bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural Impact in FPSO Life Extension: A Class Perspective
Authors: Machado Christiane L. , Chand Sudheer 
Published: November 2013

The Offshore Oil and Gas Industry has converted a large number of units from trading tankers and carriers into Floating Production, Storage and Offloading units (FPSOs). Several of these have been moored offshore Brazil during the last 15 years. Following the discovery of offshore pre-salt fields some years ago, demand for FPSOs has increased, and the forecasts for productive field lives have grown. The result of these developments is the need to extend the service lives of existing FPSOs.
The main aim of this study is to investigate FPSO structural response to environmental conditions and functional loads, considering the actual available tools for numerical simulations and Rule requirements, which currently are basic requirements for design review for Classification.
The procedure was developed from one selected FPSO converted from a trading Very Large Crude Carrier (VLCC) tanker approximately 15 years ago and includes investigation of the impact on hull behavior comparing the motion analyses of the production unit under environmental data and software capabilities available at the period of conversion and actual performance: variances in the environmental (sea scatter diagrams) datasets; updates to Classification requirements for defining offloading conditions, environmental loads, acceptance criteria and remaining fatigue life (RFL); and incorporating the most recent gauged thickness for primary structure.
The selected FPSO was evaluated according to prescriptive Rule requirements and also using finite element analysis, taking into account the previous conditions of Classification approval as well as the actual requirements and available data. Structural analysis included one global model and some local refined models to address strength, buckling and fatigue capacity of the typical portions/connections of the hull.
The comparisons performed from the results of these analyses are a crucial step toward understanding the structural capacity of the FPSO at the conversion stage, its performance during the last 15 years, and its remaining service life.
Differences were tabulated and evaluated so that a more precise level of uncertainty could be achieved for predicting the estimated remaining service life, and consequently, a new and dedicated approach to investigate the existing FPSO fleet is being generated.
FEA-Based Stability Analysis of Mudmats: Coupled Soil-Structure-Flowline Interaction Model
Authors: Abdalla Basel , Wang F. Steven , Hossain M. Kabir 
Published: November 2013

The traditional method of foundation stability assessment for subsea structures is to calculate the bearing capacity factor of safety using classical approach given in the API-RP-2A/2GEO. This classical approach can be overly conservative for foundations under complex loading conditions (e.g., multiple interacting loads). A typical example is pipeline end manifold or flowline sled, which can be subject to self-weight, structure-soil interaction, and multiple interface loads from flowline and jumpers under operational condition.
A more rigorous 3D-FEA based assessment approach is developed in this paper to achieve more accurate bearing capacity estimates for a flowline sled supported by mudmat. This fully combined global model comprises the structure (with sliding mechanism), soil foundation, jumpers, and flowline as realistically as possible so as to capture the more accurate interactions among the different parts of whole sled-soil system. The use of such advanced numerical modeling has proven to improve the mudmat bearing capacity factor of safety.
A Feasibility Study on Hybrid Use of Ocean Renewable Energy Resources Around Japan
Authors: Taniguchi Tomoki , Ishida Shigesuke , Minami Yoshimasa 
Published: November 2013

This paper addressed assessing feasibility of hybrid use of ocean renewable energy, such as wave and wind energy around Japanese coast. At first, wave and wind energy theoretical potentials were calculated and, in the second step, correlation coefficient between wave and wind energy was computed around Japanese coast. Sea area suitable for hybrid use of ocean renewable energy resources is supposed to have high potential for some types of energy resources. Furthermore, correlation of power generation between wave and wind energy resources should be low because one energy resource needs to complement another one for stabilizing power generation.
Based on the assumptions, feasibility of wind and wave energy was evaluated on some sea areas where R&D project are ongoing.
Weather Window Determination of Top-Tensioned Riser Deployment With Guidewires
Authors: Fan Bin , Thomas William J. 
Published: November 2013

To replace 20 of the 42 top-tensioned production risers for the Statoil Snorre A platform, the planned riser deployment will use a guidewire and guide frame system. A suitable weather window needed to be determined for the deployment to avoid clashing the deploying risers and adjacent connected risers. Such clashing could cause severe consequences such as connector leakage and equipment damage.
Riser collision during operation and production was studied extensively [1, 2]. However, little investigation has been conducted on clashing during deployment. Due to the importance of the disturbed wave elevation and wave kinematic effects on the riser response by earlier study [3], RIFLEX was chosen for the simulation. RIFLEX simulates the disturbed wave kinematics. However, RIFLEX has limited capabilities to model the deployment guidance system and calculate the minimum riser clearance.
This paper focuses on the simulation of the riser deployed with guidewires and guide frames and calculation of the clearance between the deploying riser and the connected risers.
First, the guide frame and 4-guidewire system (see Fig. 2 and 3) was simplified as a rigid beam and a sliding linear spring (see Fig. 4 and 5). A derivation of the relationship between the guidewire tension and deployment depth was developed and implemented into a RIFLEX model.
Second, due to different responses caused by the disturbed wave kinematics, different deploying and installed riser pairs in the well bay were selected to find the smallest clearance during a three-hour random sea state. The smallest clearance was determined from five different deployment depths and weather conditions in the initial plane of the riser pairs.
Last, a clashing criterion is discussed and used for the deployment weather window determination. This paper also points out that a slightly wider weather window could be possible, depending on the deployment depth.
Recent successful deployment of the new risers confirmed the riser installation analysis.
Overcoming Installation Challenges to Wellhead and Conductor Fatigue
Authors: Lim Tze King , Koska Ryan , Tellier Elizabeth 
Published: November 2013

