bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geomagnetic Storms in Marine Magnetometer Data at Low Latitudes
Authors: Carrier B. M. , Heinz M. 
Published: April 2017

In 2016, the authors published evidence demonstrating that strong magnetic field perturbations resulting from Earth-directed solar events can adversely affect marine archaeological survey. Based on a 95% confidence level, it was estimated that 89.7 to 100 percent of geomagnetic storms occurring on days of Kp 5 or greater will generate marine magnetometer signatures that may be misinterpreted as archaeological sites. Aggressive processing, analysis, and comparison of single instrument, total field marine magnetometer datasets were unable to isolate and remove the storm sudden onset signature. These findings, however, only demonstrated the phenomena in data collected at mid-latitudes (Carrier et al. 2016).
This paper builds on that work by presenting analysis of additional survey data collected from a low latitude region in the Gulf of Mexico. Although it is understood that geomagnetic storms affect Earth's magnetic field to a greater degree at high latitudes – that is, near the poles – and to a lesser degree at low latitudes – closer to the equator – the prevailing assumption that geomagnetic storms are not a problem in the Gulf of Mexico is unsubstantiated by the empirical evidence. Observatory datasets analyzed in this paper plainly reveal that geomagnetic storms affect Earth's magnetic field at low latitudes and external source artifacts remain in professionally-collected survey data, even after aggressive processing. Recommendations are made for marine magnetic data collection and processing methods that adequately account for geomagnetic storms, allowing for improved precision in analytical interpretation and thus improved identification of archaeological resources.
Wave Forces and Low Frequency Drift Motions in Extreme Seas: Benchmark Studies
Authors: Fonseca N. , Ommani B. , Stansberg C. T. , Bøckmann A. , Birknes-Berg J. , Nestegård A. , Hauteclocque G. de , Baarholm R. 
Published: April 2017

Abstract
The paper identifies the wave drift forces and low frequency damping induced by a wide range of extreme sea conditions on two floating units based on model test data, assesses the limitations of today's numerical procedures and proposes solutions to overcome the limitations. Since wave current interaction effects are of utmost importance, a benchmark study is carried out with several state of the art potential flow codes. CFD studies complement the numerical investigations.
Empirical wave drift force coefficients are identified by a second order signal analysis technique and the results compared with potential flow predictions and with predictions from a semi-empirical formula. The low frequency damping is a result of the identification procedure as well. On a second stage, time domain simulations are systematically performed for all tested conditions and the results compared in terms of wave frequency and low frequency motion responses. The systematic comparison between calculated responses and model test data identifies the numerical methods limitations with regard to increasing seastates and increasing current velocity.
A benchmark study with four wave-current interaction diffraction codes is presented for a Semi-submersible and, given the good agreement of results, it is concluded that the codes may be considered ready for use by the industry. CFD studies are also performed with the aim of demonstrating the present status with regard to this methodology and identify the challenges in terms of numerical modelling.
Development of Low-Corrosivity Scale Inhibitors for Low Alloys Steels
Authors: Bhandari Manojkumar , Littlehales Ian , Linares-Samaniego Sandra , Christmas Renaldo , Mancuso Sebastian 
Published: April 2017

AbstractContinous injection scale inhibitors are routinely used to control the formation of mineral scales, such as calcium carbonate and barium sulfate, within topside or subsea applications. The development of chemical injection systems to deploy scale inhibitors deep into production wells presents further challenges due to the higher temperature of the injection point. While phosphate esters, phosphonates and polymers constitute the major types of scale inhibitors applied to control scale in oilfield applications, all are known to be corrosive to Low Alloy Steels (LAS). This paper will detail the development of low corrosivity scale inhibitors for downhole systems containing LAS components within the scale inhibitor's flow path.A number of subsea fields have been developed in recent years with wellhead trees containing LAS components, in particular F22 carbon steel. F22 carbon steel has been found to be very susceptible to corrosion attack by scale inhibitors typically used in the oil field. To quantify the problem and work towards a solution, existing products covering all major generic types of inhibitors were evaluated using static immersion corrosion tests at test temperatures ranging from 180°F to 300°F; these tests revealed corrosion rates in excess of 30 mpy for these inhibitors against F22 carbon steel.Initial work involved changes to inhibitor formulations by adjustment of pH or changes to neutralization agents. Unfortunately these changes failed to reduce the corrosion rate to acceptable values. Based on the initial screening work new formulations were developed resulting in very low corrosion rates (&lt;1-4 mpy) in the presence of LAS such as F22, AISI8630 and 1018 carbon steel. Data will be shared which shows that the new scale inhibitor formulations have very similar performance compared to a typical, more corrosive subsea applied scale inhibitor.The new formulations have been qualified for downhole chemical injection through an umbilical and are currently being applied or approved for use at Gulf of Mexico and West Africa fields. Development of these low corrosivity scale inhibitors will allow operators to prevent scale issues in subsea fields without impacting the material integrity of delivery systems containing LAS components.
API 6A and 17D Bolting Stress Analysis and Fatigue Consideration
Authors: Lim J. I. , Bunch P. , Han Y. 
Published: April 2017

