An Investigation of the Stability of Colloidal Asphaltene in Petroleum Reservoirs

Abstract

Abstract Asphaltene precipitation from petroleum fluids has proved to be a difficult problem to define and study. Asphaltene problems may occur deep in the reservoir formation and cause permeability reduction as well as contribute to serious plugging problems in oil well tubing and surface facilities. The stability of a dispersion in colloid science terms refers to the resistance of the particles to flocculation. The degree of this resistance is a measure of stability. Asphaltene colloidal dispersions in petroleum reservoirs are considered physically stable if free from any changes in physical properties. This paper first examines theoretically particles (asphaltene) in crude oil to determine, if they are electrically charged, how important it is to their inter-particle repulsion (stability). The theoretical result is then compared with the surface potential and steric effect of asphaltene and/or solid in petroleum fluids. Both theoretical and experimental results indicated that the electrical charge effects of asphaltene were found to play an utterly negligible role in the interaction between asphaltene particles and either surface or other particles. The stability of colloidal asphaltene in oil was investigated and determined to be caused by the steric effect of high molecular weight material (resins) adsorbed on asphaltene particles. The aggregation kinetic rates of asphaltene were also investigated using a laser back-scattering technique and determined to be influenced by the resin chemical potential concentration and the dispersion medium solvency. The latter needs to be a "good solvent" for the resin so that the aliphatic chains can be extended and move freely, thus enhancing the steric repulsion force.