Method for extracting gas from coal seam roof complex branched well

Abstract

The invention relates to a method for extracting gas from a coal seam roof complex branched well, which comprises the following steps of: selecting a coal storage layer with the gas content larger than 8m<3> / t; determining the machine tunnel and the tail tunnel positions excavated by a working surface to be prepared, as the position of a horizontal well section of a complex branched well; confirming the layer position in which a fissure zone generated due to coal mining is located; respectively distributing the horizontal well section above a machine tunnel and a tail tunnel; confirming the positions of a well opening and a deflection point and realizing the angle gain of a large-curvature radius; by adopting a three-opening structure on a well body structure and adopting naked-eye structures for both the horizontal well and the branched wells, constructing a horizontal well section in a selected rock stratum; constructing the branched wells at both sides of the horizontal well section; constructing a downward branched well on the horizontal well section and drilling through the coal storage layer; installing extracting equipment for extracting gas; carrying out negative pressure extraction in the medium and later extracting phases for realizing one well with multiple purposes; and inspecting effects. The method is favorable for reducing the gas content, creating condition for safely and efficiently carrying out coal tunnel excavation and coal mining and really realizing one well with multiple purposes at the coal mining phase.

Description

technical field [0001] The invention relates to a method for extracting gas from a complex branch well on the roof of a coal seam. Background technique [0002] Gas pre-extraction is the main measure to solve coal roadway excavation and coal recovery. After many years of practice, there are two main forms of gas pre-extraction during the excavation process. One is to implement hanging ear drilling during the excavation process, using advanced drilling to conduct excavation while excavation. The main disadvantage is that the extraction time is difficult to guarantee. The extraction rate is low, and the contradiction between extraction and excavation is serious in the production process, which affects the excavation speed of the coal roadway, and safety accidents are often caused by ignoring the safety of the excavation speed. The other is to excavate a rock roadway above the coal seam, which is specially used for gas extraction, which is called "gas drainage roadway". Drill...

AI Technical Summary

Problems solved by technology

After many years of practice, there are two main forms of gas pre-extraction during the excavation process. One is to implement hanging ear drilling during the excavation process, using advanced drilling to conduct excavation while excavation. The main disadvantage is that the extraction time is difficult to guarantee. The extraction rate is low, and the contradiction between extraction and excavation is serious in the production process, which affects the excavation speed of the coal roadway, often ignoring safety and speeding up the excavation, resulting in safety accidents

The other is to excavate a rock roadway above the coal seam, which is specially used for gas extraction, which is called "gas drainage roadway". Drilling is the only way to extract coal seam gas. Moreover, the control range of gas extraction in rock roadways is limited. Most of the coal seam gas in the working face has not been extracted. Drilling and drainage can only be performed after the coal roadway is excavated, so the drainage time is difficult to guarantee

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