AU2021105130A4 - Method for treating hard roof through hydraulic fracturing - Google Patents
Method for treating hard roof through hydraulic fracturing Download PDFInfo
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- AU2021105130A4 AU2021105130A4 AU2021105130A AU2021105130A AU2021105130A4 AU 2021105130 A4 AU2021105130 A4 AU 2021105130A4 AU 2021105130 A AU2021105130 A AU 2021105130A AU 2021105130 A AU2021105130 A AU 2021105130A AU 2021105130 A4 AU2021105130 A4 AU 2021105130A4
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- 238000000034 method Methods 0.000 title claims abstract description 57
- 238000005553 drilling Methods 0.000 claims abstract description 45
- 238000010276 construction Methods 0.000 claims description 13
- 238000005516 engineering process Methods 0.000 claims description 3
- 239000003245 coal Substances 0.000 abstract description 12
- 230000006399 behavior Effects 0.000 abstract description 7
- 230000009286 beneficial effect Effects 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 230000003313 weakening effect Effects 0.000 abstract description 4
- 238000005422 blasting Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000005065 mining Methods 0.000 description 5
- 239000011435 rock Substances 0.000 description 5
- 239000000725 suspension Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 230000006378 damage Effects 0.000 description 4
- 238000002347 injection Methods 0.000 description 4
- 239000007924 injection Substances 0.000 description 4
- 230000002706 hydrostatic effect Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 235000019738 Limestone Nutrition 0.000 description 1
- 239000009798 Shen-Fu Substances 0.000 description 1
- 239000003034 coal gas Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C37/00—Other methods or devices for dislodging with or without loading
- E21C37/06—Other methods or devices for dislodging with or without loading by making use of hydraulic or pneumatic pressure in a borehole
- E21C37/12—Other methods or devices for dislodging with or without loading by making use of hydraulic or pneumatic pressure in a borehole by injecting into the borehole a liquid, either initially at high pressure or subsequently subjected to high pressure, e.g. by pulses, by explosive cartridges acting on the liquid
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C27/00—Machines which completely free the mineral from the seam
- E21C27/01—Machines which completely free the mineral from the seam specially adapted for removing overhanging coal
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C45/00—Methods of hydraulic mining; Hydraulic monitors
- E21C45/02—Means for generating pulsating fluid jets
- E21C45/04—Means for generating pulsating fluid jets by use of highly pressurised liquid
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
- E21D9/001—Improving soil or rock, e.g. by freezing; Injections
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C41/00—Methods of underground or surface mining; Layouts therefor
- E21C41/16—Methods of underground mining; Layouts therefor
- E21C41/18—Methods of underground mining; Layouts therefor for brown or hard coal
Landscapes
- Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Mechanical Engineering (AREA)
- Soil Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Drilling And Exploitation, And Mining Machines And Methods (AREA)
Abstract
OF THE DISCLOSURE
Disclosed is a method for treating a hard roof through hydraulic fracturing. The
method comprises the following steps: (1) measuring the stress state of a hard roof to be
fractured; (2) selecting two corresponding different fracturing schemes according to the
obtained stress state; (3) selecting drilling positions and drilling parameters and
constructing fracturing drill holes; and (4) carrying out hydraulic fracturing on the hard
roof. The method has the advantage that the two corresponding different fracturing
schemes can be adopted in accordance with the specific circumstance that crustal stress
is different. Compared with former fracturing methods, the method has the advantages
that the consideration is more comprehensive, the selection of the fracturing methods is
more flexible, the fracturing operation is more target-oriented, and fractured cracks
beneficial to weakening a coal seam overlying hard roof are formed more conveniently,
so that the hard roof is weakened, timely fracture of the hard roof is finally achieved, the
roof weighting step is shortened, strong strata pressure behaviors on a working face are
reduced, and the safety production of underground coal mines is facilitated.
ABSTRACT DRAWING - FIG 1
17952259_1 (GHMatters) P116973.AU
- 1/2
FIG I
d d d
FIG 2
A
R
C
B
FIG 3
179522411 (GHMaters) P116973.AU
Description
- 1/2
d d d
FIG 2
FIG 3
179522411 (GHMaters) P116973.AU
[01] The present disclosure relates to the treatment technology of hard roofs and specifically relates to a method for treating a hard roof through hydraulic fracturing.
