bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonlinear Dynamic Analysis of Jack-Up Platforms Exposed to Extreme Random Waves
Authors: Mirzadehniasar Jalal , Kimiaei Mehrdad , Cassidy Mark J. 
Published: August 2013

Deterministic waves with uniquely specified parameters remains widely used in the analysis of offshore platforms, even though the random nature of the sea-state is one of the main uncertainties in loading. The response of dynamically sensitive and highly redundant structures is significantly changed when random wave loading is considered. Therefore, to more confidently simulate wave loads, all of the randomness of water surface should be taken into account.
Load history also plays an important role in the nonlinear dynamic response of structures. Accordingly, an appropriate way to consider these effects is dynamic analysis of offshore platforms using random time-domain generation of the sea surface over a long period of time. However, in general, this method is very complex and time consuming. Constrained NewWave theory is an alternative method that can effectively simulate many hours of random time domain simulation for wave loading but in a more computationally efficient manner. It takes a NewWave — a deterministic wave of predetermined height that accounts for the spectral composition of the sea — and constrains it within a random background.
In this paper, both the singular NewWave and multiple constrained NewWaves are employed to simulate random sea-states in order to investigate the nonlinear dynamic response and collapse mechanisms of a jack-up platform subjected to extreme waves. Different assumptions of the behavior of the jack-up spudcan-soil interaction are considered.
An Investigation About the Trajectory Control During the Subsea Equipment Installation Using Cable
Authors: Fortaleza Eugenio , Albuquerque Daniel , Yamamoto Marcio 
Published: August 2013

Nowadays, several seafloor equipments have been developed and deployed in order to enhance the production of petroleum and natural gas from reservoirs in deep and ultra-deep waters. Thus the installation and maintenance of such seafloor equipments shall be an issue.
The most important seafloor equipment during the production phase is the “Wet Christmas-Tree” (X-tree), which is a set of valves that controls the pressure at well bottom. This equipment is installed by a Mobile Offshore Drilling Unit (MODU) after the drilling and completion are finished. Recently, beside the X-mas, a variety of subsea pumps, usually called as Subsea Booster System, have been deployed in the development of new reservoirs in deep-water. At the beginning, such subsea pumps and even other seafloor equipments had been installed by a MODU. But the high-cost of the MODUs is one of the main concerns about the installation and maintenance of the subsea equipments. One alternative to reduce the installation cost is to use cable system installed on a service boat instead the completion riser of a MODU.
This paper presents an initial investigation for the installation of a seafloor equipment using cable. The dynamic model will be featured; the dynamic analysis will be carried out using an in house developed simulation program in time-domain. Discussion about the trajectory and control of the equipment to be installed is also included.
Lateral Buckling Analysis and ECA for Pipeline With Complex Temperature Profile
Authors: Yang Zhengmao , Mageshwaran Yadhavaraj , Kittur Vijay , Lim Gerry , Chia Hong Kiat 
Published: August 2013

Lateral buckling analysis of a 32 inch export pipeline operating under high temperature and high pressure in sour service environment was evaluated in this paper. In addition Engineering Critical Assessment (ECA) as per DNV-OS-F101 Appendix A was performed to derive flaw acceptance criteria for pipeline girth weld fabrication during installation.
Due to the sour operating environment, low fracture toughness and increased fatigue crack growth rate during operation is expected. Consequently stringent tolerable flaw sizes are obtained for the pipeline sections subject to large strain arising from lateral buckling. In order to improve the reliability of the design and constructability of the pipeline, sleepers will be used to introduce vertical imperfections and initiate buckles at selected locations. In undertaking this it can be illustrated that all the potential lateral buckles are predetermined and pipeline sections with large strains are identified. The stringent tolerable flaw criteria from ECA are applied only on the identified high strain sections.
In this paper the design of sleepers and the influence of these additional sleepers on the lateral buckling behavior are investigated.
Evaluation of Pipeline Impact Damage
Authors: Alsos Hagbart S. , Igland Ragnar T. , Søreide Tore H. 
Published: August 2013

The safety of pipelines and subsea structures are key elements in subsea field developments. As part of the safety engineering, protection from dropped objects and third party impact actions is required. This article addresses this aspect. The combined response from global deflection and denting of pipelines subjected to impacts is investigated. Analysis and testing methods applied in pipeline design are presented. Focus is placed on the overall interaction between the impacting object, the deformed pipeline and energy dissipation by soil.
Typically, pipeline damage from design codes provides conservative cross sectional damage estimates. This is confirmed from both simplified and detailed FE analyses, as well as impact experiments performed by REINERTSEN AS.
One of the main objectives promoted by the authors is the importance of impact velocity and mass during impact, and not only the kinetic energy of the impact. The kinetic energy from a dropped object is unlikely to be fully dissipated as cross sectional deformation of the pipeline. Global deformations will be triggered, which implies that the dissipated energy going into local denting is reduced to a fractional value. This paper discusses the impact mechanics and seeks to estimate the fractional value by using simplified element analysis.
Small Scale Sour Fatigue Testing With Dense Phase Gases
Authors: Yu Weiwei , Vargas Pedro M. , Crowder Ben , Mishael Sam , Thodla Ramgopal 
Published: August 2013

