Method of fracturing coal-bed gas reservoir

Abstract

The invention discloses a method of fracturing a coal-bed gas reservoir and belongs to the field of coal-bed gas exploitation. The method comprises following steps: after perforation in a middle-upper part of the coal bed and a coal bed top board above the coal bed, active water fracturing fluid is pumped and injected in the coal bed top board to form a first crack; low sand ratio sand-carrying fluid and high sand ratio sand-carrying fluid are successively pumped and injected into the first crack, and a second crack communicated with the first crack is formed in the coal bed, and the extension of the second crack is promoted to form multiple branchlike cracks containing sand support agent. The low sand ratio sand-carrying fluid comprises following components by percentage of mass: 0.1-0.3% carboxymethyl hydroxypropyl guanidine gum, 1-2% KCl, 0.5-1% discharge aiding agent, 8-12% sand support agent, and water as balance; the high sand ratio sand-carrying fluid comprises following components by percentage of mass: 0.1-0.3% carboxymethyl hydroxypropyl guanidine gum, 1-2% KCl, 0.5-1% discharge aiding agent, 12-48% sand support agent, and water as balance. The method provided by the invention can form a long distance supporting seam network in the coal-bed gas reservoir, and effectively improve the yield of the coal-bed gas reservoir.

Description

technical field [0001] The invention relates to the field of coal bed gas exploitation, in particular to a method for fracturing coal bed gas reservoirs. Background technique [0002] my country's coalbed methane development is mainly concentrated in the Qinshui Basin, the Ordos Basin and the Erlian Basin. The coalbed methane reservoirs in these areas (referred to as coalbeds) include shallow coalbed methane reservoirs with a depth of less than 600 meters and middle-deep coalbeds with a depth of more than 600 meters. Coal bed gas reservoir. Among them, the content of medium and deep coalbed methane reservoirs is more than 60%, which generally has the characteristics of "dry coal" such as low porosity, low permeability, and low moisture content. The above-mentioned characteristics of the middle and deep coalbed methane reservoirs lead to low natural productivity, and it is usually necessary to fracturing them to transform the physical structure of the coalbed methane reservoi...

AI Technical Summary

Problems solved by technology

[0005] The methods provided by the prior art can not form a long-distance supporting fracture network in the coalbed methane reservoir with the characteristics of "dry coal", and the second is that the friction force between the viscoelastic fracturing fluid and this type of coalbed methane reservoir is large , difficult to reflow

Both of the above factors lead to low coalbed methane production