Abstract
The aim of the present paper is to describe the E-log-I test performed on Oil Production Wells in a brown field area in the South of Iraq. The scope was, at the time, to determine the CP current to be applied to new well casings to protect them against external surface corrosion.
Initially, CP potential measurements were performed on existing well casings equipped with oil pumps and associated VSD (Variable Speed Driver), the equipment used to manage the AC powered motor of the pump installed inside the casing.
As verified during measurements, due to the presence of pumps and VSD, the grounding network cannot be completely isolated from the casing thus invalidating test results on some structures analysed.
To this end, the final tests were performed on new well casings where pumps and associated VSD were not installed yet, obtaining the typical E-log-I curve to be used for CP system design. These tests also confirmed the hypothesis of dreinage created by grounding connection due to installed pumps and associated VSD.
The paper presents potential measurements and data analysis, provides a technical explanation of the dreinage caused by pumps VSD grounding connection, and includes instructions and photos showing the temporary system used to perform the tests and final E-log-I curve obtained.