One way generally accepted by industry to evaluate the effect of sour environment on fatigue performance of girth welds is by small scale testing in sour brines. These tests are commonly done at room temperature and pressure and therefore can only contain a maximum of 14.7psia of H2S in a gaseous phase. In comparison, very little has been published about fatigue performance in sour environments where negligible amounts or no water is present. Such condition can be found for pipelines serving in a “dry” sour environment (H2S and other gases in dense phase) with high H2S concentration.
This paper documents both small scale fatigue crack growth rate (FCGR) tests and S-N fatigue tests in a dense phase sour environment with ultra-low water content and high H2S concentration under high pressure. Fatigue life reduction factors were calculated from FCGR approach (with the name crack growth acceleration factor, CGAF) and S-N approach (with the name knockdown factor), respectively.
Industry understanding today is that water is necessary for accelerating fatigue crack growth. Quite opposite to the expected effect of water content on crack growth, even ultra-low water content (<450ppm) resulted in high crack growth rates. Crack growth rates were comparable among tests with various water contents, all ultra low. Through limited testing, no temperature dependency on crack growth rate was identified. It is postulated that hydrogen dissociation due to high pressure and high concentration may be the cause for high crack growth rates on the absence of water.
Small scale S-N tests on smooth specimens reveal that fatigue performance in ultra-low-water sour environments is the same as in air. We find that the dry gas environment dose not attack the metal surface preserving the fatigue performance.
New Installation Method for Subsea Pipelines in South China Sea
Authors: Chen Chi , Zhang Kai , Yang Tianxiao , Xiong Ouyang , Tang Qiang , Cheng Yongming 
Published: August 2013

The subsea pipelines between two platforms located in South China Sea were required to be replaced. In between the two platforms is a Floating Production Storage and Offloading (FPSO) unit including the mooring system, anchors and Pipeline End Termination (PLET). The new pipelines need to run below the FPSO and the mooring lines. This paper discusses a new installation method for the subsea pipelines in South China Sea.
There are technical challenges to install the new 18-km pipelines in Panyu oil field. On the one hand, it needs to ensure a 500-m radius safety zone from the FPSO. The pipeline laying vessel shall not work within the safety zone due to possible interference with anchor lines. On the other hand, the new pipelines have to run below the FPSO and the mooring lines in order to avoid potential interference with existing cable and riser system.
This paper considers the existing pipeline installation methods and generates a new method to install the pipelines in South China Sea. A concept of ‘dummy pipe’ is introduced to simulate the installation operation. The paper presents a series of installation sequences including assisting the pipeline laying and pulling, accurately positioning the pipelines, and protecting the existing facility. Figures are used to illustrate the installation deployment. Messenger lines were installed to run below the FPSO. The installation process was monitored. The new pipelines were installed in the field successfully. In addition, this paper further presents some recommendation for future installation practice.
Fatigue Estimation in Deepwater Risers Based on Wavelets and Second Order Blind Identification
Authors: Huang Chaojun , Nagarajaiah Satish , Varadarajan Nadathur 
Published: August 2013

The safety of deepwater risers is essential for sustainable operation of offshore platforms. The structural health monitoring (SHM) system for deepwater risers is important to detect damage and perform repairs before failure occurs. Two main sources of damage are fatigue and corrosion. Failure of the riser would not only be an economical and environmental disaster, but also have far reaching consequences affecting communities. Combining global and local monitoring can greatly increase the accuracy of damage detection and fatigue estimation. Local inspection using robotic Magnetic Flux leakage (MFL) sensors is efficient and provides high resolution estimate of wall thickness changes due to corrosion or damage, while proposed vibration-based system identification can estimate global damage locations and fatigue life.
A new SHM system for deepwater risers was recently developed to monitor damage to the risers with both global and local monitoring methods proposed in this paper. The global monitoring is achieved by wavelet transform (WT) and second order blind identification (SOBI) method, from which, the likely location of fatigue damage is estimated. Once the location of the damage is identified by the proposed Wavelets/SOBI global identification method, local monitoring is performed using a robotic crawler with MFL sensors to further estimate the extent of the damage. Local monitoring with MFL sensors is verified by experimental results. Wavelets/SOBI global identification method is verified using Gulfstream test data.
Possible applications for the proposed SHM systems are for deepwater risers and deepwater platforms. A robotic MFL crawler can be used for in-line inspection for various pipelines. The proposed damage detection method and fatigue estimation can be adapted to other offshore structures, both fixed and floating. The proposed global method can also be used to analyze Tensioned Leg Platforms (TLP). To demonstrate the applicability of the proposed Wavelets/SOBI method to risers and floating platforms, verification using Gulfstream riser field data and TLP model data is presented in the paper.
Well Control Research and Development
Authors: Ribeiro Paulo R. , Santos Otto L. A. 
Published: August 2013

