Multi-branch horizontal well gas drainage technology in goaf of coal mine

Abstract

The invention discloses a multi-branch horizontal well gas drainage technology in a goaf of coal mine, which comprises the following steps: (1) calculating the height of caving zones and fracture zones on the upper part of the goaf, determining a gas-rich area in the goaf, and determining a location layout plan for drill wells; (2) selecting well structures; (3) selecting a reasonable drilling tool assembly; (4) calculating a wellbore trajectory according to the location layout plan for drill wells in the step (1); (5) selecting appropriate drilling parameters according to the selected drilling tool assembly and formation lithology to be drilled; (6) optimizing structural parameters of main branches of wells referring to the location layout plan for drill wells in the step (1) as well as the length and width of working faces of the goaf; (7) completing the drilling according to the well design; (8) connecting and assembling ground drainage equipment; and (9) determining reasonable negative pressure extraction and gas drainage procedures according to gas concentration and permeability of a drainage interval, and completing the gas drainage in a target area. According to the invention, drainage design parameters of multi-branch horizontal wells are optimized, so that the total amount of gas drainage can be increased.

Description

technical field [0001] The invention relates to the technical field of gas drainage in goafs of coal mines, in particular to a gas extraction process in goafs of coal mines by multi-branch horizontal wells. Background technique [0002] Coal is the main one-time consumption of energy in my country. With the mining of coal, cracks appear in the overlying strata of the coal seam, and the air permeability of the overlying strata increases. It is enriched and preserved in a certain rock formation. If these enriched gases can be extracted and utilized, not only can the waste of resources be reduced, but also the potential safety hazards caused by gas can be reduced. [0003] At present, the methods of gas drainage in the goaf mainly include underground pipe drainage, surface drilling and so on. Underground pipe drainage is carried out by drilling holes in the working face being mined. Since the underground pays more attention to the gas control of the current coal mining face, t...

AI Technical Summary

Problems solved by technology

When multi-branch horizontal wells are used for drainage, the drilling cost of multi-branch horizontal wells is relatively high, and the one-time investment is relatively high. Differences in lithology, mechanical properties, and ranges of fractured zones lead to differences in the orientation and length of multi-branch horizontal wells, coupled with differences in drainage parameters, if the drilling parameters and drainage parameters under different conditions cannot be optimized, It may lead to a large difference in the amount of extraction, which not only affects the extraction effect, but also affects the economic benefits

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