Iopf Paper Qualification Testing 04 Final1

1 Copyright 2008 by ASME

Proceedings of the 3rd International Offshore Pipeline Forum IOPF 2008

October 29-30, 2008, Houston, Texas, USA

IOPF2008-922

DEEPWATER PIPE-IN-PIPE (PIP) QUALIFICATION TESTING FOR 350F SERVICE

Paul Jukes, PhD CEng. J P Kenny, Inc.

Houston, Texas, USA.

Francois Delille J P Kenny, Inc.


Gary Harrison BP America, Inc.


ABSTRACT Development of future deep water oil reservoirs in the Gulf of

Mexico (GoM), where the flowline product temperatures are approaching 350F (177C), water depths approaching 10,000ft (3050m), and tie-backs in the order of 40 miles (64.4km), requires the appropriate material selection for key pipe-in-pipe (PIP) components. These extreme flowline temperatures, water depths and distances, restrict the choices in PIP component materials, and present real challenges to the design of centralizers, waterstops seals, thermal insulation and loadshares. These challenging conditions warrant qualification testing to be undertaken on PIP components to ensure structural integrity and long-term thermal and structural performance.

This paper describes a qualification testing programme for the testing of PIP components for 350F (177C) service, and includes the testing of centralizers, waterstop seals, thermal insulation and loadshares. The following qualification tests are proposed: (i) Centralizers tests: Slippage tests, creep tests, abrasion tests, bolt relaxation and aging tests are undertaken. Structural integrity testing under installation loads and in-service conditions is undertaken to ensure no long-term creep or degradation of the material due to temperature. (ii) Waterstop seal tests: Load test, hydrostatic pressure test, elevated temperature tests and material aging tests are undertaken. The material selection for the waterstop seals are undertaken to examine the integrity of the seal at temperature. (iii) Thermal insulations tests: A number of tests undertaken on aerogel materials to evaluate the effect of prolonged exposure to temperature on thermal conductivity and mechanical integrity. Tests include checking thermal conductivity, compressive strain recovery, long-term exposure to high-temperature and aging effects on thermal conductivity and mechanical integrity. (iv) Load-share tests: A mechanical radial clamp load-share is tested to ensure performance under sustained installation loads.

Each test planned and performed, testing rationale and results are presented within the paper. Conclusions are drawn on the suitability of these qualification tests for high-temperature applications. The successful qualification testing of the components extends the

boundaries of what is possible with PIP designs and opens up the possibility of XHPHT field developments in the GOM.

KEY WORDS Aerogel, Annulus, Centralizer, Deep Water, Extra High-Pressure

High-Temperature (XHPHT), Flowlines, Load-share, Nanogel, Overall Heat Transfer Coefficient (OHTC), Pipe-in-Pipe (PIP), Pipelines, Spacers, Thermal Insulation, Waterstop.

INTRODUCTION Pipe-in-pipe (PIP) is increasingly being used for the transportation of hydrocarbons. Pipe-in-pipe flowline systems are frequently used in the GoM for subsea tie-backs where there is a requirement for high thermal performance. A PIP system consists of the inner pipe carrying the fluid encased within a larger diameter outer pipe. Figure 1 shows a typical PIP system configuration.

Fig. 1: A typical PipeinPipe configuration

The outer pipe seals the annulus between the two pipes and the annulus can be filled with a wide range of thermal insulating materials incompatible with water exposure and hydrostatic pressure. A PIP flowline has the advantage over traditional wet insulated pipelines of


allowing a lower overall heat-transfer coefficient (OHTC) or U value for the system. PIP is a common method of achieving low U values of 0.176 BTU/hr.ft2.F (1.0 W/m2K) or less, and has been used on a number of projects in both the North Sea and in the GoM. For longer subsea tie-backs, a lower OHTC allows the production temperatures of the internal contents to remain above the wax allowable temperature (WAT) and hydrate formation temperature. Low OHTC facilitates longer cool-down times during a shut-down, to prevent hydrate conditions. A shut-down time of at least 8 to 10 hours is considered to be the minimum requirement, which can be a large challenge for long tie-back distances.

