An invert emulsion drilling fluid comprising: (a) an oleaginous continuous phase; (b) a non-oleaginous discontinuous phase; and (c) a rheology additive comprising: (i) a hydrophobic amine, and (ii) an organic acid, an ester thereof, or a combination thereof; wherein the hydrophobic amine is represented by the following formula: wherein: R is a C 16-54 straight-chain or branched aliphatic, cycloaliphatic or aryl aliphatic group; R 1 and R 2 are each independently a hydrogen atom, an alkyl group, a cyanoalkyl group, an aminoalkyl group, an aryl group, an aminoaryl group, a hydroxyalkyl group, a carbonyl group, a carbonate group, an alkoxy group, or a hydroxyl group; and X is an amine group optionally substituted with an alkyl group, a cyanoalkyl group, an aminoalkyl group, an aminoaryl group, or a hydroxyalkyl group, or X is an amide group, an amine oxide group, a betaine group, an ester group, a carboxylic acid group, an ether group, a hydroxyl group, a phosphate group, a phosphonate group, a pyrrolidone group, a haloformyl group, a nitrate group, a nitrite group, a sulfate group, a sulfonate group, an imidazoline group, a pyridine group, a sugar group, or any combination thereof; and wherein the organic acid has at least one COOH group and has a solubility in water of at least 0.1 % w/w at 20°C. (a) an oleaginous continuous phase; (b) a non-oleaginous discontinuous phase; and (c) a rheology additive comprising: (i) a hydrophobic amine, and (ii) an organic acid, an ester thereof, or a combination thereof; wherein the hydrophobic amine is represented by the following formula: wherein: R is a C 16-54 straight-chain or branched aliphatic, cycloaliphatic or aryl aliphatic group; R 1 and R 2 are each independently a hydrogen atom, an alkyl group, a cyanoalkyl group, an aminoalkyl group, an aryl group, an aminoaryl group, a hydroxyalkyl group, a carbonyl group, a carbonate group, an alkoxy group, or a hydroxyl group; and X is an amine group optionally substituted with an alkyl group, a cyanoalkyl group, an aminoalkyl group, an aminoaryl group, or a hydroxyalkyl group, or X is an amide group, an amine oxide group, a betaine group, an ester group, a carboxylic acid group, an ether group, a hydroxyl group, a phosphate group, a phosphonate group, a pyrrolidone group, a haloformyl group, a nitrate group, a nitrite group, a sulfate group, a sulfonate group, an imidazoline group, a pyridine group, a sugar group, or any combination thereof; and wherein the organic acid has at least one COOH group and has a solubility in water of at least 0.1 % w/w at 20°C. (i) a hydrophobic amine, and (ii) an organic acid, an ester thereof, or a combination thereof; wherein the hydrophobic amine is represented by the following formula: wherein: R is a C 16-54 straight-chain or branched aliphatic, cycloaliphatic or aryl aliphatic group; R 1 and R 2 are each independently a hydrogen atom, an alkyl group, a cyanoalkyl group, an aminoalkyl group, an aryl group, an aminoaryl group, a hydroxyalkyl group, a carbonyl group, a carbonate group, an alkoxy group, or a hydroxyl group; and X is an amine group optionally substituted with an alkyl group, a cyanoalkyl group, an aminoalkyl group, an aminoaryl group, or a hydroxyalkyl group, or X is an amide group, an amine oxide group, a betaine group, an ester group, a carboxylic acid group, an ether group, a hydroxyl group, a phosphate group, a phosphonate group, a pyrrolidone group, a haloformyl group, a nitrate group, a nitrite group, a sulfate group, a sulfonate group, an imidazoline group, a pyridine group, a sugar group, or any combination thereof; and wherein the organic acid has at least one COOH group and has a solubility in water of at least 0.1 % w/w at 20°C. R is a C 16-54 straight-chain or branched aliphatic, cycloaliphatic or aryl aliphatic group; R 1 and R 2 are each independently a hydrogen atom, an alkyl group, a cyanoalkyl group, an aminoalkyl group, an aryl group, an aminoaryl group, a hydroxyalkyl group, a carbonyl group, a carbonate group, an alkoxy group, or a hydroxyl group; and X is an amine group optionally substituted with an alkyl group, a cyanoalkyl group, an aminoalkyl group, an aminoaryl group, or a hydroxyalkyl group, or X is an amide group, an amine oxide group, a betaine group, an ester group, a carboxylic acid group, an ether group, a hydroxyl group, a phosphate group, a phosphonate group, a pyrrolidone group, a haloformyl group, a nitrate group, a nitrite group, a sulfate group, a sulfonate group, an imidazoline group, a pyridine group, a sugar group, or any combination thereof; and wherein the organic acid has at least one COOH group and has a solubility in water of at least 0.1 % w/w at 20°C.