Shale and salt stabilizing drilling fluid

Claim 1

A method of preparing a shale and salt formation stabilizing clay-based drilling fluid comprising: admixing a predetermined quantity of ammonium chloride with an aqueous fluid, said ammonium chloride being present in an amount of from about 10 to about 70 pounds per barrel of drilling fluid; admixing a predetermined amount of sodium chloride with the aqueous ammonium chloride solution to form an aqueous ammonium chloride-sodium chloride solution, said sodium chloride being present in an amount of from about 65 to about 150 pounds per barrel of drilling fluid; and admixing a predetermined quantity of a viscosifying agent comprising a clay with the aqueous ammonium chloride-sodium chloride solution to form a clay-based drilling fluid whereby the occurrence of a substantial viscosity hump during said admixing is prevented.

Claim 2

A method of preparing a shale and salt formation stabilizing clay-based drilling fluid comprising: admixing a predetermined quantity of ammonium chloride with an aqueous fluid, said ammonium chloride being present in an amount of from about 10 to about 70 pounds per barrel of drilling fluid; admixing a predetermined amount of sodium chloride with the aqueous ammonium chloride solution to form an aqueous ammonium chloride-sodium chloride solution, said sodium chloride being present in an amount of from about 65 to about 150 pounds per barrel of drilling fluid; and admixing a predetermined quantity of a viscosifying agent comprising a clay with the aqueous ammonium chloride-sodium chloride solution to form a clay-based drilling fluid whereby the occurrence of a substantial viscosity hump during said admixing is prevented.

Claim 6

A method of preparing a clay-based drilling fluid comprising: admixing from about 10 to about 70 ppb of ammonium chloride with an aqueous fluid until the ammonium chloride substantially is dissolved; admixing from about 65 to about 150 ppb of sodium chloride with the aqueous ammonium chloride solution until a substantial portion of the sodium chloride is dissolved; admixing from about 5 to about 30 ppb of a viscosifying agent comprising a clay with the aqueous ammonium chloride-sodium chloride solution whereby the occurrence of a substantial viscosity hump during said admixing is avoided; and, adjusting the pH of the aqueous fluid to a level in the range of from about 5 to about 9 by the addition of a quantity of a pH-adjusting agent to form a clay-based drilling fluid capable of stabilizing shale and salt formations during drilling operations.

Claim 7

A method of preparing a clay-based drilling fluid comprising: admixing from about 10 to about 70 ppb of ammonium chloride with an aqueous fluid until the ammonium chloride substantially is dissolved; admixing from about 65 to about 150 ppb of sodium chloride with the aqueous ammonium chloride solution until a substantial portion of the sodium chloride is dissolved; admixing from about 5 to about 30 ppb of a viscosifying agent comprising a clay with the aqueous ammonium chloride-sodium chloride solution whereby the occurrence of a substantial viscosity hump during said admixing is avoided; and, adjusting the pH of the aqueous fluid to a level in the range of from about 5 to about 9 by the addition of a quantity of a pH-adjusting agent to form a clay-based drilling fluid capable of stabilizing shale and salt formations during drilling operations.