Subsea wells are typically drilled and completed using marine risers with subsea BOP stacks deployed from mobile drilling units. Wave and current induced riser motions are transferred to the wellhead, conductor and casing system which can then cause fatigue issues at the critical connectors and welds. In recent years, the risk of fatigue failure has increased due to the use of 5th and 6th generation rigs with larger BOP stacks, and longer well drilling and completion durations. During the design stage, the fatigue performance of the wellhead, conductor and surface casing is often overlooked.
During well construction, variations from design can occur in terms of wellhead stickup, wellhead lockdown and cement levels, both around the conductor and in the annulus between the conductor and surface casing. This paper describes analysis results showing the effect of these variations on the fatigue performance of the wellhead, conductor and surface casing. The recommended analysis load case matrix to account for these uncertainties is also presented, together with the need for as-installed assessments.
Recommendations on fatigue resistant designs with equipment configuration and specification options capable of meeting these challenges are presented. Wellhead monitoring and fatigue tracking strategies that can be implemented during drilling and workover operations to address these potential concerns and manage the risk are also discussed.
Floating Axis Wind and Water Turbine for High Utilization of Sea Surface Area: Design of Sub-Megawatt Prototype Turbine
Authors: Nakamura Takuju , Mizumukai Kentaro , Akimoto Hiromichi , Hara Yutaka , Kawamura Takafumi 
Published: November 2013

Paradoxically, sea surface area for offshore wind farms is limited in some countries like Japan. While the distance from the shore to a wind farm is limited due to the cost of electric transmission, the near shore area has considerable traffic of ships and is restricted by complex rights of local fisheries. One approach to the problem is inviting the local fishermen to the management of the wind farm. It requires higher economic performance of the wind farm than the original fishing activity in the same sea surface area.
The proposed concept is the combination of a floating wind turbine and counter-rotating water current turbine. The water current turbine partially cancels the reaction torque of electric generator and provides additional energy production from water current. The rotating axis of the turbine is not fixed in the upright position to reduce the size of supporting structure. Regular maintenance work is only in low altitude on the float. These features lead to the reduction of O&M costs and higher utilization of sea surface area.
This paper describes the prototype sub-megawatt turbine under construction and its expected economic performance.
Synthesis and Optimization of Submarine Pipeline Routes Considering VIV-Induced Fatigue on Free Spans
Authors: Baioco Juliana Souza , Blanco Juan Pablo Inza , Jacovazzo Bruno Martins , Albrecht Carl Horst , de Lima Beatriz Souza Leite Pires , Jacob Breno Pinheiro , Cardoso Carlos de Oliveira , Rocha Djalene Maria 
Published: November 2013

Researchers from Petrobras and LAMCSO/COPPE have been involved in the development and implementation of a computational tool, based on Evolutionary Algorithms, for the synthesis and optimization of submarine pipeline routes. In this tool, randomly generated candidate routes are evaluated in terms of several criteria, incorporated in an objective (or fitness) function to take into account the relevant aspects that should be considered in the design of a route.
Previous works described the initial steps taken towards the development of such tool, including the geometrical representation of a route, and some of the terms of the objective function associated with a preliminary, global step of the optimization process (such as total pipeline length, and geographical-topographical issues associated with the route geometry and to the seabed bathymetry and obstacles). Special attention was dedicated to the implementation of On-Bottom Stability (OBS) criteria such as the proposed in the DNV-RP-F109 code.
This work is focused on another aspect related to the structural behavior of the pipe under hydrostatic and environmental loadings; more specifically, fatigue induced by vortex induced vibrations (VIV) on free spans along the candidate routes. Special attention is dedicated to the implementation of the screening criteria proposed in the DNV-RP-F105 code. Case studies are presented to assess the influence of the VIV criteria on the results of the optimization tool.
Design Requirements for Floating Offshore Wind Turbines
Authors: Chen Xiaohong , Yu Qing 
Published: November 2013

