Coal mine underground gas extraction long drilled hole and coiled-tubing-in-casing perforation staged fracturing method

Abstract

The invention relates to a coal mine underground gas extraction long drilled hole and coiled-tubing-in-casing perforation staged fracturing method. The method includes the steps that first, a gas extraction long drilled hole is constructed in a mudstone or sandstone roof with a certain distance to the top boundary of a broken soft coal seam or a hard layer of the broken soft coal seam or a hard coal seam with a good coal body structure; second, a guiding shoe and a rigid casing are lowered; third, cement paste blocking is carried out on annular space between the gas extraction long drilled hole and the rigid casing so as to solidify the hole; fourth, packing staging is carried out through a mode of dragging a packer by coiled tubing, an ejector carries out sand blasting perforation, and fracturing is carried out on the annulus between the coiled tubing and the casing; fifth, a fracturing tool is lifted out, and uniform blowout of fracturing fluid is carried out. The method can solve the problems that in existing gas extraction hole-drilling, hole forming is difficult, the crack initiation position of fracturing cracks is not determined, the fracturing cracks extend short, the fracturing modification effect is poor, the extraction affecting range is small and nonuniform, and extraction duration is short, and realizes gas extraction long drilled hole forming and multi-level precise staged fracturing.

Description

technical field [0001] The invention relates to the technical field of gas control, in particular to a continuous tube perforation segmental fracturing method in long borehole casings for gas drainage in coal mines. Background technique [0002] Among all kinds of coal mine disasters, gas disaster is the biggest disaster in my country's coal mine safety production. Therefore, coal seam gas must be pre-drained in advance before coal mining to ensure safe and efficient production of coal mines. [0003] At present, the pre-drainage of coal seam gas in underground coal mines mainly adopts the methods of drilling through the bed and drilling along the bed. In order to improve the air permeability of the coal reservoir, hydraulic fracturing measures have been adopted, which has achieved certain results, but the following problems still exist: [0004] (1) It is difficult to drill gas drainage holes in broken and soft coal seams, and the drilling depth is shallow; when drilling ga...

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Problems solved by technology

[0008] The purpose of the present invention is to provide a continuous pipe perforation segmental fracturing method in the long borehole casing for underground gas drainage in coal mines, which can overcome the problem of gas drainage drilling along the coal seam in broken and soft coal seams existing in the current underground gas pre-drainage in coal mines Difficulty in forming holes, short extension of open-hole full-hole fracturing fractures, uncertain location of fracturing fractures, small and uneven drainage influence range, poor drainage effect, short duration, etc., to achieve long drilling for gas drainage Hole formation and multi-stage precise staged fracturing

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