Well control has been an inexhaustible source of research/development/innovation for the past four decades due to its impact in oil and gas exploration and production. Such an importance is based on three pillars: i) human safety, ii) environmental protection, and iii) economic issues.
Macondo incident has proved that continuing development of the subject is an issue to be tackled by oil companies to preserve and also rebuild their image to society. One of the most important aspects of well control is the development of kick simulators capable of handling increasing complexity of well geometry (diameters and trajectory), drilling fluids (synthetic drilling fluid), well location (land and offshore) and wellbore conditions (increasing pressure and temperature severity with depth). Such simulators have the following missions: i) to help the drilling engineer to make decisions during well control procedures and kick situations, ii) to provide personnel training and certification and iii) to guarantee a better understanding and interpretation of field observations.
The main objectives of the present work are three-fold: i) to present an overview of the evolution of kick modeling and simulation over the years, ii) to focus on the R&D efforts of the joint work of academia and industry to build a well control model to handle deep and ultra-deepwater drilling challenges and iii) to present a software based on that model to assist drilling engineers during well control operations.
Experimental data has been based on PVT measurements of gas and synthetic drilling fluid mixtures under HPHT conditions. Phase behavior modeling has proved to be a very important issue to be taken into account in the two-phase flow model that represents the kick circulation process.
The current work presents the results of the interaction of experimental lab work and numerical modeling to develop a kick simulator to handle complex drilling scenarios to assist drilling personnel in well control operations.
Lifecycle Fatigue Load Spectrum Estimation for Mooring Lines of a Floating Marine Energy Converter
Authors: Thies Philipp R. , Johanning Lars , Smith George H. 
Published: August 2013

One of the key engineering challenges for the installation of floating marine energy converters is the fatigue of the load-bearing components. In particular the moorings which warrant the station-keeping of such devices are subject to highly cyclic, non-linear load conditions, mainly induced by the incident waves.
To ensure the integrity of the mooring system the lifecycle fatigue spectrum must be predicted in order to compare the expected fatigue damage against the design limits. The fatigue design of components is commonly assessed through numerical modelling of representative load cases. However, for new applications such as floating marine energy converters numerical models are often scantily validated.
This paper describes an experimental approach, where load measurements from tank tests are used to estimate the lifecycle fatigue load spectrum for a potential deployment site. The described procedure employs the commonly used Rainflow cycle analysis in conjunction with the Palmgren-Miner rule to estimate the accumulated damage for individual sea states, typical operational years and different design lives.
This allows the fatigue assessment of mooring lines at a relatively early design stage, where both information from initial tank tests and the wave climate of potential field sites are available and can be used to optimise the mooring design regarding its lifecycle fatigue conditions.
A Model for Long-Term Distribution of Wave Induced Loads in Steep and Breaking Shallow Water Waves
Authors: Hansen Hans Fabricius , Lohmann Iris Pernille , Sørensen Jacob Tornfeldt , Schlütter Flemming 
Published: August 2013

A new approach to determine the design wave load on bottom-fixed structures in shallow water breaking waves is presented here. The method takes into account the effects that wave breaking has on both the wave height distribution and the wave induced loads on the structure. The loads on offshore wind turbine foundations in irregular seas with a significant amount of wave breaking are modeled in a physical wave tank. The loads are related to wave characteristics as steepness and Ursell number, and a non-linear transfer function between wave height/period and wave load is established.
Characteristic historical load events are now established by combining the transfer function with a record of the wave climate at the site. The latter is taken from a hindcast database, but could also come from site measurements. The long-term distribution of the load is estimated by adopting traditional extreme value analysis techniques to the historical characteristic loads.
Investigation on the Use of Different Approaches to Mooring Analysis and Appropriate Safety Factors
Authors: Vasudevan Sojan , Westlake Paul 
Published: August 2013

