bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Multi-Resolution Probabilistic Ocean Current Forecasting System for Offshore Energy Operations
Authors: Srinivasan Ashwanth , Sharma Neha , Gustafson Drew 
Published: April 2018

Abstract
We present a multi-resolution probabilistic ocean forecasting system designed to support offshore energy operations worldwide. The system is composed of an integrated suite of ocean circulation models including a global model of 25 km resolution, Atlantic and Indian Ocean models of 6 km resolution, and 8 fine scale models (&lt; 3 km resolution) for high-priority regions such as the Gulf of Mexico, offshore Brazil, West Africa, and the Caribbean. It expands on current ocean prediction systems through exclusive access to proprietary data streams, state-of-the-art data assimilation methods and ensemble modeling capabilities. The global and basin scale models incorporate large-scale information from satellite and in-situ observations and provide initial and boundary conditions for the regional models. The regional scale models then dynamically downscale the initial and boundary conditions to produce both deterministic and probabilistic fine-scale forecasts for regions of interest.
The system has been validated for consistency, quality, and accuracy against a suite of publicly available models and field observations (Remotely sensed observations, ARGO float data and Drifting Buoys). Results show that the system compares favorably to other leading ocean current forecasting systems such as HYCOM and the Mercator system. Experiments in the Gulf of Mexico demonstrate that the fine-scale forecasts are further improved by using proprietary data streams and when operated in an ensemble (probabilistic) mode they also provide robust quantification of uncertainty in forecasts.
The system has been operational since the beginning of 2017, providing daily 7-day forecasts of ocean currents. Additionally, 20-year hindcasts for some regions are in progress and outputs will be available for extreme value analysis for planning and structural design. It is expected that Ocean current hindcasts and forecasts through the new system will translate to increased situational awareness, reduced downtime, improved environmental protection, and safety.
Development of New CRA Grade for High Pressure High Temperature Application
Authors: Song S. , Richoux V. , Gomes C. , Decultieux F. , Néel G. 
Published: April 2018

In High Pressure High Temperature "HPHT" wells (pressure above 10 000psi/690bar, temperature above 300°F/150°C which contain CO2 (sweet corrosion) and H2S (sour service), the oil & gas operators need to select materials which are resistant in corrosive atmosphere during the well lifetime. At the same time, high strength grades are usually required to meet collapse and burst properties. The aim of the end users is to get the specific grade which can resist to corrosion while minimizing the cost, which involves qualification with corrosion tests.
The API 5CRA standard defines corrosion resistant alloy (CRA) grades for casings and tubings, from group 1 named "Super 13Cr 13-5-2" (suitable up to 356°F/180°C), to group 2 "Duplex" grades 22-5-3 (450°F/232°C) or "Super Duplex" 25-7-4 (482°F/250°C) and higher grades.
Therefore, when the well temperature is above 356°F/180°C, duplex grades or higher are commonly selected as these materials have a larger application domain at higher temperature range.
A new metallurgy was developed with high strength properties demonstrating a superior corrosion resistance at higher temperature compared to the standard Super 13Cr 13-5-2 grade and which is a cost effective solution compared to Duplex grades.
Effect of Seabed Trenching on the Holding Capacity of Suction Anchors in Soft Deepwater Gulf of Guinea Clays
Authors: Sassi Khalida , Zehzouh Slimane , Blanc Matthieu , Thorel Luc , Cathie David , Puech Alain , Colliat-Dangus Jean-Louis 
Published: April 2018

Abstract
Seabed trenching, related to large motions of relatively taut deepwater mooring systems in the long Gulf of Guinea swell, can reach the suction anchor and the chain padeye depth, thus raising serious concerns about the holding capacity of the suction anchors and the safety of the mooring systems. The potential reduction of the anchor capacity, estimated by means of 3D finite element (FE) calculations, needs to be verified by means of testing, and this is the objective of the study presented here. The paper describes the IFSTTAR geotechnical centrifuge test facility and the model soil preparation procedure for obtaining large open trenches with natural deepwater Angola clay in the swinging centrifuge. The scope of the study includes a number of holding capacity tests on suction anchors without trenches (reference cases) and with large trenches reaching the suction anchor and padeye depth. Tests were performed under vertical and inclined loading (actual case of taut deepwater moorings with significant vertical loading component), with the measurement of pore pressures at different levels below the anchor tip for verifying the effect of the trench on the reverse end bearing (passive suction) capacity. The centrifuge test results are compared with Plaxis 3D FE calculations for the purpose of comparison with previously published results. The preliminary results presented show that the REB capacity is mobilized, even with large trenches reaching the anchor and padeye depth. It is also confirmed that Plaxis 3D FE modelling offers a reliable tool for the assessment of the post-trench holding capacity of the suction anchors.
The World's First Successful Implementation of Solid Fluidization Well Testing and Production for Non-Diagenetic Natural Gas Hydrate Buried in Shallow Layer in Deep Water
Authors: Shouwei Zhou , Qingping Li , Wei Chen , Jianliang Zhou , Weixin Pang , Yufa He , Xin Lv , Liangbin Xu , Qiang Fu , Jiang Lin 
Published: April 2018

