THERMAL INSULATING FLUIDS

1 . A thermal insulating fluid comprising:

(a) a styrenic-acrylic polymeric rheological modifier;

(b) a hydrocarbon fluid;

(c) optionally a first emulsifier;

(d) optionally an inorganic salt;

(e) optionally an alkaline source;

(f) optionally a second emulsifier; and

(g) optionally an aqueous phase,

wherein the thermal insulating fluid is a yield power law fluid.

2 . The thermal insulating fluid according to claim 1 , wherein the styrenic-acrylic polymeric rheological modifier contains a styrene-based monomer substituted on the phenyl moiety, chosen from meta-methyl-styrene, para-methyl-styrene, para-propyl-styrene, para-tert-butyl-styrene, para-cyclohexyl-styrene, para-dodecyl-styrene, 2-ethyl-4-benzyl-styrene, para-(phenylbutyl)-styrene, and mixtures thereof.

3 . The thermal insulating fluid according to claim 1 , wherein the thermal insulating fluid exhibits a yield stress of higher than 10 lb f /100 ft 2 (5 Pa), more particularly of higher than 20 lb f /100 ft 2 (19 Pa) and even more particularly of higher than 60 lb f /100 ft 2 (30 Pa).

4 . The thermal insulating fluid according to claim 1 , wherein the first emulsifier is present and is selected from rosin acids, tall oil acids, fatty alcohols, fatty acids, salts thereof, polyamides, and combinations thereof.

5 . The thermal insulating fluid according to claim 1 , wherein the hydrocarbon fluid is selected from diesels, paraffin oils, mineral oil, crude oils, kerosene, and combinations thereof.

6 . The thermal insulating fluid according to claim 1 , wherein the hydrocarbon fluid comprises a mineral oil.

7 . The thermal insulating fluid according to claim 1 , wherein the inorganic salt is present and is an alkali salt or an alkaline earth salt.

8 . The thermal insulating fluid according to claim 1 , wherein the alkaline source is present and is a calcium salt, a magnesium salt or a combination thereof.

9 . The thermal insulating fluid according to claim 1 , wherein the aqueous phase is present and is selected from fresh water, acidified water, seawater and brine.

10 . The thermal insulating fluid according to claim 1 , wherein the aqueous phase is present in a ratio of oil:water of from 50:50 to 99:1.

11 . The thermal insulating fluid according to claim 1 , wherein the thermal insulating fluid is an invert emulsion.

12 . The thermal insulating fluid according to claim 1 , wherein the thermal insulating fluid does not contain an aqueous phase.

13 . The thermal insulating fluid according to claim 1 , comprising:

(a) a styrenic-acrylic polymeric rheological modifier;

(b) a hydrocarbon fluid;

(d) optionally an inorganic salt; and

(e) optionally an alkaline source,

wherein the thermal insulating fluid does not contain an aqueous phase.

14 . The thermal insulating fluid according to claim 1 , comprising:

(a) a styrenic-acrylic polymeric rheological modifier;

(b) a hydrocarbon fluid;

(c) a first emulsifier;

(d) optionally an inorganic salt;

(e) optionally an alkaline source; and

(g) an aqueous phase.

15 . A process for preparing the thermal insulating fluid according to claim 1 , comprising mixing together the styrenic-acrylic polymeric rheological modifier; the hydrocarbon fluid; and optionally one or more of the first emulsifier, the inorganic salt the alkaline source, and the second emulsifier.

16 . The process according to claim 15 , wherein the hydrocarbon fluid is added first.

17 . A method for adding a thermal insulating fluid into an annulus, comprising adding the thermal insulating fluid according to claim 1 into one or more annuli.

18 . The method according to claim 17 , wherein the annulus is positioned between a first tubing and a second tubing.

19 . The method according to claim 17 , wherein a tubing containing a fluid located within a wellbore is provided such that the annulus is formed between the tubing and a surface of the wellbore.

20 . An annulus of a well containing the thermal insulating fluid according to claim 1 .