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ABSTRACT The interest in Direct Electrical Heating (DEH) is increasing and the system is being planned for flow assurance in development of oil fields on continental shelf around the world. The DEH system is selected due to several advantages:Allow production of fields that earlier is considered as not feasible Effective solution with high heat input Easy to install and operate Reliable components Can be retrofitted on pipelines in operation Implementation require minor modification The running costs are considerably reduced compared to traditional methods utilising chemicals. At present it is installed on several subsea pipelines in the North Sea and DEH is applied actively to prevent hydrate formation during shut downs for a total accumulated use of 1 year during the lifetime of the field. For the new fields being planned with DEH there are several challenges due to extended design basis regarding:Continuously use of DEH during the lifetime of the field. Flow assurance of waxy unprocessed wellstream, requiring large heat input to the pipeline. Impact of steel armoured concrete pipe weight coating Use in shallow water Heating of risers and spool-pieces. As the pipeline is an active conductor in the heating system a special anode design is required, both to ensure sufficient grounding for the heating system and for corrosion protection regarding ac (alternating current). The design of the anode system is strongly related to time of use. This is one of the main challenges with continuous operation of DEH. Furthermore the design of the electrical cables is important regarding mechanical and thermal stresses. The lifetime of the cable depends on several factors. The lifetime of the DEH installation decreases with increasing cable temperature and with frequent use.
- Europe > United Kingdom > North Sea (0.24)
- Europe > Norway > North Sea (0.24)
- Europe > North Sea (0.24)
- (2 more...)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene (0.68)
- Facilities Design, Construction and Operation > Flow Assurance > Hydrates (0.68)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Offshore pipelines (0.67)
ABSTRACT Pipeline spans occur when a flowline is laid on a rough seabed and/or when upheaval buckling of the flowline is generated due to thermal expansion. This not only results in static and dynamic loads on the flowline at the span section, but also generates Vortex Induced Vibration (VIV) responses. The phenomenon, if not predicted and controlled properly, will result in significant damage to the pipeline integrity. The span issues can be very complicated to analyze due to the long span lengths, a rough seabed, the large number of spans, and multi-span interactions. In addition, the complexity can be more onerous and challenging when soil uncertainty, unknown residual lay tension, and variation of spans from year to year is considered in the analysis. The methodology discussed in this paper will not only highlight the most important areas in the assessment of the complex spans but also provide many technical details. The new methodology presented in this paper includes the following: The initial data assessment for seabed and wave/current is discussed and certain assumptions are made for a conservative design; Understanding of DNV design code and implementing it using advanced numerical FE tools is an evaluation basis for span analysis; In the FEA modeling, many details are discussed such as model length and concrete induced SCF (Stress Concentration Factor) at field joints; Certain sensitivity studies for concrete degradation, survey accuracy, and soil stiffness are also discussed to ensure the most conservative cases are captured. Special cares are mentioned in the ULS check for wave/current data (extreme or significant) and wave load application to interacting spans; In addition, an example of fatigue calculation for an interacting span is provided. The approach used in the methodology brings a useful guideline to the span analysis, especially in the complex span conditions.
ABSTRACT Global buckling of exposed HPHT (High Pressure / High Temperature) subsea pipelines has to be critically assessed during detailed design. By safely triggering controlled buckles at predetermined locations, snaked lay design is often the preferred method to manage lateral buckling. For a snaked lay design, a large number of sensitivity analyses would normally be performed to find an optimized configuration and verify code compliance. Because this is a very time consuming process, it is essential that the engineer acknowledges the main drivers that influence the snaked pipeline in-place behaviour. Using FE analyses, a parameter study is presented that establishes how variations in snake lay geometry influence the buckle initiation force and the resulting bending moments and strains in the buckle. Based on this, guidance of how to optimise the snake geometry is presented. INTRODUCTION The traditional method of controlling thermal buckling of subsea pipelines has been by trenching and burying, i.e. in order to constrain the pipeline configuration and prevent pipeline movement of any kind. With the trend that subsea pipelines are being designed to operate under increasingly higher temperatures and pressures, the amount of required overburden to prevent upheaval buckling is becoming more uneconomical. Designers have increasingly addressed the thermal buckling issue by adopting an approach that allows buckling to occur provided it is demonstrated that the resulting high loads and deformations are acceptable. This approach would normally involve ensuring that any axial thermal expansion is distributed among a number of controlled buckle sites rather than being concentrated at a few random locations. The common denominator for these techniques is to reduce the critical buckling force ‘Fcr’(or the buckle initiator force) at the selected locations, which in turn increases the probability that buckles occur at these locations and at the same time reduces the probability of rogue unplanned buckles.
