US Patent 8469118 Drilling fluid containing carbon nanotubes

A viscoelastic drilling fluid for drilling in underground rock formations, comprising(a) an aqueous and/or organic liquid base,(b) at least one weighting agent, in particulate form, with a mass per unit volume of at least 2 g/cm3, preferably at least 4 g/cm3, in suspension in said liquid base, and(c) carbon nanotubes with a mean diameter of between 10 and 30 nm and a specific surface in excess of 200 m2/g, preferably of between 200 m2/g and 250 m2/g and a drilling method using such a fluid.