpendicular to the upper surface of the rock sample and is located at the center of the rock sample.

[0036] S2. Mark multiple positions along the axial direction of the fracturing pipe 2, and bond rubber sleeves at each marked position to form multiple preliminary rubber sleeve blocking layers 4. Use a ruler and a marker pen to mark the positions of the rubber sleeves from the lower end of the fracturing pipe 2. The marked positions are 14 mm, 36 mm, and 58 mm away from the lower end of the fracturing pipe 2 respectively. Set the rubber sleeves to the marked positions and bond them with planting bar glue to form three preliminary rubber sleeve blocking layers 4. From the output end to the input end of the fracturing pipe 2, they are the first preliminary blocking layer, the second preliminary blocking layer, and the third preliminary blocking layer in sequence.

[0037] It should be noted that the interval distance between adjacent rubber sleeves only needs to be greater than the wire diameter of the rubber sleeve. Moreover, after the interval distance of the rubber sleeves meets the above conditions, the more rubber sleeves are sleeved, the better the sealing performance. In this embodiment, it is exemplified that 3 rubber sleeves correspond to 3 primary blocking layers of rubber sleeves. And, the multiple rubber sleeves in this embodiment are of the same batch, with little difference in size and elasticity.

[0038] Twice the wire diameter of the rubber sleeve plus the diameter of the fracturing pipe 2 is greater than the hole diameter by 0.5 mm - 1 mm. Since the rubber sleeve has a certain elasticity, when it is inserted into the drill hole, the rubber sleeve is in a compressed state. At this time, the rubber sleeve will squeeze against the hole wall. After being inserted to the specified depth, the fracturing pipe 2 is centered by using the elasticity of the rubber sleeve. The thickness of the rubber sleeve is the wire diameter of the rubber sleeve. For different experiments, different sizes of specimens and different diameters of the fracturing pipe 2, an appropriate drill hole diameter and rubber sleeve can be selected. The rubber sleeve is a fitting made of rubber, with functions such as sealing, waterproofing, and fixing, and does not react with the implanting glue.

[0039] S3. Insert the fracturing pipe 2 with the primary blocking layer 4 of rubber sleeves into the rock sample drill hole and insert and extract it repeatedly to check the adhesion effect of the rubber sleeves on the fracturing pipe 2. If the rubber sleeve falls off, bond it again. If the position of the rubber sleeve does not shift during the insertion and extraction process and the rubber sleeve does not fall off, it is determined that the adhesion effect is good, then proceed to the next step.

[0040] S4. Inject implanting glue onto each of the formed primary blocking layers 4 of rubber sleeves to form multiple implanting glue blocking layers. Specifically, insert the fracturing pipe 2 into the drill hole for a certain distance so that the drill opening of the drill hole is exactly in the interval between the first primary blocking layer and the second primary blocking layer. Use a syringe to inject implanting glue around the fracturing pipe 2 to fill the interval between the first primary blocking layer and the second primary blocking layer, forming the implanting glue blocking layer 3 at the bottom.

[0041] Insert and extract the fracturing pipe 2 repeatedly in the rock sample drill hole to check and improve the filling effect of the implanting glue. Specifically, insert and extract the fracturing pipe 2 repeatedly in the drill hole. If there is a non-filled space found, supplement the implanting glue in time. Repeat multiple times to make the implanting glue completely fill the interval and ensure the sealing performance of the next set of faults.

[0042] Before curing, the implanting glue is in the form of a paste with fluidity and slow flow, which is convenient for controllable injection into the rock sample drill hole. And the curing speed of the implanting glue is relatively slow to ensure that the implanting glue does not solidify during the hole sealing process. After curing, the implanting glue forms a solid with high strength and corrosion resistance. It can be tightly combined with the rock sample and does not chemically react with water.

[0043] The state of the bonded rebar adhesive is a viscous colloid. When injecting, the bonded rebar adhesive will adhere to the hole wall, resulting in the inability to inject the bonded rebar adhesive to a deeper level. In this embodiment, by repeatedly inserting and extracting, the bonded rebar adhesive can fall to the rubber sleeve, and during this process, the bonded rebar adhesive is continuously supplemented and injected, so that the bonded rebar adhesive completely fills the interval. When the diameter of the fracturing pipe 2 wrapped with the bonded rebar adhesive is approximately equal to the hole diameter, and at this time the injected bonded rebar adhesive begins to overflow, at this time, the injection of the bonded rebar adhesive is completed, and a blocking layer is formed. It should be noted that during the process of repeated extraction, due to the viscosity and colloid state of the bonded rebar adhesive, it will not immediately fall off when extracted, but can maintain a certain time.

