Flexible Pipe

"Flexible Pipe in Brazilian Ultra-Deep Water Fields – A Proven Solution" by A.Novitsky and S.Sertã, Technip-Coflexip

FLEXIBLE PIPE IN BRAZILIAN ULTRA-DEEPWATER FIELDS – A PROVEN SOLUTION

Authors:

Adriano NOVITSKY, Sergio SERTÃ, Technip-Coflexip , Brazil

DEEP OFFSHORE TECHNOLOGY 2002

ABSTRACT The paper will present a summary of the main achievements by Technip-Coflexip on Flexible Pipe area and applied by Petrobras on the development of Brazilian UDW fields in the Campos Basin. A great part of this technical development has been done in partnership with Petrobras through Technical Cooperation Agreements. It will also present the actual design capabilities available to face the future challenges in deeper waters. In ultra deep water, riser systems must be able to withstand high loads varying in magnitude and nature along their lengths. This means that optimization of the different sections can require the use of different designs and even different types of pipe along the length of the riser. Technical developments have contributed to provide a reliable and effective solution in terms of greater diameter structures for applications in deeper water, mainly the increase of collapse resistance, Kevlar tapes optimization, design optimization with relation to buckling resistance of armor wires and new mathematical models development and validation. These solutions have been developed either through Technical Cooperation Agreements (TCA’s) or projects with Petrobras, where the “new” structures were designed, manufactured, tested and certified by the Bureau Veritas. Some of these developments were a 6” insulated flowline for 2000m WD a 9.12” riser for 1500m WD, and a 12+EC umbilical for 2000m WD. These new flexible pipes designed and manufactured by Technip-Coflexip (formerly CSO, now Technip-Coflexip since October 2001), have been already installed in Roncador and Marlim South fields, setting the new world record for the deepest application (1890m WD) achieved on May 2002 in Roncador.

New design capabilities to tackle water depths down to 3000m, expected in Brazilian future UDW developments, are also included in this paper.


1. INTRODUCTION The developments on Brazil’s offshore segment in the last three years were remarkably important for the offshore world, due to the important achievements observed in technical areas, more specifically on the development of pipe solutions for UDW applications. Following the development of two major Petrobras fields localized in the Campos Basin, Roncador and Marlim South, Technip-Coflexip has designed, tested and installed Flexible Pipes, proving the fitness of this kind of product to UDW applications. In order to bring these two fields into production, Petrobras has demanded from Flexible Pipes manufacturers the development of products able to work within the environment condition related to these applications, to say, Floating Systems (FPSO or Semi-submersible) anchored up to 1500m WD and wells localized up to 2000m WD. The development of Flexible Pipe solutions for this demand was carried out either through Technical Cooperation Agreements between Technip-Coflexip and Petrobras, or by Technip-Coflexip itself, within projects Roncador Phase I and Marlim South Module I. During this development, the main design aspects related to UDW applications as Collapse, Reverse End-cap Effect, Lateral Buckling and Thermal Insulation, have been technically scrutinized and re-validated through qualification tests, simulating the real field conditions seen by the pipes during installation and operation phases. The objective of this paper is to present an overview of all the work that has been carried out either together with Petrobras, or by Technip-Coflexip Brazil, in order to achieve optimized and safe Flexible Pipe solutions to be applied on the development of these two major Petrobras fields. The paper will also present current status of development of Flexible solutions for the next goal to be pursued off-shore Brazil, Roncador phase II, with a floating unit anchored at 1800m WD. New technologies developed by Technip-Coflexip aimed at going deeper will be also presented.

2. MAIN DESIGN ASPECTS IN UDW APPLICATIONS Collapse In order to resist to differential pressures created by hydrostatic external pressures, a Flexible Pipe bears in its structure, collapse resistant layers. These layers can be of the type Interlocked Carcass (internal or intermediate) and/or Pressure Armour (Ex. Zeta, Teta, Psi, Flat spiral). They work together against collapse and their dimensioning is done using a validated collapse model. The current model used by Technip-Coflexip has been calibrated by over 150 collapse tests carried out on different structures of different diameters and structure layer compositions( type, thickness and materials). During the qualification process for Roncador Phase I flexible pipes (risers at 1500m WD and flowlines at 2000m WD), all the collapse tests carried out to qualify the designs were used as well to re-validate the previous Technip-Coflexip’s collapse model within the correspondent range of aplication. Following to the conclusion of this re-validation work, Technip-Coflexip was given by Bureau Veritas in may/2000, a third


