Determining residual oil saturation by injecting salts of carbonic and halocarboxylic acids

Claim 1

In a process in which a reactant-containing aqueous solution is injected into a subterranean reservoir to form tracers having different partition coefficients with mobile water and immobile oil phases of the fluid in the reservoir and measurements are made of the amounts by which the tracers are chromatographically separated in order, to determine the relative concentrations of those phases, an improvement which comprises: injecting as said tracer-forming solution an aqueous liquid which, before or soon after entering the reservoir, contains dissolved salts of at least one halocarboxylic acid in contact with at least one salt of carbonic acid in kinds and amounts suitable for reacting within the reservoir to form CO 2 and salts of water soluble acids in amounts such that measurable proportions of CO 2 are partitioned between mobile and immobile phases of the reservoir fluids and anions of said acids are dissolved substantially completely within the mobile phase of the reservoir fluid.