Fast drilling invert emulsion drilling fluids

Claim 1

A fast drilling invert oil emulsion drilling fluid having enhanced stability at elevated temperatures which comprises oil, water, a water-in-oil emulsifier, a weighting agent, a suspending agent, and a temperature stabilizing additive, wherein said oil is a refined petroleum oil fraction containing primarily straight chain paraffinic hydrocarbons and less than 1% by volume of aromatic hydrocarbons, having a viscosity less than 1.5 centipoises at 25° C., a flash point of at least 60° C., and an aniline point of at least 80° C.; wherein said water contains up to a saturation amount of NaCl or CaCl 2 ; wherein said suspending agent is an organophilic clay which comprises the reaction product of a clay selected from the group consisting of attapulgite, bentonite, hectorite, saponite, and sepiolite, and a quaternary ammonium salt having the structural formula: ##STR2## wherein R 1 , R 2 , R 3 , and R 4 are independently selected from the group consisting of C a H 2a+1-x B x , C b H 2b-1-x B x , C 6 H 5-x B x CH 2 , and mixtures thereof, 1≦a≦30, 3≦b≦30, 0≦x≦2, B is a radical selected from the group consisting of OH, Cl, Br, C 6 H 5 , and mixtures thereof, and A is a charge balancing anion, provided that at least one R contains at least 12 carbon atoms, and R 1 , R 2 , R 3 , and R 4 collectively contain at least 20 carbon atoms; and wherein said temperature stabilizing additive contains from 2 to 6 carbon atoms and from 2 to 4 polar groups selected from the group consisting of OH, NH 2 , and mixtures thereof, per molecule.