[02] Coal resources are abundant in China, coal seam occurrence conditions are relatively complex, coal seams belonging to hard roofs in coal mines of our countries account for about one third, and are distributed in more than 50% of mining areas, such as Shanxi Datong mining area, Yangfangkou mining area and Jincheng mining area; and Beijing City sub-mine, Sichuan Tianchi coal mine, Zaozhuang, Tonghua, Hegang, Shenfu and Dongsheng and other coal fields have hard roofs. The hard roof is often difficult to fall in the mining process to cause large-area suspension, a large amount of energy is easily accumulated to cause excessive stress concentration, so that strong strata pressure behaviors and rock burst are easily caused, once the hard roof is suddenly collapsed, strong impact airflow is caused, and serious hidden dangers are brought to underground safety production.
[03] The hard roof treatment method commonly used at present can be generally classified into four types: a supporting method, a blasting method, a water injection softening method and a hydraulic fracturing method. Wherein, the supporting method is a traditional passive hard roof supporting method, the hard roof cannot be treated fundamentally, and the hard roof can be prevented from falling suddenly only from the angle of supporting the hard roof. According to the blasting method, the roof can be fractured and collapsed to eliminate stress concentration and elastic energy accumulated by the roof is released, so that the possibility of rock burst is reduced, the harm of large-area suspension of the hard roof is avoided, but the blasting method is complex in construction procedure and high in cost, would cause pollution of underground air. And because of the increasing possibility of gas explosions and coal-gas outbursts, the blasting method is also unsafe. The water injection softening method is safe, can be used for underground parallel operation, and has a small influence on production, but the effect of pure water injection softening on the hard roof formed by sandstone or limestone is not obvious. For the treating hard roof method through hydraulic fracturing, high-pressure water is injected into a target layer through fracturing drilling to destroy the integrity of the hard roof, and the hard roof mainly plays a role in fracturing and secondarily plays a role in softening. The hydraulic fracturing method is an active method compared with the supporting method, is safer compared with the blasting method, and is more effective compared with the water injection softening method, so that the present disclosure provides the method for treating a hard roof through hydraulic fracturing.
[04] To overcome the defects in the prior art and achieve the purpose of treating a
17952259_1 (GHMatters) P116973.AU hard roof through hydraulic fracturing, the present disclosure provides a method for treating a hard roof through hydraulic fracturing. Corresponding different fracturing modes are selected according to the difference of crustal stress distribution states of a fracturing target layer, and fracturing cracks are generated in the hard roof, so that the hard roof can collapse timely, which is effective to avoid the damage of strong impact airflow and strong strata pressure behaviors caused by sudden collapse due to large-area suspension of the hard roof without falling.
[05] To achieve the above purpose of the present disclosure, the method for treating a hard roof through hydraulic fracturing comprises the following steps:
[061 (1) Measuring the stress state of a hard roof to be fractured;
[071 Before hydraulic fracturing drilling construction is carried out, the test of crustal stress is firstly carried out to determine the stress state of the hard roof to be fractured. Because the hydrostatic pressure state with the same horizontal stress and vertical stress hardly occurs in a shallow stratum, only the two situations that the horizontal stress is greater than the vertical stress and the horizontal stress is less than the vertical stress are considered.
[081 (2) Selecting two corresponding different fracturing schemes according to the obtained stress state;
[09] If the stress state of the hard roof to be fractured is that the horizontal stress is greater than the vertical stress, a fracturing target layer is divided into multiple layers to be fractured by adopting a vertical drilling hydraulic jetting layered fracturing method. And if the stress state of the hard roof to be fractured is that the horizontal stress is less than the vertical stress, the target layer is fractured by adopting an L-shaped drilling hydraulic jetting staged fracturing method.
[10] (3) Selecting drilling positions, drilling parameters, and constructing fracturing drill holes;
[11] No matter which one of the fracturing methods is adopted, the fracturing drill holes are arranged in parallel to the working face, and the depths of the drill holes reach the lower portion of the target layer. The drill hole interval is d, and the value is twice of the hydraulic jetting fracturing radius and can be obtained through field measurement. The number of the drill holes is n and
[12] n = /d
[131 In the formula, I is the length of the working face.
