Miscible flooding process using methane-enriched soluble oil

Claim 1

The method defined in claim 1 wherein said soluble oil comprises an admixture of liquid hydrocarbon, surface active alkyl aryl sulfonates, and a stabilizing agent.

Claim 7

A method for recovering petroleum from a subterranean reservoir penetrated by an injection well and a production well spaced apart in the reservoir, which comprises: preparing a soluble oil comprising an admixture of a liquid hydrocarbon having a viscosity above about 0.5 centipoises at 75* F., surface active alkyl aryl sulfonates, and a stabilizing agent; simultaneously injecting through said injection well and into said reservoir about 0.01 to 0.15 pore volume of an admixture of said soluble oil and a gas containing at least about 90 mol percent methane at an elevated pressure equal to or exceeding the saturation pressure of the methane-enriched soluble oil, the methane content of said mixture being less than the saturation composition at the reservoir temperature and pressure; thereafter injecting an aqueous flooding medium through said reservoir to drive said methane-enriched soluble oil towards said production well; and recovering petroleum from said production well.

Claim 12

A method for recovering petroleum from a subterranean reservoir penetrated by an injection well and a production well spaced apart in the reservoir, which comprises: preparing a substantially anhydrous soluble oil comprising an admixture of 45 to 90 volume percent of crude petroleum, 0.5 to 8 volume percent of a partially oxygenated organic liquid stabilizing agent, 4 to 30 volume percent of a mixture of preferentially oil-soluble surface active alkyl aryl sulfonates and preferentially water-soluble alkyl aryl sulfonates, said surface active agents being present in the proportion of about 1 to 15 parts of preferentially oil-soluble sulfonates per part of said preferentially water-soluble sulfonates; simultaneously injecting through said injection well and into said reservoir a series of small slugs of said soluble oil and a gas containing at least about 90 mol percent methane at an elevated pressure whereby saId methane is dissolved in said soluble oil to form a methane-enriched soluble oil, the methane content of said methane-enriched soluble oil being less than the saturation composition at reservoir conditions of temperature and pressure, and said small slugs of said simultaneously injected soluble oil and methane being alternately injected with small slugs of low salt-content water, the volume of said small slugs of low salt-content water being not greater than the volume of said preceding slug of methane-enriched soluble oil, and the combined volume of said slugs of methane-enriched soluble oil and water amounting to about 0.01 to 0.15 reservoir pore volume; next injecting 0.1 to 0.8 reservoir pore volume of an aqueous flooding medium thickened by the addition of a small amount of a water-soluble polymer; thereafter injecting water or brine to drive said fluids towards said production well; and recovering petroleum from said production well.