party Certification of the model (Figure 1) which is currently used by the group for designing Flexible Pipes against collapse, which is validated within the following range: Internal Diameter: 2.5” to 16” Water Depth: up to 3000m Structure composition: Carcass, Zeta, Teta and Flat Spiral In addition to the model re-validation, as part of new technological developments for UDW applications, Technip-Coflexip has qualified a new grade of stainless steel (High strength 304L) to be used in the manufacturing of Interlocked carcasses which has a higher yield strength, equivalent to Duplex, but at lower cost. This new material, used in some of the pipes supplied for Marlim South project, allowed a reduction on carcasses thickness, with consequent weight reduction and cost optimization. Reverse End-cap Effect In the same way as an internal pressure results in an axial tension on a pipe, when submitted to external pressure, a pipe will see an axial compression (Reverse End-cap Effect). The magnitude of this compression on a Flexible Pipe is equal to the differential pressure acting on the pipe multiplied by the diameter correspondent to the outermost sealed barrier. In case of an intact external sheath, this diameter is the external diameter of the pipe. In case of a damaged external sheath, this diameter is the external diameter of the next sealed barrier, commonly the pressure sheath for rough bore or the anti-collapse sheath for smooth bore pipes. The layer designed to withstand all the axial loads in a Flexible pipe is the tensile armour. As the tensile armours are helically applied on the pipe, they tend to move radially when submitted to axial compression. This opening movements of the armours, are restrained by the external hydrostatic pressure acting on the external sheath of the pipe. If the external sheath is damaged for any reason, and there is no other mechanical element resisting to the radial movement of the armours, they can buckle radially, creating a disorganization

Water depth up to 3000m

ID from 2.5” to 16”

Figure 1: Collapse model certification


which is commonly known as a “bird cage”. For UDW applications, where the differential pressures could increase significantly, high strength tapes are applied on the armour layers in order to prevent pipes from “bird caging”. Technip-Coflexip have been using high strength tapes in Kevlar29 material over the last 10 years. As part of the new technologies developments for UDW applications, Technip-Coflexip has also qualified a new Kevlar grade which has a higher Elasticity Modulus (Kevlar49), allowing to reduce the number of tapes for the same required resistance. This new material, used in some of the pipes supplied for Roncador and Marlim South projects, allowed a cost reduction and consequent increase on Flexible solution competitiveness. Lateral Buckling When a Flexible pipe is subjected to axial compression and cyclic bending simultaneously, the tensile armour wires, which are responsible for taking all the axial load applied to a flexible pipe, tend to move. As the radial movement is restrained either by the hydrostatic external pressure (in case of a sealed outer sheath) or by the high strength tapes (in case of damaged outer sheath), the wires will tend to move laterally. If the armours are not resistant enough, they can buckle laterally leading to a type of failure called Lateral Buckling. This phenomenon was firstly observed in may 1997 during the installation of MLS-3 production bundle in Roncador field at 1709m WD. During this operation, a 4” flexible jumper was severely loaded (bending plus axial compression) due to difficulties during the vertical connection operation, leading to its failure. After recovery of the pipe, it was detected that a Lateral Buckling had occurred. The buckle of the armours can be associated to two mechanisms; The first one occurs when the outer sheath is sealed. In this case, when the pipe is bent under axial compression, the high internal friction forces between layers restrain the wires from moving laterally, leading to a high compression stress that could reach the yield of the material and a failure by over-stress could happen. The second mechanism occurs when the outer sheath is damaged, and the internal friction forces are strongly reduced. In this case, in addition to the possibility of an over-stress, the wires could move laterally and the buckle could happen due to elastic instability (Euler mechanism). After the failure of MLS-3 jumper, a strong effort was put in place by Tecnhip-Coflexip, to generate a mathematical model to predict this phenomenon. A significant number of offshore tests, so called DIP tests (Deep Immersion Performance tests), were carried out applying differential pressure combined to bending on the pipe, simulating its installation and service conditions. The tests were performed for both conditions of external sheath; sealed and damaged. A description of the offshore DIP test is presented in chapter 3 of this paper. Figure 2 shows respectively an ROV view of one of the DIP test performed offshore for Roncador project at 2000m WD, and the expertise done after the test to verify the condition of each layer of the pipe, more specifically the armours against buckle phenomenon.


