Use of selected ester oils in drilling fluids and muds

The invert emulsion mud of claim 1 wherein said alkali reserve component includes a weakly basic metal oxide, zinc oxide, or zinc compound. .›.22. The invert emulsion mud of claim 1 wherein in component A the acid moiety of the at least one monocarboxylic acid ester contains more than about 45% by weight of either diolefinically unsaturated acids, polyolefinically unsaturated acids, or a mixture of di- and poly-

• olefinically unsaturated acids..!.23. .›.A drilling fluid.!. An invert drilling fluid that is free of mineral oil .›.for use in an invert drilling mud that.!. and is substantially free from highly hydrophilic basic materials selected from the group consisting of alkali metal hydroxides and amines selected from diethanolamine and triethanolamine, said fluid consisting of
• A. a continuous oil phase composed of at least one monocarboxylic acid ester of a C.sub.2 -C.sub.12 monofunctional alkanol wherein the monocarboxylic acid contains from 16 to 24 carbon atoms and comprises at least about 60% by weight of monoolefinically unsaturated acids and no more than about 35% by weight of di- and poly- olefinically unsaturated acids, .›.and.!.
• B. a disperse aqueous phase.›...!. , and
• C. a mildly alkaline alkali reserve component consisting essentially of lime in a quantity not exceeding above about 2 lb/bbl of said drilling
• fluid. 24. The drilling fluid of claim 23 wherein in component A has a Brooksfield (RVT) viscosity at 0.degree. to 5.degree. C. of below 50
• mPa.s. 25. The drilling fluid of claim 23 wherein in component A the oil phase contains at least about 70% by weight of the at least one
• monocarboxylic acid ester. 26. The drilling fluid of claim 23 wherein the at least one monocarboxylic acid ester of component A has a pour point and setting point below about -10.degree. C., and a flash point above about
• 100.degree. C. 27. The drilling fluid of claim 23 wherein in the at least one monocarboxylic acid ester of component A the monocarboxylic acid is
• linear. 28. The drilling fluid of claim 23 wherein in the at least one monocarboxylic acid ester of component A the alcohol moiety contains from
• 1 to 10 carbon atoms and is saturated, straight chain or branched. 29. An invert emulsion drilling mud free of mineral oil and substantially free from highly hydrophilic basic materials selected from the group consisting of alkali metal hydroxides and amines selected from diethanolamine and triethanolamine, consisting essentially of
• A. a continuous oil phase composed predominantly of at least one monocarboxylic acid ester of a C.sub.2 -C.sub.12 monofunctional alcohol wherein the monocarboxylic acid contains from 16 to 24 carbon atoms and comprises at least about 60% by weight of monoolefinically unsaturated acids and no more than about 35% by weight of di- and poly- olefinically unsaturated acids,
• B. a disperse aqueous phase,
• C. at least one emulsifier,
• D. at least one weighting agent,
• E. a viscosifier,
• F. at least one fluid loss additive, and
• G. a mildly alkaline alkali reserve component consisting essentially of
• lime in a quantity not exceeding about 2 lb/bbl of said drilling mud. 30. The invert emulsion mud of claim 29 wherein from about 5 to about 45%
• by weight of component B is present therein. 31. The invert emulsion mud of claim 30 wherein from about 10 to about 25% by weight of component B is
• present therein. 32. The invert emulsion mud of claim 29 wherein component A has a Brookfield (RVT) viscosity at 0.degree. to 5.degree. C. of below
• 50 mPa.s. 33. The invert emulsion mud of claim 29 wherein the invert emulsion mud has a plastic viscosity (PV) in the range of from about 10 to about 60 mPa.s and a yield point (YP) in the range of from about 5 to
• about 40 lb/100 ft.sup.2, as measured at 50.degree. C. 34. The invert emulsion mud of claim 29 wherein in component A the oil phase contains at least about 70% by weight of the at least one monocarboxylic acid ester.
• . The invert emulsion mud of claim 29 wherein the at least one monocarboxylic acid ester of component A has a pour point and setting point below about -10.degree. C., and a flash point above about
• 100.degree. C. 36. In the development of a source of oil or gas by drilling using a drilling mud, the improvement comprising pumping the
• invert emulsion mud of claim 2 into said source. 37. In the development of a source of oil or gas by drilling using a drilling mud, the improvement comprising pumping the invert emulsion mud of claim 6 into said source.
• In the development of a source of oil or gas by drilling using a drilling mud, the improvement comprising pumping the invert emulsion mud
• of claim 11 into said source. 39. In the development of a source of oil or gas by drilling using a drilling mud, the improvement comprising pumping
• the invert emulsion mud of claim 13 into said source. 40. In the development of a source of oil or gas by drilling using a drilling mud, the improvement comprising pumping the invert emulsion mud of claim 1 into
• said source. 41. In the development of a source of oil or gas by drilling using a drilling mud, the improvement comprising pumping the invert
• emulsion mud of claim 29 into said source.