Patent Application
20200217202
The present disclosure relates to the technical field of gas extraction of a mining-induced area in a coal mine, and in particular to a ground wellhole dedicated pipe for gas extraction of a mining-induced area.
Gas extraction performed for “a place that is already mined or a place where a coal seam is loosened due to another reason” is generally referred to as gas extraction of a mining-induced area. Specifically, vertical drilling is performed to above the coal seam through ground operations to extract gas of a pressure relief zone in front of a mining working face and gas of a subsequent gob, and drilling is directly performed in an old gob through operations to extract old gob gas. The gas is relatively easy to extract because the gas extraction of the mining-induced area is pressure relief extraction. However, in the mining-induced area, extraction drilling channels passing through a rock stratum and a coal seam of the mining-induced area are easily damaged by acting forces such as displacement, squeezing, stretching and shearing forces of the rock stratum. Since these acting forces are extremely huge, the drilling channels and their protective pipes are often easily damaged and deformed or well channels are closed at a position where the acting force between the rock stratums or between the rock stratum and the coal seam, or the like is concentrated, and therefore the gas cannot be extracted continuously and smoothly, thereby causing severe economic losses and safety risks. This is because the protective pipe is of a hollow structure which cannot withstand various huge acting forces generated by a relative movement of the rock stratum. Thus, the protective pipe may also be broken in spite of being thickened.
To protect the drilling channels (extraction channels), engineering personnel mount deflecting and telescoping protective structure apparatuses and flexible and thick-wall rigid protective structures, and the like for engineering protection at high-risk positions of the drilling channels. These apparatuses protect the drilling channels to some extent, but there are still some shortcomings. For example, a protective apparatus deflecting at a given position does not act as desired because the acting force of the rock stratum usually does not act directly on the position or a severe displacement occurs. In addition, the acting manners of the rock stratum include displacement, squeezing and stretching and so on and thus the acting forces are complex. The drilling channel may be disabled as long as one of such actions exists. The apparatus for simply preventing only one of the deflection, stretching and squeezing actions cannot achieve a purpose of effective protection. Meanwhile, these apparatuses generally are of the hollow structure, which cannot withstand the huge acting force of the rock stratum.
To solve the technical problem that the ground wellhole for gas extraction of the mining-induced area is easily damaged by the acting force of the rock stratum at present, the present disclosure provides a ground wellhole dedicated protective pipe for gas extraction of a mining-induced area.
The present disclosure provides a ground wellhole dedicated pipe for gas extraction of a mining-induced area. The ground wellhole dedicated protective pipe for gas extraction of the mining-induced area is disposed inside a ground wellhole for gas extraction of the mining-induced area. The ground wellhole dedicated protective pipe for gas extraction of the mining-induced area includes a casing and a chain that is disposed inside the casing and slidable relative to the casing, where the chain includes a plurality of chain drums and connecting pieces movably connecting adjacent chain drums, and a plurality of air holes are opened in the chain drum along an axial direction of the chain drum.
Further, an upper end and a lower end of the chain drum are both provided with a lug hole, the connecting piece is a connection ring, and the connection ring connects the lug holes of the adjacent chain drums respectively.
Further, the connection ring includes a closed connection ring and an open-closed connection ring, a plurality of chain drums are connected into one chain through the closed connection rings, and the adjacent chains are connected through the open-closed connection rings.
Further, one end of open-closed ends of the open-closed connection ring is provided with a thread insert, and the other end is provided with a screw thread-connected with the thread insert.
Further, an upper end of the casing is provided with a connection buckle, and the connection buckle is connected with the chain through a cable.
Further, a lower end of the casing is provided with a porous mesh plate, and the porous mesh plate supports the chain.
Further, a center axis of the air hole is parallel to a center axis of the chain drum.
Further, the casing is made of stainless steel.
Further, the chain drum is made of stainless steel.
Further, the connecting piece is made of stainless steel.
Compared with the prior art, the ground wellhole dedicated pipe for gas extraction of a mining-induced area of the present disclosure has the following features and advantages.
The ground wellhole dedicated pipe for gas extraction of a mining-induced area of the present disclosure can resist a change and a failure of the casing caused by a shearing force, a squeezing force and a stretching force generated by a displacement of a rock stratum simultaneously, and ensure the gas passes under one or more forces regardless of that displacement or force occurs in a protection region in the ground wellhole for gas extraction of the mining-induced area. Therefore, the protective pipe has versatility, economy and applicability compared with traditional protection methods and apparatuses.
The features and advantages of the present disclosure will become clearer after specific examples of the present disclosure are read in combination with accompanying drawings.
To describe the technical solutions in the examples of the present disclosure or in the prior art more clearly, the accompanying drawings required in descriptions of the examples of the present disclosure or the prior art will be briefly introduced below. It is apparent that the accompanying drawings described below are some examples of the present disclosure and other drawings may be obtained by those of ordinary skill in the art based on these drawings without paying creative work.