As an alternative to the offshore tests, which are very expensive and time consuming, onshore tests have been also carried out. These tests were done in a large hyperbaric chamber, inside which a bending device was installed and used to bend the pipe to a controlled radius. Submitting the sample to external pressure and bending simultaneously, the real offshore condition could be well represented . Figure 3 shows the bending apparatus and the hyperbaric chamber used for the tests. Based on the results from offshore and onshore tests, a preliminary methodology has been set and validated by Bureau Veritas for water depths up to 2000m and internal diameters up to 12”. For this range, the current methodology showed to be conservative. A Finite Element Model is currently being developed by Technip-Coflexip in conjunction with IFP. The main parameters which influence the resistance of a flexible pipe to Lateral Buckling are: -Section of wire (width and thickness) -Steel grade -Angle of armours -Amount of high strength tapes The adjustment of the above parameters in a flexible structure is an optimization work which must be done in a way to obtain the required resistance with a minimum cost.

Figure 3 : Bending device (L) used for a DIP test in hyperbaric chamber(R)

Figure 2: ROV view during a DIP test at 2000m WD and the armours in a normal shape after expertise


Thermal Insulation Roncador project required a certain level of thermal insulation in order to reduce the number of pigging operations for wax removal. Technip-Coflexip´s solution was to apply passive insulation externally to the 6” production pipe in order to reach the required TEC (Thermal Exchange Coefficient) of 2.8 W/mK. The chosen material was syntactic foam tapes, wounded on top of the external sheath of the pipe and protected by a second outer sheath. This material is composed of a base matrix of polypropylene containing microscopic glass spheres, which combines good insulating performance and pressure resistance (up to 300bar) with high flexibility for the manufacturing process. The design of the insulation layers took into account the effect of creeping of the material under high contact pressures. The creeping effect is taken into account in the design as a thickness reduction of the insulation layer. Another important aspect considered on the insulation design was the reduction of efficiency of the syntactic foam due to water absorption, resulting in an increase of the thermal conductivity of the material.

In order to validate the design regarding the required global thermal coefficient, a laboratory test of TEC was carried out on the 6” production riser simulating different states of heating flow. Also, two different insulation annulus conditions were tested, dry and flooded. A description of the test is presented on item 3 of this paper. Figure 4 shows the test results for both annulus conditions. The maximum TEC obtained was of 2.61W/mK for dry and 2.69 W/mK for flooded insulation, against 2.8 W/mK required. The obtained results showed some conservatism on the design methodology applied.

Roncador flexible pipes were installed by the Sunrise 2000 laying vessel in water depths up of 1900m. In order to verify the integrity of the syntactic foam after the passage of the pipe through the laying tensioners, a mechanical compression test under 4V shaped pads was carried out simulating installation conditions. A description of the test is presented in chapter 3 of this paper. After the test, a microscopic analysis was performed on the foam to verify any degradation on it’s structure due to the applied compression forces (100T/m). No degradation neither on the base material (polypropylene) nor in the glass spheres was observed. Figure 5 shows the material before and after the compression.

Figure 4: TEC measurements for dry and flooded insulation


Fatigue Another important aspect on the design of a Flexible Pipe is the behavior of it’s dynamic sections with regard to fatigue of it’s metallic layers. To design the risers against fatigue, design tools have been developed and validated by an extensive full scale test program. The methodology behind these tools were fully accessed and certified by Bureau Veritas. Although fatigue issues have not been, in general, the driver for Flexible design offshore Brazil, two full scale fatigue tests were performed, on Petrobras request, to qualify a 6” Production riser for Roncador (P-36) and an 11”Gas Export riser for Marlim South (P-40). The tests simulated the operating condition at 1500m and 1080m WD respectively. Both test results showed no sign of fatigue related failures neither on the flexible structural layers nor on the ancillary equipment (end-fitting and bend stiffener) connected to the sample. A third successful test was also carried out on a 12 + EC Umbilical for 1500m WD. A brief description of the dynamic test procedure is presented in chapter 3 of this paper.

