bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chain-Soil Interaction in Carbonate Sand
Authors: Frankenmolen S. F. , White D. J. , O'Loughlin C. D. 
Published: April 2016

Abstract
The design of mooring anchors of Floating LNG systems on Australia's North West Shelf (NWS) is challenging due to the high mooring loads and the seabed which comprises carbonate soils. Anchors with an embedded padeye require engineering of the chain inverse catenary and management of interfaces between the anchor and mooring system design teams. While considerable investigation of the anchor line performance in clay has been conducted, there has been limited investigation into the anchor line behavior in sand, and none in carbonate sand. The limited relevant information in the codes and standards and public domain may therefore result in over-conservative design for the ground chain, the anchors and the overall mooring system.
In order to optimize the design of the mooring systems in relation to a developing Floating LNG project, a program of chain-soil interaction tests has been performed in a geotechnical centrifuge at the Centre of Offshore Foundation Systems in the University of Western Australia. The purpose of the testing was to provide data to allow better assessment of the shape and load distribution on the chain inverse catenary of a large mooring chain at high loads in carbonate sand. The testing achieved scaled loads equivalent to the 10,000 year return period storm experienced by an FLNG facility on the NWS, and included detailed profiling of the inverse catenary at different loading stages. The program spanned a range of chain sizes and soil densities as characterized by miniature cone penetrometer tests.
This paper outlines the design considerations for chain-soil interaction and provides guidance for interface management, which sets the centrifuge modelling program in context. The results of the centrifuge program are presented and interpreted against the backdrop of conventional design assumptions and existing theories for chain-soil interaction. Using the interpreted results, a new method for the analysis of chain-soil interaction in carbonate sands is proposed, which includes the use of cone tip resistance profiles. The method and input parameters are calibrated via the centrifuge test results. The insights gained have resulted in improved design assumptions for the conditions modelled, and further refinements of the analysis approach are foreshadowed. These outcomes have led to improved estimates of the inverse catenary configurations and mooring anchor loads, and future work is anticipated to allow more general improvements to design practice.
Technology for Extension of Lifetime
Authors: Kristiansen Karstein Berge 
Published: April 2016

Abstract
Looking at statistics for subsea producing wells in North America, Brazil and Norway the numbers indicate that approximately 50% of these wells were installed before 2005. Most of them rely completely on copper based communication i.e. no fiber optics installed, or at least not used. No Standard communication standard do not exist for neither topside nor subsea in systems installed before 2005 and communication throughput tends to be in the lower range of kilobit pr. second.
A large portion of existing wells are experiencing operational problems related to performance degradation in infrastructure and equipment, and are not capable of delivering communication interfaces for upgraded instrumentation and control requirements like multiphase meters, permanent reservoir monitoring and Subsea PowerGrids.
This paper looks into solutions for increasing communication throughput while simultaneously mitigating problems due to degeneration of copper cable umbilcals in a cost efficient way. Increased throughput is utilized as expanded connectivity, delivering new standardized communication interfaces both subsea and topside, and at the same time being backwards compatible for already installed subsea equipment.
The combination of being backwards compatible with the use of standardized communication interfaces gives extended lifetime for valuable communication infrastructure; umbilicals. Large benefits of the proposed solution are also achieved during upgrading of subsea installed equipment since not all subsea installed units must be upgraded at the same time as the topside-subsea communication link are upgraded.
To be able to supply enough electrical power to new subsea units on an existing umbilical already almost fully utilized a transformer based solution are described.
For umbilicals with very low IR (Insulation Resistance) values, a transformer setup for lifetime extension of the umbilical are also described.
Successful Sweeping Control Technology Test for Offshore Heavy Oilfield—Case Study of QHD32 Reservoir in Bohai Bay
Authors: Wu Xingcai , Chen Weiyu , Xiong Chunming , Huang Bo , Meng Hongqu , Wu Qinghui , Ma Chao , Xu Hanbing , Ye Yinzhu 
Published: April 2016

