Patent ID: 7562701

Claim:
A wellhead hydraulic drive unit for operable connection to a downhole production pump via pump connecting means, the wellhead hydraulic drive unit comprising: (a) a hydraulic cylinder having an inner wall and a piston positioned within the inner wall for reciprocation within the hydraulic cylinder; (b) hydraulic fluid supply means contained within the hydraulic cylinder and fluidly communicative with the piston such that hydraulic fluid flowing through the hydraulic fluid supply means produces reciprocation of the piston within the hydraulic cylinder; (c) ram means having a bore therethrough, slideably received within the inner wall of the hydraulic cylinder and operably connected to the piston for reciprocation in response to reciprocative movement of the piston; and (d) 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; wherein a longitudinal axis of the hydraulic fluid supply means is radially offset from a longitudinal axis of the hydraulic cylinder, and a longitudinal axis of the ram means is oppositely radially offset from said longitudinal axis of the hydraulic cylinder.