# US 7,745,379 B2 · Method of insulating a subsea structure

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- Number: US 7,745,379 B2
- Document ID: US7745379B2
- Status: Granted
- Kind: B2
- Application number: 10/559,712
- Filed: 2004-06-03
- Published: 2006-07-06
- Granted: 2010-06-29
- Earliest claimed: 2003-06-04
- Assignees: Aubin Limited
- Inventors: Patrick Joseph Collins
- Web page: https://patentgrep.com/patent/US7745379B2

## CPC

- C09K 5/063: {Materials absorbing or liberating heat during crystallisation; Heat storage materials}
- E21B 17/01: Risers
- E21B 43/01: specially adapted for obtaining from underwater installations
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS

## Abstract

A method of insulating pipeline bundles used in recovering hydrocarbons from wells is disclosed. A polymeric substance, such as an orthophosphate ester, is injected into the annulus between a carrier pipe and the hydrocarbon conveying tubulars. A ferric salt, such as ferric sulphate, may be added as a gelling agent. The mixture results in a gel having a dynamic viscosity of greater than (1000) PaS. The gel insulates the inner hydrocarbon-conveying tubulars from the surrounding seawater thus helping to maintain the relatively high temperature therewithin. This in turn reduces the likelihood for chemicals, such as hydrates, to be precipitated out of the oil phase.

## Claims

### Claim 1

A method of insulating a subsea structure, the method comprising:
injecting a substance comprising a hydrocarbon into the subsea structure;
allowing said substance to form a gel, the formed gel having a dynamic viscosity of more than 1000 Pa·S;
wherein spheres enclosing hydrocarbon gas are added to the substance.

### Claim 2

A method of insulating a subsea structure, the method comprising:
injecting a substance comprising a hydrocarbon into the subsea structure;
allowing said substance to form a gel, the formed gel having a dynamic viscosity of more than 2000 Pa·S;
wherein the subsea structure comprises a conduit, said conduit enclosing a second conduit and the method comprises recovering hydrocarbons within the second conduit.

### Claim 3 (depends on 2)

A method as claimed in claim 2, wherein the gel is adapted to transfer a portion of the hydrostatic pressure on the first conduit onto the second conduit.

### Claim 4 (depends on 2)

A method as claimed in claim 2, wherein the thermal properties of the gel are varied over the length of a conduit or series of conduits.

### Claim 5 (depends on 2)

A method as claimed in claim 2, wherein the substance comprises a polymeric compound and a transition metal salt.

### Claim 6 (depends on 5)

A method as claimed in claim 5, wherein at least one of the polymeric compound and transition metal salt is encapsulated in wax.

### Claim 7 (depends on 5)

A method as claimed in claim 5, wherein the polymeric compound comprises an orthophosphate.

### Claim 8 (depends on 7)

A method as claimed in claim 7, wherein the orthophosphate comprises an orthophosphate ester.

### Claim 9 (depends on 8)

A method as claimed in claim 8, wherein the orthophosphate ester has the structure according to formula I:
wherein R is a straight or branched chain alkyl or alkaryl group having about 6 to about 18 carbon atoms and R′ is hydrogen or an aryl, alkaryl or alkyl group having about up to 18 carbon atoms.

### Claim 10 (depends on 7)

A method as claimed in claim 7, wherein about 0.3% to 3.0 wt % of the phosphate is added to the substance.

### Claim 11 (depends on 6)

A method as claimed claim 6, wherein the transition metal salt and polymeric compound are added in an equimolar ratio.

### Claim 12 (depends on 5)

A method as claimed in claim 5, wherein the transition metal salt comprises a ferric salt.

### Claim 13 (depends on 12)

A method as claimed in claim 12, wherein the ferric salt is selected from the group consisting of ferric sulphate, ferric citrate, ferric ammonium sulphate ferric ammonium citrate, ferric chloride, and ferric gluconate.

### Claim 14 (depends on 2)

A method a claimed in claim 2, wherein the conduit comprises further conduits enclosed therein.

### Claim 15 (depends on 2)

A method as claimed in claim 2, wherein the formed gel retains its integrity unsupported.

### Claim 16 (depends on 2)

A method as claimed in claim 2, wherein the substance is a pourable fluid prior to forming the gel.

### Claim 17 (depends on 2)

A method as claimed in claim 2, wherein cenospheres or microspheres are added to the substance.