Waterflooding offshore heavy oilfields features large injection-production well spacing and thick vertical oil layer. Besides, formation heterogeneity and oil-water viscosity difference exist commonly. All of the above cause injected water fingering, tonguing, and even channeling in deep reservoir, leading to low sweep efficiency, which seriously affects the technical and economical waterflooding effect.
A new set of sweep control technology (SCT) has been tested. The technology takes slug combination consisting of traditional highly viscous continuous-phase polymer gel and the new particle-type polymer dispersion with low viscosity. The particle diameter distributes from nanometer to sub-millimeter, which can be designed based on formation pore/throat sizes. The particle swells in water, but keeps no change in oil. The slug set can inhibit flowing of injected water in channels, and make injected water diverted in deep reservoir and directly access into medium-low permeability zones where more remaining oil exists, improving sweep efficiency.
QHD32 Filed has high porosity, 25~43%, high permeability, 500~18443mD, high gravity oil, with API gravity of 14.3~17.3, and effective pay thickness of 32.6m. The field started production in 2002, and up to 2012, the average oil rate per well was only 31m3/d, and oil recovery was only 5.74%, but the water cut is high, 85%. So far, totally 13 well patterns have been conducted with the sweep control technology in the field, with total injected agent amount of 102000m3. Results showed cumulative oil incremental of 100195m3, cumulative water production decrease of 185153m3, average daily oil rate per well increase of 20%, and input-output ratio of 1:10.9 under oil price of 100 USD/bbl as oil price. Even under current low oil price, 30 USD/bbl, it is still feasible economically, and the input-output ratio is 1:3.3.
Field test results show that the combined slug of highly viscous crosslinked polymer gel and new particle-type polymer dispersion can inhibit water channeling and enlarge sweeping volume. Even under low oil price, the technology has achieved success in technical and economic aspects, which provides a new IOR/EOR method for offshore waterflood heavy oil fields.
An Integrated Approach to Stampede Field Development, Deepwater Gulf of Mexico
Authors: Mohapatra Gopal , Nabasir Andry , Strauss Steve 
Published: April 2016

Abstract
Reservoir compartmentalization, stratigraphic complexity, and fluid contact uncertainty are the three key issues in the development of the Stampede field. We studied these issues in detail by integrating structural and stratigraphic interpretation and using state-of-the-art 3D dual coil seismic data, fault-seal analysis, pressure and fluid data from wells, core datasets, and logs. We used the products and knowledge from this integration effort to build the geological model. Key focus areas included: trap geometry, sealing capability of faults, environment of deposition (EOD), facies distribution, geochemical analysis of fluids, and oil-water contact (OWC) estimation. We built the geologic model honoring the data and observations to capture all the uncertainties and their ranges. We used this model for flow simulation resulting in a 10-well development plan, with six producers and four injectors for the base case.
In this paper we discuss some of the components of this multi-disciplinary effort toward the field development plan at Stampede, highlighting the challenges and solutions. The work helped us (a) incorporate fault-seal related compartmentalization into the simulation model, (b) properly represent facies types in the geological model, (c) better understand the compartments and associated OWCs, and (d) understand their impact on flow simulation and field development.
Thermal Design Approaches for Pipe-in-Pipe Tiebacks for the Transportation of HP/HT Oil and Gas
Authors: Paul Samuel , Sathananthan Ratnam , Legge Matthew 
Published: April 2016

The purpose of a pipe-in-pipe flowline is to provide a highly insulated system to minimise the transfer of heat between the transported fluids and the surrounding ambient environment. The dry environment between the concentric pipes allows high performance dry insulation to be used, ultimately achieving a thermal performance greater than that which is possible with a simpler wet insulated flowline. For the exploitation of High Pressure / High Temperature (HP/HT) reservoirs, a pipe in pipe system can provide the necessary thermal insulation and the integrity for transporting hydrocarbons at high temperatures above 120°C – the current limit of conventional wet thermal insulation.
Compared to a wet insulated pipeline, the mechanical configuration of a pipe-in-pipe is inherently more complex and consists of several components (insulation, centralisers, water stops, field joints) which all have differing heat transfer properties. The magnitude of each component’s effect on the overall thermal performance must be understood during the design to avoid either under or over insulating the system potentially leading to operational problems and/or wasted expense. However, due to the relatively complex heat transfer processes at work, very accurate quantification of the effects is often cumbersome to calculate with little or no added meaning due to greater uncertainties in other parts of the design.
However, there are cases when the design comes together in a way such that a small change in insulation thickness may tip the design into requiring a larger sleeve pipe diameter to accommodate the extra thickness. As pipes are most economically purchased in standard diameters (8, 10, 12 inch, etc.) the jump from a 14 inch to a 16 inch sleeve pipe for example not only adds significant material cost, but may have huge implications to the installability of the pipeline.
Hence before making the jump to a larger pipe diameter, it makes sense to first evaluate the basis for the required thermal performance (e.g. the criticality, operational and flow assurance impacts of a marginally reduced thermal performance), and also the calculation methodology – often conservative simplifications are included early on in the design when the fabrication and installation implications are not fully evaluated or understood.
This article aims to provide an overview of the current thermal design approaches for pipe-in-pipe systems, and to highlight the choices available to the engineering team and the areas with scope for optimisation. The relative magnitude of the various resistances to heat transfer will be quantified, with focus on the most relevant aspects of the heat transfer with respect to pipe-in-pipes.
While this paper does not address active heating, the improvements to the passive insulation discussed would directly affect the power requirements of actively heated systems.
Strategies to Monitor and Mitigate Asphaltene Issues in the Production System of a Gulf of Mexico Deepwater Subsea Development
Authors: Gonzalez Doris , Gonzalez Fabio , Pietrobon Marney , Haghshenas Mehdi , Shurn Megan , Mees Amber , Stewart Carlos , Ogugbue Chinenye , Duvivier Giles 
Published: April 2016

