Displacement coalbed methane yield increase method under combined mining of coalbed methane by vertical wells and U-shaped butted well

Abstract

The invention provides a displacement coalbed methane yield increase method under combined mining of coalbed methane by vertical wells and a U-shaped butted well. The method comprises steps as follows: (a), the U-shaped butted well is constructed along the secondary syncline axis trace and a horizontal well section is subjected to well cementation; (b), 6-8 vertical wells are constructed on syncline two wings, and cased hole completion is performed; (c), clustering perforation and staged fracturing are carried out from the far end of the horizontal well section of the U-shaped butted well; (d), the vertical wells and the adjacent horizontal well section are subjected to synchronous fracturing; (e), the vertical wells and the U-shaped butted well are subjected to drainage gas recovery; (f),when the daily gas production rate of the U-shaped butted well is reduced to 1 / 6 of the stable gas production rate and the water yield is lower than 0.5 m<3> / d, liquid carbon dioxide is continuouslyinjected from the U-shaped butted well under stable pressure; (g), the vertical wells carry out continuous drainage gas recovery, and gas and water yield and composition are monitored for a long time.On the basis of the conditions of combined mining of coalbed methane by the vertical wells and the U-shaped butted well, efficient mining of coalbed methane is realized by the displacement effect ofcarbon dioxide for methane, and the recovery ratio of coalbed methane resource can be remarkably increased.

Description

technical field [0001] The invention relates to a production increase method for displacing coalbed methane, especially a method suitable for injecting liquid carbon dioxide to replace and displace methane under the condition of joint exploitation of coalbed methane by a vertical well and a U-shaped docking well, so as to improve the gas production of vertical coalbed methane wells and the resource of coalbed methane The invention relates to a recovery factor method, which belongs to the technical field of surface mining of coal bed methane. Background technique [0002] my country is rich in coalbed methane resources, and the geological resources of shallow coalbed methane with a buried depth of 2000m are predicted to reach 36.8×10 12 m 3 , equivalent to conventional natural gas resources. Large-scale development of coalbed methane can alleviate the shortage of conventional oil and gas energy in my country, reduce the probability of coal mine gas accidents, reduce greenho...

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Problems solved by technology

[0004] Technical problem: The purpose of the present invention is to overcome the difficulty of methane desorption and large seepage resistance in low-permeability coal reservoirs under the traditional drainage and pressure-reduction mining method, as well as the short high-production time of coalbed methane production wells, difficulty in stable production, and low resource recovery. Problem, to provide a coalbed methane displacement method for joint exploitation of vertical wells and U-shaped butt-joint wells

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