Patent ID: 8309497

Claim:
A drilling fluid comprising: a carrier fluid; a weighting agent that comprises sub-micron precipitated barite having a particle size distribution such that at least 10% of particles in the sub-micron precipitated barite have a diameter below about 0.2 microns, at least 50% of the particles in the sub-micron precipitated barite have a diameter below about 0.3 microns and at least 90% of the particles in the sub-micron precipitated barite have a diameter below about 0.5 microns; a particle having a specific gravity of greater than about 2.6, wherein the particle having a specific gravity of greater than about 2.6 is not sub-micron precipitated barite; wherein the ratio of the sub-micron precipitated barite to the particle is about 10:90 to about 99:1; and a bridging agent that is not the submicron-precipitated barite or the particle, wherein the bridging agent comprises at least one degradable material selected from the group consisting of montanyl alcohol, tert-butylhydroquinone, cholesteryl nonanoate, benzoin, exo-norborneol, glyceraldehyde triphenylmethanol, propyl gallate, dimethyl terephthalate, cholecalciferol, ricinoleyl alcohol, 1-heptacosanol, 1-tetratriacontanol, 1-dotriacontanol, 1-hentriacontanol, 1-tricontanol, 1-nonacosanol, 1-octasanol, 1-hexacosanol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,17-heptadecanediol, 1,18-octadecanediol, 1,19-nonadecanediol, 1,20-eicosanediol, 1,21-heneicosanediol, 1,22-docosanediol, sucrose distearate, glyceryl monostearate, and any combination thereof.