Abstract: A pump includes a drive chamber with a drive piston and a production chamber with a production piston. The drive piston is coupled to the production piston. The pump further includes a passage in fluidic communication with the drive piston and a port fluidically coupling the passage with the production chamber. In operation, a first pressure is applied to fluid in the passage, thereby moving the drive piston. Then a second higher pressure is applied to fluid in the passage, thereby opening a valve associated with the port. In an example operation, fluid flows from the passage into the production chamber, and flushes gas out of the production chamber, thereby alleviating gas-locking. In another example operation, fluid including a treatment chemical flows from the passage into the production chamber. A surface equipment package includes a controller configured to monitor and control operation of the pump.