CN111140205A - Method for preventing coal bed gas pre-pumping well from being damaged along with recovery - Google Patents
Method for preventing coal bed gas pre-pumping well from being damaged along with recovery Download PDFInfo
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- CN111140205A CN111140205A CN201911332888.8A CN201911332888A CN111140205A CN 111140205 A CN111140205 A CN 111140205A CN 201911332888 A CN201911332888 A CN 201911332888A CN 111140205 A CN111140205 A CN 111140205A
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- 238000005086 pumping Methods 0.000 title claims abstract description 61
- 239000003245 coal Substances 0.000 title claims abstract description 57
- 238000000034 method Methods 0.000 title claims abstract description 14
- 238000011084 recovery Methods 0.000 title claims abstract description 12
- 239000011435 rock Substances 0.000 claims abstract description 56
- 238000005520 cutting process Methods 0.000 claims abstract description 29
- 238000005452 bending Methods 0.000 claims abstract description 9
- 238000004364 calculation method Methods 0.000 claims abstract description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 38
- 238000005516 engineering process Methods 0.000 claims description 5
- 238000005065 mining Methods 0.000 abstract description 21
- 238000000605 extraction Methods 0.000 abstract description 18
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000001125 extrusion Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- 238000005553 drilling Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 238000009412 basement excavation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 208000008918 voyeurism Diseases 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/006—Production of coal-bed methane
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B29/00—Cutting or destroying pipes, packers, plugs or wire lines, located in boreholes or wells, e.g. cutting of damaged pipes, of windows; Deforming of pipes in boreholes or wells; Reconditioning of well casings while in the ground
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- Engineering & Computer Science (AREA)
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- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical & Material Sciences (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
The invention belongs to the technical field of coal bed gas, and particularly relates to a method for preventing a coal bed gas pre-pumping well from being damaged along with recovery. The method comprises the following steps: (1) determining a coal seam overlying rock collapse zone and a fracture zone area; according to a key layer theory and a comprehensive histogram of a stope face, calculating the load of each overlying rock layer from top to bottom layer by using a calculation formula of the load of the overlying thick hard rock layer, further determining the position of a key layer, and establishing a caving zone, a fracture zone and a bending subsidence zone; (2) cutting the sleeve; and before the recovery influence, performing segmented annular cutting on the coal bed gas pre-pumping well casing at the bottom of the key layer. Finally, an underground extraction channel of 'a caving zone + a fracture zone + a pre-pumping well casing pipe of a section which is not deformed and damaged' is established, and further the purpose of extraction and treatment of coal bed gas in the middle and after mining of a working face and even in an old goaf is achieved.
Description
Technical Field
The invention belongs to the technical field of coal bed gas, and particularly relates to a method for preventing a coal bed gas pre-pumping well from being damaged along with recovery.
Background
The main factor of the ground coal bed gas pre-pumping well scrapping due to mining is that a pumping channel is blocked due to excessive deformation of a pre-pumping well casing during the mining influence period. The coal seam is vertically influenced by mining and is sequentially divided into a collapse zone, a fracture zone and a bending subsidence zone from bottom to top, the bending subsidence zone generally sinks integrally, the subsidence difference between rock stratums is very small, the relative movement amount between the layers is not large, great stretching, extrusion and distortion can not be generally caused to the pre-pumping well casing, and the pre-pumping well casing is mainly divided into two stages: a development stage of a caving zone and a development stage of a fissure zone.
The treatment measure of the ground coalbed methane pre-pumping well affected by underground mining is mainly to scrap and seal holes, and if the ground coalbed methane pre-pumping well is expanded from pre-mining to middle-mining, post-mining or even goaf coalbed methane extraction treatment, the service range and the service period are prolonged, and the coalbed methane comprehensive treatment cost is greatly reduced.
The ground coalbed methane pre-pumping well is used for treating coalbed methane in and after mining on a working face, and is different from the old goaf arranged ground drilling holes, the old goaf coalbed methane well is generally arranged in an area after the goaf is relatively stable in subsidence, and the drilling holes are less influenced by stratum deformation. The biggest difficulty of the ground coalbed methane pre-pumping well for treating the coalbed methane in the working face and after the coalbed methane is greatly influenced by deformation of an overlying rock stratum of a stope, the shape of the structure of a well body of the ground coalbed methane pre-pumping well and the structure of the overlying rock stratum under the influence of fully-mechanized mining and caving is analyzed by utilizing equipment such as a peeping instrument, the local deformation of a pre-pumping well casing in the ground coalbed methane pre-pumping well is found to be a key for restricting the use of the pre-pumping well casing in the working face for treating the coalbed methane in the working face and after the coalbed methane is produced, a new technology is adopted to ensure the smoothness of an extraction channel from the underground to the ground, and therefore the ground coalbed methane pre-pumping well is used.