Effect of Lateral Pipelay Imperfections On Global Buckling Design
Rathbone, A.D. (J P Kenny Pty Ltd, Perth, Australia) | Tørnes, K. (J P Kenny Pty Ltd, Perth, Australia) | Cumming, G. (J P Kenny Pty Ltd, Perth, Australia) | Roberts, C. (J P Kenny Pty Ltd, Perth, Australia) | Rundsag, J.O. (J P Kenny Norge AS Stavanger, Norway)
ABSTRACT Global buckling for exposed HPHT (High Pressure / High Temperature) subsea pipelines is an important feature that needs to be assessed during detailed design. Lateral imperfections (or horizontal out-of-straightness) due to pipelay can either be intended, i.e. due to lay route or due to unintended as-laid variations to the idealised lay route. The unintended variations to the idealised lay route can have a significant impact on the design for lateral buckling. This paper draws upon the results presented by Rundsag et al (2008) to demonstrate that there is an interaction between horizontal out-ofstraightness radius and arc length that should be considered when assessing lateral pipelay imperfections. This paper presents the proposed methodology to define and assess potential as-laid variations of the idealised lay route during detailed design. INTRODUCTION Thermal buckling of subsea pipelines has traditionally been controlled by trenching and burying the pipeline, i.e. to constrain the pipeline configuration and prevent pipeline movement. Subsea pipelines are increasingly being designed to operate at high pressure / high temperature (HPHT) which may require an uneconomical amount of overburden to prevent upheaval buckling. Pipelines are increasingly being left exposed on the seabed and allowed to buckle laterally, providing that the resulting loads within the buckle are acceptable. A popular option is to lay the pipeline in a snaked configuration so as to predispose the pipeline to buckle at route bends which are suitably spaced to ensure a limited thermal feed-in to the buckle site and hence acceptable loads in the buckle. This method has been successfully implemented in recent years on a number of projects such as the Penguins project (Matheson et al (2004)) and the Echo Yodel project (Wagstaff (2003)). Further development of the snaked-lay concept is presented by Rundsag et al (2008).
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > HP/HT reservoirs (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Piping design and simulation (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Offshore pipelines (1.00)
ABSTRACT Remotely controlled subsea welding is often required for pipeline repair and hot tapping where pipelines are installed in water depths beyond acceptable diving depths. The present investigation concerns the development of hyperbaric gas metal arc welding of X65 steel. Welding was carried out at 12–35 bar with low alloyed steel and Inconel 625 wires. All welds gave overmatch situation with respect to strength. Toughness requirements at −30°C were also satisfactory met, although the Charpy values tend to be close to the minimum required individual values of 40J due to high oxygen and fairly high nitrogen contents. The Inconel 625 weld metal toughness was very high. This was also the case for the fusion line toughness for both wires. INTRODUCTION The North Sea network of offshore pipeline transportation systems for natural gas is the world largest, comprising more than 6000km only on and from the Norwegian Continental Shelf (Berge, 2005a). For the large diameter pipes hyperbaric welding have been the dominating joining technology. This technology is now prepared to do remote operated (no need for diver intervention) pipeline repair. Ongoing development programs will push the technology further to cover 44" pipelines as well as smaller dimensions down to 4" and water depths to 1000 – 2000 meters pending on the actual need (Berge, 2004). Moreover, development of remote operated tooling systems for hottapping is ongoing. In fact, the present investigation is part of the development of robust gas metal arc (GMA) welding technology to be used in future diverless, remote controlled tie-in and hot tap welding. It will be shown that excellent mechanical properties are achievable. Materials The base metal used was API X65 pipeline steel. Two types of filler wires were applied; one low alloyed metal cored wire supplied by ESAB, denoted HBQ Coreweld, and one solid Inconel 625 wire.
- North America > United States > Texas (0.28)
- Europe > United Kingdom > North Sea (0.24)
- Europe > Norway > North Sea (0.24)
- (2 more...)