This paper presents the research in support of the development of design requirements for floating offshore wind turbines (FOWTs).
An overview of technical challenges in the design of FOWTs is discussed, followed by a summary of the case studies using representative FOWT concepts. Three design concepts, including a Spar-type, a TLP-type and a Semisubmersible-type floating support structure carrying a 5-MW offshore wind turbine, are selected for the case studies. Both operational and extreme storm conditions on the US Outer Continental Shelf (OCS) are considered. A state-of-the-art simulation technique is employed to perform fully coupled aero-hydro-servo-elastic analysis using the integrated FOWT model. This technique can take into account dynamic interactions among the turbine Rotor-Nacelle Assembly (RNA), turbine control system, floating support structure and stationkeeping system. The relative importance of various design parameters and their impact on the development of design criteria are evaluated through parametric analyses.
The paper also introduces the design requirements put forward in the recently published ABS Guide for Building and Classing Floating Offshore Wind Turbine Installations (ABS, 2013).
Power Output Performance and Smoothing Ability of an Oscillating Water Column Array Wave Energy Converter
Authors: O’Sullivan Keith , Murphy Jimmy , O’Sullivan Dara 
Published: November 2013

This paper presents the physical model testing results of a floating oscillating water column (OWC) array wave energy converter (WEC) and the power smoothing ability inherent in the OWC chamber arrangement in the structure. The device can be categorised as a very large floating structure (VLFS) with structure dynamics which may make it a suitable device on which to mount wind turbines. It incorporates 32 individual OWC chambers in a “V” shaped arrangement such that there is a phase-lag between successive wave crests in the OWC chambers as an individual wave passes the structure. This OWC array was tested in both monochromatic and panchromatic unidirectional wave fields and the motion response amplitude operators (RAO) have been calculated. The time series of absorbed power from panchromatic waves was then used as input to a simple Well’s turbine power take-off (PTO) Simulink model to estimate the electrical power produced by each chamber and the additive power produced by the 32 OWC’s. A simple control law of optimum speed of the generator was used for these simulations. The time series of total electrical power from the 32 chambers was compared to the time series of an individual chamber and the standard deviation of the signals were also compared. The OWC array achieved a much smoother power output signal than a device with one chamber. Further smoothing of the output signal is possible by increasing the inertia of the turbine however, this may have implications for the mean efficiency of the power train. A preliminary design of the Well’s turbine is included, both in terms of mechanical parts and generator rating.
This paper focusses on the power absorption and motion performance of the device and discusses the potential for the addition of wind turbines.
Propped Fracture Conductivity in Shales
Authors: Zhang Junjing , Kamenov Anton , Zhu Ding , Hill A. Daniel 
Published: November 2013

The successful development of the major shale gas plays in North America hinges upon the creation of complicated fracture networks by pumping low viscosity fracturing fluid with low proppant concentrations at high flow rate. Direct laboratory measurement of hydraulic fracture conductivity created in the networks is needed for reliable well performance analysis and fracture design optimization.
A series of experiments were conducted under realistic hydraulic fracturing conditions to measure the conductivity using a modified API conductivity cell. Natural fractures were preserved and fracture infill was kept for initial conductivity measurement. Fractures were also induced along the natural bedding planes to obtain fracture surface asperities. Proppants of various sizes were placed between rough fracture surfaces at realistic concentrations. The two sides of the rough fractures were either aligned or displaced with a 0.1 inch offset.
Results show that the hydraulic fracture conductivity of shale samples with rough surfaces can be accurately measured in a laboratory with appropriate experimental procedures and good control on experimental errors. The unpropped offset fracture can create conductivity as much as poorly cemented natural fracture, while the conductivity of unpropped matched fracture is minor. The presence of proppants can elevate the fracture conductivity by 2 to 3 orders of magnitude. Propped fracture conductivity increases with larger proppant size and higher proppant concentration. This study also indicates that within 20 hours propped fracture conductivity can be reduced by as much as 24% as shown in the longer term fracture conductivity measurements.
Predicting Well Performance in Naturally Fractured Reservoir
Authors: Hwang Yunsuk , Lin Jiajing , Schechter David , Zhu Ding 
Published: November 2013

