In a method for de-watering a gas well, the water is pumped by an inverted API pump acting as a reciprocating pump from a position in the well casing below the gas formation and the gas escapes through the well casing around the transport tubes. The reciprocating pump is driven by a downhole engine in the form of a cylinder and piston which is moved by a hydraulic pump at the surface acting to generate a flow in a hydraulic fluid to drive the piston from a start position to an end position and causing fluid to be transferred from the cylinder on the other side of the piston to a counterbalance chamber against a back pressure provided by a charge of nitrogen gas. At the end of a pumping stroke of the reciprocating pump, pressure in the hydraulic fluid from the hydraulic pump through is released to cause the back pressure of the counterbalance chamber to drive the piston back to the start position.