Patent ID: 6854515

Claim:
An in-casing wellhead hydraulic drive unit for operable connection to a downhole production pump via pump connecting means, comprising: (a) a hydraulic cylinder configured for placement within and in landed engagement with an uppermost portion of a wellhead casing, having top and bottom ends, an inner wall and a piston positioned within said inner wall for reciprocation within the hydraulic cylinder; (b) hydraulic fluid supply means coupled to the hydraulic cylinder for raising of the piston within the hydraulic cylinder; (c) ram means having a top and bottom end and a bore therethrough, slideably received within the inner wall of the hydraulic cylinder and operably connected to the piston for reciprocation in response to the piston; and (d) stationary production tube means, inserted through the bore of the ram means and connected to the hydraulic cylinder for enabling well fluid to be discharged from the well.