How to Prevent Gas Lock in Sucker Rod Pumps

Abstract

Abstract This paper contains basic knowledge and formulas that govern fluid production with sucker rod pumps and emphasizes the importance of the parameters that affect the production rate while pumping with a gas phase. The material presented is supported by field experience performed by using special operating conditions and/or special devices acting upon those parameters. INTRODUCTION In the 1950's, D.A. Connally, C.R. Sandberg and N, Stein [1] and E. Lodynsky [2] were the forerunners in studying the extremely complex pumping of a two phase system and the variations observed in the pump volumetric efficiency of this operating condition, Under elevated pressures crude oil dissolves available gas. In this multicomponent hydrocarbon fluid system, changes of pressure and temperature result in phase changes. Production formation pressure decreases while fluid flows into the well. In many cases, the flowing bottom hole pressure decreases to such an extent, that gas bubbles come out of the solution, and thus, a gas phase is present in the reservoir near the well bore. This operating condition seriously affects the pump and its production rate because pump valves do not operate properly during the pumping cycle. On the upstroke, the standing valve's opening is delayed. In addition to this, the barrel only partially fills with liquid, since gas occupies some of the barrel space. On the downstroke, the traveling valve is kept closed for a portion of its downward travel by the fluid load from above. In extreme cases gas lock can also develop, which completely stops the pumping action. Gas lock occurs then the peak pressure of the trapped gas on the downstroke is not great enough to overcome the hydrostatic load on the traveling valve. Furthermore, the pressure is not reduced enough on the upstroke to allow the standing valve to open and admit new fluid.