Patent ID: 7666820

Claim:
A borehole treatment composition comprising: an aqueous phase; a non-aqueous oil phase; emulsifiers; and, optionally, further additives, including weighting agents, fluid loss additives, viscosity regulators, wetting agents, salts, biocides, corrosion inhibitors and an alkali reserve; wherein said non-aqueous oil phase comprises an admixture of a) and c), b) and c), or a) and b) and c); wherein: a) paraffins having from 5 to 22 carbon atoms; b) internal olefins having from 12 to 30 carbon atoms in the molecule; and c) carboxylic acid esters of the formula R—COO—R′, where R stands for a linear or branched, saturated or unsaturated alkyl radical having from 15 to 25 carbon atoms and R′ denotes a saturated, linear or branched alkyl radical having from 3 to 22 carbon atoms; wherein, the ratio of the toxicity of internal olefins of chain length C 16-18 to the toxicity of the non-aqueous oil phase, in each case as measured by the Leptocheirus plumulosus acute, static 96 hour/10 day sediment toxicity test in accordance with ASTM E 1367-92 & EPA/600/R-94/025, Section 11, is less than 1.