Role of Reservoir Brine and Rock in Modulating Asphaltene Stability: Insights from Experimental Analysis

Abstract

Summary The stability of asphaltenes in crude oil is influenced by various factors, including interactions with reservoir components such as brine and rock formations. While previous research has focused on pressure and temperature effects, a comprehensive understanding of the combined impact of brine and reservoir rock on asphaltene stability is lacking. This study investigates the individual and combined influences of brine and rock formations on asphaltene stability. First, 11 crude oil samples from diverse locations were characterized using API gravity, viscosity, and saturates, aromatics, resins, and asphaltenes (SARA) fraction analysis. The elemental composition of the crude oils, including carbon, hydrogen, nitrogen, and various metals, was determined. The surface properties of asphaltenes were analyzed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). The interaction between asphaltenes and deionized water was examined through zeta potential, particle size, conductivity, and pH measurements. The behavior of asphaltenes in an 8,000 ppm NaCl solution was also investigated. The SEM analysis revealed the presence of inorganic content on the surfaces of asphaltenes, indicating interactions between asphaltenes and reservoir rock. A strong correlation between the zeta potential and sulfur content of asphaltenes was observed, highlighting the influence of sulfur compounds on surface charge and stability in heavy crudes. Additionally, the correlation between total dissolved solids (TDS) content and alkaline Earth metals and alkali metals in asphaltenes confirmed interactions between asphaltenes and reservoir brine. This interaction is likely influenced by the composition and properties of both the brine and reservoir rock. The presence of electrical charges on the asphaltene surfaces, as determined by zeta potential measurements, further supports the role of electrostatic interactions in asphaltene stability. The low precipitation tendency observed for most asphaltene samples, coupled with the abundance of negatively charged particles, underscores the importance of electrical charges in controlling stability. This study provides novel insights into asphaltene stability, highlighting the significance of surface charge and elemental composition. The results demonstrate the substantial impact of both reservoir brine and rock formations on asphaltene stability in crude oil. Further research is needed to unravel the complex mechanisms underlying these interactions and their implications in diverse reservoir environments.