Paper: Gas Interference In Rod Pumped Wells

Pumping free gas reduces pump-liquid efficiencies and alters loading on the pumping system. The rod pumping design procedure outlined in API RP IIL assumes complete pump liquid fillage and determines loads based on test data gathered from an electrical analog computer model. The Shell method is based on a mathematical solution, and the resulting loads are calculated assuming incomplete pump fillage (gas interference). Design charts similar to those used in API RP IIL for rod pumped systems are shown based on 75% liquid and 25% gas fillage of the pump. These design charts are compared to API rod design charts. In general, incomplete pump fillage alters peak loading conditions: however, loads are not significantly different in most cases from API loads. Surface pump dynamometer cards for 75% fillage are compared with100% fillage cards. The shape of the 100 and 75% pump fillage dynamometer cards are somewhat different, especially in the first half of the downstroke. The effects of pumping gas on pump efficiency are shown and explained. The optimum pump volumes and depth plus the important parameters affecting gas separation are outlined.