Claims
- 1. Well pumping apparatus comprising:
- a sucker rod pumping string;
- a frame;
- a first carriage slideably mounted to reciprocate in a vertical plane on the front of said frame;
- a second carriage slideably mounted on the back of said frame to reciprocate in cooperation with said first carriage;
- rotatable means attached to said frame;
- flexible means strung over said rotatable means and connecting said first and second carriages;
- a counterweight mounted on the second carriage;
- a piston-cylinder combination mounted on the frame for raising said first carriage;
- a reservoir for hydraulic fluid;
- a fluid pump mounted on the frame in fluid communication with the cylinder for pumping hydraulic fluid from said reservoir to said cylinder to raise the piston and carriage during the ascending phase of a pumping cycle;
- a fluid discharge line serving to discharge the fluid from the cylinder during the descending phase of said pumping cycle and connected in fluid communication with said cylinder and said reservoir;
- first and second restriction valves connected in series in said discharge line with said first valve allowing greater flow than said second valve;
- a fluid tight accumulation tank connected in fluid communication with said discharge line intermediate said two valves;
- a by-pass line extending around said first valve;
- a check valve mounted in said by-pass line to allow a back pressure buildup in the discharge line intermediate said first and second valves to be applied to said discharge line between said cylinder and said first valve whereby the volume of hydraulic discharge from the cylinder is decreased near the bottom of said descending phase of said cycle to thereby absorb the shock of said pumping string as it nears the bottom and begins said ascending phase of said pumping cycle.
- 2. Apparatus according to claim 1 wherein said flexible means comprises at least one chain and said rotatable means comprises at least one sprocket.
- 3. Apparatus according to claim 1 wherein an elongate rod engages said plunger, said rod being mounted with a part thereof to be lifted near the top of said ascending phase of said pumping cycle which moves said plunger.
- 4. Apparatus according to claim 1 wherein said back pressure build up reduces said minimum value of said rate of descent of said sucker rod pumping string substantially to zero.
- 5. Apparatus according to claim 4 wherein said back pressure build up reduces said minimum value of said rate of descent of said sucker rod pumping string to zero.
- 6. Apparatus according to claim 1 wherein said back pressure build up reduces the rate of descent of said sucker rod pumping string to a minimum value after said sucker rod pumping string has traversed at least 75% of its descending phase but before said sucker rod pumping string reaches the end of its descending phase.
- 7. Apparatus according to claim 6 wherein said second valve limits the speed of descent of said sucker rod pumping string after said minimum value has been attained to not more than about 15% of the maximum rate of descent of said sucker rod pumping string during its descending phase.
- 8. Apparatus according to claim 7 wherein said second valve limits the speed of descent of said sucker rod pumping string after said minimum value has been attained to not more than about 10% of the maximum rate of descent of said sucker rod pumping string during its descending phase.
- 9. Apparatus according to claim 1 including controlling valve means controlling the fluid communication between said pump and said cylinder, said controlling valve means including a plunger actuated by said first carriage.
- 10. Apparatus according to claim 9 including an elongate rod engaging said plunger, said rod being mounted with a part thereof to be lifted near the top of said ascending phase of said pumping cycle which moves said plunger.
- 11. Apparatus according to claim 10 wherein said flexible means comprises at least one chain and said rotatable means comprises at least one sprocket.
- 12. Apparatus according to claim 9 wherein said flexible means comprises at least one chain and said rotatable means comprises at least one sprocket.
- 13. Apparatus according to claim 1 wherein said second valve limits the rate of descent of said sucker rod pumping string to not more than about five inches per second after said minimum value of said rate of descent has been attained.
- 14. Apparatus according to claim 13 wherein said second valve limits the rate of descent of said sucker rod pumping string to not more than about two inches per second after said minimum value of said rate of descent has been attained.
- 15. Apparatus according to claim 14 wherein said second valve limits the rate of descent of said sucker rod pumping string to below about two inches per second for at least about two seconds after said minimum value of said rate of descent has been attained.
- 16. Apparatus according to claim 14 wherein said second valve limits said rate of descent of said sucker rod pumping string to below about two inches per second after said sucker rod pumping string has completed about 75% of its descending phase.
- 17. Apparatus according to claim 14 wherein said second valve limits the rate of descent of said sucker rod pumping string to not more than about one inch per second after said minimum value of said rate of descent has been attained.
