bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contribution of Axial Soil Resistance in Buckle Initiation of the HPHT Pipelines on Sleepers
Authors: Vosooghi Navid , Ivanovic Ana , Sriramula Srinivas 
Published: October 2016

The objective of this paper is to assess the impact of soil axial resistance on initiation of the buckles on sleepers. It also covers the effects of history of pressure and temperature increase on effective axial force as well as the incorporation of external pressure in the Finite Element (FE) models. This is carried out for 6″, 8″, 10″ and 12″ pipelines laying on sleepers with different heights for a range of axial soil frictions and mobilisations. Knowing the sensitivity of buckle initiation to soil parameters can help in simplifying engineering analysis by avoiding repetitive simulations for parameters with less importance.
To carry out the above, a series of FE models including normal and bi-linear axial contacts between pipeline and sleeper / seabed were built in Abaqus FE package and at the point of initiation of the buckles, the effective axial force was extracted by a Python script. FE models were validated by comparison of the simulation results with analytical solutions and experimental results from published literature.
Evaluation of CTOD Resistance Curve Test Methods Using SENT Specimens
Authors: Zhu Xian-Kui , Zelenak Paul , McGaughy Tom 
Published: October 2016

Single edge-notched tension (SENT) specimens in clamped end conditions are widely adopted in the oil/gas industry to measure fracture resistance curves in terms of the J-integral or crack-tip opening displacement (CTOD) for the strain-based design and crack assessment of onshore and offshore pipelines. Typical CTOD-R curve test methods developed for SENT specimens include CanMet, ExxonMobil, and BS 8571 methods. While CanMet determines CTOD using the J-integral conversion method via one clip gage measurement, the other two infer CTOD directly from double clip gage measurements. ExxonMobil simply uses the total measured displacements to calculate CTOD, but BS 8571 separates CTOD into elastic and plastic parts to be determined, respectively, from the elastic K factor and the plastic component of measured displacements. It is unknown if these CTOD test methods determine comparable R-curves for a same SENT test, and what are the differences between these CTOD test methods.
To answer those questions, this paper performs an experimental evaluation of the SENT CTOD test methods. A set of clamped SENT specimens are tested for pipeline steel X80 and structural steel A36. For each SENT test, the unloading compliance method and the double clip gage arrangement are used, and then CTOD-R curves obtained by different methods are evaluated. Evaluation results and conclusions are given for those SENT CTOD test methods.
Subsea Pipeline UHB Design: An Improved Analysis Approach
Authors: Liu M. , Cross C. 
Published: October 2016

A subsea pipeline operating at temperature and pressure may buckle both vertically and laterally. For a trenched and buried pipeline, the propensity to upheaval buckling (UHB) is a major design concern. Predictive UHB design is typically required at the outset to determine both trenching and backfilling requirements. Additional rockdump schedule can be established by analysing post pipelay OOS survey data incorporating appropriate safety factors based on a structural reliability analysis. The normal approach is to examine the pipeline imperfection survey statistics and data accuracy. The structural reliability analysis and load factor calculation is typically performed a priori based on the assumed imperfections using the methodology outlined in ref [1]. The additional rockdump schedule is derived from the crown of the pipeline imperfections regardless of adjacent profiles and overall backfill data.
A new pseudo energy method for UHB and OOS is proposed and discussed in this paper based on the variational principle and modal analysis.
The approach takes into account the effects of varying effective axial force, trench imperfections and vertical uplift resistance, by combining both axial friction and lateral resistance methods into a unified model. A new concept, effective uplift resistance and associated load is also introduced to deal with non-uniform backfill cover. Adjacent imperfections and backfill profiles are considered in detail. An FE model is developed to consist of 3-noded quadratic pipe elements using ABAQUS Ver 6.12 and iterations of FE analyses are performed to demonstrate the tangible benefits of the approach specifically for UHB OOS design in relation to target trenching and backfilling, leading to improved reliability and potential cost saving in UHB OOS design and rockdump installation.
Asset Integrity Assessment and Management Program for Life Preservation of a Purpose Built FPSO and Associated Subsea System Facilities
Authors: Nezamian Abe , Nicolson Robert J. 
Published: October 2016

