Upthrust in Electrosubmersible Pumps and Failure Analysis Applied Chi Square Test, Case Study Ecuador.

Abstract

Abstract The present study was carried with the purpose to determine the relationship between the operation curves of electrical submersible pumps (ESP) with possible mechanical failures when more fluid is pumped than it was designed for, the study focuses on finding relevant information that allows to identify a trend in the occurrence of premature wear in the equipment, also by applying the Chi square test it is expected to determine the existence of the relationship between failures and overproduction, leaving a probabilistic basis to sustain this operational reality. The correct well selection is fundamental, ESPs must have technical, operational similarities and even produce from the same pay zone and from the same field, this uniformity creates a baseline that facilitates the analysis between failures and operational condition of the ESPs. The statistical study is carried out from the frequency of appearance of failures, these data are later used to apply Chi square and establish if there is dependence between failures and overproduction. Overproduction has a negative effect on the equipment, in the selected wells this condition is aggravated when the well reaches a %BSW greater than 92% causing an increase in failures of 40%, this is even evident in infant mortality failures at the beginning of ESP's operational life. In working conditions within the design range, the first failures appear up to the fourth month, but in upthrust this time is shortened to the first month after the installation of the pump. The operational challenges of the wells vary over time and this dynamic of requirements must be considered as a design factor because at some point the well will increase its water production rate and the production requirements will force to modify the operational variables demanding the equipment to work outside its maximum efficiency point. This work provides a bivariate probabilistic analysis which is focused on providing additional elements to affirm with criteria that overproduction affects ESP equipment. There is a wide discussion about the operating conditions that can cause failures in ESPs, this study identifies the critical value from which the percentage of BSW affects the equipment when pumps operate in upthrust, identifying this operating variable will allow the design of pumps that consider overproduction as one of its conditions to not affect the performance. It has been widely proven that working out of range affects equipment performance, however, there is no mathematical function that describes the relationship between upthrust and generated failures, this study performs a bivariate analysis using Chi square test to establish the correlation between failures and range of operation, thus providing elements that support this link and therefore to increase the knowledge about the ESPs behavior in real conditions.