Loose blasting gas extraction technology of horizontal branch well of coal seam floor

Abstract

The invention provides a loose blasting gas extraction method of a horizontal branch well of a coal seam floor. The method sequentially comprises the following steps of selecting a coal reservoir with a gas content of more than 8m3 / t and a solid coefficient f of less than 0.5; selecting 1-2 m coal seam floor as a layer of a main horizontal well and a branch horizontal well; determining positions of a ground well mouth and a deflection point according to the layer of the main horizontal well section; using a trisected structure as a well body structure and using open hole wells as the main horizontal well and the branch horizontal well; constructing the main horizontal well and the branch horizontal well in a selected floor rock layer; placing explosive points on the branch horizontal well section, wherein the explosive points are connected with each other by lines; and detonating all explosives through the ground; and mounting gas extraction equipment to extract the gas on the ground, wherein the gas can also be extracted at a negative pressure in a coal mining stage so that the well has multiple purposes. By using the method, the gas can be extracted on a soft coal ground to eliminate outburst and furthest reduce gas outburst disasters, and the gas (coal bed gas) resources can also be developed.

Description

technical field [0001] The invention relates to gas extraction, in particular to a technique for gas extraction by loose blasting of a horizontal branch well on a coal seam floor. Background technique [0002] For coal reservoirs with high gas content and soft coal body, according to the outburst parameters in the "Regulations on the Prevention and Control of Coal and Gas Outburst", outburst accidents are easily induced during the coal mining process. Poor mechanical properties of coal mass, low permeability and strong water sensitivity are the main characteristics of this type of coal seam. [0003] The key to underground gas drainage lies in the length of the borehole and the stability of the borehole. It is difficult to construct a borehole in a soft coal seam, and the stability of the borehole is poor, making gas extraction difficult. At the same time, the permeability of the reservoir is poor, the extraction radius is small, the engineering cost is high, and the extrac...

AI Technical Summary

Problems solved by technology

The main purpose is to promote stress release, pressure relief, crush coal, and increase coal seam air permeability (some are for top coal caving, which has nothing to do with gas control). These measures are beneficial to gas control, but there are disadvantages: the risk of inducing gas outburst, coal seam The hardness must be suitable for drilling. It is easy to form holes and cause gas to exceed the limit. There is also the risk of blind blasting and blasting. When blasting, people must be withdrawn and power cut off, which will delay underground production.

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