The progressive cavity pumps system (PCP) are very successful in Colombian oil fields, however, wells operated under severely deviated conditions such as abrupt changes in deviation, high dogleg severity (3-6°/100 ft), and/or inclination angles up to 60° have generated between 3 and 5 interventions per year. These high-intervention wells are considered as critical, representing high operating costs and losses of production due to well-stop periods. The wells are typically of medium depths around 3,500 feet, have fluid rates up to 800 BFPD (BS&W > 80%), are influenced by water flooding, and operate at average speeds of 200 rpm to 300 rpm. For these critical wells we have worked to identify alternatives to reduce the repetitive failures (rods and broken tubing).
As part of an integral strategy to produce these wells with high production and high failure rate, this paper describes different operational processes and design considerations. The following topics will be discussed:
Design of wells with PCP as the artificial lift system
Challenge of artificial lifting
Redesign of sucker rod string configuration
This problem represents high lifting costs for a barrel of oil including the additional costs associated with well services and production losses due to closure periods.
As part of the solutions, a drive-rod test with modified pin was performed to improve the rod resistance and decrease the contact loads which allowed greater areas of flow, decreased flow restrictions, and less wear between tubing and rods. This change increased the run life by five times, allowing for the installation on a larger scale in a Colombian field. According to the previous results, the test was started in an additional field, confirming the success of the application in critical wells. This has provided ECOPETROL a significant economic benefit versus the conventional rods previously used in these wells under the same conditions. More than 30 wells have been selected to apply these different rods with successful results. All wells interventions regarding rods and tubing failures were reduced significantly (60% average) along with a decrease in production losses due to the associated downtime.