[0044] S5. Repeat steps S3 - S4 to fill the bonded rebar adhesive between the second preliminary blocking layer and the third preliminary blocking layer, and between the third preliminary blocking layer and the borehole orifice to form a multiple bonded rebar adhesive blocking layer 3.

[0045] S6. After standing until the bonded rebar adhesive is firmly bonded, conduct a pulsating fracturing experiment. Specifically, place the sealed fracturing rock sample 1 in a dry area and stand for more than 24 hours to make the bonded rebar adhesive completely cured, and then the pulsating fracturing experiment can be carried out on the fracturing rock sample 1. It should be noted that if the fracturing pipe 2 cannot be pulled out from the borehole, it is determined that the bonded rebar adhesive is bonded.

[0046] After the fracturing experiment is completed, the bonded rebar adhesive is knocked off from the wall of the fracturing pipe 2 by a hammer to realize the recycling of the fracturing pipe 2.

[0047] The above-disclosed are only several preferred specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. An indoor pulsating fracturing sample sealing method, characterized in that, It includes the following steps: S1. Drill a hole in the center of the fracturing rock sample (1); S2. Mark multiple positions along the axial direction of the fracturing pipe (2), and bond rubber sleeves at each marked position to form multiple preliminary rubber sleeve blocking layers (4); S3. Insert the fracturing pipe (2) with multiple preliminary rubber sleeve blocking layers (4) into the drilled hole of the rock sample, and insert and extract it repeatedly to test the adhesion effect of the rubber sleeves on the fracturing pipe (2). If the rubber sleeves fall off, bond them again. If the positions of the rubber sleeves do not shift during the insertion and extraction process and the rubber sleeves do not fall off, it is determined that the adhesion effect is good, then proceed to the next step; S4. Fill the bonding agent for reinforcing bar between two adjacent preliminary rubber sleeve blocking layers (4), and between the preliminary rubber sleeve blocking layer (4) near the input end of the fracturing pipe (2) and the hole opening of the drilled hole to form a multiple bonding agent for reinforcing bar blocking layer (3); S5. Let the sealed fracturing rock sample (1) stand still until the bonding agent for reinforcing bar is firmly bonded, and then conduct a pulsating fracturing experiment.

2. The method for sealing holes of an indoor pulsating fracturing specimen according to claim 1, characterized in that The interval distance between adjacent rubber sleeves is greater than the wire diameter of the rubber sleeve.

3. The method for sealing holes of an indoor pulsating fracturing sample according to claim 1, wherein Twice the wire diameter of the rubber sleeve plus the diameter of the fracturing pipe (2) is greater than the hole diameter by 0.5 mm - 1 mm.

4. A method for sealing holes of an indoor pulsating fracturing specimen according to claim 1, characterized in that, The rubber sleeve is a rubber fitting with sealing, waterproofing, and fixing functions that has no chemical reaction with the bonding agent for reinforcing bar.

5. A method for sealing holes of an indoor pulsating fracturing specimen according to claim 1, characterized in that, In S4, insert and extract the fracturing pipe (2) repeatedly in the drilled hole of the rock sample to check the filling effect of the bonding agent for reinforcing bar. If there is an unfilled space found, supplement the bonding agent for reinforcing bar in time. Repeat the inspection multiple times to make the bonding agent for reinforcing bar completely fill the interval and ensure the sealing of the blocking layer.

6. The method for sealing holes of an indoor pulsating fracturing specimen according to claim 1, characterized in that, The multiple rubber sleeves are produced in the same batch.

7. A method for sealing holes of an indoor pulsating fracturing specimen according to claim 1, characterized in that, Before curing, the bonding agent for reinforcing bar is in the form of a paste with fluidity and slow flow, and the curing speed of the bonding agent for reinforcing bar is relatively slow to ensure that the bonding agent for reinforcing bar does not solidify during the hole sealing process. After curing, the bonding agent for reinforcing bar forms a solid with high strength and corrosion resistance.

8. A method for sealing holes of an indoor pulsating fracturing specimen according to claim 1, characterized in that, After the fracturing experiment is completed, the bonding agent for reinforcing bar is made to fall off from the wall of the fracturing pipe (2) by knocking with a hammer.

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