We Claim:
1. Fluid having a kinematic viscosity at 40°C from 3 to 6 mm2/s, a flash point of higher than 120°C and a pour point lower than -40°C, having a boiling point in the range of from 200 °C to 400°C and a boiling range below 80°C, said fluid comprising more than 95% isoparaffins and less than 3% of naphthens by weight, a biocarbon content of at least 95% by weight, containing less than lOOppm aromatics by weight.
2. Fluid of claim 1, having a pour point lower than -50°C.
3. Fluid of claim 1 or 2, consisting of one fraction having an initial boiling point of at least 260°C and a final boiling point of about less than about 320°C, preferably less than about 310°C.
4. Fluid of claim 1 or 2, consisting of a mixture of two fractions, each fraction having a boiling point in the range 220°C-340°C, preferably 250°C-340°C, and a boiling range of less than 80°C, preferably less than 60°C, more preferably between 35 and 50°C and even more preferably between 40 and 50°C,
where at least one fraction has an initial boiling point higher than 250°C, and preferably said at least one fraction has a boiling range 285-335°C or where at least one fraction has an initial boiling point lower than 250°C, and preferably said at least one fraction has a boiling range 240-275°C.
5. Fluid of claim 1 or 2, consisting of a mixture of three fractions, each fraction having
a boiling point in the range 220°C-340°C, preferably 250°C-340°C, and a boiling
range of less than 80°C, preferably less than 60°C, more preferably between 35 and
50°C and even more preferably between 40 and 50°C,
where at least one fraction has an initial boiling point higher than 250°C, preferably
said fraction has a boiling range of 285°C-335°C,
where at least one fraction has an initial boiling point lower than 250°C, preferably
said at least one fraction has a boiling range 240-275°C,
the fluid consisting preferably of a mixture of three fractions having boiling ranges
respectively of 240°C-275°C, 250°C-295°C and 285°C-335°C.
6. Fluid of any one of the preceding claims, wherein the fluid is obtainable by the
process comprising the step of catalytically hydrogenating a feed comprising more
than 95% by weight of a hydrodeoxygenated isomerized hydrocarbon biomass
feedstock or a feed comprising more than 95% by weight of a feedstock originating
from syngas, at a temperature from 80 to 180°C, at a pressure from 50 to 160 bars,

a liquid hourly space velocity of 0.2 to 5 hr1 and an hydrogen treat rate up to 200 Nm3/tonoffeed.
7. Fluid of claim 6, wherein the feed comprises more than 98% by weight, preferably more than 99% by weight of a hydrodeoxygenated isomerized hydrocarbon biomass feedstock, and more preferably consists of a hydrodeoxygenated isomerized hydrocarbon biomass feedstock, and especially where the biomass is a vegetable oil, an ester thereof or a triglyceride thereof, the feed being more preferably a HVO feed, or wherein the feed comprises more than 98%, preferably more than 99% by weight of a feedstock originating from syngas, more preferably from renewable syngas.
8. Fluid of claim 6 or 7, wherein a fractionating step is carried out before the hydrogenating step, or after the hydrogenating step or both.
9. Fluid of any one of the preceding claims, wherein the fluid contains less than 50ppm aromatics, and preferably less than 20ppm by weight.
10. Fluid of any one of the preceding claims, wherein the fluid contains less than 1% and advantageously less than 500ppm and even less than 50ppm.
11. Fluid of any one of the preceding claims, wherein the fluid contains less than 5ppm, even less than 3ppm and preferably less than 0.5ppm sulphur.
12. Fluid of any one of the preceding claims, wherein the fluid has a biodegradability at 28 days of at least 60%, preferably at least 70%, more preferably at least 75% and advantageously at least 80%, as measured according to the OECD 306 standard.
13. Drilling fluid comprising a fluid having a boiling point in the range of from 200 °C to 400°C and a boiling range below 80°C, said fluid comprising more than 95% isoparaffins and less than 3% of naphthens by weight, a biocarbon content of at least 95% by weight, containing less than lOOppm aromatics by weight, in association with barite.
14. Drilling fluid of claim 13, wherein the fluid has the characteristics as set forth in any one of claims 1 to 12.
15. Use for improving lubricity of drilling fluids, of a fluid having a boiling point in the range of from 200 °C to 400°C and a boiling range below 80°C, said fluid comprising more than 95% isoparaffins and less than 3% of naphthens by weight, a biocarbon content of at least 95% by weight, containing less than lOOppm aromatics by weight.

16. Use of claim 15, wherein the fluid has the characteristics as set forth in any one of claims 1 to 12.