Bentonite-based grouts and related methods

A method of using a grout fluid, which comprises:

• providing a grout fluid consisting essentially of water and a bentonite-based grout, wherein the bentonite-based grout consists of from about 30 to about 40 weight percent (wt %) calcium carbonate based on a total weight of the bentonite-based grout, a bentonite, and one or more grout-setting modifiers, and excludes cementitious materials that (i) when mixed with a liquid form a plastic paste and harden or (ii) harden under dry conditions;
• introducing the grout fluid into a borehole in the earth so that the grout fluid is in contact with sidewalls of the borehole and fills the borehole;
• and
• allowing the grout fluid to set in the borehole, wherein after setting, the grout fluid has a hydraulic conductivity of between 1×10−7 cm/s and 1×10−9 cm/s.

A method of using a grout fluid, which comprises:

• providing a grout fluid consisting essentially of water and a bentonite-based grout, wherein the bentonite-based grout consists of from about 30 to about 40 weight percent (wt %) calcium carbonate based on a total weight of the bentonite-based grout, sodium bentonite, ammonium sulfate, and one or more thermally conductive materials and excludes cementitious materials that (i) when mixed with a liquid form a plastic paste and harden or (ii) harden under dry conditions;
• introducing the grout fluid into a borehole in the earth so that the grout fluid is in contact with sidewalls of the borehole and fills the borehole;
• and
• allowing the grout fluid to set in the borehole, wherein after setting, the grout fluid has a hydraulic conductivity of between 1×10−7 cm/s and 1×10−9 cm/s.