Effect of Temperature on Degradation, Adsorption and Phase Partitioning of Surfactants Used in Steam Injection for Oil Recovery

摘要

Mobility control is one of the main problems in steam flooding. Channeling through highly permeable zones and gravity override of steam lead to early steam breakthrough at the production wells. Accordingly, volumetric sweep efficiency and oil recovery are reduced. Foam has been proposed as a permeability blocking agent in steam flooding to improve oil recovery. The aim of this study is to investigate both commercially available and experimental foaming chemicals (surfactants) for their longevity under conditions typical of those found for steam injection oil recovery, namely at 400 exp 0 F (205 exp 0 C) and 300 to 500 psia (20 to 34 bars). The adsorption of surfactants on sand and clay surfaces and the partitioning of surfactants between water and oil phases were also studied. Surfactants were subjected to steam injection conditions in pressure cylinders under a nitrogen cushion for several weeks to test for thermal degradation, adsorption, and phase partitioning. Ottawa silica sand mixed with varying percentages of clay, and/or crude oil were added to the aqueous surfactant solutions to simulate field conditions. In addition, some data were taken with varying amounts of inorganic salts typical of those found in oil field brines. Surface tension, surfactant concentration, pH and electrical conductivity were measured with time. Some commercial surfactants showed a rapid decrease in concentration and pH with heating time, while other surfactants showed better high-temperature stability, with half-lives as long as several months at 400 exp 0 F (205 exp 0 C). 72 refs., 15 figs., 13 tabs. (ERA citation 10:026766)