Monovalent brine-based reservoir drilling fluid
Wellbore fluids may contain an aqueous base fluid comprising a monovalent brine, a modified starch, and a metal oxide. Methods of using wellbore fluids may include drilling a subterranean well while circulating a wellbore fluid into the subterranean well, wherein the wellbore fluid contains an aqueous base fluid comprising a monovalent brine, a modified starch, and a metal oxide.
1. A method of drilling a subterranean well, the method comprising:
drilling the subterranean well while circulating a wellbore fluid in the subterranean well, wherein the wellbore fluid comprises:
an aqueous base fluid comprising a monovalent brine;
a modified starch; and
a mixture of divalent metal oxides present at a concentration ranging from 2 pounds per barrel (ppb) to 5 ppb; wherein the wellbore fluid has no more than 3 wt % of alkaline earth metal in the wellbore fluid.
2. The method of claim 1 , wherein the modified starch of the wellbore fluid is within a range of 3 ppb to 18 ppb.
3. The method of claim 1 , wherein the wellbore fluid is used to drill a producing interval of the well.
4. A method of completing a wellbore, the method comprising:
drilling the wellbore with a wellbore fluid to form a filter cake on walls thereof, the wellbore fluid comprising:
an aqueous base fluid comprising a monovalent brine;
a modified starch; and
a mixture of divalent metal oxides present at a concentration ranging from 2 pounds per barrel (ppb) to 5 ppb; wherein the wellbore fluid has no more than 3 wt % of alkaline earth metal in the wellbore fluid;
emplacing a breaker fluid into the wellbore; and
shutting in the wellbore for a period of time sufficient to initiate breaking of the filter cake.
5. The method of claim 4 , further comprising:
gravel packing at least one interval of the wellbore.
6. The method of claim 4 , further comprising:
circulating a wash fluid through the wellbore prior to and/or after emplacing the breaker fluid.
7. The method of claim 4 , wherein the modified starch comprises at least one of corn, wheat, rice, tapioca, sago, waxy maize, waxy rice, sorghum, potato, and pea as a starch source.
8. The method of claim 4 , wherein the mixture of divalent metal oxides comprises magnesium oxide (MgO), calcium oxide (CaO), or zinc oxide (ZnO).
9. The method of claim 4 , wherein the modified starch of the wellbore fluid is within a range of 3 ppb to 18 ppb.