Evaluating drill-in fluid performance in a wellbore

1. A system comprising:

a neutron source positionable within a wellbore to emit one or more neutrons toward a formation surrounding the wellbore;

a gamma ray detector positionable within the wellbore to detect gamma rays;

a gamma ray analyzer comprising one or more processors and a non-transitory computer-readable medium storing instructions that are executable by the one or more processors to cause the gamma ray analyzer to perform operations including:

receiving data indicating detected gamma rays from the gamma ray detector;

determining, from the data indicating the detected gamma rays, an amount of activated tracer material present within the wellbore that originates from non-radioactive tracer material of drill-in fluid; and

determining, from the amount of activated tracer material, an amount of filtercake buildup on a wellbore wall, a depth of fluid-loss filtrate into the formation surrounding the wellbore, or a combination thereof.

2. The system of claim 1 , wherein the gamma ray analyzer is positionable at a surface of the wellbore.

3. The system of claim 1 , wherein the neutron source and the gamma ray detector are coupleable to a wireline, a slickline, coiled tubing, a downhole tractor, or drill pipe.

4. The system of claim 1 , wherein the neutron source is positionable within the wellbore to activate the non-radioactive tracer material of the filtercake or the fluid-loss filtrate to generate the activated tracer material that emits the gamma rays detected by the gamma ray detector.

5. The system of claim 1 , wherein the non-radioactive tracer material comprises an element from the lanthanide series.

6. The system of claim 1 , wherein the drill-in fluid comprises an aqueous base fluid and the non-radioactive tracer material.

7. The system of claim 1 , wherein the non-radioactive tracer material is present in an amount from 0.01% to 1% weight by volume of the drill-in fluid.

8. The system of claim 1 , wherein the gamma ray detector comprises a set of three gamma ray detectors in a linear arrangement.

9. A method, comprising:

depositing a drill-in fluid comprising a non-radioactive tracer material into a wellbore within a drill-in portion of a formation during a drill-in operation;

emitting, by a neutron source, neutrons into a drill-in portion of the formation surrounding the wellbore to generate activated tracer material from the non-radioactive tracer material;

receiving, at a gamma ray detector, gamma rays from the activated tracer material;

determining whether the gamma rays originate from the activated tracer material located within a filtercake, from the activated tracer material located within a fluid-loss filtrate, or both; and

determining, using data associated with the gamma rays, an amount of filtercake buildup of the filtercake on a wellbore wall, a depth of the fluid-loss filtrate into the formation surrounding the wellbore, or a combination thereof.

10. The method of claim 9 , wherein the drill-in portion of the formation comprises a reservoir containing hydrocarbons.

11. The method of claim 9 , further comprising:

emitting, by the neutron source, neutrons into a second portion of the formation different from the drill-in portion of the formation;

receiving, at the gamma ray detector, background gamma rays from the formation;

establishing, using data associated with the background gamma rays, a background energy spectrum of the formation; and

determining, using the data associated with the gamma rays and the background energy spectrum, the amount of filtercake buildup, the depth of the fluid-loss filtrate, or the combination thereof.

12. The method of claim 9 , wherein the drill-in fluid further comprises an aqueous base fluid, a viscosifier, a relative permeability modifier fluid loss control additive, and a degradable bridging agent comprising a degradable material capable of undergoing an irreversible degradation downhole.

13. The method of claim 9 , wherein the non-radioactive tracer material comprises an element selected from the group consisting of:

aluminum, barium, beryllium, cadmium, cerium, chromium, cobalt, copper, dysprosium, erbium, europium, gadolinium, gold, holmium, iodine, iridium, lanthanum, lead, lutetium, magnesium, manganese, molybdenum, neodymium, nickel, phosphorous, praseodymium, promethium, rhenium, samarium, silver, technetium, terbium, thulium, titanium, tungsten, vanadium, ytterbium, zinc, any derivative thereof, and any combination thereof.

14. The method of claim 9 , wherein the non-radioactive tracer material comprises an element from the lanthanide series.

15. The method of claim 9 , further comprising:

conveying the neutron source and the gamma ray detector downhole within the wellbore using a wireline, a slickline, coiled tubing, a downhole tractor, or drill pipe.

16. The method of claim 9 , wherein the non-radioactive tracer material comprises an element from the lanthanide series.

17. A drill-in fluid, comprising:

a base fluid;

a viscosifier;

a relative permeability modifier fluid loss control additive, a degradable bridging agent comprising a degradable material capable of undergoing an irreversible degradation downhole, or both; and

a non-radioactive tracer material capable of being activated by exposure to neutrons to generate an activated tracer material that emits gamma rays that are detectable by a gamma ray detector within a wellbore;

wherein the gamma rays that are detectable by the gamma ray detector are capable of being analyzed to determine filtercake buildup on a wellbore wall of the wellbore, a depth of fluid-loss filtrate into a formation surrounding the wellbore, or a combination thereof.

18. The drill-in fluid of claim 17 , wherein the non-radioactive tracer material comprises an element from the lanthanide series.

19. The drill-in fluid of claim 17 , wherein the non-radioactive tracer material comprises an element selected from the group consisting of:

aluminum, barium, beryllium, cadmium, cerium, chromium, cobalt, copper, dysprosium, erbium, europium, gadolinium, gold, holmium, iodine, iridium, lanthanum, lead, lutetium, magnesium, manganese, molybdenum, neodymium, nickel, phosphorous, praseodymium, promethium, rhenium, samarium, silver, technetium, terbium, thulium, titanium, tungsten, vanadium, ytterbium, zinc, any derivative thereof, and any combination thereof.

20. The drill-in fluid of claim 17 , wherein the non-radioactive tracer material is present in an amount from 0.01% to 1% weight by volume of the drill-in fluid.