Silent cracking agent and hydraulic fracturing coupling directional rock breaking method

Abstract

A silent cracking agent and hydraulic fracturing coupling directional rock breaking method comprises the following steps: firstly, designing a rock mass fracturing scheme according to directional fracturing requirements, and then forming a drill hole in a rock mass; a directional joint-cutting silent crushing device is placed in the drill hole, and the orientation of a joint-cutting hole is adjusted, so that the orientation of the joint-cutting hole is aligned with the direction needing directional fracturing; injecting water required by the reaction of the soundless cracking agent into the drill hole through a hole packer; after water injection is completed, the hole packer is sealed, and the directional crack is formed after the internal silent cracking agent expands and fractures; after the directional crack is formed, water is injected into the drill hole again, and hydraulic fracturing is carried out; and after hydraulic fracturing is completed, the joint cutting rate is calculated, if the joint cutting rate reaches 90%, the rock breaking fracturing is completed, and if not, rock breaking is conducted again till the joint cutting rate meets the requirement. The directional pipe is used for controlling the expansion force direction of the soundless cracking agent to form directional cracks, and on the basis, the hydraulic fracturing technology is used for expanding the range of the cracks generated by the soundless cracking agent, so that directional joint cutting of the rock is achieved.

Description

Technical Field

[0001] The invention relates to a rock breaking method, in particular to a directional rock breaking method coupled with a soundless crushing agent and hydraulic fracturing, belonging to the technical field of directional rock breaking of coal rock masses. Background Art

[0002] As the control of explosives becomes increasingly strict, the difficulty of using explosives to crush and fracture rocks in actual engineering projects is increasing. In addition, the demand for low-disturbance rock breaking methods is increasing in areas such as deep mining, urban transportation, tunnel excavation, and three-down projects. The many problems caused by explosive blasting, such as large disturbance, high risk, and difficulty in handling blind shots, make it difficult to meet the specific needs of engineering practice.

[0003] Silent crushing agent is a rock-breaking method with high safety, simple operation, no toxic and harmful gas, no vibration and long action time. It can be used to deal with engineering problems with poor blasting effect and high difficulty of explosives. However, silent crushing agent has problems such as poor controllability of cracking direction and small expansion force. It is difficult to achieve the effect of rock expansion and crushing under some conditions, and it is difficult to solve engineering problems with directional requirements.

[0004] Hydraulic fracturing technology is excellent in the field of rock fracturing. The effect and direction of fracturing can be controlled according to different drilling holes and water pressure outputs. However, the actual fracturing effect is greatly affected by ground stress, and when directional fracturing is required, the borehole needs to be grooved, which makes the operation difficult and has a limited range of action. Summary of the invention

[0005] The purpose of the present invention is to provide a directional rock breaking method by coupling a soundless breaker with hydraulic fracturing, by using a directional pipe to control the direction of the expansion force of the soundless breaker to form directional cracks, and on this basis, by using hydraulic fracturing technology to expand the range of the cracks generated by the soundless breaker, thereby achieving directional cutting of the rock.

[0006] In order to achieve the above object, the present invention provides a directional rock breaking method by coupling a soundless cracking agent with hydraulic fracturing, comprising the following steps:

[0007] ① According to the needs of directional fracturing, design a plan for fracturing the rock mass, including parameters such as borehole size, borehole spacing, and single-hole charge, and then drill holes in the rock mass;

[0008] ② Place the directional slit silent crushing device into the drill hole and adjust the direction of the slit hole so that the direction of the slit hole is aligned with the direction in which directional fracturing is required;

[0009] ③Inject water required for the reaction of the silent crushing agent into the borehole through the sealer;

[0010] ④ After the water injection is completed, the sealer is sealed and the internal silent cracking agent is waited for to expand and fractur e to form directional cracks; specifically, the silent cracking agent expands in volume after reacting with water, generating expansion pressure on the surrounding rock around the borehole. Under the action of the directional pipe, the compressive stress generated by the expansion and extrusion of the silent cracking agent is redistributed, changing from random direction and discontinuous pressure to fixed direction and consistent pressure.

