Laboratory Instrumented Sucker-Rod Pump

Abstract

Abstract Although sucker rod pumps are installed in nearly 90% of all oil wells in the United States and have been widely used for decades, there are many issues regarding their performance that are not well understood. This is due to the difficulty of obtaining downhole pump-performance data. Many persistent problems in sucker rod pumping including partial pump fillage, gas interference, gas locking, fluid pound, sticking valves, rod downstroke compression loading, equipment failure, reduced production, etc. are difficult to diagnose from the surface. Currently, verification of sucker-rod pump problems can only be inferred by removal of the pump at great expense. Thus, root cause analysis depends on guesswork and component analysis. Knowledge of pump characteristics downhole would allow problems to be predicted rather than simply diagnosed after they have persisted long enough to result in failure To develop a knowledge base of sucker-rod pumps, a two-fold approach is being pursued: first, instrumentation of a clear sucker-rod pump in the laboratory followed by the development of an instrumented downhole pump. The laboratory pump allows the development of diagnostic techniques where the pump performance can be verified visually. The downhole pump will allow testing at field conditions. A key element to both the laboratory and downhole instrumented pumps is measuring the compression chamber pressure — pressure within the pump barrel. The instrumentation has been designed to collect high-speed (100 samples a second) data so that transient behavior (ball chatter, etc.) can be observed. Data is being archived operating the pump under a various conditions from full to pumped-off. This paper presents results of tests with the laboratory pump that have resulted in new insights about pump friction and the development of techniques to measure dynamic and static pump friction. Analyses of the compression-chamber pressure are leading to a better understanding of what happens during that time when both valves are closed and to the development of techniques to perform real-time diagnosis determining fillage and gas locking. Laboratory data has shown that compression chamber data can be more insightful in understanding pump conditions.