Multiple hydraulic fracture treatments in reservoirs with natural fractures create complex fracture networks. Predicting well performance in such a complex fracture network system is an extreme challenge. The statistical nature of natural fracture networks changes the flow characteristics from that of a single linear fracture. Simply using single linear fracture models for individual fractures, and then summing the flow from each fracture as the total flow rate for the network could introduce significant error. In this paper we present a semi-analytical model by a source method to estimate well performance in a complex fracture network system. The method simulates complex fracture systems in a more reasonable approach. The natural fracture system we used is fractal discrete fracture network model. We then added multiple dominating hydraulic fractures to the natural fracture system. Each of the hydraulic fractures is connected to the horizontal wellbore, and some of the natural fractures are connected to the hydraulic fractures through the network description. Each fracture, natural or hydraulically induced, is treated as a series of slab sources. The analytical solution of superposed slab sources provides the base of the approach, and the overall flow from each fracture and the effect between the fractures are modeled by applying the superposition principle to all of the fractures. The fluid inside the natural fractures flows into the hydraulic fractures, and the fluid of the hydraulic fracture from both the reservoir and the natural fractures flows to the wellbore. This paper also shows that non-Darcy flow effects have an impact on the performance of fractured horizontal wells. In hydraulic fracture calculation, non-Darcy flow can be treated as the reduction of permeability in the fracture to a considerably smaller effective permeability. The reduction is about 2% to 20%, due to non-Darcy flow that can result in a low rate.
The semi-analytical solution presented can be used to efficiently calculate the flow rate of multistage-fractured wells. Examples are used to illustrate the application of the model to evaluate well performance in reservoirs that contain complex fracture networks.
Management of Change for the Marine and Offshore Industries
Authors: Verzbolovskis Maria , Ballesio Jorge 
Published: November 2013

Change is inevitable in any type of business. Successful organizations are dynamic and are constantly undergoing change, striving for innovative and cost-effective solutions to achieve sustainability in a robust and competitive business environment. Modifications may be required to equipment, operational policies, and organizational structure or personnel. History has illustrated the potential negative consequences associated with changes that are not managed appropriately. Common problems with respect to the implementation of a change include:
• changes that are not technically sound,
• lack of careful consideration of the ramifications,
• poor execution, and
• failure to effectively communicate change information to key personnel.
A Management of Change (MoC) system is a combination of policies and procedures used to evaluate the potential impacts of a proposed change so that it does not result in unacceptable risks. A thorough MoC system manages both temporary and permanent modifications in a ship or offshore unit including equipment, materials, operating procedures and conditions, and personnel. An effective MoC system will not only minimize significant impacts on safety and the environment, but will incorporate strategies in managing the associated business risks on quality, continued commerce and security.
A system requiring MoC for every modification is likely to become onerous and unproductive. This paper provides guidance for selection of the activities and systems to be subject to management of change, the life-cycle applicability, types of changes to be evaluated, and boundaries and overlaps with other administrative programs or elements. It describes key functions and interrelationships for personnel at various levels of a representative organization. In summary, this paper describes the core principles to be considered when developing and implementing an MoC program that will optimize existing safety and risk management efforts.
Sleep disturbance in adopted children with a history of maltreatment
Authors: Cuddihy Charlotte , Dorris Liam , Minnis Helen , Kocovska Eva 
Published: November 2013

This study aimed to investigate whether children with a history of maltreatment and current behaviour problems demonstrate greater sleep disruption than controls; and also whether sleep disturbances are associated with these behavioural problems using standardised carer report measures. Sixty-three participants were assessed using the Children’s Sleep Habits Questionnaire (CSHQ) (Owens, Spirito and McGuinn, 2000) and the Strengths and Difficulties Questionnaire (SDQ) (Goodman, et al., 2003). Thirty-four participants aged 5–12 years were recruited via Adoption UK – Scotland. Inclusion criteria included a history of maltreatment (confirmed from social work documents) with associated social/behavioural problems. Twenty-nine controls with no psychiatric or maltreatment history, also aged 5–12 years, were recruited from two general practices. Mean CSHQ total sleep difficulty scores were significantly higher in maltreated children than in controls (48.9 vs 23.6, P < 0.001). Rates of clinically significant sleep problems (total sleep score>41) were also higher in the maltreatment group at 50% compared to 12% in controls (P = 0.002). There was a significant association between high scores on the CSHQ and the SDQ (P < 0.000). Overall, this study suggests that behaviourally disturbed children with a history of maltreatment experience significant sleep disruption, which is in turn associated with their behavioural disturbance. This has clear implications for both clinical assessment and intervention with this vulnerable group and is worthy of further research.
Some common fixed point results in ordered partial b-metric spaces
Authors: Mustafa Zead , Roshan Jamal Rezaei , Parvaneh Vahid , Kadelburg Zoran 
Published: November 2013

Abstract
In this paper, we introduce a modified version of ordered partial b-metric spaces. We demonstrate a fundamental lemma for the convergence of sequences in such spaces. Using this lemma, we prove some fixed point and common fixed point results for

(
ψ
,
φ
)

-weakly contractive mappings in the setup of ordered partial b-metric spaces. Finally, examples are presented to verify the effectiveness and applicability of our main results.

MSC: 47H10, 54H25.