Abstract
An asphaltene threat has been identified in production wells located in a Gulf of Mexico (GOM) deepwater field. After production started from different reservoirs and the operating conditions for some of the wells reached the asphaltene precipitation onset, solid deposits were detected at different points in the production system, which caused production deferrals, disturbed the operating strategy of the field, and increased the operational expenditure. To remediate asphaltene deposition in deepwater subsea wells, a rig-less remediation costs up to $0.12 million (MM); a well intervention that requires a rig costs approximately $20 MM, and a vessel-based pumping remediation costs about $5 MM. These costs do not include the impact of production deferrals.
A plan was developed to acquire and interpret the required information to properly understand and manage the asphaltene threat. The methodology includes: Acquisition of suitable downhole reservoir fluid samples for asphaltene and wax studiesCharacterization of the reservoir fluids in the laboratory using the latest asphaltene and wax technologies.Observation of the effect of chemicals on solids builds up during field trialsSurveillance of damage near wellbore using Pressure Transient Analysis (PTA) and Multi-Rate Test (MRT)Real time monitoring of normalized nodal analysis based on frictional pressure losses.
During the characterization of the reservoir fluids, asphaltenes were identified as key risk factor for successful field development. The laboratory tests showed the propensity for solids formation and confirmed that the variety of reservoir fluids had an asphaltene deposition envelope that extended from the reservoir rock to the topsides facilities. Solids collected from pigging returns, surface equipment, and failed downhole equipment confirmed the reservoir fluid's asphaltene deposition tendency. In some cases, field trials showed that increasing the concentration of asphaltene inhibitor injection resulted in increased build-up of organic deposits. PTA and MRT enable the identification of flow restrictions from the reservoir to the permanent downhole gauge location and real-time monitoring of normalized nodal analysis help to identify where the impediment to flow is located in the production system.
This paper presents an integrated approach to evaluate the key elements of asphaltene risk for deepwater projects, the strategy to manage the issues during production implementation, and lay out the aspects to be considered in the mitigation of the negative impact of asphaltene thread in the field development plan.
Practical Applications of Structural Analysis Support to Decommissioning
Authors: Abdelaah Ahmed M A , Cresswell S M , Manzocchi G M E , Thistlethwaite C 
Published: April 2016

This paper will illustrate some of the challenges facing decommissioning in the harsh environment of the North Sea and the latest efforts spent on analytical and practical fronts to achieve a safe and efficient removal of some of the biggest North Sea structures. The need for efficiency has never been greater, with current low oil prices potentially bringing forward the decommissioning of assets that are no longer cost effective to operate.
The authors have considerable experience providing analytical support to the planning and safe decommissioning of major North Sea structures using commercial structural analysis tools and methods developed in-house. This paper describes several practical examples of the use of applied structural analysis to support the decommissioning of concrete and steel offshore platforms. Examples include: analysis support for the piecewise removal of a steel jacket structure; structural assessment of transportation of a complete topside incorporating a novel approach to define simultaneous peak response combinations; and finite element modelling methods to manage end of life production for a concrete platform prior to decommissioning and the long term degradation of concrete under reduced draw down post decommissioning.
The experience of supporting the removal of a major platform has demonstrated the importance of using a live model for real-time decision making. For the single lift removal of a heavy topsides, the statistical approach to extreme member force combinations for code checking provides efficient and safe guidance for assessment and minimizing costly strengthening. Long term analysis under decommissioned loading conditions of concrete platforms can provide sufficient confidence in long-term platform integrity in a derogated state.
The real-time analysis support is a first of its kind for a major North Sea jacket removal allowing rapid decision support to the removal operation. The random seas analysis approach is a novel and efficient change to the standard transportation design-level approach and is appropriate for a structure destined for scrap. Collaborative research with academic institutions provided the basis for industry leading probabilistic long-term degradation of large concrete structures in extreme environments.
Risk-Based Assessment of Scour Around Subsea Infrastructure
Authors: Tom Joe , Draper Scott , White David , O'Neill Michael 
Published: April 2016

