Sucker Rod String Rod Guide Service Life Estimation

Abstract The sucker rod string is equipped with rod guides that help to stabilize the sucker rod string and to prevent the contact between rods and tubing, which would end up in rod failures and tubing leaks. The scope of this paper is to present a wear study of sucker rod string rod guides performed at a testing facility to predict the wear and service life. Sucker rod pumping systems are well known for their high overall performance and their wide range of application. Nevertheless, experience and failure analysis of broken sucker rod pumping systems have shown that more than fifty percent of failures are the result of tubing wear, caused by contact with the rods. To be able to estimate the wear speed of the rod guides and thus the lifetime of the system, extensive testing of rod guides wear behavior was performed under real field conditions. The equipment was tested under realistic temperature, pressure, load, and speed conditions in the testing facility. A significant number of wear tests were performed under different conditions, and the results have shown that the weight loss and diameter decrease of the rod guides can be essential already after a few hundred hours of operation, reflecting several hundreds of kilometers of distance traveled. A size reduction of some millimeters indicates the importance of rod guide wear on the mean time between failures. A sensitivity analysis has shown the significance of the normal force and the roughness of the tubing string on the wear of the rod guides. This paper presents the conducted case study and the major findings. The gained knowledge is the basis for the development of a detailed wear prediction tool to properly estimate the lifetime of the rod guides under realistic conditions.