- 18. Apparatus according to claim 17 wherein said back pressure build up limits said minimum value of the rate of descent of said sucker rod pumping string substantially to zero.
- 19. Apparatus according to claim 1 further comprising:
- a suction line for supplying fluid from said reservoir to the inlet of said pump;
- a change-over valve having upstroke and downstroke positions;
- a pressure line for supplying hydraulic fluid under pressure from the outlet of said pump to said change-over valve; and
- a cylinder supply line extending from said change-over valve to said cylinder,
- said change-over valve, when in its upstroke position, connecting said pressure line and said cylinder supply line and, when in its downstroke position, connecting said cylinder supply line and said discharge line.
- 20. Apparatus according to claim 19 further comprising a relief line connecting the outlet of said pump to said reservoir, and a biased-closed relief valve disposed in said relief line and arranged to open when the pressure at the outlet of said pump exceeds a predetermined value greater than the design outlet pressure of said pump during said upward stroke of said sucker rod attachment means.
- 21. Apparatus according to claim 19 wherein the total volume of said accumulation tank is from about 1.5 to about 3.5 times the swept volume of said cylinder and the gas pressure in said accumulation tank is such that said accumulation tank never becomes more than about half-full of fluid.
- 22. Apparatus according to claim 21 wherein said gas pressure in said accumulation tank is adjusted so that said accumulation tank becomes at least about one third full of fluid.
- 23. Apparatus according to claim 19 further comprising two detents vertically spaced from one another and mounted on one of said first carriage and said frame and a switch mounted on the other of said frame and said first carriage so as to be capable of engaging said detents, said switch being capable of moving said change-over valve between its upstroke and downstroke positions, such that adjacent the end of said upward stroke of said sucker rod pumping string said switch will engage one of said detents, thereby shifting said change-over valve from its upstroke to its downstroke position, and adjacent the end of said downward stroke of said sucker rod pumping string said switch will engage the other of said detents, thereby shifting said change-over valve from its downstroke to its upstroke position.
- 24. Apparatus according to claim 23 wherein the spacing between said two detents is variable, thereby allowing the length of the stroke of said sucker rod pumping string to be varied.
- 25. Apparatus according to claim 19 further comprising a return line extending from said change-over valve to said reservoir without passing through said restriction valves, said change-over valve being arranged in its downstroke position to connect said pressure line and said return line.
- 26. Apparatus according to claim 25 wherein said change-over valve is pilot-operated and there is disposed in said return line a biased-closed check valve which will permit fluid to flow from said change-over valve to said reservoir but not in the opposed direction, the bias on said check valve being sufficient to provide in said return line up-stream of said check valve a fluid pressure sufficient to enable shifting of said pilot-operated valve.
- 27. Apparatus according to claim 25 wherein said change-over valve, when in its upstroke position, connects said discharge line and said return line.
- 28. Apparatus according to claim 25 wherein said change-over valve is provided with a fail-safe position wherein said pressure line is connected to said return line but said cylinder supply line is not connected to said discharge line, said change-over valve further being provided with biasing means which will cause said change-over valve to assume said fail-safe position if the power supply to said valve is cut off.
- 29. Apparatus according to claim 19 further comprising a subsidiary fluid-tight accumulation tank connected to said cylinder supply line.
- 30. Apparatus according to claim 29 wherein a cylinder supply line restriction valve is disposed in said cylinder supply line, a by-pass line extends around said cylinder supply line restriction valve, and a check valve is disposed in said by-pass line, which check valve which permits fluid flow from said cylinder to said change-over valve but not in the opposed direction.
- 31. Apparatus according to claim 29 wherein the total volume of said subsidiary accumulation tank is from about 10 percent to about 30 percent of the swept volume of said cylinder and the gas pressure in said subsidiary accumulation tank is such that said tank never becomes more than half-full of fluid.
- 32. Apparatus according to claim 31 wherein the total volume of said subsidiary accumulation tank is about 20 percent of the swept volume of said cylinder and said gas pressure in said subsidiary accumulation tank is such that said subsidiary accumulation tank becomes at least about one third full of fluid.
Parent Case Info
This application is a continuation-in-part of my copending application Ser. No. 156,780, filed June 5, 1980 now U.S. Pat. No. 4,346,620.
US Referenced Citations (16)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
156780 |
Jun 1980 |
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