Tubing buckling is a common and persistent problem encountered in Sucker Rod Pump (SRP) wells in onshore fields. This paper discusses about the optimization of rod guide spacing below the neutral point in SRP wells and development of a mathematical model for rod guide spacing.

In SRP wells, tubing below the neutral point buckles during the pump upstroke, causing frequent tubing and rod failures due to rod-on-tubing wear. The friction caused by tubing buckling increases polished rod load, pump wear and decreases lift efficiency. To avoid tubing buckling, tubing anchors and tail pipe are used for balancing of compressive force. Additionally rod guides are placed in SRP wells to prevent rod-tubing contact load but accurate spacing of rod guides is challenging task. To address this challenge, a mathematical model for rod guide spacing has been developed and validated with field data.

Lubinski et al. (1957) have analyzed tubing buckling phenomena in details and provided charts for rod guide spacing for 2″ and 2 1/2″ tubing sizes. In this paper, the work of Lubinski et al. has been carried forward. Analysis has been done for more accurate differential pressure across plunger for calculation of the compressive force in different scenarios and also generated charts for the most common tubing sizes of 2 7/8″ and 3 1/2″ for spacing of rod guides.

The developed mathematical model considers various parameters, such as specific gravity of fluid, dynamic liquid level, tubing size, and plunger diameter etc. to estimate the neutral point and optimization of rod guide spacing. The developed model has been used for more than 100 SRP wells of Indian onshore fields. This study can also be helpful in production of unconventional resources such as shale oil production and dewatering of Coal Bed Methane.

The proposed mathematical model provides accurate placement of rod guides according to the neutral point in the tubing string resulting in increased the mean time between failures. From the findings of this study, charts for spacing of rod guides have been generated for most common tubing sizes of 2 7/8″ and 3 1/2″ which will be a valuable reference for oil and gas operators in onshore fields.