3. QUALIFICATION TESTS Test Brief Through the last 5 years, more than 400 qualification tests have been carried out for Brazilian projects, mainly for UDW applications. The tested samples represent the actual product supplied to the client considering design criteria, manufacturing procedures and process. Before testing the structures a comprehensive test procedure was issued for the client for approval. A brief description of each test the structures where submitted is given hereafter. Deep water immersion performance (dip test offshore) The objective of the DIP test is to simulate the expected conditions during the installation/operation of the pipe at its maximum water depth, when it is submitted to hydrostatic pressure and bending simultaneously. The test shall assess the behavior of the tensile armors with respect to the buckling phenomena.

Figure 5: Insulation material before and after mechanical compression test


The sample is loaded on board a laying vessel and transported to an adequate deep-water location to carry out the tests where they are laid empty connected to another line (pipe-follower) using special plates to prohibit the relative rotation between each line. In order to have some back tension while positioning the samples on the seabed, a clump weight is connected to the sample free end fitting. This allows a large bending radius to be formed prior to start the test. The laying vessel is then positioned to create a small bending radius to simulate extreme loading conditions for the sample. The vessel closes the catenary as much as possible until the smallest radius is achieved, normally detected when sample starts moving laterally. From this point on, the vessel starts to move back and forward in order to impose a cycling bending which is amplified by the vessel top dynamic motions. Each sample is tested in two conditions regarding the water-tightness of external sheath; sealed (dry annulus) and damaged (flooded annulus) with a duration of 4 hours each and the ROV continuously monitor the section of the sample with minimum bend radius using marks painted on the external sheath of the test sample to evaluate the achieved bend radius (figure 6). Collars previously installed attached to the upper end fitting are released by ROV (figures 7 and 9) at pre-selected steps in order to detect any local change on the diameter of the sample and as an aid for the on site survey. If a buckle has happened the collar will stop at the point. After the dry annulus test has been performed on the sample and to simulate a damaged outer sheath condition the test is repeated with the sample annulus flooded with sea water (figure 8). At the completion of both dry and flooded annulus test the sample is brought back to shore where a comprehensive dissection is done. Dynamic fatigue test Figure 8: ROV removing the plug to flood the annulus Figure 9: Sample being brought back to vessel – collars

could be seen above the lower end fitting

Figure 6: Sample on the bottom being cycled Figure 7: Collar running along the sample and painted marks on the external sheath


This is a long duration test to simulate the loads the riser will see on its service life. To simulate the different load conditions the test is divided in several blocks comprising pairs of tension and angles based on the environmental data and floater data specified for the application. The test is done in a sample submitting it to cyclical loads of tension and bending varying simultaneously and in phase. The bending load is applied at one extremity of the sample where a bend stiffener is installed to induce rotation in a single plane. On the other end a hydraulic cylinder applies tension to the sample. During the whole test the sample is kept pressurized to its design pressure. Figure 10 shows the dynamic apparatus. Throughout the test the number of cycles, applied tension and angles (top and bottom), bending moment, internal pressure, internal and ambient temperature data are continuously recorded. At the completion of all cycling blocks the sample is fully dissected with special attention to the location where highest curvature variations occurred and on the end fitting.

Internal pressure test This test evaluate the flexible pipe structure resistance to internal pressure and is performed with the sample with end fittings assembled suspended/laid out full of water on a device that allows its free rotation and longitudinal and radial deformations. The sample is pressurized up to the structure design pressure and bleed to atmospheric pressure and in this process some data are recorded such as elongation, diameter variation and free end rotation. The sample is then re-pressurized at a controlled rate until failure having its burst pressure, failure mechanism and location recorded.

