Abstract: The invention pertains to a drilling fluid composition comprising:—at least one (per)fluoropolyether oil comprising recurring units of formula —CF(CF3)CF2O— said oil having a kinematic viscosity of 30 to 80 cSt measured according to ASTM D455 standard at 20° C. [oil (E)] and possessing a polydispersity index (PDI) of at least 1.15; and—at least one (per)fluoropolyether phosphate comprising at least one perfluoropolyoxyalkylenic chain and at least one phosphoric acid group, in its acid, amide, salt or ester form [phosphate (P)], to a method for its manufacture and to its use in a drilling rig equipment.

Abstract: 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.

Abstract: The present invention relates to 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. It also relates to a drilling method using such a fluid.