Autocontrol casing gas recovery unit for pumping wells

In order to effectively gather the casing gas from pumping wells with low casing pressure, an autocontol casing gas recovery unit has been developed. The drainage cylinder of this unit is connected to the production valve and the air cylinder is connected with casing valve through the inlet tube. The two-cylinder piston is connected through the connecting rod so that the air cylinder draws in casing gas forcibly by changes of wellhead pressure during up-down stroking in pumping wells. At up stroke, the pressure in drainage cylinder increases, the cylinder piston moves to the right, so the capacity becomes larger, pressure decreases and the casing gas is drawn in. At down stroke, the wellhead pressure decreases and air cylinder piston moves to the left under the pressure gathering pipeline, so the casing gas in air cylinder flows into the drainage pipe. This cycle repeats and the no additional power is needed in the entire working process, so the casing gas in oil wells where casing pressure is reduced to 0.1 MPa can be recovered effectively. This unit has been used in 22 wells and daily gas recovery rate is 1 352 m3 in average, which has effectively increased the utilization rate of natural gas resource.