bluuebunny/crossref_metadata_2025 huggingface dataset:
Key Development Technologies of Deep Water Oilfields in Angola
Authors: Bingyu Ji , Zhihai Chen , Huaiyin Li , Jingwei Wang , Xuebo Dang , Zhang Shiyang
Published: April 2016

Sinopec has acquired six deep water blocks in Angola. According to their geological features, a series of key technologies have been developed and applied by all partners under the leadship of operaters, covering reservoir description, reservoir engineering, production engineering, flow assurance, etc. On the Basis of a sedimentary faces study, seismic waveform and amplitude, prediction method was developed to identify turbidity sands with thicknesses of 3-5 m; fault imperviousness and connectivity were determined by using static value potential of shale smear, dynamic interference testing, and dynamic correlation of production data on both sides of the faults; individual well production capacity was evaluated by DST testing results, and residual oil was described by 4D seismic data; six development strategies were made for Angola deep water oil fields development, including fast recovery, high production rate with minimum wells, carefully feasibility study in advance, full utilization of main offshore facilities, optimization of the entire production system, and efficient operation of production facilities. Additionally, certain technical measures were successfully applied to determine development layer series, well pattern and spacing, development sequences, injection strategy, and production rate. Slug flow was minimized by riser base gas lift. Insulation and chemical injection were introduced for flow assurance. Most wells were completed with open hole gravel pack and expanding screen for sand control. Above mentioned technologies were effectively applied and proved to be successes in Block 18, Block 15/06, and Block 32, which have technical significances for the development of oilfields with similar conditions.
Top-Hole Formation Pore Pressure Assessment at Deepwater Well Sites Using a Geotechnical Approach
Authors: Trandafir Aurelian C. , Haneberg William C.
Published: April 2016

Geotechnical investigations are routinely performed in site characterization studies for offshore infrastructure development. Until present, little consideration has been given to the application of geotechnical methods to pore pressure assessment in the top-hole section of deepwater sediments. Laboratory geotechnical tests including one-dimensional consolidation tests and index property measurements on intact cores collected from pilot holes drilled at prospective well sites have the ability to provide a rigorous characterization of the normal compaction trend and in-situ porosity, which are critical in evaluations of overpressure associated with a compaction disequilibrium mechanism. This paper presents key considerations pertaining to interpretation of results from geotechnical tests in the context of top-hole formation pore pressure assessment at deepwater settings. Examples of top-hole pore pressure regime evaluation at two hypothetical deepwater wellsites are used to depict particularities related to development and interpretation of normal compaction trend describing stratigraphic sequences associated with various depositional mechanisms, likely to be encountered within the top-hole section of deepwater sediments.
Case Study on the Design of HPHT Components Using ASME Section VIII Division 2 and 3
Authors: Peters D. T. , Biagiotti S. F.
Published: April 2016

Design margins in high pressure / high temperature (HPHT) equipment vary throughout the various Codes and Standards. This paper is an overview of the design standards which can be applied to HPHT service or are currently under development.

This paper will provide a case study of the design philosophies referred to in API 17TR8 which refers heavily on ASME Section VIII Division 2 and Division 3. This will demonstrate the difference in design margins, and how the life of the components may be affected.

Design approaches such as "Design-by-Rule" or "Design-by-Analysis" are included in the standards used today. Implementation of the "Design by Analysis" methods can be very complex and require a significant amount of analytical rigor, compared to traditional "Design-by-Rule" analyses. However, the benefits of the additional rigor can be significant to allow the use of lower design margins which will minimize material while providing equal or increased theoretical design lives.

HPHT equipment is entering into operating pressure ranges that have rarely been experienced before by similar equipment. API 17TR8 does not have approved industry guidance that would support a traditional "Design-by-Rule" process. The lower design margins used by some codes can have the unintended consequence of leading to significant areas of potentially high stresses due to thinner sections and stress concentrations, which can lead to fatigue issues. A combined approach which includes lower design margins and rigorous analytical methods for the determination of the cyclic life of components can lead to robust designs which both minimize cost while improving manufacturability and reliability.
VIM Model Test of Deep Draft Semisubmersibles Including Effects of Damping
Authors: Antony A. , Vinayan V. , Madhavan S. , Parambath A. , Halkyard J. , Sterenborg J. , Holmes S. , Spernjak D. , Kim S. J. , Head W.
Published: April 2016