AbstractBased on the characteristics of shallow buried, non-trap structure and close cover, non-diagenesis, weak cementation and easy fragmentation of natural gas hydrate deposits in China, a solid fluidization well testing and production scheme to develop these kind of natural gas hydrate is proposed. The main idea is to transfer the non-diagenetic natural gas hydrate sediments buried in shallow layer of deep-water into a closed multi-phase transporting and lifting system through mechanical crushing fluidization, during the lifting riser system from seabed to surface, hydrate will be dissociated gradually based natural rule of sea water temperature rising and the hydrostatic pressure decrease with the change of water depth during the lifting process, to turn the uncontrollable decomposition process of non-diagenetic hydrate into controllable, and to achieve safe field exploitation of natural gas hydrate in the surface and shallow layer of deep-water. After the validity was verified by the laboratory experimental study, CNOOC successfully implemented the world's first solid fluidization well testing and production of marine non-diagenetic hydrate with the water depth of 1310m and the hydrate sediments layers 117~196m depth in May 2017. It means China has found an innovation way about natural gas hydrate exploration and development with self-developed key technology and tools. The implementation relied on the Deepwater Engineering & Survey Vessel "HYSY708" at the station of Li Wan 3 in the South China Sea and it was supported by fully self-developed technology, process and facilities.
Estimation of Wind and Current Load on Offshore Structures Using Wind Tunnels and CFD
Authors: Cho S. , Hwang S. , Jung J. , Sung H. , Park B. , Vazquez-Hernandez A. 
Published: April 2018

Abstract
This paper suggests the improved technology to predict the wind and current loads on offshore structures such as FPSO and Semi-submersible. Wind tunnel tests and CFD analysis are conducted and results and application methods are discussed. The characteristics of flow and extrapolation to real Reynolds number condition are also analyzed with regard to loads. To analyze the load and flow characteristics, the detail conditions of wind tunnel and CFD are investigated such as flow field and model setup and their effects on results are examined. From the comparison of wind tunnel tests and CFD, flow physics are analyzed regarding the characteristics of the flow. This paper shows the parameters which affect the wind tunnel tests and explain the reason of differences between wind tunnel tests and CFD. The flow field such as velocity profiles and turbulence is major parameter and model setup and test condition must be described as accurate as possible. The additional and new consideration for wind tunnel test is suggested based on observed results. The flow around semi-submersible differ from FPSO and different approaches are necessary considering flow characteristics. The extrapolation to real Reynolds number condition is very difficult for the offshore problem. Based on above results, the extrapolation is discussed for the estimation of wind and current loads on FPSO and Semi-submersible. The results show that new suggestions of wind tunnel test give the improved prediction and reduce the uncertainties. CFD analysis considering wind tunnel environment give more reliable results and extrapolation may afford more efficient and conservative estimation of wind and current loads. This may significantly influence the design of mooring system and offshore structure.
BOP Testing and It's Availability on Demand-A Case Study
Authors: Zulqarnain Muhammad 
Published: April 2018

Abstract
Blowout Preventer (BOP) is an integral component of defense in depth approach adopted in deepwater drilling operations. Regulatory bodies require frequent testing of these barriers, to make sure that they will be available to perform their intended functions when demand arrives. As BOP works only in demand mode, therefore the calculation of average probability of failure on demand (PFDavg) is one of the technique that can provide the critical information about the availability of these barriers.
In this study PFDavg formulation is used to carry out s systematic performance evaluation a BOP's barrier elements. A sensitivity analysis is also performed to account for some of the real demand conditions that cannot be tested during routine tests, an example is the testing of shearing capability of blind shear rams. Multilevel test formulations are used that accommodates both of proof test and partial stroke testing concepts. The interdependency of these barrier elements is modeled by using beta factor model, which account for common cause failures.
The results are presented for three flow paths of open wellbore flow, flow through drillpipe-casing annulus and flow through drillpipe. Corresponding BOP's barrier elements are used to estimate the availability of these barriers when they are demanded. The analysis results indicate high common cause failures of BOP's main control system with an average value of 0.25. Which is a significantly high dependency of both of the BOP's control pods on some of the common elements that can fail them simultaneously. The results also show that average availability of drillpipe-casing annular and open-hole barrier channels is dominated by the BOP's main control system, mainly due to its high failure rates. The analysis also revealed that a beta factor contribution significantly impacts the unavailability of drillpipe-casing annular channel barrier elements.
Results for other demand scenarios and combination of working of these barrier elements are also presented. The presented results highlight some of the critical safety measures of BOP's barrier element performance and also highlight some of the deficiency areas that need to be taken care of to improve the system's performance. It is therefore hoped that the presented results will be helpful to gain insight into different modes of operation and in improving the system's performance.
Using Weather Pattern Typology to Identify Calm Weather Windows for Local Marine Operations
Authors: Steele Edward , Neal Robert , Dankers Rutger , Fournier Nicolas , Mylne Kenneth , Newell Paul , Saulter Andrew , Skea Alasdair , Upton Jon 
Published: April 2018

