Determination of residual oil in a subterranean formation
AssigneeContinental Oil Company
InventorBurton M. Casad
Life of this patent
Estimating the term…
Abstract
A method for obtaining logging data for use in the determination of the amount of residual oil in a subterranean oil bearing formation, the method comprising the steps of logging the formation, injecting into the formation an aqueous solution of a water soluble radioactive tracer compound, logging the formation, injecting into the formation a second aqueous solution of a radioactive tracer compound which is soluble in both water and oil, and thereafter logging the formation.
Claims8
A method for obtaining logging data, for use in determination of the amount of residual oil in a subterranean oil-bearing formation which has been penetrated by the wellbore of a well and which has been subjected to waterflooding for the secondary recovery of oil therefrom, said method comprising;
- a. logging the formation to obtain logging data measurements of the natural radioactivity of the formation;
- b. injecting into the formation through said wellbore a first aqueous solution of a first compound, said first compound
- 1. being water-soluble and substantially insoluble in said residual oil;
- 2. containing at least one radioactive constituent;
- and,
- 3. being present in said first aqueous solution in an amount sufficient to provide from about 0.05 to about 5.0 microcuries of radioactivity per cc of injected fluid,
- said first aqueous solution being injected in an amount sufficient to displace substantially all of the formation water present in the zone under investigation;
- c. logging the formation after the injection of said first aqueous solution to obtain logging data measurements of the radioactivity of said formation after the injection of said first aqueous solution;
- d. injecting into said formation through said wellbore a second aqueous solution of a second compound, said second compound
- 1. being soluble in both oil and water;
- 2. having an equilibrium partition ratio, R.sub.o/w, greater than 1.0, R.sub.o/w being defined as the concentration of said second component in said residual oil divided by the concentration of said second component in water at equilibrium;
- 3. containing the same radioactive constituent present in said first compound;
- and,
- 4. being present in said second aqueous solution in an amount sufficient to provide from about 0.05 to about 5.0 microcuries of radioactivity per cc of injected fluid
- said second solution being injected in a sufficient volume to result in substantial equilibrium between the concentration of said second compound in said residual oil and said second aqueous solution in said zone under investigation;
- and,
- e. logging the formation after the injection of said second aqueous solution to obtain logging data measurements of the radioactivity of said formation after the injection of said second aqueous solution.
Dependencies are inferred from the claim text.