Method of scavenging hydrogen sulfide from sour gas well using mineral oil nanoemulsions

1 . A method of scavenging hydrogen sulfide from a sour gas well, comprising:

injecting a nanoemulsion through a borehole into a subterranean geological formation comprising a gaseous hydrocarbon composition comprising hydrogen sulfide,

wherein the nanoemulsion comprises a mineral oil, water, a surfactant, and an additive,

wherein the water is a continuous phase of the nanoemulsion,

wherein the surfactant is selected from a group consisting of a sodium dodecylbenzenesulfonate, a cetyltrimethylammonium bromide, and a nonionic polyoxyethylene detergent,

wherein the additive is selected from a group consisting of a silver salt and a copper salt when the surfactant is the sodium dodecylbenzenesulfonate or the nonionic polyoxyethylene detergent, and wherein the additive is the copper salt when the surfactant is the cetyltrimethylammonium bromide,

circulating the nanoemulsion in the borehole in the subterranean geological formation to contact the nanoemulsion with the hydrocarbon composition; and

reacting the nanoemulsion with the hydrogen sulfide in the gaseous hydrocarbon composition to form a production gas comprising less than 5 ppm of hydrogen sulfide,

wherein the nanoemulsion is circulated in the borehole while the borehole is sealed under static pressure, and

wherein a mineral oil phase of the nanoemulsion has an average particle size of 20 to 200 nm.

2 . The method of claim 1 , wherein a volumetric ratio of the mineral oil to the water in the nanoemulsion is from 1:3 to 1:5, and the nanoemulsion consists of the mineral oil, water, the surfactant, and the additive; and

wherein the additive is present in the nanoemulsion in an amount of 0.1 to 1 percent by weight (wt. %) based on a total weight of the nanoemulsion and selected from the group consisting of the silver salt and the copper salt.

3 . The method of claim 1 , wherein the nanoemulsion comprises the surfactant in an amount of 0.5 to 5 percent wt. % based on a total weight of the nanoemulsion.

4 . The method of claim 1 , wherein the subterranean geological formation further comprises a liquid hydrocarbon composition.

5 . The method of claim 1 , wherein the surfactant is the nonionic polyoxyethylene detergent, the additive is the silver salt, and a breakthrough time of the hydrogen sulfide is 720 to 760 minutes.

6 . The method of claim 1 , wherein the surfactant is the cetyltrimethylammonium bromide, the additive is the copper salt, and a breakthrough time of the hydrogen sulfide is 1140 to 1180 minutes.

7 . The method of claim 1 , wherein the surfactant is the nonionic polyoxyethylene detergent, the additive is the copper salt, and the breakthrough time of the hydrogen sulfide is 1110 to 1160 minutes.

8 . The method of claim 1 , wherein the surfactant is the sodium dodecylbenzenesulfonate, the additive is the copper salt, and the breakthrough time of the hydrogen sulfide is 1070 to 1110 minutes.

9 . The method of claim 1 , wherein the surfactant is the cetyltrimethylammonium bromide, the additive is the copper salt, and a zeta potential of the nanoemulsion is 67 to 77 mV.

10 . The method of claim 1 , wherein the surfactant is the sodium dodecylbenzenesulfonate, the additive is the copper salt, and a zeta potential of the nanoemulsion is −80 to −70 mV.

11 . The method of claim 1 , further comprising:

aging the nanoemulsion for 25 to 35 days before the injecting.

12 . The method of claim 11 , wherein the surfactant is the nonionic polyoxyethylene detergent, the additive is the silver salt, and a breakthrough time of the hydrogen sulfide is 480 to 510 minutes.

13 . The method of claim 11 , wherein the surfactant is the cetyltrimethylammonium bromide, the additive is the copper salt, and a breakthrough time of the hydrogen sulfide is 1100 to 1130 minutes.

14 . The method of claim 11 , wherein the surfactant is the cetyltrimethylammonium bromide, the additive is the copper salt, and a zeta potential of the nanoemulsion is 60 to 70 mV.

15 . The method of claim 11 , wherein the surfactant is the nonionic polyoxyethylene detergent, the additive is the copper salt, and the breakthrough time of the hydrogen sulfide is 1090 to 1130 minutes.

16 . The method of claim 11 , wherein the surfactant is the sodium dodecylbenzenesulfonate, the additive is the copper salt, and the breakthrough time of the hydrogen sulfide is 1060 to 1100 minutes.

17 . A method of scavenging hydrogen sulfide from a sour gas well, comprising:

injecting a nanoemulsion through a borehole into a subterranean geological formation comprising a gaseous hydrocarbon composition comprising hydrogen sulfide,

wherein the nanoemulsion comprises a mineral oil, water, a surfactant, and an additive,

wherein the water is a continuous phase of the nanoemulsion,

wherein the surfactant is a sodium dodecylbenzenesulfonate and the additive is a silver salt,

circulating the nanoemulsion in the borehole in the subterranean geological formation to contact the nanoemulsion with the hydrocarbon composition; and

reacting the nanoemulsion with the hydrogen sulfide in the gaseous hydrocarbon composition to form a production gas comprising less than 5 ppm of hydrogen sulfide,

wherein a breakthrough time of the hydrogen sulfide is 720 to 760 minutes.

18 . The method of claim 17 , wherein a zeta potential of the nanoemulsion is −84 to −74 mV.

19 . The method of claim 17 , further comprising:

aging the nanoemulsion for 25 to 35 days before the injecting,

wherein a breakthrough time of the hydrogen sulfide is 710 to 750 minutes, and

wherein a zeta potential of the nanoemulsion is −75 to −67 mV.

20 . A method of scavenging hydrogen sulfide from a sour gas well, comprising:

injecting a nanoemulsion through a borehole into a subterranean geological formation comprising a gaseous hydrocarbon composition comprising hydrogen sulfide,

wherein the nanoemulsion comprises a mineral oil, water, a surfactant, and an additive,

wherein the water is a continuous phase of the nanoemulsion,

wherein the surfactant is selected from a group consisting of a sodium dodecylbenzenesulfonate and a nonionic polyoxyethylene detergent,

wherein the additive is a silver salt,

circulating the nanoemulsion in the borehole in the subterranean geological formation to contact the nanoemulsion with the hydrocarbon composition; and

reacting the nanoemulsion with the hydrogen sulfide in the gaseous hydrocarbon composition to form a production gas comprising less than 5 ppm of hydrogen sulfide.