[0011] ⑤ After the directional cracks are formed, water is injected into the borehole again through the fracturing water injection pipe connected to the sealer to perform hydraulic fracturing;

[0012] ⑥After the hydraulic fracturing is completed, take out the fracturing equipment and the sealer, check the borehole and calculate the cutting rate. If the cutting rate reaches 90%, the rock breaking and fracturing is completed. If the cutting rate is less than 90%, repeat steps ②-⑤ to re-break the rock until the cutting rate meets the requirements.

[0013] The directional slitting silent crushing device used in step ② of the present invention comprises a directional tube, slitting holes, and a silent crushing agent. Two rows of slitting holes symmetrically distributed along the axis are left on the tube wall of the directional tube, and the connecting line between the symmetrical slitting holes passes through the center of the cross section of the tube body; the silent crushing agent is filled in the directional tube.

[0014] The soundless breaker of the present invention can be placed in the directional tube after being soaked and wait for the reaction to start, or it can be placed in the directional tube in a dry state and then water is injected into the directional tube to make the soundless breaker react with water.

[0015] The calculation formula of the cutting rate of the present invention is as follows:

[0016] Cutting rate = crack length / (length of the borehole equipped with directional pipe section×2).

[0017] The soundless breaker of the present invention is composed of quicklime (CaO) and inorganic compounds (SO3, Fe2O3, MgO, SiO2, Al2O3, etc.). When the soundless breaker reacts with water to generate calcium hydroxide, a large amount of heat is released and the volume increases by 2-4 times. Since the drilling space is fixed, an expansion force of 30-100MPa will be generated in the constrained space. When the generated stress exceeds the tensile strength of the rock, the rock will break.

[0018] The hydraulic fracturing technology without the above-mentioned ⑤ directly uses the cracks generated by the directional cutting of the soundless breaker as the starting point of the directional hydraulic fracturing, without the need for directional grooving again; the soundless breaker plays the role of a proppant in the hydraulic fracturing process, and while supporting the generated cracks, the swelling agent that has not yet fully reacted will continue to expand, squeezing the crack surface in the directional crack.

[0019] The tube body of the directional tube used in the present invention is made of PVC material.

[0020] Compared with the prior art, the silent breaker directional slitting technology adopted in the present invention is mainly realized by the silent breaker directional tube. The directional tube is used to control the direction of the expansion force of the silent breaker to form directional cracks. The silent breaker expands in volume when it reacts with water, and generates expansion pressure on the surrounding rock around the borehole. Under the action of the directional tube, the compressive stress generated by the expansion and extrusion of the silent breaker is redistributed, and is transformed from random direction and discontinuous pressure to fixed direction and consistent pressure. After being squeezed by the expansion force, the directional pipe will form a tensile stress concentration at the slit hole, and will preferentially break from here into two symmetrical parts. At this time, the wall of the directional pipe will be subjected to the compressive stress of the silent breaker evenly applied to the borehole wall. At this time, the compressive stress direction is perpendicular to the directional direction of the slit hole, so that the hole wall will produce a tensile stress concentration in the directional direction. Due to the characteristics of rock that is resistant to compression but not tension, fracture damage will first occur in this direction, and will continue to expand under the subsequent expansion and squeezing of the breaker to form larger cracks, thereby realizing directional slit cutting of the rock; and on this basis, hydraulic fracturing technology is used to expand the range of cracks generated by the silent breaker, thereby realizing directional expansion of the fracturing range. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the directional tube of the present invention;

[0022] Figure 2 It is a schematic structural diagram of the directional slitting and silent crushing device of the present invention;

[0023] Figure 3 This is a cross-sectional view of the directional fracturing structure of the soundless crushing agent of the present invention ( Figure 2 AA section view of

[0024] Figure 4 This is a schematic diagram of directional hydraulic fracturing according to the present invention.

[0025] In the figure: 1. directional pipe, 2. slit hole, 3. silent breaker, 4. drill hole, 5. hole sealer, 6. lead wire, 7. fracturing water injection pipe, 8. hydraulic fracturing power pump. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the accompanying drawings.

