Fatigue Reliability Assessment for Flexible Riser Armour Wires

2015 ◽  
Author(s):  
Vinícius Ribeiro Machado da Silva ◽  
Luis V. S. Sagrilo ◽  
Mario Alfredo Vignoles
Keyword(s):  
Failure Mode ◽  
Deep Water ◽  
Structural Reliability ◽  
Oil And Gas ◽  
Cost Benefit ◽  
Structural Type ◽  
Sensitivity Analyses ◽  
Fatigue Reliability ◽  
Great Expectation ◽  
Flexible Pipes

Oil and gas exploitation in regions of ultra-deep water has already been started and there is a great expectation of growth in the coming years, mainly in the region known as Pre-Salt, at Brazilian’s coast. Operators, which have the concession to exploit this region, have adopted different solutions with different configurations using rigid and flexible pipes for this initial phase. However, the last structural type mentioned shows to be much more versatile, providing attractive cost/benefit solutions to the operators, in which, only in Brazil, it is forecasted a demand about 4.000 km of flexible pipes in the next years [1]. With new challenges coming, one may ask the following question: What is the structural reliability of each failure mode of these flexible pipes? Motivated by this question, this paper has the objective to do a preliminary analysis, under the structural reliability view, of the critical failure mode for the design of flexible pipes faced in Brazil, represented by the fatigue phenomenon on metallic layers. The work assesses the fatigue reliability of the armour wires, located in the bend stiffener region, for two 6″ flexible risers configurations, free-hanging and lazy-wave. They are considered to be installed in ultra-deep water (2140m depth) and are submitted to the same external environmental loads. The fatigue reliability methodology used is based on that presented in Ref. [2] including new random variables. Sensitivity analyses are also performed for the variables that most contributes to the quantified probability of failure. Calibrated safety factors (SF) are obtained for different target failure probabilities.

Methodology for Fatigue Analysis in Flexible Pipes Based on Structural Reliability Considering S-N Bi-Linear Curve

2012 ◽  
Author(s):  
Fernando dos Santos Loureiro Filho ◽  
Edison Castro Prates de Lima ◽  
Luís Volnei Sudati Sagrilo ◽  
Carlos Alberto Duarte de Lemos
Keyword(s):  
Structural Reliability ◽  
Failure Modes ◽  
Oil And Gas ◽  
Linear Models ◽  
Fatigue Analysis ◽  
Flexible Pipe ◽  
Environmental Loads ◽  
Flexible Pipes ◽  
Different Types ◽  
Oil And Gas Companies

Flexible pipes are largely used by oil and gas companies all over the world to exploit oil and gas reserves located into the sea. These pipes are composed by different layers, each one with a specific function. The environmental loads can induce different types of failure modes in a flexible pipe. One important failure mode is associated with the fatigue damage in the tension armours. Fatigue analysis depends on various parameters that are uncertain. A reliability-based procedure to take into account these uncertainties in the fatigue analysis of flexible pipes has been recently proposed [1]. In this methodology the S-N curves have been modeled by a one-slope model. The present work expands this methodology in order to consider S-N bi-linear models.

Lazy-Wave Buoyancy Length Reduction Based on Fatigue Reliability Analysis

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Vinícius Ribeiro Machado da Silva ◽  
Luis V. S. Sagrilo ◽  
Mario Alfredo Vignoles
Keyword(s):  
Reliability Analysis ◽  
Cost Reduction ◽  
Structural Reliability ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Fatigue Reliability ◽  
Gas Industry ◽  
Deep Waters ◽  
Sea Bed ◽  
Length Reduction