AbstractAPI 6A and 17D, specifications provide the design basis for surface and subsea production equipment bolting in the oil and gas industry. These documents provide both design stress allowables and material requirements for bolting. API defined bolt preload requirements are 0.5 times the material minimum yield strength and 0.67 times the minimum yield strength for API 6A and 17D, respectively. The maximum allowable stress in the bolt due to pressure, thermal and external loading is defined to be 0.83 times the minimum yield strength based on the nominal stress in the bolt at the minimum root diameter.Given these design criteria this paper evaluates the peak stresses in the threads for both principal stresses and combined component stresses and correlates them to the nominal stress in the bolt to define a stress concentration factor (SCF) value based on bolt size. Three bolt sizes, 1", 2" and 3" were evaluated where each bolt was modeled as a single bolt assembly simulating a nut to bolt connection, a flange thickness and a threaded API body. Each design was evaluated using B7 bolt, 2H nut and API 75K body material properties. The finite element analysis (FEA) considered both elastic and elastic-plastic material properties for comparison of results. Using the results of the FEA, stress range vs. cycles, S-N, and fatigue characteristics of the bolt assembly were evaluated based on the nominal bolt stress range vs. the root radius stress range in the highest stressed threads. The S-N fatigue life predictions for bolting are evaluated based on mean stress and peak stress ranges in the bolt threads. As an alternate to S-N evaluation, the stress distribution at the root radius of the thread was input into the fracture mechanics analysis as a weight function for calculating crack tip stress intensity. The analysis is based on elastic stress distribution in the threads and an assumed intial defect size based on nondestructive examination (NDE) inspection. Issues of defining material fatigue properties for loading conditions of bolt threads and the environment of saltwater with cathodic protection (CP) are addressed.
Cyclic Ratcheting Resistance of Buried Pipelines
Authors: Thusyanthan N. I , Wang J. , Haigh S. K. , Robert D. J. 
Published: April 2017

Abstract
Upheaval buckling (UHB) is a common issue for high pressure and high temperature (HPHT) pipelines. The out-of-straightness (OOS) of the buried pipelines combined with the high axial compressive forces induced by the extreme operating conditions causes the pipeline to move upwards till the downward soil resistance is sufficient to resist any further movement. As the pipeline mobilise upwards, the gap underneath is soon filled up by soil particles from around the pipe. As a result, when pipelines cool down during temporary suspension in operation, they cannot return to their original position. As pipelines undergo many thermal cycles of start-up and shout-down during the lifetime, a pipeline OOS feature can progressively move upwards and eventually lead to failure even if it was designed safely against UHB in the original profile. This phenomenon of cyclic pipe movements upwards is known as pipeline ratcheting, which is the driving mechanism behind many UHB pipeline failure cases. This paper presents insight into ratcheting and results of small scale experiments that were conducted at the Schofield Centre, University of Cambridge, to model the ratcheting response of pipelines buried in saturated sands. The results obtained have shown that the critical upward mobilization at which ratcheting is initiated is a function of soil critical state friction angle and pipeline diameter. The pipeline downwards force on the soil during shut-down is the other parameter affecting the initiation of ratcheting. This paper presents valuable insight on ratcheting and mitigating upheaval buckling of pipelines to the design engineers.
Asphaltene Onset Pressure Uncertainty and Other Asphaltene Issues in Field Development Planning
Authors: Dumont Hadrien , Garcia German , Mullins Oliver C. , Nighswander John , Mishra Vinay K. , El-Khoury Jules , Chen Li , Lake Patrick 
Published: April 2017