This paper presents the results of the analyses of a twelve line catenary mooring system using a quasi-static method in the frequency domain, and uncoupled and coupled dynamic methods in the time domain. The latter is found to produce significantly higher tensions. The reasons for these differences are investigated.
The minimum line tension safety factors required by design codes do not distinguish between uncoupled and coupled dynamic analyses and some codes use the same factors even for quasi-static analyses. Consequently, the present mooring system passes the acceptance criteria based on quasistatic frequency domain and uncoupled dynamic time domain analyses but does not meet the same criteria when a coupled dynamic time domain analysis is employed.
It is understood that because the coupled time domain analysis determines the vessel motions using all forces the accuracy of mooring line tension estimation will be improved over other methods. Hence the application of less conservative safety factors is proposed.
Riser Dynamic Analysis Using WKB-Based Dynamic Stiffness Method
Authors: Cheng Yongming , Vandiver J. Kim 
Published: August 2013

Risers are fluid conduits from subsea equipment to surface floating production platforms. The integrity of a riser system plays a very important role in deepwater developments. Riser dynamic analysis is an important part to the system design. This paper investigates riser dynamic analysis using the WKB-Based dynamic stiffness method.
This paper first presents a theoretical formulation of the dynamic stiffness method. It then combines the dynamic stiffness method with the WKB theory, which assumes that the coefficients in the differential equation of motion are slowly varying. The WKB-based dynamic stiffness method is derived and a frequency dependent shape function is expressed implicitly. The Wittrick and Williams (W-W) algorithm is further extended to solve eigen value problem for a general non-uniform marine riser.
Examples of non-uniform riser are analyzed and the results show the efficiency of this method. In addition, a pipe-in-pipe riser system is analyzed for natural frequencies and mode shapes using the WKB-based dynamic stiffness method with the W-W algorithm. The characteristic of the mode shapes is described for such a riser system.
Stiffness Modeling, Testing, and Global Analysis for Polyester Mooring
Authors: Kwan C. T. , Devlin Paul , Tan Pao-Lin , Huang Ken 
Published: August 2013

This paper summarizes one of the studies conducted by the ABS Joint Industry Project (JIP), “Polyester Rope Stiffness Modeling, Testing, and Analysis”. The objective of this study was to collect and investigate results of past studies, test procedures and data, code requirements, and fiber rope mooring analysis methods dealing with polyester rope stiffness. Based on the results of the study, conservative and practical stiffness models, test data analysis, and mooring analysis method were developed. The results from this study have been incorporated in the 2011 ABS Guidance Notes on The Application of Fiber Rope for Offshore Mooring [13]. Major conclusions of this study are as follows:
1. The 2-slope static-dynamic model is the best approximation for the complex fiber rope elongation behavior. It is based on rigorous research and allows efficient mooring analysis using typical commercial software.
2. Stiffness testing should be conducted to generate stiffness equations and design charts instead of design stiffness values. The design stiffness values can be obtained from these equations and design charts. A practical procedure for test data analysis is recommended.
3. Mooring analysis can be efficiently conducted in frequency or time domain with commercial mooring analysis software based on the recommended stiffness model.
Commissioning Software on New Build Drillships: Lessons Learned
Authors: Lanier Greg 
Published: August 2013

Commissioning software on a drillship involves many programmers, some located remotely, where all personnel are under time pressure to quickly complete the software tasks. Managing software changes under these conditions is difficult; leading to a deviation of the personnel involved in the project. Deviations from quality procedures in many cases lead to loss of time and negatively impact software quality. As an example, software on three of the drilling control chairs was updated and the fourth drilling control chair was missed, which causes improper integration and potentially leads to safety issues and ultimately downtime.
Maintaining software quality during commissioning of the ship is very challenging and becomes more complicated when control system software interfaces have not been verified before commissioning. Early verification of the software provides a known foundation and opportunity to discover concept errors and software defects in advance. Before commissioning, updates and changes can be evaluated more carefully, helping to provide thoughtful consideration of options and impact of the changes to the system’s software as a whole.
At the Factory Acceptance Test (FAT), the software verification may not occur and sometimes the software in the control system is only to demonstrate mechanical functions of the hardware. This leads to insufficiently tested and thus, unacceptable software being delivered with the equipment initially.
The Human Machine Interface (HMI) is another piece of software that has to be updated to match the changes made to the control system software it is connected to. In some cases, the personnel programming the HMIs are separate from the personnel programming the control system, which leads to failed functions and delays.
Software changes of any form must be controlled throughout the process. Modifications made to one software function can affect previously approved and working functions which may lead to unexpected functioning of the software. To mitigate these errors, regression testing of the functions is essential. Without doing so, defects introduced during commissioning may not be discovered until the operational phase of the ship, which can prove much more costly so late in the process.
Following the management of change program requires commitment and communication because of the extensive details involved with all programs.
Effort must be expended to keep communication between programmers functioning smoothly. They have to maintain a common goal and focus on the software change and management should enforce software quality procedures.