The application of thermal insulation to subsea oil and gas equipment is essential both for the technical feasibility and for the economic viability of a project, particularly in deep water and ultra deep water developments. The benefits of thermal insulation are firstly a higher production rate by maintaining high oil temperature and increasing flow rates. Secondly lower processing costs by elimination of the requirement to reheat crude oil for water separation upon its arrival at the platform. Thirdly the prevention of hydrate and wax formation by maintaining the oil temperature above that at which hydrates form, in turn eliminating pipe blockages which would increase production costs. Fourthly, the elimination of the need for methanol injection to overcome the problems described above. Fifthly a reduction in the requirement for internal cleaning of pipes (known as pipe pigging). Accordingly, thermal insulation can make the difference between a project being viable or not.

Many systems exist for attempting to maintain the temperature of the extracted oil as it passes through those portions of the delivery pipework that are exposed to the cooling effects of sea water, to the recovery platforms or wellheads. Electrical heating elements may be attached to the pipework, the pipework may be surrounded by annular tubing that may or may not contain electrical heating elements or heat exchange tubes for pumped fluid heating. However, such arrangements are clearly expensive to install and cumbersome to maintain, whereas passive insulation systems rely only on maintaining the temperature of the extracted crude oil or gas by preventing heat loss. Passive insulation is provided by many types of expanded solid but clearly the limitations and requirements for installation in a subsea environment limit the materials to those which can be rendered impermeable to the ingress of sea water, resistant both to the range of absolute temperatures experienced and the temperature differential across the insulation, while being sufficiently resilient to resist the flexural and impact stresses pertinent to installation, transport and service.

Items of subsea equipment which benefit from thermal insulation include, wellheads and Xmas trees, spool pieces, manifolds, risers and pipe field joints. Clearly any insulation material or system must be capable of being easily formed into complex shapes to accommodate the components of a pipe line assembly. Previously syntactic foams have been used with some success.

However problems can be encountered in harsh subsea conditions where the glass of the microspheres may dissolve. Also such systems generally require rubber flexibilisers which are quite expensive. All proportions in this specification are expressed as weight

percentages.

According to the present invention there is provided a thermal insulation material for use subsea, the material comprising a platinum cured silicone resin matrix, and up to 45% of a micronised polymer.

The silicone resin may be a two part system, and may be curable at room temperature. The micronised polymer may be included in a first part of the resin system prior to mixing of the first part with the second part of the system. Some of the micronised polymer may be included in the second part of the resin system prior to mixing thereof with the first part of the resin system.

The first part of the resin system may be a base part, and may include a crosslinker which may have a reactive Si-H group, and may be

poly(hydromethylsiloxane-co-dimethylsiloxane). The first part may also include a coupling agent.

The second part of the resin system may be a catalyst part, and may contain a platinum catalyst.

The second part may include a material with vinyl groups, which material may be poly(vinylmethylsiloxane-co-dimethylsiloxane). The second part may include a silicone dye. The second part may include a coupling agent.

The silicone resin may contain more of the first part relative to the second part, and may contain at least two times as much of the first part as the second part, and may contain up to thirteen times as much of the first part as the second part.

The micronised polymer may be cryogenically ground.

The micronised polymer may have a particle size of between 20 and 300 microns, and more particularly between 50 and 200 microns.

The micronised polymer may be any of polypropylene (PP),

polystyrene (PS), polytetrafluoroethylene (PTFE), polycarbonate (PC), polyether ether ketone (PEEK). The invention also provides a thermal insulating structure applied to substrate for use subsea, the structure including a material according to any of the preceding eleven paragraphs.

Embodiments of the present invention will now be described by way of example only:

Example 1

This comprises a cured material where resin A is a poly

(hydromethylsiloxane-co-dimethylsiloxane), and resin B is a poly

(vinylmethylsiloxane-co-dimethylsiloxane).