Today, it is not uncommon for PIP designs to be considered in water depths up to 10,000ft (3,050 meters) and flowline temperatures up to 350F (177C) (1).

This paper is part of significant analysis works related to extra high-pressure and high-temperature PIP designs sponsored by a major operator (2, 3). The study targets the Gulf of Mexico (GoM), where subsea production wells may be drilled at water depths (WD) to 10,000 feet (3,050m), with a flowing product temperature to 350F (177C), and system shut-in pressure of 65ksi (64.8MPa). These temperatures can present real challenges in the design, and failure modes have to be addressed (4). Also high axial loads can lead to lateral buckling, and mitigation methods are necessary, such as thermal expansion management with the use of sleepers, which is integrated into the design philosophy (5, 6).

As a result of the relatively high temperatures, it is important to determine the effect of these temperatures on the components that make up the PIP system. A PIP system consists of a number of additional components, such as centralizers, waterstop seals and loadshares. It is important to gain an understanding of the effects of temperature on the material strength and durability, and to ensure that there is no long-term degradation of the structural performance. These issues are addressed within this paper.

PIP COMPONENTS Centralizers, waterstops, thermal insulation and loadshares

make up a PIP system. The function of each component is briefly described, and issues associated with high temperatures are addressed.

Centralizers

Depending on the thermal insulation type, centralizers are placed between the inner and outer pipes at regular intervals. The function of the centralizers in a PIP system are to support the inner pipe centralized within the outer pipe, prevent possible damage to the PIP thermal insulation between the inner and outer pipes, and to transfer loads between the inner and outer pipes.

The distance between the spacers will depend on the loading to which the section of the PIP will be subjected. This spacing may be two meters for reeled pipelines, and four to six meters for S-lay and J-lay installation methods. The presence of centralizers provides heat loss paths and can present cold spots, reducing the overall thermal performance of the PIP system. For high-temperature flowlines, the temperature can reduce the structural integrity of the centralizers, and lead to deformations that could crush the thermal insulation.

Ability to undertake the functions of the centralizers successfully at high temperatures requires the spacer material to tolerate high temperatures without excessive deflections and maintain structural integrity. Compression loads on centralizers are a key aspect in their design.

Traditional lower temperature service centralizers are made of a nylon material that exhibits good resistance to abrasive wear. Other materials, such as injection-molded thermoplastic polypropylene, have a temperature limitation of about 266F (130C).

The selection of an appropriate material for high-temperature applications is difficult. Tests during this project on a proposed centralizer material resulted in cracks in the centralizer due to the material being too brittle. Other materials are presently being sourced. Waterstops The fundamental driver for waterstops is to avoid flooding the entire annulus of a PIP due to a single defect in the outer pipe of the system. To avoid this unlikely result, most designers have opted to include waterstops capable of preventing flooding of the entire annulus by isolating the breach in the outer pipe between adjacent waterstops. The waterstops must reliably seal the annulus against the maximum water pressure expected on the seabed.

The spacing of the waterstops can be arbitrary, but there are some practical considerations to provide guidance. The first constraint is the maximum tolerable temperature loss from a flooded section or sections. It may be acceptable to tolerate one or two flooded segments with a predicted temperature loss during steady state production of perhaps 5-20F. Burial of the pipeline will mitigate temperature loss over the flooded section, and may constrain waterstop spacing to the amount of spare pipeline repair materials available. The acceptable temperature loss is determined by a flow assurance specialist.

Waterstop spacing is also constrained by the amount of spare materials (pipe, insulation, centralizers, etc) available for a single repair. Assuming an accidental flooding of one segment during construction, there should be enough spare material available for repairs. It may be unacceptable to lose any reasonable length of insulation, and in that case the spacing would be solely governed by material constraint. The above waterstop spacing constraints should be considered and evaluated in a project during the final design work to determine final spacing. A spacing of 3,000 feet (914 m) is a representative value.