Numerical Study On Failure of X52 Wrinkled Pipelines Subjected to Bending Deformation
Zhang, Yonghong (Department of Civil and Environmental Engineering, University of Windsor Windsor, Ontario, Canada) | Das, Sreekanta (Department of Civil and Environmental Engineering, University of Windsor Windsor, Ontario, Canada) | El-Tawil, Wafaa M. (Department of Civil and Environmental Engineering, University of Windsor Windsor, Ontario, Canada)
ABSTRACT Two full-scale tests on X52 grade NPS12 oil/gas pipeline show that this pipeline is able to maintain its integrity and does not rupture when subjected to monotonic bending deformation and moderate to high internal pressure. However, this kind of test is expensive and time consuming and thus, an alternative tool using finite element method was developed to study the behavior of wrinkled pipeline under similar load-deformation condition. This finite element model uses true nonlinear material and non-linear geometry. A special contact and sliding algorithm was used to model the folding and sliding behavior of the inside surfaces of the wrinkle. The finite element model was validated with the data obtained from the full-scale tests. A good agreement was obtained between the post-wrinkling behaviors obtained from the test and from the numerical analysis. This paper discusses the numerical modeling technique that was used in this study and the results obtained from the study. INTRODUCTION North American oil and gas industry uses steel pipelines as the primary mode for transporting natural gas, crude oil, and various petroleum products. In Canada alone, about 700,000 km of oil/gas pipelines are in operation. Many additional pipelines projects especially in West Canada and Alaska of various scales such as Mackenzie Gas Project and Alaska Highway Pipeline are underway. The majority of these pipelines run below ground (Yukon Government, 2006). Field observations of buried oil/gas pipelines indicate that the subsurface geotechnical movements with or without thermal loads can introduce large forces and displacements on buried pipelines resulting in localized curvature, strains, and associated deformations in the pipe wall. Often the local deformations of the pipe wall results in local buckling of the pipe wall (called "wrinkling") and, in its post-buckling range of response, local buckles (wrinkles) in the pipe wall grow under sustained deformations.
- North America > Canada (1.00)
- North America > United States > Alaska (0.45)
Burst Capacity Solutions For Submarine Pipeline With Long Corrosion Defects
Chen, Yanfei (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology Dalian, Liaoning Province, China) | Li, Xin (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology Dalian, Liaoning Province, China) | Jin, Qiao (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology Dalian, Liaoning Province, China) | Zhou, Jing (State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology Dalian, Liaoning Province, China)
ABSTRACT Based on the elastic-plastic, large-deformation finite element method, the failure behaviour and burst capacity of submarine pipeline with long longitudinal corrosion defects exposed to internal pressure are studied. The effect of corrosion length and corrosion location on burst capacity is discussed as well. From the FE results, a set of limit solutions are proposed to predict failure pressure of submarine pipeline made of X60 steel with long longitudinal corrosion defects. The burst capacities predicted by the proposed solutions are compared with the results from laboratory tests and various assessment methods. Consequently, it is concluded that solutions proposed in this paper are in extremely good agreement with the experimental data and give more accurate predictions than the existing assessing methods. INTRODUCTION Offshore pipelines, which are the arteries of the oil and gas industry, have been widely used as one of the most economical ways of transmitting oil and gas from an inlet point, typically an offshore platform or an onshore compressor station, to an outlet point, typically another offshore platform or an onshore receiver station. Due to the harsh marine environment, the damage of pipeline is inevitable which may result in not only economical loss but also severe environmental pollution characterized by (MMS, 1995). Long corrosion is a potential damage pattern of offshore pipelines. According to ASME B31G corrosion length beyond 20Dt is defined as long corrosion defects. Long internal corrosion defects usually appear at the bottom of pipeline around the 6 O'clock position due to the media transporting characteristics, while long external corrosion defects usually occur near the damage part of protective coatings. Intensive researches have been conducted on the failure mechanism and safety evaluation of corroded offshore pipelines. For example, Freire et al. (2006) performed nine burst tests of API X60 pipeline with simulated external long corrosiondefects subjected to internal pressure only
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Offshore pipelines (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
Unburied Offshore Pipeline Stability Analysis Based On Non-linear Relationship Between Pipeline And Carbonate Soil
Takatani, Tomiya (Department of Civil Engineering, Maizuru National College of Technology Maizuru, Kyoto, Japan) | Kaya, Takanori (Department of Civil Engineering, Gifu University Gifu, Japan)
ABSTRACT The purpose of this paper is to investigate the stability of an unburied offshore pipeline resting on carbonate soil under severe storm condition. Pore pressure accumulation and pipeline movement during cyclic loading caused by waves and currents are numerically investigated. Both drag and lift forces are numerically obtained for 100 years return period storm condition using the Fourier decomposition method. Non-linear spring element is used to simulate a slip phenomenon between pipeline and seabed. The effects of both bi-linear and tri-linear spring element models on the pipeline movement and pore pressure response are numerically investigated. Pipeline movement during cyclic loading greatly depends on the mechanical properties of non-linear spring element. INTRODUCTION It is very important in pipeline design to investigate the stability of an unburied offshore pipeline under severe storm condition. The cyclic movement of pipeline due to drag and lift forces caused by waves and currents will lead to pore pressure build up in the seabed around the pipeline. The pore pressure accumulation will reduce the effective strength of the seabed soil and degrade its bearing capacity. In particular, an increase of horizontal displacement of the pipeline may lead to a sudden break-out, which has a serious influence on the safe operation of the pipeline. It is therefore very important for design engineers to evaluate the stability of an unburied offshore pipeline by considering pore pressure accumulation in the seabed soil around the pipeline under severe storm condition. This can be achieved by carrying out numerical analyses (Taiebat and Carter, 2000; Zhang et al., 2001; Takatani, 2005a; 2005b; 2006; 2007) and simulations (Zhang et al., 2002; Takatani and Randolph, 2003) based on experimental data of pore pressure build up during horizontal cyclic loading.
