Desenvolvimento de metodologia para determinação de alcalinidade por cromatografia iônica em amostras de matriz hipersalina características do pré-sal

Abstract

The CO2 injection into oil reservoirs for geological storage or enhanced oil recovery process (EOR) are alternatives used to reduce the emissions of this gas to the atmosphere. To predict the behavior of the injected CO2 over the years, a set of chemical analyzes and mathematical modeling are carried out. In this scenario, the alkalinity content of the reservoir formation water is of great importance, since the CO2 injection will cause a series of reactions that can affect the mineral dissolution and precipitation processes, affecting the safety and quality of storage. The most widespread technique for alkalinity analysis is potentiometric titration, which has the disadvantage of requiring large sample volumes and providing inaccurate results. Therefore, the development of a methodology with more reliable results and that uses a smaller sample volume is necessary. This way, the objective of this work was to use ion chromatography, as a methodology to determine alkalinity in samples with similar composition to the formation waters found in the Brazilian Pre-Salt reservoirs, comparing the results obtained with potentiometric titration and an alternative methodology, UV-visible spectrophotometry. The comparison between the results obtained using the three methodologies demonstrated that ion chromatography show potential to alkalinity determination. However, there were significant differences between the new methodology and the others, indicating that the sample preparation mode had interference in the result, and that the methodology needs optimizations that allow a better recovery of the analyte of interest.