Hydraulic cylinder to apply tension

Hydraulic cylinders to apply bending

Figure 10: Sample placed on the dynamic fatigue bench


Thermal exchange coefficient measurement To perform this measurement one should guarantee a steady heat flow across the sample structure. This is obtained by sealing with a good insulation material both ends of a representative sample from the surrounding environment where freezing water is kept. An electrical heater is placed inside the sample with water and dissipates heat at a controllable and continuous power rate. To measure the temperature gradient at different pair of points, inside the sample wall and on the outer sheath, thermocouples are placed and their readings are gathered. For a given electrical power the temperature gradient between a pair of thermocouples will vary until the steady flow is reached. Repeating this process with different power levels the coefficient which provides the heat loss (Watt) of 1m of line when subjected to 1°C difference between its internal and external surfaces can then be obtained. Figure 11 shows the the test assemble. External pressure test The structure resistance to external pressure is evaluated on this test that is done with the sample placed empty inside a hyperbaric chamber with or without end fitting assembled. In case the sample is assembled with end fittings their sealing system can be also verified usually with the maximum differential pressure acting during 24 hours after an initial stabilization. In both cases the chamber is pressurized with water at a controlled rate until the collapse of the sample. The collapse pressure, failure description, and location are recorded. A cylindrical piece of the outer sheath is removed to guarantee that the external pressure is acting directly on the pressure barrier and in case of smooth bore pipes the external pressure shall act on the leak proof intermediary polymeric layer.

Figure 12: View of a sample carcass after being collapsed

Figure 11: Thermal Exchange coefficient test of Roncador 6” flowline


Tensile test To simulate the passage through the laying vessel sheave this test is done over a device that associate tension and bending acting over the sample. This device is a bend jig with the same bend radius and transverse profile of the sheave. The sample is positioned empty and without internal pressure over the bend jig and is uniformly tensioned a little over the laying tension by means of hydraulic jacks on both its extremities. After the tension is kept for a period of one hour the longitudinal deformation and outside diameter are measured being the same measurements repeated after the tension is released to obtain the residual values. Figure 13 shows the bending test apparatus at Vitória site. Combined tensile and pressure test This test simulates the condition when the pipe is submitted to tension and internal pressure simultaneously being the sample placed straight and full of water in a tension bench. The test pressure is set to the operating pressure and kept during the whole test period then the sample is tensioned at a controlled rate until failure. Neither leakage nor failure is accepted until tension reaches two times the operating tension. The rupture tension, failure mechanism and location are recorded. Radial mechanical compression test During the laying process on board the line withstand tension driven by its own weight and compressive load driven by tensioners. To simulate this operation the sample is placed empty and with no internal pressure in a tension bench equipped with a special compressive device that simulates the laying vessel tensioners with regard to geometry of shoes and the number of belts. The laying tension is than applied to the sample at a controlled rate and kept constant during the whole test. The compressive crushing load is increased up to a pre-determinate value and kept constant for a period of one hour. In the loaded condition and after completely unloading the sample it’s inside diameter are measured in two positions 90° apart in the sample’s middle transverse section.

Figure 13: View of the 3m radius bend jig


Outer sheath holding system To assure that the end fitting outer sheath holding system properly grips the outer sheath when the line is laid and during its operation this test is done. It consists of placing a short line sample with only the outer sheath hold the same way it is on the actual end fitting by means of a dummy one. On the other end the outer sheath is pulled by another fitting up to the outer sheath ultimate loading.

4. PROVEN TECHNOLOGY OFFSHORE BRAZIL Flexible pipes have been extensively used offshore Brazil for the last 25 years. The first lines were installed in 1978 at Garoupa field at 160m WD. Today, there is approximately 4000 Km of flexible pipes operating in Campos Basin, including risers, flowlines and umbilicals. Approximately 95% of these pipes have been supplied by Technip-Coflexip. About 550 flexible risers are installed on the 28 units operating today in the Campos Basin (Jackets, SS´s, FPSO´s, and FSO´s). The advantages in terms of easy installation and recoverability associated to fast manufacturing and competitive cost, have made the flexible solution very present in the development of Brazilian fields. A recent example of the advantages of flexible solution in Brazil was experienced in Roncador project, where, for a scope of approximately 500Km of pipes, the flexible solution showed to be more competitive than the carbon steel rigid one and was then chosen by Petrobras as the solution for the phase 1 of the project. Several kilometers of insulated flexible flowlines have recently been recovered in Roncador (figure 17) for further re-utilization in the future field arrangement. This shows the benefit of the recoverability aspect offered by flexible pipes.