Abstract
The cost and complexity of offshore operations, combined with the vulnerability of equipment to prevailing conditions, requires weather-sensitive decisions to be made to ensure the continued accessibility and availability of marine assets. In the current economic context, this is especially important since the robust (timely) identification of calm weather windows has the potential to save many thousands of dollars per day in unplanned downtime and vessel contracting, allowing large efficiencies in sequencing, mobilisation and demobilisation costs if decisions are taken at the earliest possible opportunity. As forecasts extend weeks to months ahead, it is well known that predictability limits make the direct characterisation of small-scale weather events all but impossible, but there still remains a considerable amount of useful information contained within the large-scale weather circulation types. These circulation types, termed ‘weather patterns’, have a strong influence on the variability of marine wind and wave fields. Here, we present a new method for the tracking of calm weather windows out to several weeks ahead. Using a 34-year hindcast to elicit the daily maximum significant wave height experienced at the location of interest – and an analysis of the associated weather pattern under which they occurred – the circulation types are linked to the viability of offshore operations on a local scale. When subsequently applied in forecast mode, this method can enable earlier decision-making than is typically done at present. As weather patterns are more predictable than the actual weather itself at long lead-times, knowledge of the corresponding historic wave heights can enable identification of expected conditions within a probabilistic weather pattern forecasting system. In addition, the approach facilitates contingency planning; further supporting improved decision-making and reduced operational costs for the offshore oil and gas and marine renewable energy sector.
Derivation of Continuous Irreducible Water Saturation and Pore Throat Aperture Distribution from Well Logs in an Offshore Brownfield
Authors: Li Ting , Zhou Xin , Cui Yunjiang , Xu Jinxiu , Liu Huan 
Published: April 2018

Abstract
In this case study, we propose a new petrophysical workflow to evaluate an offshore mature field. In the field studied, hydrocarbon production mainly comes from sandstone reservoirs with good permeability and low water salinity. The operator typically drills deviated wells and runs Logging While Drilling (LWD) tools to make timely completions decisions. The petrophysical properties critical for these decisions are porosity, permeability, irreducible water saturation (Swi) and total water saturation (Sw). Occasionally, Nuclear Magnetic Resonance (NMR) logs are run to characterize Swi and permeability, but are only available in select wells. The challenge for the petrophysicist is to make the most of the commonly available measurements and compute the petrophysical properties required for decision making.
We propose a technique that derives continuous Swi and pore throat radius distribution from porosity and permeability logs. When the well is cored, continuous permeability can be obtained through core calibration. When only basic well logs are available, permeability is typically estimated from a porosity-to-permeability relationship, which is derived from core data in an offset well. We then usea well established relationship to compute pore throat radii from interpreted porosity and permeability logs for a range of mercury saturations. We can further construct a synthetic Mercury Injection Capillary Pressure (MICP) curve from mercury saturation and capillary pressures (Pc) corresponding to different pore throat radii. Since Swi varies with Pc, we can apply a Pc cutoff on the synthetic MICP curve to obtain Swi. This cutoff can be determined empirically or from height above free water level.
From the level-by-level synthetic MICP curves, we can also construct a histogram of pore throat radius at each depth level. This plot provides valuable visual aid that helps interpreters identify good quality rocks.
To validate this method, we calculated the bound water volume (BFV) from synthetic MICP and compared it to BFV derived from NMR T2 distribution. There is an excellent agreement between the two computed BFV curves. The proposed workflow is only meant to provide a rock quality evaluation when log data is scarce. For accurate characterization of Swi and rock quality in complex reservoirs, more advanced measurements are recommended.
Flexible Riser Remnant Life Assessment Using Artificial Neural Networks and Advanced Inspection Methods
Authors: Francis Kirk , Chaves Victor 
Published: April 2018