Semisubmersible platforms are good candidates for hydrocarbon exploration and production in the Gulf of Mexico (GoM) and elsewhere. These platforms are a preferred choice for deep-water applications involving higher design throughput. A dry tree application of semisubmersible provides the benefit of having improved well control, direct vertical well access, easy access to production equipment, reduced capital expenditures and other dry tree benefits. These are in addition to the benefits that a semisubmersible platform has over spars and tension leg platforms (TLPs). A public-private partnership has sponsored multiple projects since 2009 with the aim of maturing a dry tree semisubmersible design that is cost-effective and safe like spars and TLPs. Due to the deeper draft of the semisubmersibles proposed for the dry tree applications, vortex induced motion (VIM) is an area of concern that needs to be addressed during the design stage. The research work presented here is a part of the "Vortex Induced Motion Study for Deep Draft Column Stabilized Floaters."

The effect of additional damping due to mooring lines and risers on the VIM response of a deep draft semisubmersible is an area of focus of the ongoing project. CFD-based predictions show a significant reduction in the VIM response when additional damping is considered. With the intent of validating the CFD models and to further understand the effect of additional damping on the VIM response, a model test campaign was conducted with different levels of applied additional damping. The paired column semisubmersible and conventional semisubmersible platforms were tested, with and without damping and the results are discussed here. In addition, during model testing, the conventional semisubmersible hull was equipped with a column force measurement system to measure the hydrodynamic forces on the individual columns.

The results of the study show that damping plays a significant role in reducing the platform VIM which directly impacts the estimated fatigue damage of mooring lines and risers, and which in turn can reduce the overall cost of the system.
Prevention and Control of Corrosion-Induced Asphaltene Deposition
Authors: Sung Chi-An , Tavakkoli Mohammad , Chen Andrew , Vargas Francisco M.
Published: April 2016

Although multiple problems occur simultaneously in oil production, the solution strategy is typically presented by addressing one problem at a time. The objective of this work is to provide insight into the detrimental effect of iron ions, which are produced as a result of corrosion, on the asphaltene precipitation and deposition tendency during oil production. Furthermore, we aim to provide means to control these adverse effects by using chelating agents. In a series of experiments, a model oil system, which was prepared by dissolving asphaltenes in toluene, was put in contact with aqueous solutions of iron ions to study the effect of these species on the stability of asphaltenes using the indirect method. Also, a new experimental setup, consisting of a multi-section Teflon column packed with carbon steel spheres was built to quantify the deposition of asphaltenes under different operating conditions. This device was used to study the effect of the aqueous iron solutions on the asphaltene deposition tendency. It was found that the solubility of iron species is relatively high in the oil phase, compared to other cations, and that unlike other metals iron has a significant destabilizing effect on the asphaltene system. Furthermore, the multiphase systems that were analyzed in the column that is packed with carbon steel spheres, showed increasing deposition as the concentration of iron in the aqueous phase increased. A chelating agent was tried to reduce the adverse effect of iron and successful results were obtained. A systematic study was conducted to analyze the effect of different variables on the iron-induced asphaltene precipitation. Charge of metal ions, pH, and emulsified water do not seem to affect the asphaltene precipitation tendency as much as the iron concentration. In this work we account for the corrosion of pipelines and asphaltene deposition and the interrelation between them. According to the evidence that we have found, the corrosion of pipelines might be an aggravating cause for asphaltene deposition in wellbore and surface facilities. By addressing the corrosion problem, asphaltene deposition might actually subside.
A Novel Approach to Replacing a Gravel Pack Completion Using Hydraulic Screens to Remove the Annular Gap
Authors: Oddie K. , Clark M. , Arnestad E. S. , Davidian T. , Ravndal M. , Evans J.
Published: April 2016

Achieving flow performance in openhole sand control completions often requires removal of the annular gap between the screen section and wellbore. For the first time in the industry, patented hydraulic screen technology has been used to provide wellbore support and overcome the challenges associated with gravel packing in depleted reservoirs with low operational margins.

This paper demonstrates how new technology has been adopted by an operator in Norway to provide effective downhole sand control in an offshore environment faced with continuous reservoir pressure depletion. Detailed job planning and evaluation of risks when adopting new technology is described.

