Estudo da incrustação de carbonato de cálcio sobre aço-carbono em meio simulado de água produzida de petróleo de elevada salinidade.

Abstract

In brazilian pre-salt production, high levels of carbon dioxide (CO2) in the associated gas and high salinity in the water, and the high levels of calcium ions, cause problems related to corrosion and scale. The build-up of these products in the internal wall pipes reduces the internal diameter and can impact the production flow guarantee. For brazilian pre-salt reservoirs, the study and knowledge of calcium carbonate (CaCO3) scales become topics of crucial importance to guarantee the flow in the process production, taking into account the long paths flowed by the fluids and the accessibility difficult. Parameters related both to substrate and the environment can influence CaCO3 precipitation mechanisms and can impact both to development and selection of chemical scale inhibitors, as well as the use of mechanical and chemical removal methods. In this study, the effect of steel surface roughness on calcium carbonate scale has been studied in a high salinity brine containing sodium bicarbonate (NaHCO3) and calcium chloride (CaCl2), simulating pre-salt produced water and under flow conditions. An electrochemical cell is proposed and developed for this study. The scale build-up was analysed by using techniques such as Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersion X-ray Spectroscopy (EDS) contact angle and electrochemical measurements. Considering the test solution and the equipment adopted to simulate flow conditions, this study demonstrates that surface roughness influences the calcium carbonate scale formation and affects the calcium carbonate polymorphs associated with the corrosion process.