A system for recovery of gas trapped by fluid and particulate matter in a well includes a device with a lower valve for controlling flow of fluid into the cavity and an upper valve for controlling flow of the fluid and suspended solids out of the cavity. The device also includes: a gas line for providing a stream of pressurized gas to push on fluid in the cavity in a compression stroke which closes the lower valve and opens the upper valve and to exhaust contained gas from the cavity during an exhaust stroke when infiltration of fluid into the cavity raises the fluid level; an effluent line for allowing exit of the fluid and suspended solids during the compression stroke; and a probe line providing powering pair of probes for initiating and halting entry of the stream of pressurized gas into the cavity.