Sucker Rod Pump Design Modification to Avoid Pump Floating Phenomena in Heavy-Oil, Low API Wells to Enhance the Production Rate

Abstract

Producing heavy oil from shallow wells using rod pump applications requires careful design considerations especially for down hole components to achieve maximum production rate and maximize the run life. This paper highlights a successful case study of one such heavy oil sucker rod pump well, in the North Kuwait field of Kuwait Oil Company (KOC), where the rods were specially designed to penetrate through the viscous oil and address the pump floating problem to achieve uninterrupted pump operation. Conventionally, as a rule of thumb for the shallow wells, the rod design initially constituted of twenty percent sinker bars and eighty percent sucker rods. This was to add weight on the pump for stability and proper balancing. In the case of this well, with the same design philosophy employed, it was observed that the pump floated over the viscous oil. The maximum pump fillage was observed to be less than fifty percent. Eventually operational changes were made by reducing the speed and operating at maximum stroke length. However this still did not bring any improvement. Hence, specific design modifications were made in the rod string and the pump size to be able to solve the pump floating problem, achieve maximum production rate, and operate at the maximum possible efficiency. Following the design change, it was observed that the pump was now able to penetrate through the viscous crude effectively. This increased the pump fillage to 75% consistently, enhancing the production rate. It was also observed to improve the unit balancing. This well design was considered as part of the pilot in heavy oil project in north Kuwait field. Since the floating pump phenomena is expected in KOC heavy wells, this design would be employed on similar sucker rod operated wells and neighboring wells suffering from the same well conditions. It is expected that by overcoming this operational issue there will be considerable cost savings and production enhancements.