# US 10,479,919 B2 · Method for drilling a hydrogen sulfide-containing formation

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- Number: US 10,479,919 B2
- Document ID: US10479919B2
- Status: Granted
- Kind: B2
- Application number: 16/359,100
- Filed: 2019-03-20
- Published: 2019-07-18
- Granted: 2019-11-19
- Earliest claimed: 2017-10-04
- Assignees: King Fahd University of Petroleum and Minerals
- Applicants: King Fahd University of Petroleum and Minerals
- Inventors: Salah El-Din Elkatatny; Reyad Awwad Shawabkeh; Mohamed Ahmed Nasr El-Din Mahmoud
- Web page: https://patentgrep.com/patent/US10479919B2

## CPC

- C09K 8/08: containing natural organic compounds, e.g. polysaccharides, or derivatives thereof
- C09K 8/032: {Inorganic additives}
- C09K 8/16: characterised by the inorganic compounds other than clay
- C09K 8/532: Sulfur
- E21B 21/003: {Means for stopping loss of drilling fluid (plastering the borehole wall E21B33/138)}
- E21B 41/02: in situ inhibition of corrosion in boreholes or wells
- C09K 2208/20: Hydrogen sulfide elimination
- E21B 21/062: {by mixing components}
- E21B 43/26: by forming crevices or fractures
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS

## Abstract

A drilling fluid composition comprising an aqueous base fluid, a viscosifier, and a H2S scavenger comprising copper nitrate, wherein the drilling fluid composition has a H2S sorption capacity from about 4.0 to about 6.0 gram per one milliliter of the drilling fluid composition; and a method of drilling a subterranean geological formation using thereof are provided. Various embodiments of the drilling fluid composition and the method are also provided.

## Claims

### Claim 1

A method of drilling a wellbore into a hydrogen sulfide-containing subterranean geological formation, comprising:
driving a drill bit to form the wellbore into the subterranean geological formation thereby producing a formation fluid that contains H2S; and
injecting a drilling fluid composition into the subterranean geological formation through the wellbore,
wherein the drilling fluid composition comprises
an aqueous base fluid,
a polymeric viscosifier, and
a H2S scavenger comprising copper nitrate, wherein the H2S scavenger is present in an amount of 0.5-5 lbs/bbl based on the volume of the drilling fluid composition, and
wherein copper nitrate present in the drilling fluid composition reacts with H2S present in the formation fluid to form copper sulfide;
recovering the copper sulfide from the drilling fluid composition; and
treating the copper sulfide with nitric acid to regenerate copper nitrate while concurrently forming elemental sulfur.

### Claim 2 (depends on 1)

The method of claim 1, wherein the wellbore is a horizontal or a multilateral wellbore.

### Claim 3 (depends on 1)

The method of claim 1, wherein a temperature of the wellbore ranges from 50 to 200° C.

### Claim 4 (depends on 1)

The method of claim 1,
wherein the wellbore contains a casing that is made of at least one metal selected from the group consisting of stainless steel, aluminum, and titanium, the casing is exposed to a gaseous mixture containing up to 12 vol % of H2S, and
wherein a corrosion rate of the casing is no more than 0.0006 lb/ft2 after 6 hours of contacting with the drilling fluid composition.

### Claim 5 (depends on 4)

The method of claim 4, wherein the corrosion rate of the casing is no more than 0.00084 lb/ft2 after 24 hours of contacting with the drilling fluid composition.

### Claim 6 (depends on 1)

The method of claim 1,
wherein the formation fluid is produced for at least 1 hour but no more than 4 hours, and
wherein a concentration of H2S in the formation fluid is no more than 40 ppm.

### Claim 7 (depends on 1)

The method of claim 1, further comprising:
circulating the drilling fluid composition within the wellbore for at least 30 minutes but no more than 3 hours, after the injecting.