The current downturn of the oil and gas industry force managers to take hard decisions about the continuity of projects, resulting in delays, postponements, or even their cancellation. In order to keep with them, the rush for cost reduction is a reality and the industry is pushing the involved parties to be aligned with this objective. The Brazilian presalt region, characterized by ultra-deep waters, faces this scenario where flexible risers in lazy-wave configurations are usually adopted as a solution to safe transfer fluids from sea bed until the floating unit. The smaller the buoyancy length, the cheaper the project becomes, reducing the necessary amount of buoys and the time spent for its installation. This paper investigates the possibility of buoyancy length reduction of lazy-wave configurations by using structural reliability methods on fatigue failure mode. The application of the fatigue reliability approach considers four 6 in flexible riser configurations: an original lazy-wave, a lazy-wave with less 30% of buoyancy length, another one with less 50% of buoyancy length and a free-hanging. Failure probabilities and safety factor calibration curves are shown for each configuration and compared among themselves. The results indicate the possibility of defining a lazy-wave configuration with smaller buoyancy lengths, reaching 75% of reduction without changing the preconized high safety class. Structural reliability analysis is available to help engineers understand the driving random variables of the problem, supporting the actual scenario of cost reduction for better decision-making based on quantified risk.

Lazy-Wave Buoyancy Length Reduction Based on Fatigue Reliability Analysis

2017 ◽  
Author(s):  
Vinícius Ribeiro Machado da Silva ◽  
Luis V. S. Sagrilo ◽  
Mario Alfredo Vignoles
Keyword(s):  
Reliability Analysis ◽  
Safety Factor ◽  
Cost Reduction ◽  
Structural Reliability ◽  
Oil And Gas ◽  
Random Variables ◽  
Oil And Gas Industry ◽  
Potential Method ◽  
Fatigue Reliability ◽  
Length Reduction

When the profit scenario of an industry changes, the continuity of some projects can be at risk. The current downturn of the oil and gas industry force managers to take hard decisions about the continuity of projects, resulting in delays, postponements or even the cancellation of forecasted projects. In order to keep with these projects, the rush for cost reduction is a reality and the industry is pushing the involved parties to be aligned with this objective. The Brazilian Pre-Salt region, characterized by ultra-deep waters, is an example of this scenario. Subsea structures represented by flexible risers, which are responsible for the flow assurance of oil, gas and water, are forecasted to have a demand about 4.000 km in the next years. Usually, in these type of applications, lazy-wave configurations are adopted, increasing the costs of the solution with the necessity of the buoyancy modules acquisition. The smaller the buoyancy length is the cheaper the project become, reducing the necessary amount of buoys and the time spent for its installation. These type of solutions can probably carry with it a high level of conservatism, imposed by the use of standardized safety factors, and can potentially be optimized with the adoption of probabilistic approaches within the chain of analysis. The objective of this paper is to assess the possibility of buoyancy length reduction of lazy-wave configurations by using structural reliability methods of analysis. The focus stays on the evaluation of the fatigue of the armour wires located at the bend stiffener region, one of the most critical failure mode for the design of flexible pipes in offshore Brazilian installations. As already discussed in Ref. [1], many variables can influence on such kind of analysis. Based on this previous study, the first six random variables, identified to be the most important ones, are taken to carry out the analysis. The fatigue reliability approach considers four 6” flexible riser configurations: an original lazy-wave, a lazy-wave with less 30% of buoyance length, another one with less 50% of buoyance length and a free-hanging configuration. Failure probabilities and safety factor calibration curves are shown for each presented configuration and compared among themselves. The results indicate the possibility of defining a lazy-wave configuration with smaller buoyancy lengths, reaching 75% of reduction without changing the preconized high safety class at last year of its operational time. Safety factor curves shows to have similar behavior no matter the configuration considered. Structural reliability analysis comes as a potential method to help engineers to have a better understanding on the driving random variables of the problem, giving a support for the actual cost reduction scenario and for better decision-makings based on quantified risk.