[14] When the vertical drilling hydraulic jetting layered fracturing method is adopted, the value of the layered fracturing interval delta hi is 1 m. And when the L-shaped drilling hydraulic jetting staged fracturing method is adopted, the drilling horizontal section is arranged parallel to the target layer in the advancing direction of the working face, and the staged fracturing interval delta h2 can be taken as the face width of the working face in consideration of economic benefits and fracturing effects.
[15] (4) Carrying out hydraulic fracturing on the hard roof.
[161 After hydraulic fracturing drilling is completed, fracturing operations can be started, and fracturing pipe columns are dragged from the bottoms of drilled holes in the reverse drilling construction direction to carry out layered or staged fracturing operations.
2 17952259_1 (GHMatters) P116973.AU
[171 The present disclosure has the following beneficial effects:
[181 According to the method, by utilizing the difference of the fracturing cracks formed by hydraulic fracturing in different crustal stress states, two corresponding different fracturing schemes are selected to form horizontal or vertical cracks, through of the cracks is achieved by the reasonable arrangement of the drilling interval and the fracturing interval, and therefore the following beneficial effects are achieved:
[19] Two corresponding different fracturing schemes are adopted according to the different crustal stress conditions, so that the method is more targeted, flexible, and comprehensive;
[20] Through fracturing, cracks are generated more easily, and the integrity of the hard roof is weakened;
[21] (3) The hard roof can be weakened in a controlled manner by controlling the fracturing process, so that the strength of the hard roof is reduced. And
[22] (4) The hard roof can timely collapse, the roof weighting step is shortened, strong strata pressure behaviors on a working face are reduced. And the damage of sudden collapse due to large-area suspension of the hard roof without falling is avoided.
[231 FIG. 1 is a schematic diagram of vertical drilling hydraulic jetting layered fracturing;
[24] FIG. 2 is a profile of a parallel working face of vertical drilling hydraulic jetting layered fracturing;
[25] FIG. 3 is a schematic diagram of L-shaped drilling construction;
[261 FIG. 4 is a schematic diagram of L-shaped drilling hydraulic jetting staged fracturing;
[271 FIG. 5 is a profile of a vertical working face of L-shaped drilling hydraulic jetting staged fracturing.
[28] Reference signs in the attached figures: 1, vertical drill hole; 2, fracturing fracture; 3, L-shaped rill hole; 1, length of working face; d, fracturing drill hole interval; delta h, layered fracturing interval; delta h2, staged fracturing interval; A, L-shaped rill hole vertical section; B, L-shaped drill hole deflecting section; C, L-shaped drill hole horizontal section; and R, L-shaped drill hole turning radius.
[29] The method is proposed in view of the fact that many large coal mines in China have hard roofs and need the requirement for treating the hard roofs. Different corresponding fracturing schemes are selected according to different stress states of the hard roof to be fractured, so that fracturing cracks capable of effectively fracturing a coal seam overlying hard roof can be formed, which make the hard roof weaken and help achieve the timely fracture of the hard roof. And roof weighting step is shortened, strong strata pressure behaviors are reduced. Finally, the damage of strong impact airflow and strong strata pressure behaviors caused by sudden collapse due to large-area suspension of the hard roof without falling is avoided.
[30] The specific implementation process is described below with reference to the
3 17952259_1 (GHMatters) P116973.AU attached figures:
[311 (1) Measuring the stress state of a hard roof to be fractured;
[32] Before hydraulic fracturing drilling construction is carried out, the stress state of the hard roof to be fractured is firstly determined. Because the hydrostatic pressure state with the same horizontal stress and vertical stress hardly occurs in a shallow stratum, only the two situations that the horizontal stress is greater than the vertical stress and the horizontal stress is less than the vertical stress are considered. And different fracturing schemes are formulated according to the two conditions.
[331 (2) Selecting two corresponding different fracturing schemes according to the obtained stress state;
[34] If the stress state of the hard roof to be fractured is that the horizontal stress is greater than the vertical stress, horizontal fracturing fractures are easily formed. For this stress state, a fracturing target layer is divided into multiple layers to be fractured by adopting a vertical drilling hydraulic jetting layered fracturing method. If the tested stress state of the hard roof to be fractured is that the horizontal stress is less than the vertical stress, vertical fracturing fractures are easily formed. For this stress state, the target layer is fractured by adopting an L-shaped drilling hydraulic jetting staged fracturing method.
