Tubing and Rod Failure Analysis in Rod Pumped Wells in an Indian Western Oil Field

Abstract

Summary Sucker rod pump (SRP) is the most popular form of artificial lift, used in one of the western assets of Oil and Natural Gas Corporation (ONGC). It has been used to produce both vertical and deviated wells. In one of the mature fields, frequent tubing and sucker rod failures have been witnessed in both vertical and deviated SRP wells with mean time between failures (MTBF) as low as 4–5 months, which resulted in frequent workover and associated workover cost and production loss. Rubbing between tubing and sucker rod in deviated wells and bending of rods and tubing in vertical and deviated wells below the rod and tubing neutral point in wells experiencing higher compressive load, as a result of loads caused by the frictional and viscous forces inside the tubing string, such as the mechanical pump friction, the friction between the rods and fluid, the fluid and tubing, the tubing and rods, and the friction due to the fluid flowing through valves, has resulted in wearing of downhole equipment and holes in tubings. The paper analyzes the cause of failures and presents a comprehensive method to mitigate/minimize sucker rod and tubing failure. The study presented in this paper finds its application in a few candidate wells of ONGC, for the first time, where increased MTBF was achieved by the successful adoption of the said method. In addition, the present study has brought uniqueness by integrating the existing knowledge to bring out a rigorous workflow for maximizing the life of SRPs leading to considerable value addition to sucker rod operations of the candidate wells of ONGC. The suggested approach was useful in formulating a novel strategy to minimize the rod and tubing failure by application of a proposed workflow that includes (1) defining a computational method to estimate lateral loads acting along the rod string in deviated wells and to estimate tubing and sucker rod neutral point, (2) quantification of the number of guides to be placed below the neutral point and at points where the lateral load is high, and (3) estimation of the depth of the tubing anchor or length of the tail pipe to eliminate/minimize tubing buckling. The proposed method finds its validation in the field application, which is elaborately discussed in this paper.