The material of Example 1 is formed by mixing the following first base part and second catalyst part, the latter of which includes a silicone dye and also a platinum catalyst, and also an inhibitor which controls the reaction rate

Base Part

Catalyst Part

Total 407.3

The cured material can be formed as follows. Resin part A is weighed and placed in a vacuum mixer and full vacuum applied (28 inHg minimum) for 20 minutes. The vacuum is removed and the mixer opened. The micronised polymer of the first base part which in this instance is polystyrene is weighed and added to the resin part A. This is again placed under full vacuum (28 inHg minimum) and mixed for 20 minutes.

The vacuum is then removed and the mixer opened. The sides and base of a mixing bowl as well as the mixing blades are scraped so that unmixed material is brought to the centre of the mixing bowl. This is again placed under full vacuum (28 inHg minimum) and again mixed for 20 minutes.

The catalyst part is made by weighing the resin part B and silicone dye and placing these in a vacuum mixer and mixing for 20 minutes with a full vacuum applied (28 inHg minimum). The vacuum is then removed and the mixer opened.

In some instances it is also required to provide micronised polymer in the second catalyst part also, and if so this would be added at this point.

Material from the base and sides of a mixing bowl and also the mixing blades can be removed and brought to the centre of the mixing bowl and further mixed for 20 minutes under full vacuum (28 inHg minimum).

The base and catalyst parts can be mixed as follows. A required weight of the base part is placed in a vacuum mixer under full vacuum (28 inHg minimum) and mixed for 20 minutes. The vacuum is removed and the mixer opened and a required amount of the catalyst part is added and mixed under full vacuum (28 inHg minimum) for 20 minutes. Again mixture from the sides and the base of the mixing bowl as well as on the mixing blades can be removed for subsequent mixing again under full vacuum (28 inHg minimum) for a further 20 minutes. The vacuum is then removed and the liquid mixture can be decanted.

This material can be applied to components for use subsea such as a well head, Christmas tree, spool piece, manifold, riser or pipe field joints. An anti corrosion coating and a primer are first applied to an article to which material is to be applied. A mould is then applied around the article, and the material is pumped into the mould. Once the material is cured the mould can be removed.

The material may cure at room temperature, but the cure rate can be increased by heating the mixture to a temperature of up to 80° C. This can be achieved using heated moulds or heating blankets.

Formulae for three further materials will now be provided, which materials may be produced and applied in a similar material to example 1.

Example 2

Base Part

Material g

Resin A 5029.5

Micronized polypropylene (PP) 2335.3

Coupling agent 23.4

Total 7388.2 Catalyst Part:

Example 3

Example 4

Material g Mass percentage

Micronized polypropylene (PP) 2335.3 30.0

Resin A 5029.5 64.00

Resin B 419.6 5.32

Coupling agent 23.4 0.30

Dye 13.0 0.17 Total 7820.8 100

Base Part

Material g

Resin A 5029.5

Micronized polypropylene (PP) 2155.5

Coupling agent 21 .6

Total 7206.6

Catalvst Part

In these examples a ratio of around 12: 1 is provided for the base part to catalyst part. These parts react by an addition curing mechanism. This mechanism involves the catalytic addition of Si-H across a double bond. The catalyst is platinum and the reaction occurs slowly at room temperature or more quickly at elevated temperatures. An inhibitor controls the reaction rate. Part B resin forms bridges between the chains of the Part A resin. The curing formula is illustrated below.

Mixtures according to the invention have been found to provide a number of advantageous features. For instance the material acts as a flexibiliser (crack stopper), thereby obviating the requirement for a separate relatively expensive rubber flexibiliser or similar.

There are no glass microspheres in such materials, which avoids the potential problem of the glass in the microspheres dissolving. Materials according to the invention have been found to provide good water and heat resistance, and particularly relative to existing insulation materials.

It is to be realised that a wide range of modifications may be made to without departing from the scope of the invention. For instance different materials and/or relative proportions may be used. In addition to the examples shown with polystyrene and polypropylene, the micronised polymer could be any of polytetrafluoroethylene (PTFE), polycarbonate (PC), or polyether ether ketone (PEEK). The material could be applied to a substrate in a different way. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.