[351 (3) Selecting drilling positions, drilling parameters, and constructing fracturing drill holes;
[361 No matter which one of the fracturing methods is adopted, the fracturing drill holes are arranged in parallel to the working face, and the depths of the drill holes reach the lower portion of the target layer, so that the hard roof begins to fracture from the lower surface of the hard roof under the action of tensile stress. The drill hole interval is d, and the value is twice of the hydraulic jetting fracturing radius and can be obtained through field measurement; the number of the drill holes is n, and
[371 n = l/d
[381 In the formula, I is the length of the working face.
[391 When the vertical drilling hydraulic jetting layered fracturing method is adopted, according to a Polish roof classification method, when the roof characteristic index L is 35 to 60, the roof is a cracked roof. And the roof locally falls off and is soft, is gradually hard from the lower limit to the upper limit, and is easy to become a falling roof. When the value of L is 60 to 130, the roof is a good roof, the roof is an extremely good roof which is relatively stable to stable gradually from the lower limit to the upper limit, the working condition is good, and falling is difficult. And when the value of L is 130 to 250, the roof is a hard roof. According to the roof classification method, the roof characteristic index is as follows:
[40] L = 0.016 DxRm
[41] In the formula, D is the average layer thickness of rock, mm;
[42] R. is the compressive strength of rock, MPa.
[431 Because the hard roof is weakened with the purpose of weakening the hard roof to be fractured and collapsed timely without being suspended in a large area, the hard roof is prevented from being excessively weakened to be inconvenient to support, the roof characteristic index L of the fractured hard roof is the mean value 95 of 60 to
4 17952259_1 (GHMatters) P116973.AU
130. Because the compressive strength of the hard roof generally varies between 60 MPa and 200 MPa, the average layer thickness D of rock is obtained.
[44] D < 95/(0.016x60) ~ 99mm
[45] Therefore, the layered fracturing interval delta hi is 1 m, and vertical fracturing drill hole arrangement and fracturing schematic diagrams are as shown in FIG. 1 and FIG. 2.
[461 When the L-shaped drilling hydraulic jetting staged fracturing method is adopted, firstly, L-shaped drilling construction is carried out, a hydraulic top drive drilling machine is adopted to carry out vertical section construction at the ground drilling position through the advanced directional drilling technology. And then the angle of a gyrator is adjusted to carry out deflecting section construction (as shown in FIG. 3). To make the effect of fracturing and weakening the hard roof remarkable, a drill rod is adjusted to the position parallel to the hard roof in the advancing direction of the working face at the lower portion of the hard roof to be fractured for drilling. During hydraulic fracturing, due to the existence of adjacent fracturing drill holes, the expansion of fracturing cracks can be induced to a certain extent, so that the fracturing drill hole interval d can be appropriately reduced, the fracturing cracks penetrating through the whole row of fracturing drill holes can be formed, and the fracturing effect is improved. In consideration of economic benefits and fracturing effects, the staged fracturing interval delta h2 can be taken as the face width of the working face, and L-shaped fracturing drill hole arrangement and fracturing schematic diagrams are shown in FIG. 4 and FIG. 5.
[471 (4) Carrying out hydraulic fracturing on the hard roof.
[481 After hydraulic fracturing drilling is completed, fracturing operations can be started, and fracturing pipe columns are dragged from the bottoms of drilled holes in the reverse drilling construction direction to carry out layered or staged fracturing operations.
[49] Compared with former fracturing methods, the method has the advantages that the consideration is more comprehensive, the selection of the fracturing methods is more flexible, the fracturing operation is more target-oriented, and fractured cracks beneficial to weakening a coal seam overlying hard roof are formed more conveniently, so that the hard roof is weakened, timely fracture of the hard roof is finally achieved, the roof weighting step is shortened, strong strata pressure behaviors on a working face are reduced, and the safety production of underground coal mines is facilitated.
[50] It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.
[51] In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.
