GEL PARTICLES WITH TAGS FOR LABELING DRILL CUTTINGS

1 . A method, comprising:

providing a first liquid comprising a polymer and a first tag;

providing a drilling fluid comprising a member selected from the group consisting of an oil-based mud and a water-based mud;

combining the first liquid with the drilling fluid to form a second liquid comprising gel particles disposed in the drilling fluid, the gel particles comprising the polymer and the first tag; and

flowing the second liquid into an underground formation during drilling of the underground formation at a first time.

2 . The method of claim 1 , wherein the gel particles attach to cuttings formed while drilling the underground formation.

3 . The method of claim 2 , further comprising:

collecting the cuttings;

providing an excitation source to the cuttings; and

based on whether a fluorescence signal is measured from the cuttings, determining whether gel particles comprising the first tag are present on the cuttings.

4 . The method of claim 2 , further comprising:

collecting the cuttings;

extracting the first tag from the gel particles attached to the cuttings to form a third liquid comprising the first tag;

measuring a fluorescence of the third liquid; and

based on the measured fluorescence of the third liquid, determining a depth at which the cuttings were formed.

5 . The method of claim 1 , wherein:

the drilling fluid comprises an oil-based mud; and

the gel particles have a size of 100 μm to 2 mm.

6 . The method of claim 1 , wherein:

the drilling fluid comprises a water-based mud; and

the gel particles have a size of 1 mm to 5 mm.

7 . The method of claim 1 , wherein the gel particles comprise the first tags hydrogen-bonded to the polymer.

8 . The method of claim 1 , wherein a concentration of the first tags in the gel particles is 20 ppm to 100 ppm.

9 . The method of claim 1 , wherein a ratio of the drilling fluid to the first liquid is from 10:1 to 1000:1.

10 . The method of claim 1 , wherein the polymer comprises hydroxyl groups.

11 . The method of claim 1 , wherein the polymer has a molecular weight of 100 kD to 500 kD.

12 . The method of claim 1 , wherein the polymer comprises a member selected from the group consisting of a polyvinyl alcohol (PVOH), a modified PVOH, a PVOH copolymer, a modified PVOH copolymer, a guar gum, a polysaccharide, a polyacrylamide, a polyacrylic acid, and a butendiol vinyl alcohol (BVOH).

13 . The method of claim 1 , wherein the first tag comprises a member selected from the group consisting of a dye, a metal complex and a halide-substituted organic acid.

14 . The method of claim 1 , further comprising:

providing a fourth liquid comprising a polymer and a second tag;

providing the drilling fluid;

combining the fourth liquid with the drilling fluid to form a fifth liquid comprising gel particles disposed in the drilling fluid, the gel particles comprising the polymer and the second tag; and

flowing the fifth liquid into an underground formation during drilling of the underground formation at a second time,

wherein:

the second tag is different from the first tag; and

the second time is different from the first time.

15 . The method of claim 14 , wherein the gel particles comprising the second tag attach to cuttings formed while drilling the underground formation.

16 . The method of claim 15 , further comprising:

collecting the cuttings;

providing an excitation source to the cuttings; and

based on whether a fluorescence signal is measured from the cuttings, determining whether gel particles comprising the second tag are present on the cuttings.

17 . The method of claim 15 , further comprising:

collecting the cuttings;

extracting the second tag from the gel particles attached to the cuttings to form a sixth liquid comprising the second tag;

measuring a fluorescence of the sixth liquid; and

based on the measured fluorescence of the sixth liquid, determining a depth at which the cuttings were formed.

18 . The method of claim 1 , wherein the second liquid is flowed into the underground formation via a drill pipe.

19 . A system comprising:

a first liquid comprising a polymer;

a second liquid comprising a tag;

a mixer configured to mix the first and second liquids to provide a third liquid comprising the polymer and the tag; and

a drill configured to drill a borehole into an underground formation, the drill comprising a line configured to circulate a drilling fluid in the borehole, the drilling fluid comprising a member selected from the group consisting of a water-based mud and an oil-based mud,

wherein:

an output of the mixer is in fluid communication with the line so that, during use of the system:

the third liquid flows from the mixer to the line to combine the third liquid and the drilling fluid;

combining the third liquid and the drilling fluid forms a fourth fluid which comprises gel particles; and

the gel particles comprises the polymer bonded with the tag.

20 . The system of claim 19 , wherein:

the drill forms cuttings during the drilling and the drilling fluid circulates the cuttings to a surface above the underground formation; and

the gel particles attach to at least a portion of the cuttings.