US 4,571,939 AGranted

Hydraulic well pump

AssigneeOtis Engineering Corporation

InventorWilliam W. Dollison

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Abstract

A hydraulic well pump for operating a pump sucker rod string including a hydraulic cylinder assembly for raising and lowering the sucker rod string and a fluid counterbalancing system for offsetting the combined weight of the reciprocating service equipment, the fluid column above the pump plunger, and the sucker rod string. One counterbalancing embodiment includes an air supported piston on the movable cylinder exposed to an air chamber below the air piston functioning independently of the hydraulic and power and logic system of the pump. Another counterbalancing system embodiment uses a hydraulic fluid accumulator connected into the system fluid power and logic for supercharging the hydraulic power pumps during the lift stroke and providing opposing force during the downstroke. Also disclosed are: a stroke length multiplier apparatus including a multi-layered strip metal tension member; a pump stroke sensor and control for adjusting stroke end limits and lengths; and a fluid logic system for controlling stroke acceleration and deceleration.

Claims16

Dependent claims

A system for operating a sucker rod string connected with a well pump comprising:

a double-acting fluid cylinder having opposing power ends;
means for connecting said cylinder with said sucker rod string for raising and lowering said string to operate said pump;
means for supplying pressurized fluid alternately to the cylinder ends including a direction control movable between extend and retract conditions to extend and retract said cylinder;
drive means for shifting said direction control;
control means for operating said drive means responsive to the extend and retract movements of said cylinder;
including limit valves positioned to simulate the hydraulic cylinder extend and retract stroke end locations, said limit valves being movably mounted for changing the location of each limit valve and the distance between said limit valves for selectively adjusting the length of the strokes of said hydraulic cylinder and the end limit of the extend and retract strokes of said cylinder, cam operator means for opening and closing each of said limit valves at said end locations and means connecting said cam operator means with said hydraulic cylinder whereby said cam operator means simulates the extend and retract strokes of said hydraulic cylinder, said means connecting including a flexible cable secured at a first end with said hydraulic cylinder and connected with said cam operator means to move said cam operator means;
movable sheave means connected with said cam operator means and fixed sheave means spaced from said movable sheave means, means biasing said movable sheave means away from fixed sheave means, and said cable is reeved over said movable and fixed sheave means and secured along the second end thereof at a fixed location;
and means for applying a fluid counterbalancing force into said cylinder for offsetting the combined weights of said sucker rod string, a production fluid column in a well bore above said pump, and movable surface equipment supported on said cylinder.

5 more elements

A well pumping jack for operating a sucker rod string connected with a well pump comprising:

a double-acting hydraulic cylinder assembly including a base, a stationary piston rod secured along the lower end through said base extending upwardly therefrom, an annular stationary piston secured along an upper end portion of said piston rod, a cylinder movable positioned around said annular piston, a cylinder cap secured on the upper end of said cylinder defining with said cylinder and said annular piston a hydraulic fluid extend chamber within said cylinder above said annular piston, an annular closure between the lower end of said cylinder and said piston rod below said annular piston defining with said annular piston, said cylinder, and said piston rod an annular hydraulic fluid retract chamber below said annular piston, said piston rod having ports along an upper portion thereof below said annular piston for admitting hydraulic fluid to said retract chamber, a flow conductor disposed in spaced concentric relation within said piston rod connecting through said annular piston at an upper end thereof into said extend chamber and connecting through said base for admitting hydraulic fluid into said cylinder assembly to said extend chamber, the outer surface of said flow conductor and the inner surface of said piston rod defining an annular hydraulic fluid flow passage within said piston rod around said flow conductor for hydraulic fluid flow to said annular retract chamber, and flow passage means including a flow coupling in said base communicating with said annular hydraulic fluid flow passage;
an idler sheave platform mounted on the upper end of said cylinder of said hydraulic cylinder assembly;
idler sheave means mounted on said sheave platform;
flexible tension member means secured at a first fixed end with said hydraulic cylinder assembly platform, extending over said sheave means and downwardly therefrom to a movable second end;
means on said second end of said tension member for securing said tension member with a well pump sucker rod string;
hydraulic fluid power and logic circuity connected with said hydraulic cylinder assembly for extending and retracting said movable cylinder to raise and lower said second movable end of said tension member including movably positioned limit valves for sensing the end position of each said extend and retract stroke, said valves being adapted to be selectively positioned for varying said end of each of said strokes and varying the length of said strokes, cam means secured in movable relation with said limit valves for engaging and operating said limit valves, a flexible member having a first end connected with said hydraulic cylinder and a second portion spaced from said first end coupled with said cam means for moving said cam means to simulate the movement of said hydraulic cylinder;
a hydraulic fluid reversing valve for directing flow to the opposite ends of said hydraulic cylinder assembly;
means for operating said reversing valve including a rotary hydraulic drive motor actuated responsive to said limit valves and a scotch-yoke coupled between said drive motor and said reversing valve for operating said reversing valve;
and a hydraulic counterbalance system including an annular counterbalance piston and cylinder mounted around said hydraulic cylinder for offsetting the combined weights of said sucker rod string, a column of well fluid in a well bore above a well pump operated by said pumping jack, and the movable components of said pumping jack supported by said movable hydraulic cylinder.

6 more elements

Dependencies are inferred from the claim text.