Waterstops must be able to sustain the temperature effects from the inner pipe for the life of the project. There is a waterstop seal on the market that fits between the pipes and is activated by the tightening of screws. High-temperature waterstop seals are presently being developed and tested. The material of the seals is a high-performance plastic and has been demonstrated to tolerance temperatures to 350F (177C), although the long-term service life could not be guaranteed. Thermal Insulation

The thermal insulation placed in the annulus of the PIP system is a key component, and allows a low OHTC if the thermal performance (k-factor) is good. There are various types of thermal insulation on the market, such as polyurethane, rock-wool, fiberglass, and aerogel.

The short-term loading during installation and the long-term loading due to startup / shut down loading are important factors to consider when choosing thermal insulation for the life of the project. Also, no long-term thermal degradation of the insulation can occur during the life of the project.

It is important that the thermal insulation demonstrate acceptable performance for high temperatures, without degradation of the thermal or structural performance due to aging. The k-factor for


each proposed material should be checked, and aging of the materials at elevated temperatures, should be investigated to ensure performance and structural integrity.

Aerogel is a nanoporous solid, originally developed during the 1930s. This insulation is suitable for PIP applications, and is classed as a high-tech material with excellent thermal properties compared to PU foam.

Aerogel is a high-performance thermal insulation used in a variety of forms and conditions, and is one of the worlds best insulating solids. It has many advantages: it is lightweight, water repellant, highly porous, has a unique microstructure, high surface area, translucent or IR-opacified, and is available in a number of grades. It achieves high levels of thermal insulation due to the entrapped air in its micropore structure. It has extremely low thermal conductivity, 0.008-0.013 BTU/hr.ft.F (14 - 22 mW/m.K) and is stable from -321 to 662F (-196 to 350C). It is water resistant and can be dried if there is water ingress.

Aerogel allows the design of pipelines with overall system 'U' values significantly less than 0.176 BTU/hr.ft2.F (1.0 W/m2K) without compromising the overall external dimensions of the PIP system. Loadshares

Load shares are necessary to redistribute gravity loads between the inner and outer pipes of an un-bonded PIP. Without load shares, the accumulated in-situ compression load in the inner pipe can reach 30% to 50% of yield strength (4). Upon startup, the added thermal expansion compression can result in failure (axial collapse-rupture) of the inner pipe due to combined axial compression and internal pressure loads. Load shares combined with pre-tensioning of the inner pipe prior to establishing the load share coupling redistributes the PIP gravity loads to realize a much lower in situ axial compression load in the inner pipe.

To be effective the pre-tension must be performed before excessive friction between the inner and outer pipes prevent the desired distribution of the pre-tension load. Practically, this implies that the load share spacing should be something less than the water depth, although it might approach or equal the water depth. Detailed FEA is performed to validate the load re-distribution achieved for a selected spacing by load shares and pre-tensioning (7, 8).

Mechanical loadshares seem to be the preferred method of choice. This method employs a bi-radial clamp which mechanically locks the inner and outer pipes together. Although these clamps are relatively expensive, it is presently the only viable method. As these components are steel, there are no long-term degradation issues. Finite Element Analysis (FEA) should be undertaken to avoid a global collapse-rupture in a PIP flowline. TESTING OF PIP COMPONENTS

J P Kenny recently undertook a series of tests for a major operator in the Gulf of Mexico region. The objectives of the tests were to qualify PIP components for extra high-temperature and extra high-pressure conditions. In the following section, the different components tested are described, and results from the tests are presented.

The tests were undertaken for the base case of an 8 inner pipe, 12 outer pipe, with a maximum operating temperature of 350F (177C).

Centralizer Tests Centralizers are used to avoid the loading that could crush the

thermal insulation. Installation loads can be particularly large during reeling, and the centralizers are tested in compression for the maximum loads seen during the reeling process.

Operational conditions need to be considered, and degradation of the material due to temperature, long-term creep, and structural integrity are all issues related to the performance of the centralizer. These high temperatures severely restrict the material selection available for pipe-in-pipe centralizers. Based on the temperature, a modified Polyphenylenesulphide (PPS) material was selected for testing, based on its characteristics of having high thermal mechanical strength, high hardness and rigidity, high creep strength and excellent wear characteristics.

