Performance Analysis and Field Testing of a Compact Dual-Piston, Hydraulic Sucker Rod Pumping Unit

Abstract

ABSTRACT An analysis and evaluation of a new conpact dual acting piston hydraulic sucker rod pumping unit is presented. The hydraulic unit offers some unique advantages over that of a conventional rotary beam unit. In particular stroke length and speed are readily changed by simple adjustments made to the hydraulics. For deep wells larger hydraulic piston cylinders are interchangable without having to replace the entire unit in order to meet pumping requirements. Performance data is presented which compares the hydraulic unit against selected conventional rotary beam pumping units. The performance analysis is based upon an optimum sucker rod design for a beam unit as a function of producing depth. Comparison of the hydraulic unit against conventional beam pumping units are made for the following cases; (1) a 72 inch stroke hydraulic unit operating at a constant pumping speed versus API 80 and API 114 beam units, (b) a 96 inch stroke hydraulic unit operating at constant pumping speed versus API 114 and API 160 beam units, (c) a 144 inch stroke hydraulic unit operating at a constant pumping speed versus API 228 and API 320 beam units. In each of these cases the beam pumping units were assumed to be operating at optimum pumping speeds for a given pump setting depth. To asist in the performance evaluation of the hydraulic unit versus that of a conventional beam pumping unit a 72 inch stroke hydraulic unit was installed in a well of depth 3800 feet located in Payne County, Oklahoma and operated for a period of 14 months. During this time numerous accoustical well sounding and dynamometer tests were performed on this unit as a means of monitoring its performance. Simultaneously, an offset well with identical downhole lifting equipment producing from the same depth and equipped with an API 114 beam pumping unit was monitored with the same test equipment. Field dynagraph cards and their analysis are presented which provided a quantative comparison of the hydraulic unit versus the beam unit. From the performance analysis and the actual field tests of the dynamometer and acoustical well sounding information the results obtained verify that the hydraulic unit is superior to that of a conventional beam pumping unit over a wide range of operating conditions. In particular, the hydraulic unit will normally operates at lower rod stresses and at the same-time move more fluid since the pumping efficiency of the hydraulic unit exceeds that of the beam pumping unit. This fact is verified by the near ideal dynagraph obtained for the hydraulic unit. Other advantages of the hydraulic unit including economic considerations are discussed as well as potential applications where the hydraulic unit will offer distinct advantages over its beam counterpart.