Method for draining coal seam gas

Abstract

The invention relates to a method for draining coal seam gas, belonging to a method for pre-draining coal seam gas in coal mines. According to the invention, the technical problem that the existing methods for draining coal seam gas are low in drainage efficiency is solved. The technical scheme of the method for draining coal seam gas comprises the steps of: firstly opening at least one butt hole drill site in a coal mine underground preparation roadway, constructing a 30-50m long butt drill hole from the butt hole drill site to a target coal seam, lowering a seamless steel sleeve to the butt drill hole and solidifying the hole by high-quality cement, then opening a ground drill site at the far end of a designed drainage area, horizontally and directionally drilling a horizontal directional main branch hole along the target coal seam toward the underground butt drill hole, butt-jointing the horizontal directional main branch hole with the underground but drill hole, enclosing the ground orifice, arranging an orifice control valve on the head of the seamless steel sleeve, connecting the control valve with a coal mine underground gas drainage pipe network, and carrying out gas drainage by using a coal mine gas drainage pump.

Description

technical field [0001] The invention relates to a method for extracting coal seam gas, which belongs to a method suitable for coal mines to pre-extract coal seam gas in developed areas or adjacent areas. Background technique [0002] Coal mine gas (also known as "coal bed methane", the main component is methane) is one of the main disasters that threaten the safety of coal mine production, and it is also a clean energy with abundant reserves. At present, mines threatened by gas disasters in my country (especially high gas mines) have generally adopted the pre-pumping method to prevent and control gas disasters, and utilize the extracted gas. [0003] At present, coal mine gas extraction methods can be generally divided into two categories: surface drilling extraction and underground extraction. Among them: surface drilling drainage can be divided into vertical well drainage and horizontal directional drilling drainage; underground drainage includes two forms: underground dr...

AI Technical Summary

Problems solved by technology

The disadvantages are: 1) The drainage and depressurization cycle is long, and the well holes must be far away from the coal mine production and operation area, so as to ensure that the gas well will not be damaged by the mining activities of the coal mine during the effective production period

3) The burial of the drainage operation site and the gas pipeline needs to occupy land, which increases the cost and has adverse effects on the ecological environment

The disadvantages are: 1) Due to various factors, the quality of downhole drilling and sealing is low, the air tightness is poor, and the produced gas gas is mixed with downhole air to varying degrees, resulting in low methane concentration. Generally, it can only be used as a gas-fired boiler. air source for heating or power generation

At present, there is still a large amount of produced gas in domestic coal mines, which cannot be used because the methane concentration is too low, so it can only be directly discharged into the atmosphere, causing environmental pollution

2) Due to the limitation of downhole operation space, the power of downhole drilling rig equipment is low, the labor intensity of workers is high, the efficiency of drilling operation is low, and the production investment is large

3) Due to the limitation of the equipment capacity of the drilling rig, the drilling holes for underground construction are generally small in diameter, short in distance, and low in gas production capacity per hole. Usually, it can only be compensated by increasing the hole density, which requires a lot of manpower, material and financial resources.

4) Due to the small height difference between the coal mine underground roadway and the coal seam, the liquid column pressure of the drilling fluid is not enough to form an effective support for the hole during drilling. Mining channel is not conducive to gas drainage

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