Prevention and Control of Corrosion-Induced Asphaltene Deposition
Vargas, Francisco M.
Master of Science
Although in oil production multiple problems occur simultaneously, the solution strategy is typically presented by addressing one problem at a time. The objective of this thesis is to provide insight into the detrimental effect of iron ions, which are produced as a result of corrosion or contact with seawater in reservoirs, on the asphaltene precipitation and deposition tendency during asphaltene production. Furthermore, this work aims to provide means to control these adverse effects by using a chelating agent. In a series of experiments, a model oil system, which was prepared by dissolving asphaltenes in toluene, was put in contact with aqueous solutions of iron ions to study the effect of these species on the stability of asphaltenes using the indirect method. In addition, other potential variables were included in this work to analyze their effects on asphaltene precipitation, such as the presence of emulsified water, salinity, acidic pH, and metallic ions valence. It was found that the solubility of iron species is relatively high in the oil phase, compared to other cations, and that unlike other variables has a significant destabilizing effect on the asphaltene system. Also, a new experimental setup, consisting of a multi-section PTFE column packed with carbon steel spheres was built to quantify the deposition of asphaltenes under different operating conditions. This device was used to study the effect of the aqueous iron solutions on the asphaltene deposition tendency. It was identified that iron ions in the bulk phase, iron oxide on metallic surfaces, and higher surface roughness potentially increase the tendency of asphaltene deposition. The correlation between the corrosion of pipelines and asphaltene deposition was determined in this work. A chelating agent, Ethylenediaminetetraacetic acid (EDTA), was tried to reduce the detrimental effect of iron and successful results were obtained. It can be concluded that EDTA enables to restore asphaltene stability in the presence of iron ions. According to the evidence obtained from this work, the corrosion of pipelines might be an aggravating cause for asphaltene deposition in wellbore and surface facilities. By addressing the corrosion problem, asphaltene deposition might actually subside.
Corrosion; Asphaltene deposition; Asphaltene precipitation