Abstract
This paper presents the results of a study conducted to investigate the corrosivity of wet-sour crude oil wells and to examine the performance of several potential chemical inhibitors. Recently, wet-sour crude oil wells have been experiencing increased water cuts and corrosion issues. Previously, under these environments, protection of downhole equipment was attributed to the formation of passive iron sulfide films/layers. In this work, we study the natural inhibition of two crude oil samples and the effect of different levels of synthetic and live brines. For corrosion inhibition, we evaluated the performance of several commercially available chemicals in terms of partitioning, demulsification and thermal stability, as well as their inhibition efficiency under continuous and batch treatments scenarios. Uniform/general corrosion is the focus of this paper. Localized corrosion will be addressed in subsequent studies which require prolonged test durations.
Ranking the performance of candidate chemical inhibitors was based on the following criteria: a) the chemical must show high corrosion inhibition efficiency in both brine and brine/crude oil mixtures with more emphasis on the latter case; b) high thermal stability or increase in thermal stability due to heating; c) sufficient partitioning into the aqueous phase; and d) minimum demulsification effect, which will ensure corrosion inhibitor availability to protect downstream carbon steel facilities. Based on the lab results, initial rankings for continuous and batch treatments were determined. Considering the corrosion inhibitors performance and ranking under each criteria mentioned above, an overall ranking for both continuous and batch treatments was obtained and was proposed for field test-trials. This work emphasizes a holistic approach when evaluating corrosion inhibitors, including chemical and physical contributions by the crudes, the aqueous phase, and the gas mixture.