Floating facilities for production, storage and offtake (FPSO) and other offshore production facilities have been used safely and reliably throughout the oil industry for many years. Asset Integrity is increasingly important to optimising safety and operational life and asset performance efficiency. Operators need to comply with Corporate, Regulatory and Certification requirements but recognise that developing and managing an effective and compliant Asset Integrity Management System is both time consuming and costly.
Review of operational history of existing large FPSOs around the world indicated low confidence in operational life expectancy and to achieve the design life without possible dry docking or major repair. FPSOs have certain loading characteristics and damage consequences that make them different to other offshore installations and conventional ships, and often more challenging to maintain and operate. Maintenance and inspection campaigns are important inputs in the Asset Integrity Management (AIM) system of FPSOs and other floating offshore facilities. Considering that the unit shall stay on site during the whole life of the field, where disconnection or the removal of the mooring system is not planned, a comprehensive methodology for the asset integrity management, survey, inspection, testing, maintenance and repair of the unit during this period needs to be developed and subject to review based on the results of the scheduled inspections and audits. So as well as class and statutory requirements, inspection and survey, maintenance and repair plans should reflect the required availability, functionality, survivability and durability of the unit, giving due regard to its field life, as part of the safety management of the facility. Risk Based Integrity management methodology has been adopted in several projects and is an important tool to establish a rational inspection campaign for structural components, mainly for those located in areas where access is critical and operational constraints are an important parameter. This paper gives an overview of the challenges and discusses various aspects of ageing related to FPSO facilities, represented risk to the integrity of a facility and the required procedures and reassessment criteria for maintaining the structural integrity. This paper also provides an overall view on the regulatory requirements, documentation and calibrations/validations of the original design values to maintain the safety level by means of a maintenance and inspection programs balancing the ageing mechanisms and improving the reliability of assessment results. A brief summary of an example project of an asset integrity assessment and management program for life preservation of a purpose built FPSO and associated subsea system facilities is presented.
A Study on the Wave Drift Forces Calculation on Two Floating Bodies Based on the Boundary Element Method: Attempt for Improvement of the Constant Panel Method
Authors: Li Qiao , Tsubogo Takashi , Ikeda Yoshiho , Nihei Yasunori 
Published: October 2016

The boundary element method (BEM) which can solve the boundary integral equations is used to calculate the velocity potential on the floating bodies. The equation is discretized by the higher order BEM or the constant panel method. The constant panel method is relatively easy to compute the velocity potential. However the near field method cannot evaluate the wave drift forces and moment accurately, when the velocity potential is computed by the constant panel method.
In the article, a new numerical technic of the constant panel method is proposed. Then it is easy to take advantage of the near field method to calculate the wave drift forces and moment, especially considering two floating system. In addition, the results of the fluid forces calculated by new method are compared to the other methods results. At last the hydrodynamic interaction between two floating bodies is assessed in the calculation of the wave exciting forces and the wave drift forces.
Retracted: “Numerical Investigation Into the Effects of Top Water-Bearing Zone on Steam and Gas Push” [ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering, Volume 8: Polar and Arctic Sciences and Technology; Petroleum Technology, Busan, South Korea, June 19–24, 2016, Conference Sponsors: Ocean, Offshore and Arctic Engineering Division, ISBN: 978-0-7918-4999-6. Paper No. OMAE2016-54268, pp. V008T11A010; 6 pages; doi:10.1115/OMAE2016-54268]
Authors: ASME  
Published: October 2016

This paper was not presented at the conference. ASME does not hold the copyright. December 21, 2018.
Copyright © 2018 by ASME
A Transient Model for Hydraulic Simulation of Bullheading and Pressurized Mud Cap Drilling
Authors: Ghauri Abrar Akram , Fjelde Kjell Kåre , Frøyen Johnny 
Published: October 2016

Bullheading is the process of pumping fluids into the well without circulating back to surface. This operation can be carried out for several reasons. In well control, this can be an alternative well kill approach in situations where conventional kill methods do not apply. When considering the pressurized mud cap drilling technique, bullheading is used for controlling pressures when drilling highly fractured and vugular carbonate formations. Bullheading is also carried out for killing production wells prior to workover operations.
For a bullheading operation to be successful one need to ensure that the correct flow rate is chosen to overcome gas migration. This countercurrent to downward flow situation is best described using transient flow simulators to correctly predict what kind of rates and fluid volumes that are required. In addition, a transient flow model can also predict what kind of pressures that will be experienced during the operation to ensure that equipment and fracture pressure limitations are not exceeded.
This paper aims at giving an overview of the application and challenges associated with bullheading operations for different type of well operations including the pressurized mud cap drilling technique. Then a mathematical model and a numerical scheme (AUSMV) that can be used for simulating the transient dynamics of a bullheading operation will be described. The drift flux model combined with a slip law will be used.
Here special emphasize will be given on describing how we made the numerical scheme second order to reduce effects associated with numerical diffusion. The numerical boundary treatment and handling of flow regime transitions will also be described since one will here alternate between different conditions like cocurrent, countercurrent and downward flow.
Two simulation scenarios will be considered. In the first example, a kick scenario will be considered and it will be shown how the transient model can be used to predict the effect of using different bullheading rates when trying to kill the well. Both time and depth variables will be visualized. The model can also predict how large volumes are required for a successful bullheading operation for a given rate.
In the second example, it will be shown how the model can be used for simulating the alternating conditions experienced in a pressurized mud cap drilling operation. Here one will have a situation where surface pressure will build up if a kick is migrating in the closed annulus and if the pressure reaches a certain level, the kick has to be bullheaded back into the formation. This process can be repeated several times.
The paper will show that the transient model proposed can provide good insight into the dynamics of bullheading and pressurized mud cap drilling. The model seems to be robust in handling the alternating flow conditions. Finally, some words will be said with respect to what is considered as important with respect to improving the modelling.
Probabilistic Analysis of the Collapse Pressure of Corroded Pipelines
Authors: Oliveira Nara , Bisaggio Helio , Netto Theodoro 
Published: October 2016