[0027] A directional rock breaking method using a silent breaker coupled with hydraulic fracturing comprises the following steps:

[0028] ① According to the needs of directional fracturing, a plan for fracturing the rock mass is designed, including parameters such as borehole size, borehole spacing, and single-hole charge, and then a borehole 4 is opened in the rock mass;

[0029] ② Place the directional slitting silent crushing device into the drill hole 4, and adjust the direction of the slit hole 2 so that the direction of the slit hole 2 is aligned with the direction in which directional fracturing is required;

[0030] ③ Inject water required for the reaction of the silent crushing agent 3 into the borehole 4 through the hole sealer 5;

[0031] ④ After the water injection is completed, the sealer 5 is sealed, and the internal silent cracking agent is waited for to expand and fractur e to form directional cracks; specifically, the silent cracking agent 3 expands in volume after reacting with water, and generates expansion pressure on the surrounding rock around the borehole. Under the action of the directional pipe 1, the compressive stress generated by the expansion and extrusion of the silent cracking agent is redistributed, and the compressive stress is transformed from random direction and discontinuous pressure to fixed direction and consistent pressure.

[0032] ⑤ After the directional crack is formed, water is injected into the borehole 4 again through the fracturing water injection pipe 7 connected to the sealer 5, and the hydraulic fracturing power pump 8 provides the water injection pressure to perform hydraulic fracturing;

[0033] ⑥ After the hydraulic fracturing is completed, the fracturing equipment and the sealer 5 are taken out together, the borehole 4 is checked and the cutting rate is calculated. The calculation formula of the cutting rate is: cutting rate = crack length / (length of the borehole equipped with the directional pipe section×2); if the cutting rate reaches 90%, the rock breaking and fracturing is completed. If the cutting rate is less than 90%, repeat steps ②-⑤ to re-break the rock until the cutting rate meets the requirements.

[0034] like Figure 1 and Figure 2 As shown, the directional slit silent crushing device of the present invention comprises a directional tube 1, slit holes 2, and a silent crushing agent 3. Two rows of slit holes 2 symmetrically distributed along the axis are left on the tube wall of the directional tube 1, and the connecting line between the symmetrical slit holes 2 passes through the center of the cross section of the tube body; the silent crushing agent 3 is filled in the directional tube 1; the tube body of the directional tube 1 of the present invention is made of PVC.

[0035] When the soundless breaker of the present invention reacts with water to generate calcium hydroxide, a large amount of heat is released and the volume increases by 2-4 times. Since the drilling space is fixed, an expansion force of 30-100 MPa will be generated in the constrained space. When the generated stress exceeds the tensile strength of the rock, the rock will break.

[0036] The soundless breaker 3 of the present invention can be put into the directional pipe 1 after being soaked and wait for the reaction to start, or it can be loaded into the directional pipe 1 in a dry state and then water is injected into the directional pipe 1 to make the soundless breaker react with water; the soundless breaker of the present invention is composed of quicklime (CaO) and inorganic compounds (SO3, Fe2O3, MgO, SiO2, Al2O3, etc.), which is the prior art. The present invention mainly utilizes that the rock breaking principle of the soundless breaker is substantially changed after reacting with water in the directional pipe 1, so that the stress is redistributed, and the compressive stress generated by the rock at the cut hole is concentrated by evenly distributing the disordered compressive stress on the wall of the directional pipe, so as to preferentially cause damage and finally form a two-dimensional directional crack, specifically: the volume of the soundless breaker 3 expands after reacting with water, and an expansion pressure is generated on the surrounding rock around the borehole 4. The compressive stress generated by the expansion and extrusion of the soundless breaker 3 under the action of the directional pipe 1 is redistributed, and the compressive stress is changed from random direction and discontinuous pressure to fixed direction and consistent pressure. After being squeezed by the expansion force, the oriented tube 1 will form a tensile stress concentration at the slit hole, and will preferentially break into two symmetrical parts from this point, such as Figure 3 As shown, at this time, the wall of the directional pipe 1 will be subjected to the compressive stress of the silent crushing agent 3 uniformly applied to the wall of the borehole 4. At this time, the direction of the compressive stress is perpendicular to the directional direction of the cutting hole, so that the hole wall produces tensile stress concentration in the directional direction. Due to the characteristics of rock that is resistant to compression but not to tension, fracture damage will first occur in this direction, and will continue to expand under the subsequent expansion and extrusion of the crushing agent to form larger-sized cracks, thereby realizing directional cutting of the rock.