The type of tests undertaken when testing centralizers are as follows:

Slippage Tests; Abrasion Test; Creep Tests; Bolt Relaxation Test; Aging Test.

The test program that J P Kenny is presently undertaking is still ongoing, however some of the preliminary findings are presented (9). Slippage Tests. The aim of the slippage test is to ensure the centralizer does not slip on the flowline under installation and in-service loads. A typical test set-up for the slippage test is shown in Figure 2.

Fig. 2: Centralizer slippage test setup Both sets of centralizers tested suffered brittle failures prior to reaching the weld bead, which meant that the test was abandoned and the centralizer could not pass over the weld bead. Figure 3 shows a failed centralizer from the slippage test.


Fig. 3: A failed specimen from slippage test

Abrasion Tests. The abrasion test consists of passing a centralizer over a number of weld roots. A winch is used to pull the flowline assembly along the length of an 80 ft (24m) trough. A total of 17 runs were intended, equating to 119 weld beads passed. However, after five complete passes (35 welds), the centralizer suffered brittle failure.

As a result of the brittle failures, for both the slippage and abrasion tests, the other tests were abandoned, and a search is still continuing for an appropriate material suitable to 350F (177C) with acceptable ductility.

Conclusions following the tests are that there is no single thermoplastic capable of meeting the stringent demands covering both insertion case and service conditions for a centralizer, and the solution relies on a substrate, possibly such as a pultrusion being overlaid with a cast polyamide material. Such configurations could offer the temperature requirement local to the inner pipeline, and the necessary creep and abrasion resistance to cater for insertion. Waterstop Seal Tests

Testing of the waterstop seals is necessary to ensure the seal can undertake the hydrostatic loads in the event of flooding. Due to the high-temperature of the inner pipe, sealing tests at temperature are also undertaken to ensure that material degradation of the seal does not impact the integrity of the seal. A test is performed to examine the integrity of the seal at temperatures of 350F (177C) and a water-depth pressure equivalent to 4500ft. Figure 4 shows a typical arrangement of the waterstop seal and clamp arrangement to be used in a PIP. The following tests are undertaken for the testing of PIP waterstop seals (10):

Load Tests Hydrostatic Pressure Test Elevated Temperature Test Material Aging Test

Load Tests. Assuming a breach of the outer pipe, the hydrostatic pressure will create an axial load on the waterstop seal and clamp. A force based on water-depth pressure of 4500ft (1372m) was used. The test load was 90.2Te (885kN), and this included a load factor of 1.1. The load was applied for 5 minutes, and no slippage occurred. The test was deemed successful.

Fig. 4: Field proven waterstop seal

Pressure Tests. A further requirement of the seal is to provide leak-free sealing of the large pressures that occur in the PIP annulus if the outer pipe is breached. The purpose of this test is to verify the pressure and sealing capacity of the waterstop seal. The seal was enclosed in a special pressure test rig consisting of bolted end flanges. The seal was tested to 375bar (37.5MPa), which includes a safety factor of 1.25. A pressure based on water-depth of 10,000ft (3050m) was applied. The seal was examined after the test, and no permanent seal damage was observed. Below is a picture of the pressure test apparatus and setup.

Fig. 5: Waterstop seal pressure test in progress

Elevated Temperature Test. In the event that an outer pipe breach occurs, the water in the annulus will be heated due to the temperature of the inner pipe. Hence it was important to verify the temperature resistance capacity of the waterstop seal. The seal was tested at 383F (195C) with a test factor of 1.1. The applied pressure was 375 bar (37.5MPa), and represents 10,000ft (3050m) water depth with a test factor of 1.25. A range of different seal materials was investigated.


The final seal type used a hydrogenated nitrile butadiene rubber (HNBR) lip, and a thermoplastic body, as shown in Figure 6.

