Method for extracting coalbed gas through water and coal dust drainage and a device thereof

摘要

A method for extracting coalbed gas. A wellhead device delivers power fluid into a downhole power fluid pipe in a well shaft, and conveys the fluid to a pump in a pump cylinder connected with the downhole power fluid pipe. The pump sucks in formation fluid via a suction inlet, mixes the fluid with the power fluid to produce a mixed fluid, and conveys the mixed fluid to ground surface. The mixed fluid containing coal dust travels at a flow rate greater than a sedimentation rate of the coal dust, passes though the wellhead device, and flows to the ground surface, thereby preventing a sedimentation of the coal dust. The suction inlet of the pump reaches a lower boundary of a coalbed so as to prevent coal dust from burying the coalbed, and the coalbed gas automatically shoots through an annular space of a well shaft casing.