5 17952259_1 (GHMatters) P116973.AU
Claims (2)
1. A method for treating a hard roof through hydraulic fracturing, comprising the following steps: Step one, measuring the stress state of a hard roof to be fractured; Step two, selecting two corresponding different fracturing schemes according to the obtained stress state. If the stress state of the hard roof to be fractured is that the horizontal stress is greater than the vertical stress, a fracturing target layer is divided into multiple layers to be fractured by adopting a vertical drilling hydraulic jetting layered fracturing method. If the stress state of the hard roof to be fractured is that the horizontal stress is less than the vertical stress, the target layer is fractured by adopting an L-shaped drilling hydraulic jetting staged fracturing method; Step three, selecting drilling positions and drilling parameters and constructing fracturing drill holes, wherein no matter any one of the two different fracturing schemes is adopted, the fracturing drill holes are arranged in parallel to the length direction of the working face, and the depths of the drill holes reach the lower portion of the target layer. The fracturing drill hole interval is d, and the value is twice of the hydraulic jetting fracturing radius. The number of the drill holes is n, n = Ud And in the formula, I is the length of the working face, and the computed result is round; If the vertical drilling hydraulic jetting layered fracturing method is adopted, the value of the layered fracturing interval delta hi is 1 m, and layered fracturing is carried out upwards from the bottoms of the drill holes. And If the L-shaped drilling hydraulic jetting staged fracturing method is adopted, a drilling horizontal section is arranged parallel to the fracturing target layer in the advancing direction of the working face, and the value of the staged fracturing interval delta h2 is the face width of the working face. And Step four, carrying out hydraulic fracturing on the hard roof, wherein from the bottoms of the drill holes, fracturing pipe columns are dragged in the reverse drilling construction direction to perform layered or staged fracturing operation.
2. The method according to claim 1, wherein in step three, when L-shaped drilling construction is carried out, a hydraulic top drive drilling machine is adopted to carry out vertical section construction at the ground drilling position through the directional drilling technology. And then the angle of a gyrator is adjusted to carry out deflecting section construction.
6 17952259_1(GHMatters) P116973.AU
－1/2－ 09 Aug 2021 2021105130
FIG. 1
FIG. 2
FIG. 3
17952241_1 (GHMatters) P116973.AU
－2/2－ 09 Aug 2021 2021105130
FIG. 4
FIG. 5
17952241_1 (GHMatters) P116973.AU
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| Application Number | Priority Date | Filing Date | Title |
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| AU2021105130A AU2021105130A4 (en) | 2021-08-09 | 2021-08-09 | Method for treating hard roof through hydraulic fracturing |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2021105130A AU2021105130A4 (en) | 2021-08-09 | 2021-08-09 | Method for treating hard roof through hydraulic fracturing |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114293989A (en) * | 2021-11-23 | 2022-04-08 | 北京科技大学 | Anti-scour method for segmented hydraulic fracturing area of near-vertical huge-thickness coal seam |
| CN114673497A (en) * | 2022-03-08 | 2022-06-28 | 中国矿业大学(北京) | Suspended roof treatment method based on hard roof direction control cracking |
| CN115853548A (en) * | 2023-03-01 | 2023-03-28 | 华能煤炭技术研究有限公司 | Method for plugging water flowing fractured zone of coal seam roof |
| CN116607940A (en) * | 2023-06-24 | 2023-08-18 | 中煤科工集团重庆研究院有限公司 | Directional hydraulic fracturing pre-fracturing device |
-
2021
- 2021-08-09 AU AU2021105130A patent/AU2021105130A4/en not_active Ceased
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114293989A (en) * | 2021-11-23 | 2022-04-08 | 北京科技大学 | Anti-scour method for segmented hydraulic fracturing area of near-vertical huge-thickness coal seam |
| CN114293989B (en) * | 2021-11-23 | 2022-09-02 | 北京科技大学 | Anti-scour method for near-vertical ultra-thick coal seam subsection hydraulic fracturing area |
| CN114673497A (en) * | 2022-03-08 | 2022-06-28 | 中国矿业大学(北京) | Suspended roof treatment method based on hard roof direction control cracking |
| CN115853548A (en) * | 2023-03-01 | 2023-03-28 | 华能煤炭技术研究有限公司 | Method for plugging water flowing fractured zone of coal seam roof |
| CN116607940A (en) * | 2023-06-24 | 2023-08-18 | 中煤科工集团重庆研究院有限公司 | Directional hydraulic fracturing pre-fracturing device |
| CN116607940B (en) * | 2023-06-24 | 2024-07-16 | 中煤科工集团重庆研究院有限公司 | Directional hydraulic fracturing pre-fracturing device |
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