Fig. 6: A typical HNBR / plastic seal (10)

Hydrogenated nitrile butadiene rubber (HNBR) has an

intriguing combination of properties. Like other elastomers, the HNBR material has high tensile strength, low permanent set, very good abrasion resistance and high elasticity. But in HNBR, these are complemented by good stability from thermal ageing and better properties at low temperatures compared to other heat- and oil-resistant elastomers. This combination of properties makes it particularly suitable for a high-temperature waterstop seal.

Fig. 7: Pressure / temperature versus time

Temperature and pressure was held at 375 bar (37.5MPa) and

383F (195C) respectively for 24 hours. Upon inspection of the seal following removal from the rig, it was clear that the thermoplastic body had tolerated the pressure and temperature combination loading. There were no leaks past the seal during the test. The sealing lip showed no visible signs of damage or deterioration.

Material Aging Tests. The purpose of these tests was to investigate the integrity of the seal due to thermal aging. The method of testing is based on the Arrhenius principle, which artificially ages the material by applying a temperature greater than its service condition to accelerate the deterioration. A temperature of 554F (290C) for 6 days, which is equivalent to 30 years service at 350F (177C), was applied.

As the inner pipe will be operating at 350F (177C) continuous service there will be a considerable temperature drop to the outer pipe wall at seabed ambient temperature (typically 37-41F (3-5C)) in the actual service condition. It was assumed for test purposes that the average temperature across the whole seal is approximately 194F (90C) during its working life. Based on this, age testing was carried out at and based against the actual 194F (90C) average. It was decided that this would give a more accurate conclusion regarding the actual material service life.

Tests undertaken at 554F (290C), and using the Arrhenius principle, showed that the material would still be serviceable at 350F (177C) for up to 30 years. For the test at 350F (177C) the material was unaffected over a 42 day test period. Thermal Insulation Testing

The primary objectives of these tests are to evaluate the effect of exposure to extreme operating temperatures of 350F (177C) and compressive stresses (due to pipe laying and lateral buckles). The compressive stresses are applied for prolonged periods of time to determine the insulation performance and mechanical integrity of the aerogel material. Two different types of material tests were undertaken to examine this effect.

The first test evaluates the thermal conductivity of the material after aging at the maximum operating temperature, and the second evaluates the mechanical integrity of the material after thermal aging under installed conditions by unidirectional compression loading. The compression loading deformation is limited by centralizers. Worst case deformation is likely to occur in the pipe straightener during reel-lay; however this is prior to aging. Subsequent in-situ deformations are probably less, but the material will be thermally aged.

The testing of the thermal insulation has a number of specific objectives, as follows:

To evaluate the thermal insulation of the XHPHT PIP system;

Obtain thermal conductivity at different levels of compression and different mean temperatures;

Ensure no long-term degradation of the thermal properties of the aerogel insulation, such as thermal conductivity;

Mechanical testing of the material to understand how it behaves under compression;

Ensure that compressive loads are not detrimental to the thermal performance;

Assess thermal aging effects on structural integrity of the aerogel.

The following tests were successfully undertaken on aerogel materials:

Thermal conductivity; Compressive strain recovery after static loading - resilience; Hydrophobic threshold;


Long-term exposure of high-temperature on shrinkage; Aging effect of high-temperature on thermal conductivity

and mechanical integrity. Nanogel Aerogel Thermal Insulation

Nanogel aerogel from Cabot Corporation is a particularly thermally efficient insulation material. It is an extremely lightweight and ultra-high performance insulation material that can be used in PIP systems as a substitute for typical insulation materials, such as PUF. Nanogel aerogel is produced by drying a gel to produce a solid material that consists of a lattice structure of the gel material with nanometer-sized pores dispersed throughout the material. The size of the pores (~20-40 nm) is smaller than the mean free path of air (~60-100 nm) and consequently gas phase conduction is greatly reduced as a heat transfer mechanism. The thermal conductivity ranges from 0.008-0.013 BTU/hr.ft.F (14 - 22 mW/m.K).

