Method for drilling a wellbore with a weighted hydrogen sulfide scavenger fluid
A drilling fluid composition comprising an aqueous base fluid, a viscosifier, and a H 2 S scavenger comprising copper nitrate, wherein the drilling fluid composition has a H 2 S 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.
1. A method of drilling a wellbore with a weighted H 2 S scavenger fluid, comprising:
driving a drill bit to form the wellbore into a subterranean geological formation thereby producing a formation fluid that contains H 2 S; 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 weighting agent in an amount of from 5 wt % to 15 wt % based on the total weight of the drilling fluid composition,
a viscosifier in an amount of from 0.5 to 5.0 wt %, based on the total weight of the drilling fluid composition, and
a H 2 S scavenger consisting of copper nitrate, and
wherein copper nitrate present in the drilling fluid composition reacts with H 2 S 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.
2. The method of claim 1 , wherein the wellbore is a horizontal or a multilateral wellbore.
3. The method of claim 1 , wherein a temperature of the wellbore ranges from 50 to 200° C.
4. 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 H 2 S, and
wherein a corrosion rate of the casing is no more than 0.0006 lb/ft 2 after 6 hours of contacting with the drilling fluid composition.
5. The method of claim 4 , wherein the corrosion rate of the casing is no more than 0.00084 lb/ft 2 after 24 hours of contacting with the drilling fluid composition.
6. 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 H 2 S in the formation fluid is no more than 40 ppm.
7. 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.