Erik Tietz, P.E., and Arun Sriraman; UPCO, Inc.
There are a variety of sucker rod grades available today for different pumping environments. In order to optimize the run time of an oil well, it is very critical to choose the correct sucker rod grade for a particular application. There are a lot of physical attributes (engineering attributes) which need to be considered for design aspects of a rod string. Some of the engineering concepts are yield, tensile, load carrying capability, stress-strain curves, elongation, reduction of area and toughness. The first segment of this paper addresses these sucker rod concepts using stress-strain curves. One of the most well known practical problems faced in the field is the selection of sucker rod grade in a high load and corrosive environment. The obvious choice becomes a KD grade sucker rod because HS (High Strength) rods due to their mechanical properties should not be used in corrosive environments. As a result of this, the end users had no choice except to overload KD rods in corrosive environments. UPCO, Inc. has developed and tested a new grade of sucker rod which can be used in higher load wells where high strength rods are not an option due to corrosive nature of the well. The second segment of this paper addresses the development of the new grade of
sucker rod (SD). SD grade of sucker rods fills the application gap between KD and HS rods. SD rods have better load carrying capability than a KD rod and a better toughness than a HS rod.