Abstract
Scour poses a significant risk to infrastructure placed on mobile seabeds. Seabed mobility is common on the North West Shelf of Australia, in parts of the North Sea, and also occurs in the deepwater Gulf of Mexico, due to loop currents. Scour can undermine structures and, for shallow-skirted mudmat foundations, there can be significant consequences including excessive settlements, tilt and loss of bearing and sliding capacity. However, scour mitigation via engineered protection is costly, and to be avoided if possible.
This paper describes a new quantitative risk-based approach for assessing the susceptibility of subsea infrastructure to scour processes. This probabilistic scour assessment accommodates measurable uncertainties in metocean and seabed conditions, using new characterization techniques. The approach allows operators and owners to better assess the optimum strategy to address scour risk, selecting from mitigation during installation or in-service monitoring, prediction and remediation.
The paper describes (i) best practice approaches for assessing scour susceptibility and propagation rates with and without engineered protection, (ii) new methods for determining the applicable seabed and metocean inputs, (iii) a probabilistic framework for encompassing uncertainties, and (iv) how this approach can be applied in project applications.
Our probabilistic method of assessing and presenting scour risk produces a distribution of estimates of scour depth and time rate. By capturing and quantifying the full range of uncertainties, this method facilitates decision-making by showing the range of potential outcomes and allowing the associated costs and consequences to be evaluated. This approach is superior to deterministic ‘worst case’ calculations, which are often used to assess scour susceptibility.
In summary, this paper provides operators and owners with an improved methodology to unlock Capex and Opex savings through more accurate and informed scour assessments.
Vertical Input for Seismic Analysis of Offshore Structures
Authors: Zanoli O. , Smerzini C. , Parker E. J. 
Published: April 2016

AbstractThe vertical spectral shape suggested by the main offshore codes does not reflect actual earthquake behavior. The problem is exacerbated in time history analysis, as the incorrect spectral shape leads to unrealistic scaling of records. Vertical spectra from codes are compared to published measurements from offshore sites and the results of numerical modeling. The effects of the water column and the mismatch between code spectra and real time histories are illustrated. Results of the spectral matching show that the vertical spectral shape defined by offshore codes leads to over conservative vertical time histories at short periods.Often vertical response is expressed as a fraction of the horizontal spectral acceleration at the same frequency (V/H ratio). Current practice regarding V/H is reviewed, considering design codes and recent research. Conventional V/H ratios are compared to sea bottom measurements by Boore and Smith (1999) which highlight the peculiarities of offshore sites. A relatively simple numerical analysis of vertically propagating compressive waves is used to evaluate vertical amplification and the effect of the water column for a case history.Current practice shows a certain degree of variability among the codes/papers. For onshore sites, there is consensus that V/H&gt;1 at low periods but that vertical is less than horizontal at long periods. Boore and Smith's seafloor recordings suggest that offshore motions have very low vertical motion compared to onshore conditions, especially at low periods. The numerical modeling shows that the vertical response is mainly controlled by the water layer, which induces a strong deamplification at the resonance period of P waves within the water layer. Such an effect is in agreement with the findings of Boore and Smith (1999).The paper highlights the poor definition of the vertical seismic spectra for offshore sites in seismic codes and makes a first step towards the development of more reliable vertical spectra. The overconservatism induced by the code vertical spectra on definition of time histories is presented to stimulate future developments.
Investigations into the Fatigue Strength of CRA Lined Pipe
Authors: Johnston Carol , Nageswaran Channa , London Tyler 
Published: April 2016

Pipes that experience sour service need to resist that corrosive environment. One method for achieving corrosion resistance is by lining the inside of the pipe with a corrosion resistant alloy (CRA), such as stainless steel or a nickel based alloy. This has the advantage of being much cheaper than either making the pipe from the CRA or metallurgically bonding CRA to the pipe (ie clad pipe). Lined pipe is gaining popularity, and has so far been used successfully in applications where applied strain levels are low, however more data is needed on its fatigue strength and its behavior when subjected to high levels of applied strain. A Joint Industry Project (JIP), funded by Petrobras, BG Group, Saipem, Tenaris, Technip, Cladtek and HMC, was run by TWI Ltd and INTECSEA to investigate and generate data on CRA lined pipe.
The JIP included full scale resonance fatigue testing, allowing the failure location of lined pipes to be investigated, development of an ultrasonic inspection procedure for lined pipe, small scale mechanical tests to generate materials data and calculation of stress intensity factors specific to the lined pipe geometry. This paper presents a summary of the work carried out.
The significance of the paper is that it describes a body of work carried out in the field of CRA lined pipe, helping operators and those at the front-end engineering design (FEED) stage to choose lined pipe, with the resulting cost savings.