Patent ID: 7285515

Claim:
Compositions of biodegradable oil-based drilling fluids, the compositions being inverted emulsions specifically formulated to be compatible with the oil phase, wherein such compositions comprise, on a weight basis: a) of from 48 to 75% of a continuous oil phase essentially made up of fatty acid methyl esters of natural source oils; b) of from 22 to 42% of an aqueous phase compounded with a finely dispersed alkali metal halide; c) of from 2 to 8% a of at least, one emulsifying agent consisting essentially of fatty acids soaps suitable to yield an oil-in-water emulsion; d) of from 0.5 to 1.0% a of a viscosifying agent of the organophilic clays type; e) of from 0.1 to 0.5% of, at least, one fluid loss polymeric additive, from the class of polyacrylates; f) of from 0.1 to 0.5% of, at least, one antioxidant additive selected from the group consisting of butylated-hydroxy-anisole (BHA), butylated-hydroxy-toluene (BHT), tert-butyl-hydroquinone (TBHQ), and 2,6, di-tert-butyl-p-cresol (DBPC); g) of from 1 to 3% a of a metallic oxide able to cause an alkaline reaction in order to produce in situ the fatty acids soaps and provide an alkaline reserve to the compositions.