Laboratory Investigation of High-Temperature Surfactant Flooding

Abstract

Summary Experiments were conducted to evaluate the use of surfactants for improving heavy-oil recovery from the hot-water zone in a steamflood. Criteria used to screen surfactants for this high-temperature application included thermal stability, interfacial activity, and surfactant flood performance. The thermal stabilities of several classes of sulfonate surfactants were measured. Surfactants exhibiting no thermal decomposition at elevated temperature (500°F [260°C]) were identified. The phase behavior between heavy crude oil (14.5°API [0.969 g/cm3]) and surfactant solution was determined over a temperature range from 150 to 350°F [65 to 177°C]. Regions of high interfacial activity were generated by the addition of salt to the brine phase. Interfacial tension (IFT) measurements confirmed the high salinity requirement of the selected surfactant/brine/oil system at elevated temperature. High-temperature (200 to 350°F [93 to 177°C]) surfactant floods were performed to study the effect of several variables on tertiary oil recovery. Variables studied included preflush slug size, surfactant slug size, surfactant concentration, flood temperature, core material, and mobility control. Improved oil recovery was obtained when a salinity-gradient flood design was used. For the most favorable systems, incremental oil recoveries up to 14% PV were achieved. Estimates of field performance indicate an 8 to 32% increase in oil recovery when surfactant is used with steam.