Vortex Induced Vibrations of Deep Water Risers: Sensitivity to Current Profile, Shear and Directionality

2014 ◽  
Author(s):  
Rafael Vergara Schiller ◽  
Marcelo Caire ◽  
Pedro Henrique Affonso Nóbrega ◽  
Elizabeth Passano ◽  
Halvor Lie
Keyword(s):  
Deep Water ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Offshore Structures ◽  
Sensitivity Analyses ◽  
Current Profile ◽  
Boundary Current ◽  
Gas Industry ◽  
Vortex Induced Vibrations ◽  
Se Brazil

Slender offshore structures such as risers experience vortex induced vibrations (VIV) when they are exposed to currents and accumulate significant fatigue damage through that process. VIV will depend on several structural properties of the riser and on the current profile that the structure is exposed to. In deep water regions, risers will be subject to intricate circulation systems that impose currents profiles which may vary in intensity, shear and direction throughout the water column. The increased complexity of currents will make the prediction of VIV more difficult and represents a clear challenge to the Oil and Gas Industry. The objective of this study is to investigate how selected properties of a current profile affect the development and excitation of VIV for a deep water tensioned riser. We employ a semi-empirical frequency-domain program to perform a series of numerical sensitivity analyses where the riser model is subject to current profiles that vary in complexity and include uniform profiles, linearly-sheared profiles and more realistic profiles that represent offshore boundary current regimes from SE Brazil. We address the sensitivity of the VIV response to current intensity, shear and directionality. Our results demonstrate that those properties of the current profile have significant influence on the range of VIV modes that are excited and on the VIV response. Overall, uniform profiles produced the largest responses and the linearly-sheared profiles demonstrated the large range of VIV modes that can be excited. The realistic profiles also excited a broad range of VIV modes and variations between the profiles produced changes in the VIV response. This study highlights the need to further understand how complex current profiles in the offshore region affect VIV development in comparison to simpler profiles that are recurrent in model test conditions.

Tubarão Martelo Field Riser System: Shallow Water Challenging

2015 ◽  
Author(s):  
Elton J. B. Ribeiro ◽  
Zhimin Tan ◽  
Yucheng Hou ◽  
Yanqiu Zhang ◽  
Andre Iwane
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Oil And Gas ◽  
Vertical Motion ◽  
Oil And Gas Industry ◽  
System Configuration ◽  
Wave Load ◽  
Gas Industry ◽  
Campos Basin ◽  
Water Problem

Currently the oil and gas industry is focusing on challenging deep water projects, particularly in Campos Basin located coast off Brazil. However, there are a lot of prolific reservoirs located in shallow water, which need to be developed and they are located in area very far from the coast, where there aren’t pipelines facilities to export oil production, in this case is necessary to use a floating production unit able to storage produced oil, such as a FPSO. So, the riser system configuration should be able to absorb FPSO’s dynamic response due to wave load and avoid damage at touch down zone, in this case is recommended to use compliant riser configuration, such as Lazy Wave, Tethered Wave or Lazy S. In addition to, the proposed FPSO for Tubarão Martelo development is a type VLCC (Very Large Crude Carrier) using external turret moored system, which cause large vertical motion at riser connection and it presents large static offset. Also are expected to install 26 risers and umbilicals hanging off on the turret, this large number of risers and umbilicals has driven the main concerns to clashing and clearance requirement since Lazy-S configuration was adopted. In this paper, some numerical model details and recommendations will be presented, which became a feasible challenging risers system in shallow water. For instance, to solve clashing problem it is strictly recommended for modeling MWA (Mid Water Arch) gutter and bend stiffener at top I-tube interface, this recommendation doesn’t matter in deep water, but for shallow water problem is very important. Also is important to use ballast modules in order to solve clashing problems.

