Foaming of crude oil: Effect of acidic components and saturation gas

Abstract

Foaming tendency of crude oil is diverse due to the variance in crude oil components. Crude oil viscosity, asphaltene, and resin contents have been studied in general, but the specific surfactant molecules that stabilize crude oil foam are not identified. Carbon dioxide oftentimes accompanies hydrocarbon gases in reservoirs rich in natural CO2 and fields where CO2 enhanced recovery is implemented. Crude oil acidic components and carbon dioxide may have considerable significance to foam formation and defoaming kinetics. We studied the effect of acidic components and saturation gas on foaming of crude oils with pneumatic and depressurization tests respectively. Foaminess, foamability and time to half collapse are used to characterize foaming of oils. We present a new piecewise model that can be divided into two segments with almost equal timescales to fit the collapse curve and we use parabola function and expdec1 function to model the two segments respectively. The t values at the intersection of two segments are approximately the same as time to half collapse. Model parameter A is close to foamability. Increase in the rigidity of the interface and viscosity of the bulk liquid may account for excellent foam stability of some acids/oil systems. Some acidic crude oil components, for example, naphthenic acids, long-chain fatty acids, increase foaminess significantly, suggesting that crude oil antifoams combined with reagents that will react with some acidic components may have better performance.