Injection-production process for prolonging service life of coalbed methane production well group by injecting carbon dioxide

Abstract

The invention discloses an injection-production process for prolonging the service life of a coalbed methane production well group by injecting carbon dioxide, and belongs to the technical field of coalbed methane development. The method comprises the following steps: selecting a coalbed methane production well group which has produced continuously, taking a central well as a CO2 injection well and a peripheral well as a gas recovery well, and utilizing the displacement and replacement effects of CO2 on CH4 to improve the daily gas production rate of the gas recovery well and prolong the service life of the coalbed methane production well group; in the step-type injection increasing and pressure increasing stage, the bottom hole pressure of the CO2 injection well is rapidly increased in a step-type daily injection rate increasing mode; in the pressure-limiting injection displacement stage, the bottom hole pressure of the CO2 injection well is maintained to be lower than the minimum principal stress of the coal reservoir; in the gas-driven water energy generation inhibition stage, inhibition of gas-driven water on gas production of a gas recovery well is eliminated by increasing the stroke frequency of a pumping unit; cO2 is injected for displacement in the yield increasing stage of the gas recovery well, and CH4 is replaced, so that the yield increasing effect of the gas recovery well gradually appears; in the intermittent drainage and mining stage, the concentration of CO2 in produced gas is inhibited from exceeding the limit by irregularly shutting in the well; in the well site reclamation stage of the gas recovery well, the liquid CO2 is continuously injected by closing the gas recovery well, and continuous storage of CO2 in the well group range is achieved.

Description

technical field [0001] The invention relates to the technical field of enhanced development of coalbed methane and carbon emission reduction, in particular to an injection-production process for injecting carbon dioxide to prolong the service life of a coalbed methane production well group. 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 greenhouse gas emissions in coal mine production, and produce significant economic, environmental, safety and social benefits. [0003] The Carboniferous Permian Coal-bearing Basin in North my country, represented by the southern Qinshui Basin in Shanxi Province,...

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Problems solved by technology

[0004] Technical problem: the purpose of the present invention is to overcome the problems existing in the prior art, to provide an injection-production process for prolonging the service life of coalbed methane production well groups by injecting carbon dioxide, and to solve the problem of traditional coalbed methane production wells and production well groups relying solely on drainage to reduce water consumption. Under pressure mining, the high production time is short and the gas production rate decays rapidly, resulting in the short service life of coalbed methane production wells and production well groups

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