[0037] like Figure 4 As shown, the hydraulic fracturing technology of the present invention has two new technical features on the original basis after being combined with the directional slitting of the soundless breaker. The first is that there is no need to perform grooving and orientation again, and the cracks generated by the directional slitting of the soundless breaker can be directly used as the starting point of directional hydraulic fracturing; the second is that the expansion agent plays the role of a proppant during the fracturing process, and the expansion agent that has not fully reacted will continue to expand while supporting the generation of cracks, and squeeze the crack surface in the directional crack. The crack expansion direction of conventional hydraulic fracturing shows disorder, and it is necessary to pre-groove the hole wall to form a stress concentration point to achieve directional expansion of the crack. However, pre-grooving is difficult and costly, and the size of the groove is limited, making it difficult to support large-scale directional fracturing of rocks. By combining with the directional slitting of the soundless breaker, the generation of large-scale directional cracks can be achieved, thereby reducing the grooving work and achieving better directional fracturing effects. When the fracturing water flows into the cracks in the borehole, the small particles of the silent breaker 3 in the borehole 4 will also enter the cracks, acting as a proppant to maintain the open state of the cracks. The silent breaker that has not yet completely reacted will continue to react after entering the cracks with the fracturing water, further generating expansion pressure on the cracks, expanding the range of the cracks, and achieving directional expansion of the fracturing range.

[0038] The existing single silent breaker directional slitting technology has a slitting hole spacing of 0.4-0.5m, and single hydraulic fracturing cannot control the crack direction. The silent breaker of the present invention combined with hydraulic fracturing can achieve a slitting hole spacing of 4-6m, which greatly improves the slitting efficiency, reduces production costs, and can accurately control the crack expansion direction.

[0039] An implementation example of the present invention is given

[0040] Take a working face of a certain mine as an example. The coal seam of this working face is located in the middle of the Taiyuan Formation. It has a glassy luster and is a scarce coking coal. The coal seam inclination of the working face is 0-8°, with an average slope of 4°. The cross section of the tunnel is rectangular, 3.1m high, 4.6m long, and 1644m long. After the tunnel is cut and the tunnel is left, it will be used as a transportation tunnel for the next working face. The roof of the cut section above the coal seam is mudstone (0.7m) and fine sandstone (12.8m), and the roof stability is good; the direct bottom is sandy mudstone, which has a small degree of swelling and softening when exposed to water.

[0041] Field tests of single silent breaker topping, single hydraulic fracturing topping and topping coupled with the silent breaker and hydraulic fracturing of the present invention were carried out on the working face, 10 boreholes were tested for each method, the drilling depth was 9m, the angle was 17°, and the diameter was 48mm. The drilling spacing for the topping test using only a silent breaker was 400mm, the drilling spacing for the single hydraulic fracturing topping was 4m, and the drilling spacing for the topping test using the present invention was 4.5m.

[0042] After the test, a borehole peep instrument was used to observe the cracks in the borehole and calculate the cutting rate. The test results show that only two cracks were generated along the cutting line when drilling with a single silent cracking agent, and the cutting can be directed, with an average cutting rate of 81%; single hydraulic fracturing cannot control the crack expansion direction and cannot achieve the goal of directional cutting; the silent cracking agent coupled with hydraulic fracturing of the present invention cuts the top cracks along the pre-cracking direction, and the directional cutting effect is excellent. The average cutting rate of the tested boreholes is 93%, which is 12% higher than that of the single silent cracking agent, the cutting effect is better, and the borehole spacing is 11.25 times higher than that of the single silent cracking agent, which greatly reduces the engineering workload and operation time, reduces the cost, and improves the actual production efficiency.