Abstract
Deepwater fields, such as those encountered in the Gulf of Mexico (GoM), often exhibit reservoir tar deposits and asphaltene instability (Dumont et al, 2012, Mullins et al, 2016). This instability may manifest itself within the reservoir in the form of out of equilibrium asphaltene gradients and tar deposits. These tar deposits can present drilling hazards which are a major nuisance for drilling operations, and can force operators to drill multiple sidetracks or bypass wells. This of course leads to increase well spend and rig time usage. For instance, the last two years showed that approximately 5% of the wells drilled in the GoM encountered severe drilling issues related to asphaltenes/tar deposits. Even more critical and concerning, is that asphaltene instability can have major implications for field developments, stretching expenditure risks beyond a single well to that of an entire field.
From a flow assurance point of view, comingling incompatible oil produced from different zones or reservoirs can precipitate, and worse, deposit asphaltenes in the production path even when the unmixed oils are individually stable. Thus for reservoir management and field development plan, tar deposits can seal off aquifer support and have a detrimental impact on the productivity index of the field. During field development planning, it is essential to know the Asphaltene Onset Pressure (AOP) of the produced oils at reservoir conditions and its change with pressure and temperature along the wellpath. In addition, for unstable oils, AOP gradients variations across the field should be evaluated as AOP can vary largely as a result of Reservoir Fluid Geodynamics (RFG) processes occurring within the reservoir. For instance, fluid mixing due to a secondary charge into a reservoir after trap filling increases the AOP of the resulting oil. In addition, the non-homogeneity of AOP can then be mislabeled as AOP laboratory uncertainty. As AOP field variability can impact all aspects of the journey of the oil to surface, (well placement, completion, recovery factor, injection for pressure support, surface facility, and subsea equipment) and because no model exist to predict AOP gradients, the measurement and the evaluation of these AOP gradients, coupled with simple chemistry understanding are key inputs to a successful field development plan. This paper discuss AOP gradients within a reservoir, their impact on Field Development Plan (FDP), their origin, and proposes a methodology to characterize them.
Assessing the Variability in Intensity and Width of the Loop Current Eddy High Speed Band from Airborne Ocean Surface Current Measurements
Authors: Schiller R. V. , Zhang M , Smith R. , Medina M. , Williams B. 
Published: April 2017

Abstract
The specific position and variability in width and intensity of the high speed band of currents associated with Loop Current Eddies (LCEs) is of significant interest to offshore operators in the Gulf of Mexico. This is particularly the case when undertaking drilling or offshore development operations and the activities may be located close to or inside the LCE. A study of the Remote Ocean Current Imaging System (ROCIS) data from May 2015 has been undertaken to provide further insight into the variability in intensity and width of the LCE high speed band. We defined the band to be limited by the 0.75 m/s (~1.5 knots) threshold, a typical limit for offshore operations in the Gulf of Mexico. Preliminary results show relevant spatial and temporal variability. The width of the high speed band ranged between ~40–100 km, depending on the state of the LCE, interactions with surrounding eddies and the geopgraphical location of the measurements. Peak speeds ranged from about 1m/s to 1.9 m/s. The shape of the speed profile across the band was also variable. Some cases presented a strong correlation with the Sea Surface Temperature (SST) front of the LCE, where speeds dropped significantly outside of the front. The identification of a few patterns of the high speed band was a promising result within the ongoing effort to derive expected relationships between LCE metrics such as high speed band witdth, intensity, LCE area and strength of the SST front.
Ultra-Deepwater Production System: Model Test Study of Cylindrical FPSO in GoM Hurricane Conditions
Authors: Vidic-Perunovic J. , Lee L. , Glomnes E. B. , Mercier R. S. , Head W. J. 
Published: April 2017

Abstract
To address the challenges of Gulf of Mexico (GoM) Lower Tertiary exploitation, alternative FPSO concepts are studied by the industry. This paper documents Phase 2 of a UDW RPSEA study which had as its main objective the validation of a production concept based on a permanently moored cylindrical FPSO designed by Sevan Marine with steel catenary risers (SCR). The present work focuses on model testing of the cylindrical FPSO hull design, performed at the Offshore Technology Research Center (OTRC) at Texas A&M University in College Station, in May 2016. The experiments were performed at a scale of 1:64. The model was subjected to the Central GoM Hurricane environmental conditions. The process of analysis includes extreme hurricane waves, wind, and currents, combined with ultra deep water, to demonstrate the feasibility of the concept in the GoM. This combination implicates complex hydrodynamic behavior of the hull, mooring and riser system. Thus, the model test provides better understanding of the new concept performance. Model test results, including motions and mooring loads, are compared with numerical predictions for a series of test cases. The importance of viscous effects on motions of the cylindrical unit and of the green water effect is discussed. Finally, to assess the feasibility of the hull and riser system, the numerical results of a hybrid approach, full scale, coupled riser analysis are presented, as based on measured hull motions and environmental conditions. This is finally followed by a discussion of the implications of technical and regulatory aspects of the FPSO concept. Following the project criteria, the present system based on SCR configuration seems feasible; however optimization of hull and mooring system is necessary to improve green water and viscous effects on hull motions in extreme current.
The paper represents one sub-scope of the RPSEA study "Low Cost Flexible Production System for Remote Ultra-Deepwater Gulf of Mexico Field Development.", Project No. 10121-4404-03.
Risk-Based Asset Management: Global Implementation
Authors: Supry J. , Schwartz T. 
Published: April 2017

