Wellhead assembly for hydraulic pumping system

A wellhead assembly to seal and suspend an in-casing hydraulic drive unit for a downhole pump, the hydraulic drive unit being of a type having a hydraulic cylinder, a driven element within the hydraulic cylinder, and one or more hydraulic fluid supply lines providing hydraulic fluid to drive the driven element, the wellhead assembly comprising:

• a) one or more pressure-containing wellhead body members forming a vertical bore extending therethrough and forming a production bore at an uppermost portion of the vertical bore;
• b) a hydraulic pump hanger retained and sealed within the vertical bore of the one or more wellhead body members, the hydraulic pump hanger comprising:
• i) a lower end configured to suspend and seal the hydraulic cylinder of the hydraulic drive unit;
• ii) a bore extending vertically therethrough and communicating with the production bore;
• iii) at least one hydraulic line to communicate with the one or more hydraulic fluid supply lines of the hydraulic drive unit;
• iv) a hydraulic inlet port communicating with each hydraulic line;
• and
• v) a check valve sealed in each hydraulic inlet port;
• c) a stem port formed in the one or more wellhead body members and aligned to communicate with each hydraulic inlet port;
• d) a valve actuating stem sealed in each stem port to actuate each check valve between a normally closed position and an open position to open and close each check valve;
• and
• e) at least one hydraulic injection port formed through the wall of the one or more wellhead body members to supply hydraulic fluid to one or more of the hydraulic inlet ports.