Hydraulically actuated downhole pump with traveling valve

A hydraulic pump, comprising:

• an engine barrel;
• a pump barrel;
• an engine piston movably disposed in the engine barrel, wherein the engine piston divides an inner volume of the engine barrel into a first engine volume and a second engine volume, and the engine barrel has an engine inlet port connecting to the inner volume;
• a pump piston movably disposed in the pump barrel, wherein the pump piston divides an inner volume of the pump barrel into a first pump volume and a second pump volume, the first pump volume has an outlet port, and the second pump volume has an intake port;
• a middle rod connecting the engine piston and the pump piston, wherein the middle rod has a rod passage selectively connecting the first engine volume and the first pump volume;
• a first check valve disposed in the pump piston to control flow from the first pump volume to the second pump volume;
• and
• a second check valve disposed to control flow from the first pump volume through the outlet port of the pump barrel.

A method for pumping production fluid from a wellbore, comprising:

• stroking a pump piston disposed in a pump barrel repeatedly between an upstroke and a down stroke, wherein the pump piston divides the pump barrel into a first pump volume and a second pump volume, and includes a pump flow path between the first pump volume and the second pump volume;
• during each upstroke,
• drawing production fluid into the second pump volume through an intake port of the pump barrel;
• and
• discharging fluid in the first pump volume through a discharge port of the pump barrel;
• and
• during each down stroke,
• flowing the production fluid in the second pump volume to the first pump volume via the pump flow path while the discharge port remains closed.