Colloidal-crystal quantum dots as tracers in underground formations

Patent metadata

Field	Value
Publication number	US-10125601-B2
Application number	US-201113041276-A
Country	US
Kind code	B2
Filing date	Mar 4, 2011
Priority date	Mar 4, 2010
Publication date	Nov 13, 2018
Grant date	Nov 13, 2018

Abstract

Colloidal-crystal quantum dots as tracers are disclosed. According to one embodiment, a method comprises injecting a solution of quantum dots into a subterranean formation, and monitoring a flow of the quantum dots from the subterranean formation to determine a property of the subterranean formation.

First claim

What is claimed is:

1. A method, comprising:
injecting a solution of independent and distinct quantum dot tracers containing one or more quantum dots surface-modified with ligands that render the quantum dots water-soluble into a subterranean formation, and monitoring a flow of the quantum dot tracers from the subterranean formation to determine a pore volume of the subterranean formation, wherein the quantum dot tracers have a diameter of about 1 nm to about 150 nm, and wherein the quantum dot tracers are also thermally stable in a hydrothermal environment, wherein at least one of:
the quantum dot tracers comprise a combination of conservative and reactive tracers,
the quantum dot tracers comprise conservative tracers and the solution further comprises a supplemental reactive tracer, or
the quantum dot tracers comprise reactive tracers and the solution further comprises a supplemental conservative tracer.

2. The method of claim 1 , wherein the quantum dots have a core-shell structure.

3. The method of claim 1 , wherein the quantum dots include a semiconductor material substantially encapsulated by a layer composed of oxides of silicon, titanium, zinc, tungsten, molybdenum, copper, iron, nickel, tin, niobium, aluminum, cadmium, and mixed metal oxides from compounds listed above.

4. The method of claim 1 , wherein the monitoring is done using size exclusion chromatography with a fluorescent detector.

5. The method of claim 1 , wherein the method further comprises the step of fracturing the subterranean formation prior to the injecting of the quantum dot tracers.

6. The method of claim 1 , wherein the injecting step occurs simultaneously with the step of fracturing the subterranean formation.

7. The method of claim 1 , wherein the subterranean formation is a geothermal reservoir.

8. The method of claim 1 , wherein the subterranean formation is an oil reservoir.

9. The method of claim 1 , wherein the quantum dot tracers include a continuous silica film enclosing the quantum dots.

10. The method of claim 1 , further comprising varying the diameter of the quantum dot tracers to vary the diffusivity of the quantum dot tracers.

11. The method of claim 1 , wherein the quantum dots comprises a semiconductor material.

12. The method of claim 11 , wherein the semiconductor material is selected from the group consisting of cadmium, lead, zinc, mercury, gallium, indium, cobalt, nickel, iron, or copper as a cationic component and sulfide, selenide, telluride, oxide, phosphide, nitride, or arsenide as an anionic component and combinations thereof.

13. The method of claim 1 , wherein the quantum dots include a scale inhibitor attached thereto.

14. The method of claim 13 , wherein the scale inhibitor is selected from the group consisting of polycarboxylates, polacrylates, polymaleic anhydrides, and combinations thereof.

15. The method of claim 1 , wherein determining a pore volume of the subterranean formation includes quantifying a flow-rate of the quantum dot tracers and calculating a pore volume of the subterranean formation based upon the flow rate of the quantum dot tracers.

16. The method of claim 15 , wherein the flow-rate is quantified using the flow of quantum dot tracers from the subterranean formation.

17. The method of claim 15 , wherein the flow-rate is quantified using the quantum dot tracers within the subterranean formation.

18. The method of claim 1 , wherein the ligands are hydrophilic ligands.

19. The method of claim 18 , wherein the hydrophilic ligands are an alkane, alkene, or alkyne functionalized with one or more transit control groups selected from the group consisting of: thiol groups, amine groups, hydroxyl groups, carboxy, and amide groups, citrate groups, halide groups, and combinations thereof.

20. The method of claim 18 , wherein the hydrophilic ligand is attached to the quantum dot through a coupling group selected from the group consisting of amino coupling groups, mercapto coupling groups, hydroxyl coupling groups, carboxy-silane coupling group, and combinations thereof.

21. The method of claim 1 , wherein the quantum dot tracers comprise a plurality of the quantum dots substantially encapsulated into a single oxide nanosphere.

22. The method of claim 21 , wherein the oxide nanosphere includes a plurality of quantum dots that all fluoresce at a common wavelength.

23. The method of claim 21 , wherein the oxide nanosphere includes an organic polymeric compound.

24. The method of claim 1 , wherein the quantum dot tracers are injected with a carrier fluid.

25. The method of claim 24 , wherein the carrier fluid is selected from the group consisting of water, fracture fluids, petroleum-based solvents, and combinations thereof.

Assignees

• Rose Peter E
• Bartl Michael H
• Univ Utah Res Found

Inventors

• Rose Peter E
• Bartl Michael H

Classifications

• E21B47/1015 Primary

  Fixed Constructions · mapped topic

• E21B47/11 Primary

  using tracers; using radioactivity · CPC title