Miscible Waterflooding Using a Phosphate Ester Solubilizer

Abstract

Abstract A simple micellar solution or microemulsion has been tested for its oil displacement capabilities in a sandstone core. The micellar solution was prepared using crude oil, water and a phosphate prepared using crude oil, water and a phosphate ester surfactant. Phase studies at 74 degrees F showed that a micellar solution existed when the phosphate ester surfactant concentration was 4 to 8 percent by volume or greater in a sour crude oil and water system. Similar concentration requirements were exhibited by a sweet crude oil-water system. Tests at elevated temperatures showed that the microemulsions tended to degrade as temperature was increased. Partial and total neutralization of the acid surfactant improved the microemulsions tolerance of higher temperatures. Oil displacement tests showed that the micellar solution employed was capable of displacing 90 percent of the core's oil saturation. Slug floods of 30 percent PV and larger yielded an oil displacement percent PV and larger yielded an oil displacement efficiency of 90 percent also. Water-driven slugs were employed. Displacement efficiencies exhibited by oil-rich and water-rich micellar solutions were slightly different. These differences are explored via dilution arguments. Introduction Numerous patents and publications have appeared regarding the use of micellar solutions or microemulsions for secondary recovery of oil and the stimulation of water injection wells. These papers report the use of certain petroleum sulfonates as the solubilizing agent. The excellent capabilities of the petroleum sulfonates has been demonstrated. The purpose of this study was to explore the oil displacement merits and certain phase characteristics presented by a different solubilizer - a mono substituted presented by a different solubilizer - a mono substituted ortho phosphate ester. The surfactant employed is manufactured by BASF Wyandotte Corp. and marketed as KLEARFAC AA-420. This surfactant is an anionic, biodegradable liquid that exhibits solubilizing properties within a broad pH spectrum 17 Used primarily in metal cleaning and textile processing, its capability of recovering oil has not been previously studied. Preliminary phase behavior studies showed that KLEARFAC AA-420 was an excellent solubilizer of crude oil and water. This characteristic prompted a series of oil displacement tests plus further phase behavior tests at elevated temperatures.