Determining residual oil saturation by radioactively analyzing injected CO2 and base-generating tracer-providing solution

Claim 2

A process for determining the relative concentrations of oil and water phases in a subterranean reservoir comprising: (A) injecting into the reservoir a first reactant-containing aqueous solution which, at least soon after entering the reservoir, contains solutes that include, or become inclusive of, at least one each of (1) a detectable radioactive material, (2) a detectable amount of dissolved CO 2 , (3) a selectively water-soluble reactive material capable of substantially increasing the solution pH and thus causing a significant proportion of the dissolved CO 2 to be converted to dissolved bicarbonate ion, and (4) a detectable amount of a selectively water-soluble tracer material, whereby an aqueous solution of tracers, having different partition coefficients relative to the oil and water phases within the reservoir, is formed; (B) displacing the first aqueous solution to a selected location within the reservoir by injecting a second aqueous solution which contains substantially the same concentration of CO 2 present in the first aqueous solution prior to conversion of the CO 2 to bicarbonate but is free of any radioactive material, reactive material, or tracer material, whereby said first aqueous solution of tracers contacts the reservoir oil and CO 2 conversion occurs; (C) producing fluid from the reservoir; and (D) radioactively measuring the chromatographic separation between the arrival of at least one selectively water soluble tracer, and the arrival of the depletion in CO 2 concentration resulting from the CO 2 conversion, whereby the relative concentrations of the oil and water phases within the reservoir are determined.

Claim 3

The process of claim 1 in which the pH of the fluid being injected is adjusted to approximate that of the aqueous fluid in the reservoir being tested.

Claim 4

The process of claim 1 in which the amount of CO 2 and the kinds and amounts of the base-generating reactant are arranged to provide said significant decrease in CO 2 concentration within a selected relatively short time after being displaced into the selected location in the reservoir.

Claim 5

The process of claim 1 in which the produced fluid is produced by backflowing fluid into a well through which the aqueous solution were injected into the reservoir.

Claim 6

The process of claim 1 in which the produced fluid is produced from a well other than the one through which the aqueous solutions were injected.

Claim 7

The process of claim 1 in which the concentration of dissolved bicarbonate ion resulting from the conversion of dissolved CO 2 is detected as one tracer of the mobile fluid phase.

Claim 8

The process of claim 1 in which the concentrations of the tracers in the produced fluid are measured at the well site and the temperature of the reservoir being treated is undesirably high relative to a use of an organic ester tracer-forming material.

Claim 9

The process of claim 1 in which the selectively water-soluble tracer material is selected such that it is capable of reacting with water to form a water-soluble-only tracer material.

Claim 10

A process for determining the relative concentrations of oil and water phases in a subterranean reservoir comprising: (A) injecting into the reservoir a first aqueous solution which is substantially devoid of bicarbonate ion; (B) injecting into the reservoir a second reactant-containing aqueous solution which, at least soon after entering the reservoir, contains solutes that include, or become inclusive of, at least one each of (1) a detectable radioactive tracer material, (2) a detectable amount of dissolved CO 2 containing radioactive carbon atoms, (3) a selectively water-soluble reactive material capable of substantially increasing the solution pH and thus causing a significant proportion of the dissolved CO 2 to be converted to dissolved bicarbonate ion, and (4) a detectable amount of a selectively water-soluble tracer material, whereby an aqueous solution of tracers, having different partition coefficients relative to the oil and water phases within the reservoir, is formed; (C) displacing the first aqueous solution to a selected location within the reservoir by injecting a third aqueous solution which is substantially devoid of bicarbonate ions, radioactive material, reactive material, or tracer material, whereby said second aqueous solution of tracers contacts the reservoir oil and CO 2 conversion occurs; (D) producing fluid from the reservoir; and (E) radioactively measuring the chromatographic separation between the arrival of at least one selectively water soluble tracer, and the arrival of the depletion in CO 2 concentration resulting from the CO 2 conversion, whereby the relative concentrations of the oil and water phases within the reservoir are determined.

Claim 11

A process for determining the relative concentrations of oil and water phases in a subterranean reservoir comprising: (A) injecting into the reservoir a first aqueous solution which is substantially devoid of bicarbonate ion; (B) injecting into the reservoir a second reactant-containing aqueous solution which, at least soon after entering the reservoir, contains solutes that include, or become inclusive of, at least one each of (1) a detectable radioactive tracer material, (2) a detectable amount of dissolved CO 2 containing radioactive carbon atoms, (3) a selectively water-soluble reactive material capable of substantially increasing the solution pH and thus causing a significant proportion of the dissolved CO 2 to be converted to dissolved bicarbonate ion, and (4) a detectable amount of a selectively water-soluble tracer material, whereby an aqueous solution of tracers, having different partition coefficients relative to the oil and water phases within the reservoir, is formed; (C) displacing the first aqueous solution to a selected location within the reservoir by injecting a third aqueous solution which is substantially devoid of bicarbonate ions, radioactive material, reactive material, or tracer material, whereby said second aqueous solution of tracers contacts the reservoir oil and CO 2 conversion occurs; (D) producing fluid from the reservoir; and (E) radioactively measuring the chromatographic separation between the arrival of at least one selectively water soluble tracer, and the arrival of the depletion in CO 2 concentration resulting from the CO 2 conversion, whereby the relative concentrations of the oil and water phases within the reservoir are determined.

Claim 12

The process of claim 9 in which the second injected aqueous solution contains C 14 labeled CO 2 .

Claim 13

The process of claim 10 in which the first injected aqueous solution contains a selectively water-soluble radioactive material which provides emissions distinguishable from those of C 14 and both types of those emissions are used in detecting the arrival of the mobile phase fluid tracer.