Study on the Characteristics of Well Completion Technology in Deepwater Oil and Gas Field Development

2021 ◽  
Vol 3 (8) ◽  
pp. 70-72
Author(s):  
Jianbo Hu ◽  
◽  
Yifeng Di ◽  
Qisheng Tang ◽  
Ren Wen ◽  
...  
Keyword(s):  
Deep Water ◽  
Deep Sea ◽  
Oil And Gas ◽  
Gas Field ◽  
Marine Research ◽  
Field Development ◽  
Research Technology ◽  
Well Completion ◽  
Development Capacity ◽  
Exploration And Development

In recent years, China has made certain achievements in shallow sea petroleum geological exploration and development, but the exploration of deep water areas is still in the initial stage, and the water depth in the South China Sea is generally 500 to 2000 meters, which is a deep water operation area. Although China has made some progress in the field of deep-water development of petroleum technology research, but compared with the international advanced countries in marine science and technology, there is a large gap, in the international competition is at a disadvantage, marine research technology and equipment is relatively backward, deep-sea resources exploration and development capacity is insufficient, high-end technology to foreign dependence. In order to better develop China's deep-sea oil and gas resources, it is necessary to strengthen the development of drilling and completion technology in the oil industry drilling engineering. This paper briefly describes the research overview, technical difficulties, design principles and main contents of the completion technology in deepwater drilling and completion engineering. It is expected to have some significance for the development of deepwater oil and gas fields in China.

Estimating Zonal Flow Contributions in Deep Water Assets From Pressure and Temperature Data

2017 ◽  
Author(s):  
A. Rashid Hasan ◽  
Rayhana N. Sohel ◽  
Xiaowei Wang
Keyword(s):  
Turbulent Flows ◽  
Deep Water ◽  
Fluid Pressure ◽  
Zonal Flow ◽  
Temperature Data ◽  
Sensitivity Analyses ◽  
Momentum Balance ◽  
Flow Profile ◽  
Flowing Fluid ◽  
Energy And Momentum

Producing hydrocarbon from deep water assets is extremely challenging and expensive. A good estimate of rates from multiple pay zones is essential for well monitoring, surveillance, and workover decisions. Such information can be gleaned from flowing fluid pressure and temperature; deep-water wells are often well instrumented that offers such data on a continuous basis. In this study a model is presented that estimates zonal flow contributions based on energy and momentum balances. Kinetic and heat energy coming from the reservoir fluid to the production tubing is accounted for in the model. The momentum balance for wellbore takes into account differing flow profile in laminar and turbulent flows. In addition, when sandface temperature data are not available, a recently developed analytical model to estimate the effect of Joule-Thompson expansion on sandface temperature was used to estimate sandface temperature from reservoir temperature. The model developed can be applied to any reservoir with multiple pay zones and is especially useful for deep-water assets where production logging is practically impossible. Available field data for multiphase flow was used to validate the model. Sensitivity analyses were performed that showed accurate temperature data is essential for the model to estimate zonal contribution accurately.

scholarly journals Elements constituent for the design of a riser system in areas deep water and extreme deep water applied for offshore drilling

2020 ◽  
Vol 6 (3) ◽  
pp. 127-144
Author(s):  
Marius STAN ◽  
◽  
Valentin Paul TUDORACHE ◽  
Lazăr AVRAM ◽  
Mohamed Iyad AL NABOULSI ◽  
...  
Keyword(s):  
Working Conditions ◽  
Water Depth ◽  
Deep Water ◽  
Environmental Conditions ◽  
Oil And Gas ◽  
Operational Mode ◽  
Exploration And Exploitation ◽  
Offshore Drilling ◽  
The Stability ◽  
Marine Platform

Riser systems are integral components of the offshore developments used to recover oil and gas stored in the reservoirs below the earth’s oceans and seas. These riser systems are used in all facets of the development offshore process including exploration and exploitation wells completion/intervention, and production of the hydrocarbons. Their primary function is to facilitate the safe transportation of material, oil and gases between the seafloor oceans and seas and the marine platform. As the water depth increases, the working conditions of this system becomes challenging due to the complex forces and extreme environmental conditions which are impacting the operational mode as well as the stability. In this paper several aspects concerning riser mechanics and the behaviour of the riser column will be evaluated against different operational situations.

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