Abstract
This paper presents a methodology that is currently being utilized to assess the remnant life of flexible risers. The objective is to accurately determine whether flexible risers can safely continue to operate by determining the current condition of the annulus and armor wires, and determining the remnant life using advanced analysis methods in combination with inspection data.
The inspection part of this method consists of ultrasonic scanning of the flexible riser in key locations to confirm whether the annulus is dry or flooded and, if flooded, determine the remaining tensile wire thickness. The results of the ultrasonic scanning are then used in combination with global and local riser analysis to determine the remnant fatigue life of the riser. In order to have a more refined and realistic numerical model, time-domain irregular wave approach is used. However, the combination of the need for detailed nonlinear models and the demand for long time series simulations makes this type of analysis extremely time consuming. The method proposed to reduce computational costs in this type of numerical model is a hybrid methodology that combines Finite Element Analyses (FEA) and Artificial Neural Networks (ANN). The proposed hybrid methodology aims to predict the loads at a defined section of the flexible riser. Firstly, using short FEA simulations to train the ANN, and then using only the ANN and the prescribed global riser response to get the remainder of the stress time histories.
Results to date have shown that the general assumptions used on corrosion rates and the regular wave dynamic analysis approach are each very conservative, and significant life extensions have been justified based on the results of the combined inspection and analysis method. The use of these methods has the potential to confirm the acceptability of flexible riser life extension beyond the original design life, or to confirm the acceptability to continue to operate with annulus conditions outside the original design specification.
The use of ANN for flexible riser fatigue analysis and the use of ultrasonic scanning to determine the present conditions of the flexible riser annulus and armor wires are each advanced techniques in flexible riser integrity management. When combined together as this paper proposes, these methods provide both a current status of the flexible pipe integrity as well as a forecast of the remaining allowable life, allowing key field decisions to be made quickly and accurately.
Big Data in the Digital Oilfield Requires Data Transfer Standards to Perform
Authors: Neri Philip 
Published: April 2018

The digital oilfield is evolving with the number of sensors and measuring devices and the frequency of data sampling both increasing dramatically, which is the onset of what is commonly referred to as Big Data. These increases are needed as the motivation for the collection and transmittal of data has moved from the remote observation of operations to the remote operation of increasingly automated systems, as well as the goal of reliable prediction tools that improve efficiency.
A lot is written and discussed about how to handle Big Data in the context of data management and analytics. However, the task of transferring the digital information from the field to the back office is critical. This is built on advances in standards for data formats, metadata and transmission protocols that have been published to support the digital oilfield of the future. The first advance has been the larger amount of metadata, providing detailed information on the data source's characteristics, eventual transformations to the data (by who, using what tools, etc.) and prior vetting. The second one is to replace transmission protocols based on polling different servers with streaming processes that do away with inefficient interrogation, handshake and packaging overheads.
The implementation of these improved standards allows operators to build solutions that involve different vendors. A test was put in place involving an active North Sea drilling operation, with data being transferred to onshore observers both at the operator's facilities and on the premises of a service provider. Data was streaming on to the screens of both observing parties less than one second after the event took place on the rig. This compares to lag times of 15 to 20 seconds using polling methods. The bandwidth usage was approximately 1/10 compared to previous methods, such that more sensors could be added to the data transmittal.
With more immediate access to a much broader and richer set of data both at the operator's facilities and also at the premises of many contractors, service providers in particular could make more educated assessments of developing situations on the rig, which in several cases avoided the need for a team to go to the offshore rig, thus reducing the number helicopter flights to the offshore installations and accounting for fewer people-on-board (POB), which contributed to lower HSE exposure and lower costs.
Combining DWS Depressurization Method and Heat Injection to Improve the Hydrate Recovery
Authors: Sun Ting , Chen Yuan , Zhao Ying 
Published: April 2018

Abstract
Natural gas hydrate (NGH) is a new kind of clean resource with a large reserve and wide distribution, which is considered as an important alternative energy. While extracting natural gas hydrate using the method of depressurization, the temperature will decrease for the absorption of heat in the process of hydrate decomposition, which may cause the formation of ice or the re-formation of hydrate and further cause the reduction of natural gas recovery; meantime, the decomposition of natural gas hydrate will cause the decrease of formation pressure, as a result, water coning may occur, which will also cause the reduction of natural gas recovery.
The DWS (downhole water sink) method has shown that this technology could increase oil production and control water coning when exploiting oil. This paper adopted this technology and made some improvements to fit in the exploitation of natural gas hydrate. The objective of this paper is to determine the improvement degree of natural gas recovery and whether it can effectively control water coning using the method of combining DWS depressurization method and heat injection method.
In this paper, the mathematical model of natural gas hydrate exploitation is built first, then numerical simulation is used to compare three natural gas hydrate production methods - common depressurization method, DWS depressurization exploitation method and the method of combining DWS depressurization method and heat injection. The simulation results confirm that the combined method has better recovery by showing a big increase of recovery factor comparing to the other methods. The results also give a large reduction of water cut.
The simulation experiments clearly show that the main advantage of using the method of combining DWS depressurization method and heat injection method is that it is easy to control the recovery process and water coning. For this method, production process could be optimized for maximum recovery and minimum water production by seeking a best combination of gas and water production rates.