A Comprehensive Feasibility Study of a Production Technique to Lift Extra-Heavy, High-Viscosity Oil with an ESP System Demonstrates Improvement of Flow Assurance and Oil Production
Authors: Franco E. , Cardenas N. , Leon F. , Rivadeneira J. , Ortiz J. , Gomez E. , Huaca A. , Guerreo X. , Carrera J. , Izurieta F. , Arias E. , Preciado F. 
Published: September 2024

An Ecuadorian oil company recorded multiple early failures of electric submersible pumps (ESP) due to harsh fluid conditions. The extra-heavy (9°API) and high-viscosity (10,000) oil at surface stopped production from a new promising reservoir with approximately 400 million barrels of oil reserves. An oil service company studied the feasibility of injecting hot water in the wellbore to lift the viscous fluid using an ESP by reducing oil's viscosity and improving flow assurance conditions from downhole to surface.

The studied production technique injects field-produced hot water in the wellbore through a dual concentric tubing string, controlling injection flow rate and pressure with self-regulated downhole valves, to prevent pressure interference with the reservoir's productivity. The hot water heats the oil, reducing fluid viscosity through the ESP and the tubing. A comprehensive technical feasibility study was carried out by a multidisciplinary team of domain experts using a transient-state, multiphase fluid flow simulator to integrate reservoir performance, fluid dynamics, completion architecture, and ESP operation into one holistic, robust model to analyze various production and sensibility scenarios over time in a selected well candidate.

The holistic study demonstrated the proposed production technique could be a cost-effective, technically feasible solution to resume production from the promising reservoir that contained the extra-heavy, high-viscosity oil. On the ESP system side, there was a substantial increase of pump efficiency by 7 times, while the motor's working temperature was reduced by 12%, two factors that would help to extend ESPs run life. For the fluid, the simulation of the production technique proved how injecting hot water would improve fluid mobility, showing a reduction of surface fluid viscosity from 10,000 cP to 1,000 cP, while downhole viscosity dropped from 900 cP to 240 cP; thus, the friction losses in the tubing string declined by 89%. Such improvement in flow assurance conditions and ESP efficiency had one main benefit compared to a conventional ESP configuration producing the extra-heavy oil in the same well candidate: optimization of oil flow rate by 20%. Furthermore, economics of the well improved by the extension of ESP run life expectancy, avoiding workovers, and optimizing flow rate. The innovative production technique represented a more cost-effective solution than a conventional ESP installation by 5.4 times

This technique emerges as a solution to meet the challenges presented by the extra-heavy, high-viscosity oil in the studied reservoir; it could allow the operator to reactivate production in 15 wells, where other implemented production configurations have failed to avoid early ESP failures caused by flow assurance problems. The study of the proposed method proved it is technically feasible and is more cost-effective than a conventional ESP configuration.