Abstract
The pressure to operate safely in risk-sensitive industries such as oil and gas is always present, with many offshore drillers still struggling to define and practice effective safety-driven maintenance principles on a routine basis, given the dynamic and inherently dangerous nature of drilling. This has given rise to the concept of establishing line of sight between health, safety and environmental (HSE) assessments in the form of critical asset performance standards (CAPS) to link preventive maintenance to safety while aligning with global and regulatory standards.
Working with leading offshore oil and gas drilling contractors, performance standards are created to reference the systems and controls in place used to mitigate the risk of major accident events (MAEs), monitor asset performance with critical operating parameters (COPs) and ensure compliance with regulatory driven requirements.
Performance standards serve as the "Line of Sight" to link HSE cases and preventive maintenance (PM) procedures for safety and environmental critical equipment (SECE) on offshore oil and gas drilling units. Acceptance criteria and COPs are then referenced in the standards to designate which MAE control measures are in place with the goal to reduce the risk of a MAE to as low as reasonably practicable (ALARP). The maintenance tasks are then optimized to capture the key COPs for real-time operational analysis.
Each performance standard provides the link between a comprehensive HSE case and applicable maintenance plans providing clearly defined acceptance standards allowing measuring, monitoring, trending, and appropriate corrective actions as necessary. Global variation can be effectively resolved and managed using the performance standards.
Leveraging the pertinent information captured within a safety case, performance standards are developed and then implemented within preventive maintenance tasks through a computerized maintenance management system (CMMS). Combined with a formalized best practice review process, the CMMS is utilized to quantitatively analyze the effectiveness of the implementation of the performance standards.
This paper will review actual global implementation efforts with leading drilling contractors for the oil and gas industry to show how the development of performance standards provides the baseline for operational excellence. By making this information accessible, the process can be continuously refined and applied throughout the drilling community to provide a safer and more productive environment.
Determining and Optimizing Design Loads for Mobile Offshore Drilling Units Using Fuel Air Explosion Modeling Scenarios
Authors: Weinberg Michael 
Published: April 2017

Abstract
A study was performed to provide develop guidance regarding design basis blast loads for mobile offshore drilling units (MODU). Release of flammable materials may result in a vapor cloud explosion (VCE) which can apply damaging blast loads to critical areas of the MODU. Computational Fluid Dynamic (CFD) modeling was used to perform a dispersion and explosion analysis. This analytical technique is ideally suited to account for offshore geometries and wind patterns. The analysis showed that the controlling loads for the critical areas were from releases on the main deck. The screening level load developed from this study will assist MODU design by providing a defined load case at the initiation of the design process.
Seabed Scour Considerations for Marine Renewable Energy Facilities
Authors: Stevens Robert F. , Smith Kevin , Soosainathan Lawrence , Fisher James , Mekkawy Mohamed M. , Rahim Amir , O'Connell Daniel P. 
Published: April 2017

Abstract
The Geotechnics Sub-Committee of the American Society of Civil Engineers (ASCE) Coasts, Oceans, Ports, and Rivers Institute (COPRI) Marine Renewable Energy (MRE) Committee is preparing a guide document for marine renewable energy foundations. That guide would use standard design codes for fixed foundations and mooring anchors in API RP 2GEO and DNV. This paper focuses on seabed scour.
Seabed scour can affect the siting, design, installation and operations of marine renewable energy facilities. The Bureau of Ocean Energy Management (BOEM) specifically requires an assessment of seabed scour in the Construction Operations Plan (COP) that must be submitted and approved by BOEM before construction of renewable energy facilities in the US Outer Continental Shelf (OCS). This paper discusses why scour is an important consideration for marine renewable energy facilities, what factors can contribute to scour, how the severity of sediment mobility depends on the interrelationship between the ocean bottom and the seafloor, and how the installation of marine renewable energy facilities can alter the dynamic equilibrium among the many factors that contribute to the dynamic morphology of the seafloor. Options available for avoiding, protecting against, or mitigating scour are also discussed.