Paper: Operation of Hydraulic Pumping Units

Hydraulic pumping units are classified as surface or sub-surface. Our discussion refers only to surface units which reciprocate a sucker rod string connected to a sub-surface plunger pump. Hydraulic unites may be classified as counterbalanced or non-counterbalanced. The counterbalance is provided by weights or compressed gas. Our discussion will be based on compressed gas- counterbalanced units and non-counterbalanced units.