Patent ID: 6116025
Filing Date: 2000-09-12
Classification: F04B

Abstract:
A pumping unit, mounted at least approximately at surface elevation, which supports and vertically reciprocates a rod string and downhole pump, said pumping unit comprising reciprocally applied linear drive means, and counterbalance means which applies an upwardly directed counterbalance force to said rod string throughout the stroke cycle of said pumping unit, the improvement in combination therewith comprising a dynamic upstroke reversal and downstroke reversal system, said system comprising:downward force means which comprises:cylindrical downward force cavity means;downward force piston surface means within said downward force cavity means, said downward force piston surface means at least indirectly connected to, and arranged to move reciprocally with, said rod string;a selected volume of enclosed downward force compression space in communication with said downward force cavity means;a selected amount of compressed downward force gas contained within said downward force cavity means and said downward force compression space, the flow of said downward force gas between said cavity means and said compression space unimpeded;said downward force gas exerting a downward force upon said downward force piston surface means, said downward force transferred to said rod string in a downward direction, throughout said stroke cycle of said pumping unit, said downward force varying in value from a maximum at the top of the stroke, to a minimum at the bottom of said stroke;upward force means which comprises:cylindrical upward force cavity means;upward force piston surface means within said upward force cavity means, said upward force piston surface means at least indirectly connected to, and arranged to move reciprocally with, said rod string;a selected volume of enclosed upward force compression space in communication with said upward force cavity means;a selected amount of compressed upward force gas contained within said upward force cavity means and said upward force compression space, the flow of said upward force gas between said cavity means and said compression space unimpeded,said upward force gas exerting an upward force upon said upward force piston surface means, said upward force transferred to said rod string in an upward direction, throughout said stroke cycle of said pumping unit, said upward force varying in value from a maximum at said bottom of said stroke, to a minimum at said top of said stroke;the sum of said upward force and said downward force having a value of zero at a common point within the central portion of said upstroke and said downstroke, respectively,said sum of said upward force and said downward force further comprising a downwardly directed upstroke reversal force which increases from said zero value at said common point, to its maximum value at said top of said stroke, and, respectively, an upwardly directed downstroke reversal force which increases from said zero value at said common point, to its maximum value at said bottom of said stroke.