Disclosure of Invention
The invention aims to provide a method for preventing a coal bed gas pre-pumping well from being damaged along with extraction, and the production period of the coal bed gas pre-pumping well is prolonged, so that the aim of using the ground coal bed gas pre-pumping well for extraction and treatment of coal bed gas in and after working face extraction is fulfilled. The technical scheme of the invention comprises the following specific steps:
(1) determining a coal seam overlying rock collapse zone and a fracture zone area;
according to a key layer theory (when multiple layers or groups of hard rock layers exist in overburden rocks, the lower part of a main key layer generates more obvious separation deformation, and the breakage of the main key layer causes large-amplitude settlement of the earth surface) and a comprehensive histogram of a stope face, the load of each overburden rock layer is calculated layer by layer from top to bottom by utilizing a calculation formula (1) of the load of the overburden thick hard rock layer, the position of the key layer is further determined, and a caving zone, a fracture zone and a bending subsidence zone are established;
in the formula, qm|n: the nth layer loads, KN, the mth layer; em: the m-th layer elastic modulus, Mpa; h ism、hi: the thickness of the mth layer and the ith layer, m; gamma rayi: volume weight of rock of i-th layer, KN/m3。
If the load of the n +1 th layer is smaller than that of the n-th layer, i.e. qm|n+1＜qm|nAnd if not, continuously calculating the load of the n +2 th layer to the n-th layer.
(2) Cutting the sleeve;
before the recovery is influenced, mature technologies such as energy-gathering cutting bullets, mechanical cutters or hydraulic cutters are applied to the bottom of the key layer to perform segmented annular cutting on the coal bed gas pre-pumping well casing. In particular to the annular cutting of the pre-pumping well casing above a straddle zone, a fracture zone and a curved subsidence zone. After cutting, the pre-pumping well casing does not have production accidents such as displacement and dislocation due to the cementing action of the well cementation cement sheath. When the recovery is influenced, the pre-pumping well casing after the cutting in the coal seam overlying strata collapse zone and the fracture zone area collapses or displaces along with the strata, the integrity of the casing at the upper part of the deformation section is not influenced, and finally an underground pumping channel of the pre-pumping well casing of the collapse zone, the fracture zone and the section which is not damaged by the deformation is established. And further, the purpose of coal bed gas extraction and treatment in the working face, after mining and even in the old goaf is realized.
Different from the prior art, the invention at least comprises the following beneficial effects:
1. the matching investment is low, and the realization is easy. The ground coalbed methane pre-pumping well is used for extracting the coal in the working face and after the coal is extracted, so that the original site and facilities can be effectively utilized, and land acquisition, well site construction, road construction and matched power supply lines are not needed.
2. The coal bed gas is continuously treated before, during and after the ground coal bed gas is pre-pumped, and the treatment effect of the coal bed gas is improved. On the basis of regional pre-extraction, continuous extraction is carried out in the mining influence stage, during mining and after mining, and the extraction amount of coal bed gas is improved. In the excavation influence stage and the stoping process, the permeability of the coal bed is further improved due to the pressure relief of the coal bed, and the extraction of coal bed gas is facilitated; after mining, the potential safety hazard brought to coal mine production by coal loss in a goaf and coal bed gas emission in surrounding coal rocks can be effectively relieved.
3. The design can pertinently select the easily-collapsed and deformed area of the coal bed roof rock stratum, and perform segmented annular cutting on the coal bed gas well casing in the area, when the extraction is influenced, the pre-pumping well casing after the cutting in the coal bed roof collapse area and the fracture zone area collapses or displaces along with the rock stratum, the integrity of the casing at the upper part of the deformed section is not influenced, and finally, an underground extraction channel of the collapse area, the fracture area and the pre-pumping well casing which is not deformed and damaged is established.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
Fig. 1 is a schematic diagram of a well bore structure of a method for preventing a coalbed methane pre-pumping well from being damaged along with recovery according to the invention.
Fig. 2 shows physical and mechanical parameters and key layers of all stratums of temple minerals.
