Pumping Unit Having Zero-Imbalanced Beam, Lagging Counterweights, and Setback Crank Point

Abstract

A surface unit can operate as a longer stroke unit to reciprocate a rod string for a downhole pump in a well. The unit has an end weight that gives the walking beam and head a zero-imbalance about the unit's fulcrum point. The unit can also operate as a phased unit in which the counterweights of the crank arms lag behind the pivot connection and/or the crank point is disposed rearward of the equalizer bearing of the walking beam.

What is claimed is: 
     
         1 . A surface pumping unit operated by a prime mover for reciprocating a rod load for a downhole pump in a well, the unit comprising:
 a frame disposed at surface and having a fulcrum point;   a beam being pivotable at the fulcrum point of the frame, the beam having first and second ends, the first end having a head connecting to the rod load extending from the well, the second end having a first bearing point and having an end weight disposed rearward of the first bearing point, a forward section of the first end of the beam and the head disposed forward of the fulcrum point having a forward weight, a rearward section of the second end of the beam and the end weight disposed rearward of the fulcrum point having a rearward weight, the forward weight being balanced relative to the rearward weight;   a crank arm connected to the prime mover and rotatable thereby about a crank point;   a counterweight disposed on the crankarm; and   a pitman arm connected between the first bearing point on the beam and a second bearing point on the crank arm, the second bearing point being disposed between the counterweight and the crank point.   
     
     
         2 . The unit of  claim 1 , wherein the crank arm rotated by the prime mover about the crank point translates the pitman arm to oscillate the beam on the fulcrum point and reciprocates the rod load along the wellbore axis. 
     
     
         3 . The unit of  claim 1 , wherein the frame comprises:
 a base disposed at the surface; and   a post extending from the base to the fulcrum point along a line from vertical.   
     
     
         4 . The unit of  claim 1 , wherein the beam defines a straight axis having first and second sections, the first section from the fulcrum point to a face of the head having a first length (A), the second section from the fulcrum point to the first bearing point having a second length (C);
 and wherein the first length (A) is greater than the second length (C).   
     
     
         5 . The unit of  claim 1 , wherein the fulcrum point comprises a saddle bearing; wherein the first bearing point comprises an equalizer bearing; and wherein the second bearing point comprises a crank pin bearing. 
     
     
         6 . The unit of  claim 1 , further comprising:
 another crank arm connected to the prime mover and rotatable thereby about another crank point; and   another pitman arm connected between another first bearing point on the beam and another second bearing point on the other crank arm,   wherein the pitman arms connect with an equalizer beam at the first bearing point.   
     
     
         7 . The unit of  claim 1 , further comprising a gear reducer operably connecting the crank point to the prime mover. 
     
     
         8 . The unit of  claim 1 , wherein the crank point is centered vertically below the first bearing point on the beam when the beam is situated horizontally. 
     
     
         9 . The unit of  claim 8 , wherein the first bearing point is disposed at a first horizontal dimension (C) along the beam relative to the fulcrum point; and wherein the crank point is disposed at a second horizontal dimension (I) relative to the fulcrum point, the second horizontal dimension (I) being approximately equal to the first horizontal dimension (C). 
     
     
         10 . The unit of  claim 8 , wherein the crank arm defines a longitudinal axis, the second bearing point being disposed along the longitudinal axis of the crank arm. 
     
     
         11 . The unit of  claim 8 , wherein the crank arm defines a longitudinal axis, the second bearing point being disposed offset at an angle from the longitudinal axis of the crank arm. 
     
     
         12 . The unit of  claim 1 , wherein the crank point is situated vertically rearward below the first bearing point on the beam when the beam is situated horizontally. 
     
     
         13 . The unit of  claim 12 , wherein the first bearing point is disposed at a first horizontal dimension (C) along the beam relative to the fulcrum point; and wherein the crank point is disposed at a second horizontal dimension (I) relative to the fulcrum point, the second horizontal dimension (I) being greater than the first horizontal dimension (C). 
     
     
         14 . The unit of  claim 12 , wherein the crank arm defines a longitudinal axis, the second bearing point being disposed along the longitudinal axis of the crank arm. 
     
     
         15 . The unit of  claim 12 , wherein the crank arm defines a longitudinal axis, the second bearing point being disposed offset at an angle from the longitudinal axis of the crank arm. 
     
     
         16 . A surface pumping unit operated by a prime mover for reciprocating a rod load for a downhole pump in a well, the unit comprising:
 a frame disposed at the surface and having a fulcrum point;   a beam being pivotable at the fulcrum point of the frame, the beam having first and second ends, the first end having a head connecting to the rod load extending from the well, the second end having a first bearing point and having an end weight disposed rearward of the first bearing point;   a crank arm defining a longitudinal axis, the crank arm connected to the prime mover and rotatable thereby about a crank point;   a counterweight disposed on the crankarm; and   a pitman arm connected between the first bearing point on the beam and a second bearing point on the crank arm, the second bearing point being disposed between the counterweight and the crank point and being disposed offset at an angle from the longitudinal axis of the crank arm.   
     
     
         17 . The unit of  claim 16 , wherein a forward section of the first end of the beam and the head disposed forward of the pivot point having a forward weight, a rearward section of the second end of the beam and the end weight disposed rearward of the pivot point having a rearward weight, the forward weight being balanced relative to the rearward weight about the pivot point. 
     
     
         18 . The unit of  claim 16 , wherein the crank point is situated vertically rearward below the first bearing point on the beam when the beam is situated horizontally. 
     
     
         19 . The unit of  claim 18 , wherein the first bearing point is disposed at a first horizontal dimension (C) along the beam relative to the fulcrum point; and wherein the crank point is disposed at a second horizontal dimension (I) relative to the fulcrum point, the second horizontal dimension (I) being greater than the first horizontal dimension (C). 
     
     
         20 . A reciprocating pump system for a well, the system comprising:
 a downhole pump disposed in the well; and   a pumping unit according to  claim 1  or  claim 16  disposed at the surface and coupled to the downhole pump by a rod string.