Figure 15: Detail of the compressive device simulating a 3 belt tensioner

Figure 14: View of the tension bench with the compressive device

Figure 16: Detail of the sample outer sheath at the completion of the test


The barrier of 1000m WD offshore Brazil was broken in 1994, with the connection of well MRL-4 in Marlim field. Since then, fields like Marlim, Albacora, Barracuda and Espadarte, located below 1000m WD, have been put into production through flexible pipes. Following the development of Roncador and Marlim South fields, several flexible pipes were installed offshore Brazil in ultra deep waters (up to 1900m WD). Table 1 below, summarizes the proven technology of flexible pipes operating today in Brazil. As already presented in this paper, in addition to be already in operation (field proven), these technologies have been validated through extensive qualification test programs, simulating their design conditions.

Type of Pipe Field Unit Deepest Installation WD

Qualification WD

2,5” Gas Lift Riser/Flowline Marlim South P-40 1080/1025 1500 4” Production Riser Marlim P-40/P-36 1080/1360 1500 4” Gas lift Flowline Roncador FPSO-II 1709 2000

6” Production Risers Marlim South / Roncador P-40/P-36 1080/1360 1500 6” Water Injection Risers/Flowlines

Marlim South P-40 1080/1288 1500

6” Production Flowlines (insulated)

Roncador FPSO-Brazil pre installation

1900 2000

6” Water Injection Risers/ Flowlines

Roncador FPSO-Brazil 1290/1805 (to be installed in 2003)

1500/2000

8” Production Riser/Flowline

Marlim South P-40 1080/1220 1500

8” Water injection Flowline Marlim South P-40 1400 1500 9.13” Production Riser Marlim South/Roncador P-40/P-36 1080/1360 1500

11.13” Export Riser Marlim South P-40 1080 1080 Electro Hydraulic Umbilical

Riser 9+3+CE Roncador FPSO-Brazil 1290m (to be

installed in 2003) 1500

Electro Hydraulic Umbilical Flowline 9+3+CE

Marlim P-26 1250 2000

Table 1: Flexible pipe proven technology offshore Brazil

Figure 17: 6” Insulated flexible pipe being recovered by Sunrise2000 for further re-use


5. NEXT CHALLENGE – RONCADOR PHASE II

The next target in terms of water depth offshore Brazil is the development of the phase II of Roncador field. For this phase, the production unit will be installed in 1800m WD and the wells will be located in water depths up to 2000m. In line with this new requirement, Technip-Coflexip has put in place a test program to qualify risers (up to 9.13” ID) for 1800m WD, what will represent the new world record for flexible risers in terms of water depth. The scope of program will include Collapse, TEC (Thermal Exchange Coefficient) and Offshore (DIP) tests. The new designs are based on the already qualified and installed structures for Roncador phase I and Marlim South, utilizing the same structural concept (same type of layers), materials and design methodology, with some improvements in order to reach 1800m. It is possible that large diameter pipes (11” and bigger) will be also required for the oil export lines. New flexible configuration concepts are currently being studied by Technip-Coflexip in order to answer to this demand. For this phase of development, a series of global dynamic analysis focusing the TDP region was performed, taking into account the variation of some parameters like: -Bending stiffness due to temperature -Soil stiffness -Influence of armours and insulation annulus condition (dry or wet) -Pipe/Soil friction coefficient -Damping coeficient A parametric comparative analysis was carried out and showed that, although these parameters could influence the results of curvature and axial compression in the TDP region obtained from the global analysis, no major impact was observed to the point of jeopardizing the Flexible solution for this application.

6. NEW TECHNOLOGIES FOR GOING DEEPER Aiming to allow Flexible Pipes to reach deeper water depths, Technip-Coflexip is currently working on new technologies (profiles, materials and concepts). These new technologies will improve flexible structure resistance to collapse, tension, reverse end-cap effect, lateral buckling and also reduce pipe submerged weight, which are the main design drivers in UDW applications. A brief description of some of these new developments related to collapse and tensile resistance are presented below (ref [2]): Improvement on Collapse resistance In order to increase collapse resistance of a flexible pipe, three alternatives can be envisaged:

- Increase the cross-section area (amount of steel) - Increase the stiffness (or bending inertia) of the cross-section - Increase the strength of the material

The first alternative, to increase the cross-section area, results in weight increase, which is not desirable in UDW risers. The chosen solutions were then to increase the stiffness and strength of the collapse resistant layers.