In the figure: 1. key formation C12, 2, key formation C10, 3, key formation C8, 4, 3# coal seam, 5, pre-pumping well casing, 6, cutting ring.
Detailed Description
For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
A method for preventing a coal bed gas pre-pumping well from being damaged along with recovery comprises the following specific steps:
(1) determining a coal seam overlying rock collapse zone and a fracture zone area;
according to the key layer theory and the comprehensive histogram of the stope face, the calculation formula of the loads of the overlying thick and hard rock layers is utilized, the loads of the overlying rock layers are calculated layer by layer from top to bottom, the position of the key layer is further determined, and a caving zone, a fissure zone and a bending subsidence zone are established.
(2) Cutting the sleeve;
before the stoping is influenced, mature technologies such as energy-gathering cutting bullets, mechanical cutters or hydraulic cutters are applied to the bottom of the key layer to perform segmented annular cutting on the coal bed gas pre-pumping well casing 5. When the recovery is influenced, the pre-pumping well casing 5 after the cutting in the coal seam overlying strata collapse zone and the fracture zone area collapses or displaces along with the strata, the integrity of the casing at the upper part of the deformation section is not influenced, and finally an underground pumping channel of the pre-pumping well casing of the collapse zone, the fracture zone and the section which is not damaged by the deformation is established.
The main factor of the ground coal bed gas pre-pumping well scrapping due to mining is that a pumping channel is blocked due to excessive deformation of a pre-pumping well casing 5 during the mining influence period. The coal seam is longitudinally influenced by mining and is sequentially divided into a collapse zone, a fracture zone and a bending subsidence zone from bottom to top, the bending subsidence zone generally sinks integrally, the subsidence difference between rock stratums is very small, the relative movement amount between the layers is not large, great stretching, extrusion and distortion can not be generally caused to the pre-pumping well casing 5, and the damage of the pre-pumping well casing 5 mainly comprises two stages: a development stage of a caving zone and a development stage of a fissure zone.
The invention will now be described in further detail with reference to fig. 1, taking the coal seam No. 3 of the temple coal industry as an example.
(1) Development stage of the caving zone. The old top of the No. 3 coal seam is sandstone or argillaceous sandstone with the thickness of 10-20 m, the texture is hard, and the old top is a first key layer in an overlying rock layer of the No. 3 coal seam. When fully-mechanized top caving mining is carried out, the gravity formed by the old top and the follow-up layer thereof is far greater than the tensile and anti-extrusion strength of the casing, and the casing 5 of the pre-pumping well is locally and strongly stretched, extruded and distorted along with the collapse of the old top, so that the whole casing 5 of the pre-pumping well is locally blocked, and the ground coalbed methane pre-pumping well is scrapped.
(2) Stage of fissure zone (fault zone) development. The deformation caused by the pre-pumping well casing 5 in the crack zone mainly comprises vertical pulling force and horizontal shearing force. In the development process of the crack zone, the sinking periods and the sinking amounts of all key layers are inconsistent, so that the pre-pumping well casing 5 is subjected to a certain vertical pulling force between the key layers. The shear force caused by the rock stratum dislocation is mainly born in the horizontal direction, so that the pre-pumping well casing 5 is locally extruded and deformed.
According to the theory of a key layer and a comprehensive histogram of a certain working face of a temple river mine, the load of each overlying rock layer is calculated layer by layer from bottom to top by using a calculation formula of the load of the overlying thick hard rock layer, and three hard rock layers, namely a key rock layer C8, a key rock layer C10 and a key rock layer C12, of the overlying rock layer of the working face are obtained, wherein the key rock layer C8 controls 1 soft rock layer, and the key rock layer C10 controls 1 soft rock layer.
The breaking distances of the key rock stratum C8, the key rock stratum C10 and the key rock stratum C12 are calculated by utilizing a rock stratum breaking step distance calculation formula, the breaking distance of the key rock stratum C10 is slightly smaller than that of the key rock stratum C8, the breaking distance of the key rock stratum C12 is larger than that of the key rock stratum C10 and the key rock stratum C8, therefore, the key rock stratum C12 is a main key layer, the key rock stratum C8 and the key rock stratum C10 are sub-key layers, a collapse zone is arranged below the key rock stratum C8, a fracture zone is arranged between the key rock stratum C8 and the key rock stratum C10, a bending subsidence zone is arranged between the key rock stratum C10 and the key rock stratum C12, and the distribution table of the key layers is shown in figure 2.
