Abstract: An aqueous sol used in CO2 foam flooding, one of EOR flooding methods for recovering crude oil by injection into the oil reservoir of an onshore or offshore oil field, the aqueous sol increasing foam stability even over a substantial period of time, at high temperatures and pressures, and in salt water, thus improving crude oil recovery rate. The aqueous sol for increasing stability of froth or emulsion in a mixture containing carbon dioxide, water, and oil in CO2 foam flooding of EOR, the sol including silica particles having an average particle diameter of 1 to 100 nm as measured by dynamic light scattering and having surfaces at least partially coated with a silane compound having a hydrolyzable group, the silica particles serving as a dispersoid and dispersed in an aqueous solvent having a pH of 1.0 to 6.0 serving as a dispersion medium.

Abstract: An aqueous sol used in CO2 foam flooding, one of EOR flooding methods for recovering crude oil by injection into the oil reservoir of an onshore or offshore oil field, the aqueous sol increasing foam stability even over a substantial period of time, at high temperatures and pressures, and in salt water, thus improving crude oil recovery rate. The aqueous sol for increasing stability of froth or emulsion in a mixture containing carbon dioxide, water, and oil in CO2 foam flooding of EOR, the sol including silica particles having an average particle diameter of 1 to 100 nm as measured by dynamic light scattering and having surfaces at least partially coated with a silane compound having a hydrolyzable group, the silica particles serving as a dispersoid and dispersed in an aqueous solvent having a pH of 1.0 to 6.0 serving as a dispersion medium.

Abstract: An aqueous sol used in CO2 foam flooding, one of EOR flooding methods for recovering crude oil by injection into the oil reservoir of an onshore or offshore oil field, the aqueous sol increasing foam stability even over a substantial period of time, at high temperatures and pressures, and in salt water, thus improving crude oil recovery rate. The aqueous sol for increasing stability of froth or emulsion in a mixture containing carbon dioxide, water, and oil in CO2 foam flooding of EOR, the sol including silica particles having an average particle diameter of 1 to 100 nm as measured by dynamic light scattering and having surfaces at least partially coated with a silane compound having a hydrolyzable group, the silica particles serving as a dispersoid and dispersed in an aqueous solvent having a pH of 1.0 to 6.0 serving as a dispersion medium.

Abstract: There is provided a highly branched hydrocarbon based surfactant for stabilizing a water/supercritical carbon dioxide microemulsion. A surfactant comprising: a sulfate compound of Formula (1): R1—OSO3M??(1) (where R1 is a C6-30 hydrocarbon group having a branched chain; and M is a hydrogen atom, an alkali metal, ammonium, a basic amino acid residue, an alkanolamine residue having a C2-3 hydroxyalkyl group, or an aliphatic alkanolammonium) for stabilizing a water/supercritical carbon dioxide microemulsion.

Abstract: There is provided a highly branched hydrocarbon based surfactant for stabilizing a water/supercritical carbon dioxide microemulsion. A surfactant comprising: a sulfate compound of Formula (1): R1—OSO3M??(1) (where R1 is a C6-30 hydrocarbon group having a branched chain; and M is a hydrogen atom, an alkali metal, ammonium, a basic amino acid residue, an alkanolamine residue having a C2-3 hydroxyalkyl group, or an aliphatic alkanolammonium) for stabilizing a water/supercritical carbon dioxide microemulsion.

Abstract: A surfactant for water/supercritical carbon dioxide microemulsions that can achieve high water dispersion ability, water/supercritical carbon dioxide microemulsion forming ability under a moderate condition, and high water solubilization rate and that reduces burden on the environment and ecosystem. Provided are a surfactant for stabilizing a water/supercritical carbon dioxide microemulsion including a compound of Formula (I) and a water/supercritical carbon dioxide microemulsion including the surfactant.

Abstract: There is provided a highly branched hydrocarbon based surfactant for stabilizing a water/supercritical carbon dioxide microemulsion. A surfactant comprising: a sulfate compound of Formula (1): R1—OSO3M ??(1) (where R1 is a C6-30 hydrocarbon group having a branched chain; and M is a hydrogen atom, an alkali metal, ammonium, a basic amino acid residue, an alkanolamine residue having a C2-3 hydroxyalkyl group, or an aliphatic alkanolammonium) for stabilizing a water/supercritical carbon dioxide microemulsion.

Abstract: A surfactant for water/supercritical carbon dioxide microemulsions that can achieve high water dispersion ability, water/supercritical carbon dioxide microemulsion forming ability under a moderate condition, and high water solubilization rate and that reduces burden on the environment and ecosystem. Provided are a surfactant for stabilizing a water/supercritical carbon dioxide microemulsion including a compound of Formula (1) and a water/supercritical carbon dioxide microemulsion including the surfactant.