ESP Challenges in an EOR Project After Breakthrough. An Analysis of Continuous Improvement for ESP Designs Towards the Reduction of OPEX

Abstract

Abstract Generally, the main concern in a well expected to be affected by a waterflooding effect is the readiness of the flow range to be handled; however, new findings had showed us that this is one of several other concerns that can be expected, such as scale deposits, sulfurs, asphaltenes, and sand migration. In influenced wells the main concern is to have a design that suits correctly to the flow range before and after the breakthrough; however, other fluid properties with a large influence during this process may be underrated. The scope of this project is to explain the symptoms of each cause of Electric Submersible Pumps (ESP) failure to determine what can be done to improve operational expenses (OPEX) by tracking ESP failures ranging from as low as 90 days up to 900 days and performing a detailed dismantle and failure analysis (DIFA), combining reservoir data, tear-down information, and sampling composition analysis triggered evidence and patterns that previously were not identified. Several simulations were evaluated during the run life of the studied ESPs prior and after the breakthrough aiming to determine head degradation and power consumption. This information was cross checked with the historical production and downhole ESP parameters, showing a clear correlation between the evidence obtained in the ESP tear down with observed behavior while working. In Ecuador, where this study took place, the waterflooding projects are mainly low-salinity waterflood (LSWF) projects, where the water is taken from a water-producing reservoir. Based on salinity and water cut trends of the producer well, the water immersion process to the producer well or most known as breakthrough, was detected during the lifetime span of the ESP. After creating head and power consumption trends with several simulations, the effect of the fluid change over the ESP system was quantified. In some cases, head degradation of up to 65% was detected. Also, unexpected power consumption above 30% was identified in the system. By correlating the samples, these effects were classified and associated with different reservoirs, and it was found that the main reasons for the symptoms were deposits, mainly carbonates and sulfurs, in wells where no historical similar issues were recorded previously. The second finding was that changes in historical fluid viscosity may have led to the generation of asphaltene deposits. Finally, the third finding was fines migration causing ESP plugging and, in some cases, filling the well rathole. It is important to have in place a holistic process after the breakthrough to properly understand the failure mechanism of the system. In the studied of the 24 failed ESPs with a breakthrough process, based on the results, improvement of the hardware and a new chemical treatment were adopted to attack the cause of the ESP failure.