Patent ID: 7012043

Claim:
A drilling fluid for use in drilling wells through a formation containing a clay that swells in the presence of water, the drilling fluid comprising: (a) an aqueous based continuous phase; (b) a weight material; and (c) a clay hydration inhibition agent that comprises: (i) a polyether amine with the following formula: H 2 N—X—[OCH 2 CH 2 ] x —[OCH 2 CH(CH 3 )] y —NH 2 wherein X is a straight or branched chain aliphatic with less than about 5 carbon atoms; x is number greater than 0 to about 15; and y is a number from 0 to about 1, and (ii) a polyetheramine derivative, wherein the polyether amine derivative comprises 4,13-diaza-18-crown-6, hexaethyleneglygol triamine; oligomeric triethyleneglycol diamines with the following general formula: H 2 N—(CH 2 CH 2 —[OCH 2 CH 2 ] 2 —NH) x —H where x is an integer from about 2 to about 5; and branched polyether diamine derivatives with the following formula: and optionally, an oligomeric triethyleneglycol diamine with the following average structure: H 2 N—(CH 2 CH 2 —[OCH 2 CH 2 ] 2 —NH) x —H where x varies from about 1 to about 4.