Sweetening of sour gas wells

1 . A well system, comprising:

a production tubing disposed in a wellbore from a terranean surface into a subterranean zone to a first depth in the wellbore, the subterranean zone comprising a formation fluid that comprises a hydrocarbon fluid having a first concentration of an acid gas, the first concentration being greater than a threshold concentration of acid gas; and

a second tubing disposed in the wellbore and within the production tubing to a second depth in the wellbore less than the first depth, the second tubing comprising an outlet configured to circulate a second fluid into the formation fluid disposed in the production tubing, the outlet disposed at a longitudinal end of the second tubing at the second depth, the second depth between 500 feet and 2,000 feet, and the second fluid configured to dilute the formation fluid in the production tubing to a second concentration of the acid gas that is less than the threshold concentration.

2 . The well system of claim 1 , further comprising a well head disposed at the terranean surface to support the production tubing in the wellbore, the well head comprising an insertion spool connected to the second tubing independently from the production tubing.

3 . The well system of claim 2 , wherein the second tubing comprises a flexible well tubing supported within the production tubing by the insertion spool.

4 . The well system of claim 3 , wherein the flexible well tubing comprises coiled tubing.

5 . The well system of claim 2 , wherein the second tubing is fluidly connected to a source of the second fluid, the source of the second fluid comprising at least one of a sweet gas pipeline, a second wellbore, or a fluid treatment facility.

6 . The well system of claim 1 , wherein the outlet of the second tubing comprises a nozzle configured to inject the second fluid into the formation fluid in the production tubing.

7 . The well system of claim 1 , wherein the outlet of the second tubing comprises a plurality of perforations through the second tubing, the plurality of perforations configured to direct injection of the second fluid into the formation fluid in the production tubing.

8 . The well system of claim 1 , wherein the second fluid comprises a sweet gas comprising a concentration of the acid gas that is less than 20 parts per million.

9 . The well system of claim 1 , wherein the second tubing comprises a fluid valve configured to control a flow of the second fluid out of the outlet.

10 . A method, comprising:

supporting a production tubing in a wellbore from a terranean surface into a subterranean zone to a first depth in the wellbore, the subterranean zone comprising a formation fluid that comprises a hydrocarbon fluid having a first concentration of an acid gas, the first concentration being greater than a threshold concentration of acid gas;

supporting a second tubing in the wellbore and within the production tubing to a second depth in the wellbore less than the first depth, the second depth between 500 feet and 2,000 feet in the wellbore;

guiding, with the second tubing, a second fluid to an outlet of the second tubing at a longitudinal end of the second tubing at the second depth; and

circulating, with the outlet of the second tubing, the second fluid into the formation fluid disposed in the production tubing, the second fluid configured to dilute the formation fluid in the production tubing to a second concentration of the acid gas that is less than the threshold concentration.

11 . The method of claim 10 , wherein supporting the second tubing in the wellbore and within the production tubing comprises supporting, with an insertion spool of a wellhead, the second tubing independently from the production tubing.

12 . The method of claim 11 , wherein guiding the second fluid to the outlet comprises guiding the second fluid from a fluid source through the second tubing, the fluid source comprising at least one of a sweet gas pipeline, a second wellbore, or a fluid treatment facility, the second tubing being fluidly connected to the fluid source.

13 . The method of claim 12 , wherein the fluid source comprises the second wellbore,

the method comprising producing sweet gas from the second wellbore, and

at least a portion of the second fluid is sourced from the sweet gas from the second wellbore.

14 . The method of claim 12 , wherein the fluid source comprises the fluid treatment facility,

the method comprising receiving, at the second tubing, a sweet gas from the fluid treatment facility, and

at least a portion of the second fluid is sourced from the sweet gas from the fluid treatment facility.

15 . The method of claim 10 , wherein the outlet comprises a nozzle, and circulating the second fluid into the formation fluid disposed in the production tubing comprises injecting, with the nozzle, the second fluid into the formation fluid in the production tubing.

16 . The method of claim 10 , wherein the outlet comprises a plurality of perforations through the second tubing, and circulating the second fluid into the formation fluid disposed in the production tubing comprises injecting, with the plurality of perforations, the second fluid into the formation fluid in the production tubing.

17 . The method of claim 10 , wherein the second fluid comprises a sweet gas comprising a concentration of the acid gas that is less than 20 parts per million, and

in response to circulating the second fluid into the formation fluid, producing a diluted formation fluid having a concentration of the acid gas that is less than the threshold concentration.

18 . The method of claim 10 , comprising controlling, with a fluid valve in the second tubing, a flow of the second fluid to the outlet.