Historically, the electric-submersible-pump (ESP) system has been the most cost-effective artificial-lift technology to draw down deep wells with flow rates of more than 200 STB/D. In lower-rate wells, other technologies such as rod pump systems have proven to be more cost effective. However, in recent years the long-stroke pumping unit has extended the rod-lift operating envelope to the point that rod lift now provides competitively effective pumping in wells traditionally using ESPs.
The case study within this paper focuses on a mature well located in a Petrobell's field in South America, Cachiyacu 1, in which a production decline rendered the existing ESP system oversized for the well conditions. The operator was seeking a more efficient lift solution before ESP failure due to down-thrust operation. A comparison of energy consumption, efficiencies, and operating expenses (OPEX) was used to evaluate the two artificial-lift options—a smaller ESP system or a long-stroke pumping unit.
This study compares the costs of power and workovers between an ESP and a long-stroke pumping unit. It shows that over a well-documented period of time, the long-stroke pumping unit reduces power consumption by providing greater operational efficiency than ESPs at similar depths and rates. The long-stoke pumping unit also reduces workover costs with less expensive downhole components.
This operator realized significant financial savings and reduced energy usage by choosing the long-stroke pumping unit. Although both the ESP system and the long-stroke pumping unit can deliver similar production rates, in this case, the long-stroke pumping unit was able to provide a higher production rate than the ESP. The LSPU also provided a more cost effective option in this application (CAPEX & OPEX).