Fluid inertia consideration in sucker rod pump diagnosis

Abstract

artificial lift in the U.S.A. It has been reported numerous times in the literature to exceed 85% of non-flowing well's lift systems. The efficient maintenance and operation of these wells is essential for them to remain profitable and productive petroleum assets. Diagnostic models have been developed to determine the working condition of down hole pumps in rod pump operations. Several methods have been used with good success to interpret surface measurements in order to diagnose and monitor pump conditions. However, existing state-of-the-art diagnostic models neglect fluid-inertia forces. In shallow wells with large lifting rates, dynamic fluid forces can be significant and result in poor diagnostic model performance. This research is motivated by the need for a diagnostic model that can more accurately and reliably diagnose wells with significant dynamic fluid loads. In this research, an accurate and useful finite difference diagnostic model that considers fluid inertia forces has been developed. The model is verified with simulated results and validated with field data. Additionally, the effects of fluid inertia are investigated in order to quantify when these forces are significant and this new model is applicable. The diagnostic model developed in this research is the first to consider dynamic fluid forces. It can be applied to rod pumped systems operating in a range where dynamic forces due to the acceleration of the fluid column are significant. These wells are typically shallow, high rate wells. The tables developed during this research are useful for determining the operating conditions in which this model is most applicable. In conclusion, this fluid inertia diagnostic model is very useful for monitoring and diagnosing the condition of rod-pumped wells that are difficult to diagnose due to large dynamic fluid forces.