Claims

1. A directional rock breaking method using a silent cracking agent coupled with hydraulic fracturing, characterized in that: The following steps are involved: ① According to the needs of directional fracturing, a plan for fracturing the rock mass is designed, including parameters of borehole size, borehole spacing, and single-hole charge, and then a borehole is opened in the rock mass (4); ② placing a directional slitting silent crushing device into the drill hole (4), and adjusting the direction of the slitting hole (2) so that the direction of the slitting hole (2) is aligned with the direction in which directional fracturing is required; ③ Injecting water required for the reaction of the soundless crushing agent (3) into the borehole (4) through the hole sealer (5); ④ After the water injection is completed, the sealer (5) is sealed, and the internal silent cracking agent is waited for to expand and fractur e to form directional cracks; specifically, the silent cracking agent (3) expands in volume after reacting with water, and generates expansion pressure on the surrounding rock around the borehole. Under the action of the directional pipe (1), the compressive stress generated by the expansion and extrusion of the silent cracking agent is redistributed, and the compressive stress is transformed from random direction and discontinuous pressure to fixed direction and consistent pressure. ⑤ After the directional cracks are formed, water is injected again into the borehole (4) through the fracturing water injection pipe (7) connected to the sealer (5) to perform hydraulic fracturing; ⑥ After the hydraulic fracturing is completed, the fracturing equipment and the sealer (5) are taken out together, the borehole (4) is checked and the cutting rate is calculated. If the cutting rate reaches 90%, the rock breaking and fracturing is completed. If the cutting rate is less than 90%, repeat steps ②-⑤ to re-break the rock until the cutting rate meets the requirements.

2. A directional rock breaking method of coupling a soundless cracking agent with hydraulic fracturing according to claim 1, characterized in that: The directional slitting and silent crushing device comprises a directional tube (1), slitting holes (2), and a silent crushing agent (3). Two rows of slitting holes (2) symmetrically distributed along an axis are left on the tube wall of the directional tube (1), and the connecting line between the symmetrical slitting holes (2) passes through the center of the cross section of the tube body; the silent crushing agent (3) is filled in the directional tube (1).

3. A directional rock breaking method of coupling a soundless cracking agent with hydraulic fracturing according to claim 2, characterized in that: The soundless breaker (3) is soaked and placed in the directional tube (1) to wait for the reaction to start, or it is placed in the directional tube (1) in a dry state and then water is injected into the directional tube (1) to allow the soundless breaker to react with water.

4. A directional rock breaking method of coupling a soundless cracking agent with hydraulic fracturing according to claim 3, characterized in that: The calculation formula of the cutting rate is as follows: Cutting rate = crack length / (length of the borehole equipped with directional pipe section×2).

5. A directional rock breaking method of coupling a soundless cracking agent with hydraulic fracturing according to claim 3, characterized in that: Silent crushers are composed of quicklime and inorganic compounds. When the silent crushers react with water to form calcium hydroxide, a large amount of heat is released and the volume increases by 2-4 times. Since the drilling space is fixed, an expansion force of 30-100MPa will be generated in the constrained space. When the stress generated exceeds the tensile strength of the rock, the rock will break.

6. A directional rock breaking method of coupling a soundless cracking agent with hydraulic fracturing according to claim 3, characterized in that: Hydraulic fracturing technology directly uses the cracks generated by the directional cutting of silent breakers as the starting point of directional hydraulic fracturing, without the need for further grooving and directional fracturing; the silent breakers act as proppants in the hydraulic fracturing process, supporting the generation of cracks while the swelling agent that has not fully reacted will continue to expand, squeezing the crack surface within the directional cracks.

7. A directional rock breaking method of coupling a soundless cracking agent with hydraulic fracturing according to claim 3, characterized in that: The body of the directional tube (1) is made of PVC.

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