The important salient features of aerogel are as follows: Pure aerogel in granular form Worlds best insulating solid Lightweight Hydrophobic (water repellant) Highly porous Unique microstructure (fractal) Elastically compressible (springy)

Fig. 8: Lattice arrangement of Nanogel Aerogel

The lattice arrangement of Nanogel aerogel is shown in Figure 8.

The use of opacifiers, such as carbon black or titanium dioxide, are introduced into the aerogel to minimize radiation effects. A number of

thermal conductivity and mechanical property tests were undertaken (11) as described in the following sections. Thermal Conductivity Tests

The first step of the test method is aging of the opacified aerogel. The most extreme operational thermal gradient that the aerogel will experience in the XHPHT pipe-in-pipe system is 310F (154C), based on 350F (177C) internal contents temperature, 40F (4C) seawater on the outside of the carrier. The samples of aerogel were conservatively aged at 350F (177C) in glass containers, under 0% compression, in an oven for 0, 1, 2 and 4 weeks to evaluate effects of thermal aging.

The first set of thermal conductivity measurements was undertaken at 0% material compression. Tests were undertaken in accordance with ASTM C518. Conductivity measurements were made over a range of mean sample temperatures of 14F, 55F, 100F, 145F, and 176F (-10C, 13C, 38C, 63C, and 80C) with the hot and cold plate boundary temperatures.

The maximum mean testing temperature equipment was limited to 176F (80C) whereas the mean temperature of the XHPHT system is 195F (91C) (assuming seawater at 40F (4C) and product at 350F (177C)). This compromise is considered to have negligible impact on the results.

Thermal conductivity tests were also undertaken at 15% and 30% compression, to represent the expected levels of installed compression.

The results did show a downward trend for the tests aged for four weeks, however the trend was not statistically significant. Figure 9 and 10 show typical set of results for thermal conductivity for 0% and 30% compression respectively. The graphs also show the effect of age and temperature on the thermal conductivity.

Fig. 9: Thermal Conductivity (mW/mK) for

0% Compression

The results of the thermal conductivity testing demonstrated; A very tight standard deviation in the test results. Thermal conductivity increases with temperature Thermal conductivity was not affected by aging. Effect of compression on thermal conductivity

demonstrated some improvement in k-factor due to pore-size reduction


Fig. 10: Thermal Conductivity (mW/mK) for

30% Compression Mechanical Integrity Tests

Ageing tests were undertaken at 0%, 15% and 30% compression. Aging effects were investigated in material sample holder with different compression levels. The material sample holder consisted of polytetrafluoroethylene (PTFE) cylinder, 1.52 inner diameter, and two cylindrical, aluminum plates locked in place with machine screws. By varying the quantities of aerogel material it was possible to produce samples with different compression levels, as shown in Figure 11.

Fig. 11: Sample holders for mechanical integrity testing

The aging system consisted of placing the mechanical test specimens in the cold/hot plate system. Thermocouples were used to measure the temperature. Figure 12 shows a typical sketch of the aging setup for mechanical integrity test samples.

The Youngs Modulus for the test specimens was determined using an Instron 5500R uniaxial mechanical testing machine. The compressive testing consisted of ten, 5% strain compression cycles. The 5% strain level represents the level of strain experienced by the aerogel during laying and operation. Compression cycles for various aged samples were 0, 1, 2 and 4 weeks at 0%, 15% and 30% pre-compression. The results are shown in Figure 13.

Fig. 12: Aging setup for mechanical integrity test samples

Fig. 13: Young s Modulus (MPa) for 0%, 15%, 30%

compression over four weeks aging

Results of mechanical testing of aerogel material showed the following;

Youngs Modulus increased with the level of compression; Aerogel aged up to four weeks at 350F (177C) does not

show any statistically significant aging effects on mechanical stiffness;

Cabots Nanogel aerogel material does not thermally age while operating continuously at temperatures up to 350F (177C).

The tests were successful and it can be concluded that Cabots Nanogel aerogel is suitable as thermal insulation for XHPHT PIP systems. Mechanical Clamp Loadshare Tests

A mechanical radial clamp will be inserted in the annulus of the PIP. The purpose of testing of a mechanical clamp loadshare is to ensure performance as a loadshare component in the PIP system. Load tests were successfully performed on the loadshare.