Numerals of the drawings are described as follows: 1—a casing, 2—a chain drum, 21—an lug hole, 22—an air hole, 3—a porous mesh plate, 41—a closed connection ring, 42—an open-closed connection ring, and 421—a thread insert.
As shown in
In the example, the chain drum 2 is a cylinder made of stainless steel, an upper end and a lower end of the chain drum 2 are both provided with an lug hole 21. The connecting piece in the present example preferably is a connection ring, and the connection ring is connected to the lug holes of the adjacent chain drums 2 respectively. The connection ring includes a closed connection ring 41 and an open-closed connection ring 42, which are both made of stainless steel. One end of open-closed ends of the open-closed connection ring 42 is provided with a thread insert 421, and the other end of open-closed ends of the open-closed connection ring 42 is provided with a screw thread-connected with the thread insert 421. In a production process, a plurality of chain drums 2 are connected into one chain through the closed connection rings 41. For example, in
Before the drilling operation of the mining-induced area is completed without obvious deformation, regions of different rock strata liable to deformation, displacement and squeeze are pre-determined according to geological data and a detection situation obtained during drilling, and a chain is disposed at the position of the region where the casing 1 is located. If an operation manner of drilling and disposing the casing 1 from top to bottom is adopted, a connection buckle, for example, a hook, is disposed at an upper end of the casing 1, the connection buckle is connected to the chain with a particular length through a cable, and the chain is hung inside the casing 1, where the length of the chain goes beyond the above region. If an operation manner of drilling and disposing the casing 1 from bottom to top is adopted, a porous mesh plate 3 is disposed at a lower end of the casing 1, the porous mesh plate 3 supports the chain, where the length of the chain goes beyond the above region. Of course, no matter which of the above operation manners is adopted, the chain may also be disposed over the whole length of the casing 1.
As shown in
The ground wellhole dedicated protective pipe for gas extraction of a mining-induced area in the present example can resist the change and the failure of the casing 1 caused by the shearing force, the squeezing force and the stretching force generated by the displacement of the rock stratum simultaneously, and ensure the gas passes under one or more forces no matter what displacement or force occurs in a protection region in the ground wellhole for gas extraction of the mining-induced area. Therefore, the protective pipe has versatility, economy and applicability compared with traditional protection methods and apparatuses. Specific effects are described below.
1. Since the chain disposed inside the casing 1 has a particular length, a protective scope of the casing is substantially same or slightly smaller than the chain length. Thus, protection of linear length may be performed without accurately determining a position of displacement of the rock stratum. However, since the position of one point is protected by the traditional method and protective apparatus, it is required to accurately determine the easily-displaced position of the rock stratum. However, it is very difficult to accurately determine the easily-displaced position of the rock stratum. When the protective apparatus is disposed inside the casing 1, it is also very difficult to align the position of the protective apparatus with the easily-displaced position of the rock stratum.
2. As long as the chain is not broken or crushed, no matter what stress acts on the casing 1, it can be effectively ensured that an inner diameter of the casing 1 is not changed greatly, that is, a gas passing capability is not changed obviously. However, the traditional method and protective apparatus can only resist or eliminate the change of one acting force, for example, the deflecting protective apparatus can only have an effect on the shearing action, without obvious protective effect on the squeezing and stretching forces. For example, if the casing 1 is made flexible, the pipe has the protective effect on stretch without protective effect on squeezing e and shearing actions.
From the perspective of a single action effect, the ground wellhole dedicated pipe for gas extraction of a mining-induced area in the present example has superiority. From the perspective of an anti-squeezing force, to prevent the casing 1 from being broken due to squeeze or prevent the casing 1 from being closed and air-blocked due to squeeze, a solution is generally adopted to thicken a pipe wall of the casing 1 to increase a pressure bearing capability. However, the thickness of the pipe wall is limited, and therefore a pressure bearing capability thereof is also limited. From the perspective of anti-stretching and anti-shearing forces, since it is not required to give a special consideration to the anti-squeezing capability of the casing 1 during an application of the ground wellhole dedicated pipe for gas extraction of a mining-induced area in the present example, a material with good plasticity may be selected for the casing 1. However, in other methods and protective apparatuses, contradiction exists when the material of the casing 1 is selected, that is, when a soft material or a plastic material is selected, the material does not have anti-squeeze capability, and when an anti-squeezing hard material is selected, the material does not have anti-stretching and anti-shearing capabilities.
4. When the ground wellhole dedicated pipe for gas extraction of a mining-induced area in the present example is adopted, the inner diameter of the casing 1 remains basically unchanged at any time. Therefore, the gas passing capability inside the casing 1 also remains stable, which has a positive significance on stability and economy of an extraction system. Further a surplus design coefficient is reduced during system design.
Of course, the above descriptions are not intended to limit the present disclosure, and the present disclosure is also not limited to the above examples. Changes, modifications, additions or substitutions made by persons skilled in the art shall also be encompassed in the scope of protection of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201710777105.1 | Sep 2017 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2018/095653 | 7/13/2018 | WO | 00 |
