A method for drilling boreholes or wellbores in a subterranean formation using a drilling fluid which does not have added to it any organophilic clays, the drilling fluid comprising: (a) an invert emulsion base comprising a blend of one or more esters and one or more isomerized, or internal, olefins, wherein the esters comprise at least 10 and up to 99 weight percent of the blend; said esters being comprised of C 12 to C 14 fatty acids and 2-ethyl hexanol or C 8 fatty acids and 2-ethyl hexanol, and said olefins having 40 to 70 weight percent C 16 and 20 to 50 weight percent C 18; (b) one or more thinners, selected from at least one of the following groups: (i) a compound having the formula: R-(C 2 H 4 O) n (C 3 H 6 O) m (C 4 H 8 O) k -H where R is a saturated or unsaturated, linear or branched alkyl radical having 8 to 24 carbon atoms, n is a number ranging from 1 to 10, m is a number ranging from 0 to 10, and k is a number ranging from 0 to 10; and (ii) a non-ionic surfactant, said surfactant being the reaction product of at least one oxide, selected from the group comprising ethylene oxide, propylene oxide and butylene oxide, with C 10-22 carboxylic acids or C 10-22 carboxylic acid derivatives containing at least one double bond in position 9/10 and/or 13/14 having structural units of the general formula: where R 1 is a hydrogen atom, or an OH group, or a group OR 2, and where R 2 is an alkyl group of 1 to 18 carbon atoms, or an alkenyl group of 2 to 18 carbon atoms, or a group of the formula: and where R 3 is a hydrogen atom, or an alkyl group of 1 to 21 carbon atoms, or an alkylene group of 2 to 21 carbon atoms. (c) one or more emulsifiers; and (d) one or more weighting agents, wherein the method comprises: drilling in the subterranean formation using the drilling fluid; stopping drilling to cause the drilling fluid to form a gel structure to suspend drill cuttings and weighting materials; and resuming drilling to cause the drilling fluid to revert to a flowable or liquid state immediately upon resumption of drilling. (a) an invert emulsion base comprising a blend of one or more esters and one or more isomerized, or internal, olefins, wherein the esters comprise at least 10 and up to 99 weight percent of the blend; said esters being comprised of C 12 to C 14 fatty acids and 2-ethyl hexanol or C 8 fatty acids and 2-ethyl hexanol, and said olefins having 40 to 70 weight percent C 16 and 20 to 50 weight percent C 18; (b) one or more thinners, selected from at least one of the following groups: (i) a compound having the formula: R-(C 2 H 4 O) n (C 3 H 6 O) m (C 4 H 8 O) k -H where R is a saturated or unsaturated, linear or branched alkyl radical having 8 to 24 carbon atoms, n is a number ranging from 1 to 10, m is a number ranging from 0 to 10, and k is a number ranging from 0 to 10; and (ii) a non-ionic surfactant, said surfactant being the reaction product of at least one oxide, selected from the group comprising ethylene oxide, propylene oxide and butylene oxide, with C 10-22 carboxylic acids or C 10-22 carboxylic acid derivatives containing at least one double bond in position 9/10 and/or 13/14 having structural units of the general formula: where R 1 is a hydrogen atom, or an OH group, or a group OR 2, and where R 2 is an alkyl group of 1 to 18 carbon atoms, or an alkenyl group of 2 to 18 carbon atoms, or a group of the formula: and where R 3 is a hydrogen atom, or an alkyl group of 1 to 21 carbon atoms, or an alkylene group of 2 to 21 carbon atoms. (i) a compound having the formula: R-(C 2 H 4 O) n (C 3 H 6 O) m (C 4 H 8 O) k -H where R is a saturated or unsaturated, linear or branched alkyl radical having 8 to 24 carbon atoms, n is a number ranging from 1 to 10, m is a number ranging from 0 to 10, and k is a number ranging from 0 to 10; and (ii) a non-ionic surfactant, said surfactant being the reaction product of at least one oxide, selected from the group comprising ethylene oxide, propylene oxide and butylene oxide, with C 10-22 carboxylic acids or C 10-22 carboxylic acid derivatives containing at least one double bond in position 9/10 and/or 13/14 having structural units of the general formula: where R 1 is a hydrogen atom, or an OH group, or a group OR 2, and where R 2 is an alkyl group of 1 to 18 carbon atoms, or an alkenyl group of 2 to 18 carbon atoms, or a group of the formula: and where R 3 is a hydrogen atom, or an alkyl group of 1 to 21 carbon atoms, or an alkylene group of 2 to 21 carbon atoms. (c) one or more emulsifiers; and (d) one or more weighting agents, wherein the method comprises: drilling in the subterranean formation using the drilling fluid; stopping drilling to cause the drilling fluid to form a gel structure to suspend drill cuttings and weighting materials; and resuming drilling to cause the drilling fluid to revert to a flowable or liquid state immediately upon resumption of drilling. drilling in the subterranean formation using the drilling fluid; stopping drilling to cause the drilling fluid to form a gel structure to suspend drill cuttings and weighting materials; and resuming drilling to cause the drilling fluid to revert to a flowable or liquid state immediately upon resumption of drilling.