Fig. 14: A typical arrangement of a load share clamp

Load Test. The maximum expected axial load for the loadshare was determined using finite element analysis FEA (7, 8). For a water depth of 4500ft (1372 m), the test load was 193.6Te (1900kN) and this included a load factor of 1.1. The load was applied using a series of four calibrated hydraulic pistons and a calibrated hydraulic hand pump. The full test load was applied for one hour.

Figure 15 A loadshare clamp axial load versus

clamp activation chart The results showed no slippage of the clamp. No further movement occurred, as shown in Figure 15. No buckling of the inner pipe occurred, and the test was successful. CONCLUSIONS

This paper describes a qualification testing programme for the testing of PIP components for 350F (177C) service, and includes the testing of centralizers, waterstop seals, thermal insulation and loadshares. Conclusions from the testing program are;

Centralizers. The test program was not successful. The main challenge is finding a material suitable to 350F. Materials tested to date have failed due to lack of ductility (brittle behavior).

Waterstop Seals. Waterstop seals were tested for structural loading and thermal testing, and the seal passed all aspects of the testing.

Thermal Insulation. The Nanogel aerogel material tested does not thermally age while operating continuously at temperatures up to 350F (177C). The material is very well suited for PIP insulation applications in XHPHT systems.

Loadshares. The tested design is suitable for accepting a load of 176Te.

The qualification testing of the components presented within this paper extends the boundaries of what is possible with PIP designs and opens up the possibility of XHPHT field developments in the GOM.

ACKNOWLEDGMENTS The author would like to thank all that have provided input into

this work, especially BP, Cabot Corporation, TEKMAR and Devol Engineering Ltd.

REFERENCES [1] Jukes, P and Harrison, G. An XHPHT Pipe-in-Pipe Design for

Installation By S-lay, J-lay and Reel-lay Methods, Proceedings of IOPF2006-16, Houston, Texas, USA, October 24-25, 2006.

[2] J P Kenny Inc., Extra High-Pressure High-Temperature Pipe-In-Pipe Design Study, Internal Report, Rev. 0, July 2006.

[3] J P Kenny Inc., XHPHT Pipe-In-Pipe Design Study: sensitivity for additional water depths (7,750ft and 10,000ft), Internal Report, Rev. 0, July 2006.

[4] Harrison, G. and McCarron, W. Potential Failure Scenario for High-Temperature, Deepwater Pipe-in-Pipe, Proceedings of Offshore Technology Conference, OTC# 18063, May 2006.

[5] Jukes, P., A Design Philosophy for Lateral Buckling in Deepwater, Proceeding of ASME International Petroleum Technology Institute, IOPF# 2006-002, Oct. 2006.

[6] Jukes, P., Wang, J., Eltaher, A., and Harrison, G. A General Flowline Thermal Expansion Design Philosophy Employing Buckle Initiators and Piles, Proceeding of IOPF, Houston Texas, USA, October 23-25, 2007.

[7] J P Kenny Inc., XHPHT Component Testing & Further FEA - Local Loadshare FE Study, Internal Report, Rev. B, June 2007.

[8] Sun, J.J., Jukes, P and Eltaher, A., Finite Element Analysis of Loadshare for the Installation of Pipe-in-Pipe Flowline by S-lay and J-lay Methods, Oceans 07 MTS/IEEE Conference, Vancouver, Canada, 29th Sept-4th Oct, 2007.

[9] Devol Engineering Ltd, HPHT Pipe-in-Pipe Centralizer Evaluation, Document No. CDT 6676 CR, Feb. 2008

[10] TEKMAR, 8/12 pipe-in-pipe waterstop seal development programme test report, 7th Issue, 6th Oct. 2008.

[11] Cabot Corporation, Nanogel Aerogel Material Qualification Testing Report, June 2007.

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Iopf Paper Qualification Testing 04 Final1