The stratum of the caving zone is determined to be C2-C7 through comprehensive field measurement, namely the height of the stratum between the 3# coal seam 4 and the key rock stratum C8 is about 21.97 m.
(2) Before the stoping is influenced, mature technologies such as energy-gathering cutting bullets, mechanical cutters or hydraulic cutters and the like are applied to the bottom of the key layer to perform segmented annular cutting on the coal bed gas pre-pumping well casing 5; forming a cutting loop.
(3) When stoping is influenced, the pre-pumping well casing 5 after cutting in the coal seam roof collapse zone and the fracture zone area collapses or displaces along with the rock stratum, the integrity of the pre-pumping well casing 5 at the upper part of the deformation section is not influenced, and finally an underground extraction channel of the collapse zone, the fracture zone and the pre-pumping well casing at the section which is not deformed and damaged is established, so that the purpose of extraction and treatment of coal bed gas in the middle mining and the post-mining of the working face and even in the old mined-out area is realized.
The method can pertinently select the easily-collapsed and deformed area of the overlying rock stratum of the coal seam, and perform segmented annular cutting on the casing of the coal seam gas well in the area, when the extraction is influenced, the collapsed zone of the coal seam roof and the pre-pumping well casing after the cutting in the fractured zone area collapse or displace along with the rock stratum, the integrity of the casing at the upper part of the deformed section is not influenced, and finally, the underground extraction channel of the collapsed zone, the fractured zone and the pre-pumping well casing which is not deformed and damaged is established.
Claims (2)
1. A method for preventing a coal bed gas pre-pumping well from being damaged along with recovery is characterized by comprising the following specific steps:
(1) determining a coal seam overlying rock collapse zone and a fracture zone area;
according to a key layer theory and a comprehensive histogram of a stope face, calculating the load of each overlying rock layer from top to bottom layer by using a calculation formula of the load of the overlying thick hard rock layer, further determining the position of a key layer, and establishing a caving zone, a fracture zone and a bending subsidence zone;
(2) cutting the sleeve;
before the stoping influence, carrying out segmented annular cutting on the coalbed methane pre-pumping well casing at the bottom of the key layer, specifically, carrying out annular cutting on the pre-pumping well casing above a cross-falling zone, a fracture zone and a bent sinking zone.
2. The method for preventing the coal bed gas pre-pumping well from being damaged along with the recovery according to claim 1, wherein the cutting method of the coal bed gas pre-pumping well casing is the technologies of energy-gathering cutting bullet cutting, mechanical cutter cutting or hydraulic cutter cutting.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911332888.8A CN111140205A (en) | 2019-12-20 | 2019-12-20 | Method for preventing coal bed gas pre-pumping well from being damaged along with recovery |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911332888.8A CN111140205A (en) | 2019-12-20 | 2019-12-20 | Method for preventing coal bed gas pre-pumping well from being damaged along with recovery |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104405283A (en) * | 2014-10-22 | 2015-03-11 | 山西蓝焰煤层气集团有限责任公司 | Technique for extracting gas from L-shaped ground drilling well in mining area |
| CN204511348U (en) * | 2015-04-08 | 2015-07-29 | 沈旭 | A kind of abandoned well novel multi-layer casing cutting device |
| CN108952669A (en) * | 2018-07-23 | 2018-12-07 | 中煤科工集团重庆研究院有限公司 | A kind of minery L-type surface well level course position preferred method |
-
2019
- 2019-12-20 CN CN201911332888.8A patent/CN111140205A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104405283A (en) * | 2014-10-22 | 2015-03-11 | 山西蓝焰煤层气集团有限责任公司 | Technique for extracting gas from L-shaped ground drilling well in mining area |
| CN204511348U (en) * | 2015-04-08 | 2015-07-29 | 沈旭 | A kind of abandoned well novel multi-layer casing cutting device |
| CN108952669A (en) * | 2018-07-23 | 2018-12-07 | 中煤科工集团重庆研究院有限公司 | A kind of minery L-type surface well level course position preferred method |
Non-Patent Citations (5)
| Title |
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| 崔秀奇: "地面瓦斯预抽井随回采破坏机理浅析及改造措施", 《煤》 * |
| 王志强等: "再论采场"三带"的划分方法及工程应用", 《煤炭学报》 * |
| 钱鸣高，缪协兴: "采场上覆岩层结构的形态与受力分析", 《岩石力学与工程学报》 * |
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