Oil and gas offshore pipelines are one of the main components of a subsea system. A major accident can have a great economic impact due to loss of revenue and the expenses involving actions to mitigate damages to the environment. Therefore, investment in accident prevention through a carefully designed inspection and maintenance plan is necessary. In this scenario, many companies have changed their procedures to ensure the structural integrity of their pipelines — from a model that incorporates empirical safety factors and periodic inspections to another, based on methods that consider concepts of structural reliability to establish risk based inspections.
The collapse pressure of pipelines containing corrosion defects is usually predicted by deterministic methods, either numerically or through empirical formulations. The severity of each individual corrosion defect can be determined by comparing the differential pressure during operation with the estimated collapse pressure.
However, loads and resistance parameters have uncertainties which define the basic reliability problem. These uncertainties are related to the geometric and material parameters of the pipe and the operational conditions. In recent years, many studies have been developed using reliability concepts in order to predict the probability of failure of a corroded pipeline at any given time. The main problem in assuring the integrity and safe operation of pipelines lies in obtaining the necessary accurate prediction of their future condition.
A simple deterministic procedure for estimating the collapse pressure of pipes with narrow and long defects has been recently proposed by Netto (2010). This formulation was based on a combined small-scale experimental program and nonlinear numerical analyses accounting for different materials and defect geometries.
Probabilistic failure analyses of pipelines considering different failure mechanisms have been performed by different authors over the last decade. Limit state functions similar to the mentioned above, coupled with reliability algorithms such as the first-order second-moment (FOSM) iterative method, the Monte Carlo integration method, and the first-order and second-order reliability methods (FORM/SORM) are generally used. The analyses take into account the natural spread of material properties, geometric and operational parameters, and the uncertainties associated with the sizing of eventual corrosion defects. In this paper, Netto’s deterministic formulation and the crude Monte Carlo method were used to obtain the reliability of corroded pipelines under external hydrostatic pressure.
This approach provides a method to predict the probability of collapse of a corroded pipeline along its operational life. It applies concepts of structural reliability to evaluate the detrimental effect of corrosion damages, giving the basis to develop a risk based maintenance strategy.
VIM Simulation Method on a Cylindrical Floating Structure
Authors: Fujiwara Toshifumi 
Published: October 2016

A cylindrical floating structure can basically experience Vortex-induced Motion (VIM) in strong current. Since the VIM on the structure with long term low-frequency motion causes fatigue damage of the structure’s mooring lines and risers, precise VIM assessment is needed for the safety evaluation of them. In the standard of the International Organization for Standardization ISO19901-7, ‘Specific requirements on stationkeeping systems for floating offshore structures and mobile offshore units’, for instance, a concrete method of assessing VIM displacement is not represented in the standard document, though the requirement on the VIM demands to do the assessment on the basis of proper ways.
Then in this paper, a VIM simulation method on a floating structure with circular cylinder form, that is, for example a Spar, a MPSO (Mono-column type floating Production Storage and Offloading) and so on, is shown using the wake-oscillator model. Transverse VIM is only treated since it is dominant factor on the fatigue damage of the mooring lines and risers. The assessment quality of the simulation method on the transverse VIM of floaters in current is confirmed by model test data.
Copula-Based Bivariate Modelling of Significant Wave Height and Wave Period and the Effects of Climate Change on the Joint Distribution
Authors: Vanem Erik 
Published: October 2016

