Device and method for water drainage and gas production by pressure control and gas lift

A method for water drainage and gas production by pressure control and gas lift, comprising:

• utilizing a device for water drainage and gas production by pressure control and gas lift for collecting formation gas,
• wherein, the device comprises
• an inner pipe, an intermediate pipe and an outer pipe buried in a coalbed methane well and configured to be nested with each other,
• a first space inside the inner pipe is in fluid communication with an air compressor and a gas-liquid separation device;
• a second space is provided between the inner pipe and the intermediate pipe, wherein the second space is in fluid communication with the air compressor and the gas-liquid separation device;
• and
• a third space is provided between the intermediate pipe and the outer pipe, wherein the third space is in fluid communication with a collecting channel for the coalbed methane;
• wherein, the first space and the second space fluidly communicate in a unidirectional manner, and the second space and the third space fluidly communicate in a bidirectional manner;
• gas lift valves and a pressure-control valve are arranged on the inner pipe, wherein the pressure-control valve is opened or closed based on the pressure in the second space;
• the pressure-control valve is connected with the air compressor, and controls the operation of the air compressor.