Coal bed gas U-shaped well segmented step-by-step drainage method

Abstract

The invention relates to the technical field of coal bed gas drainage, in particular to a coal bed gas U-shaped well segmented step-by-step drainage method. Three drainage stages are divided accordingto the characteristic of the track of a large-tilt-angle coal bed U-shaped well; the stage that the initial liquid level of the coal bed gas well reaches a critical desorption pressure point serves as the first drainage stage; the stage that the critical desorption pressure point reaches the liquid level 20 m above a target coal bed top plate serves as the second drainage stage; the stage of following drainage serves as the third drainage stage. Different drainage stages of the large-tilt-angle coal bed U-shaped well are definitely divided, and it is guaranteed that the coal bed gas well canbe stably depressurized and desorbed; fracture points of the U-shaped well serve as key points of drainage control, drainage of the coal bed gas well can be more precisely controlled, all coal bed sections can be fully desorbed, and the situation that as the liquid level is reduced too fast, a coal bed is massively exposed, and desorption of the coal bed gas is not facilitated is avoided.

Description

technical field [0001] The invention relates to the technical field of coalbed methane drainage, in particular to a step-by-step step-by-step depressurization drainage method for U-shaped coalbed methane wells. Background technique [0002] Conventional vertical well development has a small impact range, low single well production, and poor economic benefits, while horizontal wells have the advantage of penetrating more cleat fracture systems, communicating with a large number of fracture channels, expanding the area of ​​drainage, depressurization and gas release, and allowing more As more gas enters the main channel, horizontal wells, as an efficient development technology for low-permeability coal reservoirs, have been increasingly used in the exploitation of coalbed methane. [0003] However, coal seams, as gas-generating beds and reservoirs of coalbed methane, have the characteristics of low porosity, low permeability, low mechanical strength, strong heterogeneity, and ...

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Problems solved by technology

[0005] The main purpose of the present invention is to provide a method for step-by-step step-by-step depressurization and extraction of U-shaped coalbed methane wells, so as to solve the problems of unstable output and poor gas production effect caused by unreasonable drainage systems in the horizontal well drainage process. question

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