- North America (0.46)
- Europe (0.28)
- Asia (0.28)
Structural Condition Identification For Free Spanning Submarine Pipelines
Feng, Xin (School of Civil and Hydraulic Engineering, Dalian University of Technology Dalian, China) | Zhou, Jing (School of Civil and Hydraulic Engineering, Dalian University of Technology Dalian, China) | Li, Xin (School of Civil and Hydraulic Engineering, Dalian University of Technology Dalian, China) | Hu, Jia-shun (School of Civil and Hydraulic Engineering, Dalian University of Technology Dalian, China)
ABSTRACT The operational performance of the free spanning submarine pipeline is closely related to the structural condition. However, due to the underwater environment and condition evolution, it is very difficult to exactly obtain the information about the structural condition of the free spanning submarine pipeline. In this paper, we propose a novel methodology to identify the structural condition with the vibration responses of the free spanning submarine pipelines. Firstly, the nonlinear kernel discirminant analysis (KDA) was adopted to identify the structural condition of the free spanning submarine pipelines. Secondly, the condition-sensitive features, such as natural frequencies, normalized frequencies and frequency change ratios, were proposed in the study. Finally, the feasibility and effectiveness of the proposed approach was numerically studied. The analytical results demonstrate that the proposed approach can identify effectively each condition of free span for on-line monitoring of the submarine pipelines. INTRODUCTION Submarine pipelines play an important role in the process of oil and gas exploitation, which is regarded as the lifeline of sub-sea oil and gas transmission. Over a rough seabed or on a seabed subjected to scour, pipeline free span is unavoidable when contact between the pipeline and seabed is lost over an appreciable distance. If natural frequency of free span is approximately equivalent to the vortex shedding frequency, the free span may suffer the vortex-induced resonance and consequently fatigue damage can occur, which severely threatens normal operation in a submarine pipeline system. A substantial research effort related to various aspects of free span pipelines have been seen during past yeas. Park et al.(1997) studied static and dynamic behavior of free spanning pipeline, and proposed an allowable length of free span. Meanwhile, the variation of allowable lengths is examined for specialized boundary conditions.
- North America > United States (0.46)
- North America > Canada > British Columbia (0.28)
ABSTRACT The aim of this first symposium on strain-based design of pipelines was to bring together a multidisciplinary group of industry experts to discuss the challenges of designing pipelines subjected to high strain. The symposium included nearly fifty presentations and comprehensive proceedings covering all aspects of strain-based design. This review summarizes the key themes of the symposium including projects, design, mechanics, assessments, materials, and testing. The work presented at the symposium shows the broad range of efforts underway to address the challenges of strain-based design of pipelines as well as the work remaining to be completed to have an industry-wide consistent solution. Rather than simply providing a compilation of these various studies, this review aims to assess the work within each topical area collectively. This assessment of the state of the art and remaining challenges from the symposium will serve as a backdrop for the Second (2008) ISOPE Strain-Based Design Symposium. INTRODUCTION The ever increasing consumption of energy worldwide has led to the strong demand for development of known oil and gas resources in remote locations. These potential development locations are often far from major population centers because of the harsh natural environments in these parts of the world. Often cited are the vast resources both on- and offshore in and around the arctic circle. Environmental loads from offshore ice, discontinuous permafrost, and seismic activity impose a strain demand on the pipelines needed to bring the oil and gas to population centers from these remote resources. Similar arctic challenges persist into regions of ice flow and permafrost beyond the arctic circle, including regions currently under development such as Sakhalin Island (Russia''s far east) and offshore eastern Canada, shown in Figure 1.
- North America > Canada (0.68)
- Asia > Russia > Far Eastern Federal District > Sakhalin Oblast (0.24)
- Asia > Russia > Far Eastern Federal District > Sakhalin Island > Sea of Okhotsk (0.24)
- Overview (0.68)
- Research Report > New Finding (0.46)
- Geology > Geological Subdiscipline > Geomechanics (0.68)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.48)