This invention provides zinc-free aqueous brine compositions. These zinc-free aqueous brine compositions have a density of about 14.3 pounds per gallon or more, and a true crystallization temperature of about 20° F. or less, and comprise water and one or more inorganic bromide salts, with the provisos that when calcium bromide is present, one or more other water-soluble inorganic salts are also present, when lithium bromide is present, calcium bromide is absent, when bismuth(III) bromide is present, one or more other water-soluble inorganic salts are also present, and for a true crystallization temperature of about 10° F. or less, when manganese(II) bromide is present, one or more other water-soluble inorganic salts are also present.
Processes for forming these zinc-free aqueous brine compositions are also provided.

A method for drilling a tunnel through a formation must address environmental concerns. One tunneling method comprises the steps of: preparing a mixed metal-viscosified drilling fluid including bentonite, a mixed metal viscosifier and controlling pH to 8.5 to 9.5 to permit a reaction between the bentonite and the mixed metal viscosifier; adding at least one of: (i) calcium sulfate and (ii) a potassium salt; and pumping the drilling fluid while drilling the tunnel with the pH lowered to 7-9. The amount of mixed metal viscosifier used can be limited such that the weight ratio of mixed metal viscosifier to MBT reaches up to 1:30. In the event that there is a problematic increase in viscosity, a non-toxic anionic thinner can be added to the drilling fluid. One such anionic thinner is a polyacrylate.

A method for drilling a tunnel through a formation must address environmental concerns. One tunneling method comprises the steps of: preparing a mixed metal-viscosified drilling fluid including bentonite, a mixed metal viscosifier and controlling pH to 8.5 to 9.5 to permit a reaction between the bentonite and the mixed metal viscosifier; adding at least one of: (i) calcium sulfate and (ii) a potassium salt; and pumping the drilling fluid while drilling the tunnel with the pH lowered to 7-9. The amount of mixed metal viscosifier used can be limited such that the weight ratio of mixed metal viscosifier to MBT reaches up to 1:30. In the event that there is a problematic increase in viscosity, a non-toxic anionic thinner can be added to the drilling fluid. One such anionic thinner is a polyacrylate.

A wellbore fluid comprising a first aqueous base fluid and a plurality of silica nanoparticles suspended in the first aqueous base fluid. The nanoparticles are present in the fluid in an amount to have an effect of decreasing a crystallization temperature by at least 4 to 55° F. as compared to a second aqueous base fluid without the silica nanoparticles.

A wellbore fluid comprising a first aqueous base fluid and a plurality of silica nanoparticles suspended in the first aqueous base fluid. The nanoparticles are present in the fluid in an amount to have an effect of decreasing a crystallization temperature by at least 4 to 55° F. as compared to a second aqueous base fluid without the silica nanoparticles.

A wellbore treatment fluid comprising: a base fluid; and a water-soluble salt, the salt comprising: a cation; and an anion, wherein the anion is selected from phosphotungstate, silicotungstate, phosphomolybdate, and silicomolybdate. The treatment fluid can have a density greater than or equal to 13 pounds per gallon. A method of treating a portion of a subterranean formation penetrated by a well comprising: introducing the treatment fluid into the well.

A wellbore treatment fluid comprising: a base fluid; and a water-soluble salt, the salt comprising: a cation; and an anion, wherein the anion is selected from phosphotungstate, silicotungstate, phosphomolybdate, and silicomolybdate. The treatment fluid can have a density greater than or equal to 13 pounds per gallon. A method of treating a portion of a subterranean formation penetrated by a well comprising: introducing the treatment fluid into the well.

Coated nanoparticles include nanoparticles with a cationic coating, such that the nanoparticles have a net-positive charge. The cationic coatings may be selected from an amino acid, a polysaccharide, a polyamine, an acrylate polymer, a dendrimer, a copolymer, a histone, a protein, an ester, or combinations thereof. The coated nanoparticles may be incorporated into methods for improving an amount of oil recovered during enhanced oil recovery. The methods may include introducing an aqueous drilling fluid comprising coated nanoparticles to a carbonate reservoir and injecting drilling fluid comprising the coated nanoparticles into the carbonate reservoir to displace oil in the carbonate reservoir and thereby enhance the oil recovery.

Coated nanoparticles include nanoparticles with a cationic coating, such that the nanoparticles have a net-positive charge. The cationic coatings may be selected from an amino acid, a polysaccharide, a polyamine, an acrylate polymer, a dendrimer, a copolymer, a histone, a protein, an ester, or combinations thereof. The coated nanoparticles may be incorporated into methods for improving an amount of oil recovered during enhanced oil recovery. The methods may include introducing an aqueous drilling fluid comprising coated nanoparticles to a carbonate reservoir and injecting drilling fluid comprising the coated nanoparticles into the carbonate reservoir to displace oil in the carbonate reservoir and thereby enhance the oil recovery.

The present disclosure provides methods and systems for treatment fluids including an iodide brine. In some embodiments of the present disclosure, an oil-based treatment fluid in the form of an invert emulsion comprising an aqueous internal phase and an oil external phase, wherein the aqueous internal phase comprises an iodide brine is provided. The treatment fluid may be introduced into at least a portion of a well bore penetrating at least a portion of a subterranean formation.