Figure 20: Efficiency of pressure vaults

To increase the strength, a new carcass material for sweet service application (High strength 304L) has been qualified. For sour applications, the 22-05 Duplex is still used, but the available strip thickness has been increased from 9mm to 15mm. For medium corrosive application the new 23-04 Duplex, which has the same mechanical behavior as the high strength 304L, was qualified. The benefits of the new carcasses are shown in figure 18, where an example for a 12” pipe is presented. To increase the stiffness of the cross-section, a new vault profile (PSI) has been developed. This new profile maximizes the bending inertia, which resists the ovalization of the pipe, minimizing the weight due to its concave shape (figure 19). In order to qualify this new solution, a collapse test was performed on a 12” pipe sample with a 15mm thick Duplex carcass. The collapse occurred at 338 bar for a predicted value of 308 bar. A full scale fatigue test is also on-going to qualify this profile for dynamic applications. An example of the benefits from using this new profile can be seen in figures 18 and 20.

Vaults efficiency( total weight = f(Pcollapse)Zéta - Téta - Psi

150 200 250 300 collapse pressure 12 " (bars)

ZétaTéta

Psi

Figure 19: PSI static and dynamic profiles

+19%+42%

+67%+100%

0 500 1000 1500 2000 2500 3000

Sweet

Sour Collapse WD for 12" flexible

New carcass and vaultNew carcassOld design

Figure 18: Benefits of new carcasses


Improvement on Tensile resistance In order to increase the axial tension capability of flexible pipes, a new material for tensile armours has been developed. This new material is composed of Carbon fiber filaments involved by a resin matrix and covered by a chopped strand material (figure 22). The Carbon fiber composite material presents a very high specific strength, low density, high fatigue resistance and low sensitivity to ageing in a wet corrosive environment. The combination of these properties make carbon fiber composite material very interesting for riser applications in ultra deepwaters (figure 21). A weight reduction up to 50% can be achieved, replacing the conventional steel armour wires by carbon fiber wires with a minimum UTS of 2700 MPa, allowing to reach water depths down to 3000m. The high longitudinal strength performance of this composite material is linked to the alignment of the fibers within the composite, to the integrity of the fiber/matrix interface and to the manufacturing process. A wide, successfully completed, qualification program (ref [1]) was put in place to qualify flexible pipes with carbon fibers. In addition to this program, a new fatigue test on a 12” pipe using carbon fiber armours, high strength carcass and PSI vault is on-going in order to qualify a completely optimized solution for UDW applications.

7. CONCLUSIONS The latter successful offshore developments carried out in Brazil represented a significant step forward in the technological evolution to produce oil in UDW. The cumulated experience acquired from Roncador Phase I and Marlim South projects represents today an important reference for other new UDW developments and a strong motivation to go deeper. Particularly, in the Flexible Pipe technology area, these projects meant an unique opportunity to develop new Flexible products and widen the range of application of this solution. Flexible pipes of ID in the range between 2.5” to 11” have been successfully qualified and installed offshore Brazil, in water depths from 1000 to 2000m, confirming the suitability of this solution for UDW applications. Recent studies showed that water depths in excess of 3000m could be reached with Flexible Pipes, if some

UD Carbon fiber compositeChopped Strand Mat

Figure 21: Flexible pipe with Carbon Fiber armours

Figure 22: Carbon fiber arrangement


new technologies of profiles (PSI) and materials (Carbon fiber) are used. These new technologies are currently being validated by full scale test programs and will be available for utilization soon.

References: [1] "Development of light weight flexible risers for ultra deepwater applications", A. T. Do, A. Felix-

Henry, Technip-Coflexip, P.Odru, H.Campion, IFP, Deep Offshore Technology 2000. [2] "Light weight flexible pipes for ultra deepwater applications", A. Coutarel, A. T. Do, F. Dupoiron,

Technip-Coflexip, Offshore Pipeline Technology Conference 2001.

Documents

Flexible Pipe