The joint distribution of several met-ocean variables is required for risk assessment and load and response calculations in marine engineering. For example, a joint description is needed to construct environmental contours for probabilistic structural reliability analyses. Typically, the joint distribution of significant wave height and wave period is required as a minimum.
This paper presents a study on various bivariate modelling techniques for the joint distribution of significant wave height and zero-crossing wave period, i.e. a conditional model, a bi-variate log-normal model and several meta-models based on parametric copulas. Each of the models is fitted to data generated from a numerical wave model for the current climate and for two future climates consistent with the RCP 4.5 and RCP 8.5 scenarios. Thus, the objective of this study is twofold. First, the joint models obtained by the various modelling techniques will be compared. Secondly, the potential effect of climate change on the simultaneous distribution of significant wave height and wave period will be explored.
The results indicate that straightforward application of many of the most common families of copulas fails to capture the dependence structure in the data, and that the conditional model performs better than these naive approaches. However, if more advanced copula construction techniques are applied, significant improvements can be achieved. The results also suggest that significant wave height and zero-crossing wave period tend to be more correlated in a future climate, at least in the extremes.
Evaluating Vibration Performance of a Subsea Pump Module by Full-Scale Testing and Numerical Modelling
Authors: van Beek Pieter J. G. , Pereboom Hajo P. , Slot Harmen J. 
Published: October 2016

Prior to subsea installation, a subsea system has to be tested to verify whether it performs in accordance with specifications and component specific performance evaluation criteria. It is important to verify that the assembled components work in accordance with the assumptions and design criteria used in the detailed engineering. These criteria also cover the vibration performance. In the current study, the pump module within the Åsgard subsea compression station has been subjected to such system evaluation test, including its vibration performance. Vibrations may be caused by internal and external flow through a complex process that is affected by numerous factors such as the piping geometry, flow and operating conditions and also the fluid properties. When severe, mechanical vibrations can lead to fatigue failure of the equipment components.
One of the major parameters that affects the vibration response of the subsea piping is the surrounding water. It is generally known that surrounding water does participate in some vibration modes by adding mass to the total, dynamic mass participating in the vibration. Therefore, resonant frequencies of a piping system will have different values for non-submerged and submerged cases. In addition, the surrounding water can also lead to higher damping of the vibration modes.
In this paper the effect of submerging a pipe system in water is quantified, by analyzing the changes in damping coefficient and the characteristics of measured pipe vibration in-situ. This is achieved by analysis of full-scale frequency response tests performed on a subsea pipe system within the pump module in both non-submerged and submerged conditions. The results are used for validation of numerical techniques that are used to quantify pipe vibration in submerged conditions. Different modeling techniques for the submerged case are investigated.
It is shown that the effects from the surrounding water on pipe vibrations are different for small-bore piping than that for main piping. Furthermore the different modeling approaches and general observations and trends in damping coefficients are discussed and compared with the measurements.
Estimation of Stick-Slip Characteristics by Simulation With Actual Drilling Data
Authors: Inoue Tomoya , Katsui Tokihiro , Ishiwata Junya , Matsuo Miki Y. , Rheem C. K. 
Published: October 2016

Stick-slip, a term for the spontaneous torsional vibrations occurring on a drill bit, is a critical problem in offshore drilling because of the damage it causes to the drill bits. Moreover, it leads to crushing or grinding of the sediment layer, which is a critical problem especially in scientific drilling where the purpose is to recover core samples from the layers.
To detect the occurrence of stick-slip and its fundamental characteristics onboard in real-time, we developed an analytical model is developed to express the torsional motions at the drill bit, leading to the stick-slip phenomenon. The analytical model includes the unknown frictional torque at the drill bit, which depends on the properties of the drilling layers and is a dominant factor for demonstrating the stick-slip phenomenon. This study proposes a method to determine the frictional torque by integrating the analytical model with the surface drilling data. It would be advantageous to identify the characteristics of stick-slip from the surface drilling data. The method is validated with the results of small-scale model experiments in a water tank to observe the stick-slip phenomenon.
Furthermore, we acquired the actual drilling data, which are surface drilling data and downhole data, during the drilling operation of the scientific drilling vessel Chikyu.
This study focuses on attempts to estimate the stick-slip characteristics by the simulation based on the established analytical model with actual surface drilling data acquired during the drilling operation of the scientific drilling vessel Chikyu, and a comparison with the downhole data including the bit motions.
Effects of Curvature on Slamming Loads
Authors: Weber John B. , Das Raj , Battley Mark 
Published: October 2016

Much research has been directed at understanding and predicting water slamming loads for a range of geometries of varying rigidity and size. Analytical and numerical studies focused on slamming of cylindrical rigid bodies are present in literature but there are relatively few experimental studies useful for validation purposes, none of which methodically investigate a range of curvatures. Despite the current understanding of slamming loads and structural responses, high speed marine vehicles still experience slamming related failures in operation.
In this study, nominally rigid, singly curved prismatic specimens of varying curvature are subjected to constant velocity water impacts relevant to those encountered by high performance offshore racing yachts and other high-speed craft.
Peak impact forces of 14 to 52 kN were recorded while testing specimens with radii ranging from 0.300 to 5.000 m. Experimental peak impact force and event impulse are found to be significantly lower than predicted by numerical and small scale empirically derived methods. A modification is introduced which improves the empirical model.