The Effect of Iron Bearing Minerals on Surfactant Adsorption in Chemical Enhanced Oil Recovery Applications
A declining number of oil field discoveries has led to an increased interest in enhanced oil recovery (EOR) technologies to produce residual oil and gas deposits where natural pressure drives and artificial lift capabilities have been exhausted. A technique whereby surfactant solutions (surfactants, co-surfactants, polymers, etc.) are injected into reservoirs to reduce the interfacial tension, alter the wettability of the reservoir rocks and maintain a favorable endpoint mobility ratio can become economically viable. Surfactant losses due to adsorption is one of the major hurdles to be overcome with this EOR technique. The purpose of this research is to examine the effect of iron-bearing minerals within the reservoir on surfactant adsorption rates. To observe these effects, a series of dynamic adsorption measurements were conducted using sand packs containing varying amounts of iron-bearing minerals, including siderite and illite, using an internal olefin sulfonate surfactant. To measure the rate of adsorption, iron and surfactant concentrations were monitored in the produced fluid. From the study, it was found that surfactant adsorption showed a proportional relation with the iron content within the clay. It also appeared that surfactant partitioning was proportional to the amount of clay present, regardless of iron content. This partitioning is likely due to a surfactant layering effect that occurs due to charge shielding.