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Back pressured hydraulic pump for sucker rod

Back pressured hydraulic pump for sucker rod description/claims

This application claims the benefit of U.S. Provisional Application No. 60/859,676 filed Nov. 17, 2006, the disclosure of which is incorporated by reference herein.

In certain embodiments, the invention relates to a method and apparatus for operating a hydraulic cylinder to actuate a downhole pump coupled to the cylinder via a sucker rod linkage. In one aspect, the invention relates to a derrick useful for oil and gas operations.

Mechanical pump jacks have been used for many years in the oil and gas industry to remove liquids from deep wells. Typically, a rocking beam is connected at one end to a string of sucker rods which actuates a downhole pump mechanism and is counterbalanced with heavy weights at the other end to reduce the uplift force required to raise the sucker rod and liquids contained in the well.

One of the drawbacks of this arrangement is that the sucker rod string follows a generally nonadjustable sinusoidal velocity profile. Certain well applications may be limited by a maximum permissible upstroke and/or downstroke velocity. When coupled with the fixed sinusoidal motion of the rocking beam, the velocity limitation constrains the overall stroke rate, and therefore the overall well production rate. Furthermore, the loads generated by the dynamics of the system may dictate that the well is best operated according to some profile other than the generally nonadjustable sinusoidal profile. The overall efficiency of the system and component life may be improved by reciprocating the well according to an alternate velocity profile. A system which permits adjustment of the stroke velocity profile would be very desirable.

Hydraulic systems, which permit a greater degree of control of the velocity of the sucker rod string, are known. In general, these systems utilize a secondary cylinder or pressure area to assist the primary cylinder and provide counterbalance. Since the upstroke and downstroke forces are in the same direction, some of the energy put into the system on the upstroke may be recovered, through the use of counterbalance, on the downstroke. However, the addition of another cylinder to the system reduces reliability, often increases overall height, and increases system complexity. A hydraulic unit that provides a means for counterbalance without the addition of a second cylinder would create a simpler, more space efficient, and inherently more reliable machine.

An additional shortcoming of both existing prior art hydraulic and mechanical systems is that no means are provided for diagnosing the development of problems downhole. For example, failure of the pump, leakage in the pump, changes in the liquid makeup in the well, dry bottom conditions in the well, excessive sucker rod drag, will all manifest themselves by changes over time in the work increments being done by the unit. A system to track these increments to permit diagnosis of problems downhole would be very desirable.

Pump jacks do not require a derrick for operability. A derrick is required for a hydraulic actuator for sucker rod. A derrick which is easy to transport and assemble and is inexpensive would be very desirable for use with hydraulic sucker rod actuator systems.

It is an object of this invention to provide a hydraulic system for actuating a well sucker rod that provides equivalent or superior efficiencies as compared to a counterbalanced mechanical system.

It is a further object of this invention to provide a hydraulic system for actuating well sucker rod that permits infinite control over the sucker rod velocity profile.

It is a further object of this invention to provide a hydraulic system for actuating well sucker rod that provides for the recordation of measurements so that downhole hole problems can be quickly identified and corrected if necessary.

It is another object of this invention to provide a derrick which is highly suitable for use with a hydraulic sucker rod system.

It is another object of this invention to provide methods for controlling the velocity profile of reciprocating well sucker rod.

In one embodiment of the invention, there is provided an apparatus comprising a hydraulic cylinder assembly, a load connected to the cylinder, a reversible hydraulic pump assembly, a pressurized supply of hydraulic fluid, first and second conduits for hydraulic fluid, and a control system. The hydraulic cylinder assembly comprises a cylinder sealed by an upper head and a lower head and carrying a piston which divides the hydraulic cylinder assembly into an upper chamber and a lower chamber. The load is connected to the piston and urges it toward the lower head. The first conduit for hydraulic fluid connects the reversible hydraulic pump assembly in fluid flow communication with a lower chamber of the hydraulic cylinder assembly. The second conduit for hydraulic fluid connects the reversible hydraulic pump assembly in fluid flow communication with the pressurized supply of hydraulic fluid. The pressurized supply of hydraulic fluid is compatible with the hydraulic pump assembly. The control system is operably associated with the reversible hydraulic pump assembly to cause hydraulic fluid to flow back and forth between the lower chamber of the hydraulic cylinder assembly and the pressurized supply of hydraulic fluid.

Use of the pressurized source of hydraulic fluid permits the load to be raised and lowered with less delta P being generated by the hydraulic pump.

Another aspect of the invention provides a tripod derrick. The derrick comprises a first leg, a second leg, and a third leg, each leg having an upper end and a lower end. The derrick further comprises a first runner strip and a second runner strip each having a first portion and a second portion and a hinge connecting the first portion and the second portion. The derrick further comprises a tip-top assembly and a cross-brace beam. The tip-top assembly is connected to the upper end of each of the first leg, the second leg, and the third leg. The first runner strip and the second runner strip are positioned side by side and parallel to each other and the cross brace beam connects the first portion of the first runner strip and the first portion of the second runner strip at a position near the hinge. The lower end of the first leg is mounted to the cross brace beam near a location midway between the first runner strip and the second runner strip. The lower end of the second leg is mounted to the first portion of the first runner strip, the cross brace being connected between the second leg and the hinge, and the lower end of the third leg is mounted to the first portion of the second runner strip, the cross-brace being connected between the third leg and the hinge. The legs are laid out in a triangular pitch and are inclined inwardly and upwardly toward the tip-top assembly.

The hinges permit the derrick to be assembled at ground level and then tipped into an upright orientation, as well as permitting the unit to be quickly lowered to permit work-over crews to access the well.

• Provisional Patent
• Utility Patent

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