An Improved Model for Sucker Rod Pumping

Abstract

Abstract An improved model for predicting the behavior of sucker rod pumping installations is presented. This model incorporates the dynamics of the liquid columns as well as the sucker rod string through a system of partial differential equations. This system of equations is solved by a modified method of characteristics on a digital computer. The model predicts the polished-rod and pump dynamometer cards and incorporates the effects of liquid inertia and viscosity. The model is capable of simulating a wide variety of pumping conditions for which liquid physical properties are important. The information physical properties are important. The information predicted by the model is useful in the design and predicted by the model is useful in the design and operation of sucker rod pumping installations. Introduction Sucker rod pumping is the primary artificial lift method used in the U.S. Thus, there is a need for an accurate sucker rod pumping model to assist in the design and simulation of sucker rod pumping installations. Recently there has been a substantial effort to develop sucker rod pumping models that can be solved with the aid of a pumping models that can be solved with the aid of a digital computer. These efforts, however, have been restricted solely to the analysis of the dynamics of the sucker rod string. As such, these models ignore the dynamics of the fluid and tubing columns as well as the fluid physical properties. This study overcomes one of these shortcomings by including the dynamics of the fluid as well as the rods. Thus, it is now possible to analyze the effects of fluid physical properties on a sucker rod pumping installation. The computer program for sucker rod pump system design that was written to implement the following model is very general. The program includes the effects of motor slip, different types of pumping units, various inertial effects in the surface equipment, tapered rod strings, fiberglass rods, sinker bars, unanchored tubing, gas interference, fluid pound, etc. However, the purpose of the current study is to illustrate the effects of fluid properties on a sucker rod pumping installation. As a properties on a sucker rod pumping installation. As a result, the following assumptions are made to segregate more accurately the effects of the fluid column from other effects:fluid column contains no gas,tubing is anchored, andprime mover has no slip. These assumptions are not necessary components of the model, and are used in the current study only for the purpose of illustration. purpose of illustration. For additional information about the computer program for sucker rod pump system design, contact the program for sucker rod pump system design, contact the authors.