The case study describes a producer well drilled to 2580 m, at a maximum deviation of 30º, and temperature approximately 90ºC. With the sand control equipment run to depth closed ended, the liner hanger and hydraulic screens are set by surface applied pressure. When set, the screens extend radially to close the annular gap and provide wellbore support; production ports in each screen provide the flow path from the reservoir to production tubing. The liner hanger packer was set and reservoir isolation barrier valve closed in the same trip providing testable barriers, prior to displacing the well for upper completion operations.

The paper outlines how adopting new technology challenges openhole gravel packing and delivers effective downhole sand control in a depleted reservoir. The operator has demonstrated savings associated to operational planning, logistics, HSE risks and rig time. Production rates meet expectations with all screens contributing to flow.
Key Performance Indicator System for Deepwater Flow Assurance Operations
Authors: Canon Javier M. , Yau Sarah , Catheya Thierry
Published: April 2016

The industry is good at identifying risks, but in some instances is less proactive in ensuring the effectiveness and robustness of risk mitigating barriers. This becomes critical in deepwater Flow Assurance (FA) operations as latent threats, such as hydrate blockages can lead to significant financial losses. With this in mind, a multi-layered Key Performance Indicator (KPI) system was developed and implemented in 2 operating deepwater fields offshore Angola. Continuous use of the tool over a 2-year span has helped materialize a substantial positive business impact.

Conceptually, the solution sought was three fold: (1) design of a multi-layered KPI system with low level PIs used for monitoring and high level KPIs used for reporting, (2) creation of an automation tool to minimize data processing time, allowing engineers to concentrate on analysis and (3) engagement of an external contractor with the appropriate technical and organizational capabilities to generate periodic reports in a timely manner. Unlike other single-criterion approaches, the FA KPI system is built bottoms-up using clearly defined thresholds while capturing the influence of several contributing factors. These features have proved important in understanding the complexities around FA threats while adapting to an ever-evolving operation. The solution also emphasized transparency, maintainability, scalability and documentation as the ultimate goal is to make a system adaptable not only to a larger local operation but also to other operating regions.

Periodic FA KPI reports have been crucial in assessing the current state of the operation. The systematic layered-approach of this system has helped convey to senior management the robustness of both design and operational protective measures against flow assurance threats at a glance, through simple graphical representations, yet allowing engineers to peel off the layers and facilitating the identification of root cause(s) of the different issues. The information gained from this system has also allowed informed decisions to be made leading to the introduction of changes in strategies and operating procedures.

Finally, FA KPI reports have uncovered subtle aspects of the operation, e.g. operator errors in trying to follow overly-complex instructions. The need for sharing this type of information openly, in the right context, has been recognized as a key lesson learned to improve the way in which deepwater fields are operated.
Effective Procedure Design and Use: What Do Operators Need, When Do They Need It, and How Should It Be Provided?
Authors: Peres S. C. , Mannan M. S. , Quddus Noor
Published: April 2016

Recently, there has been much discussion regarding incorrect procedure use being related to many of the incidents in industrial settings. This has justifiably led to many focusing on procedure presentation, design, and accuracy. At the same time there is some discussion a-foot that there may be an over-reliance on procedures and too little analysis of the entire human system integration and human machine interface.

Based on insights from observations of and interviews with workers in industrial settings doing procedures, applications of two standard Human Factors methods (user testing and task analysis) are applied to three typical reason that operators do not adhere to procedures.

The analyses presented here illustrate that the basic method of user testing (field validation for this paradigm) can be leveraged to decrease the likelihood of mismatches between the standardized procedure and the methods used in the field as well as the methods used for on the job training. Further, task analyses can be used to identify what type of supports (e.g., check lists, in hand written procedures) will best support human performance for performing different types of tasks given the frequency that these tasks are performed.

The chief usefulness of the information available in these discussions is in the application of basic Human Factors methods to a problematic domain for many industries—procedure adherence. By using methods designed to identify and accommodate the capabilities and constraints of the human, the quality and adherence of standardized procedures can be improved. Moreover, the results of this work can serve as a springboard for more exploring more productive operational safeguards that properly account for missteps and errors that sometimes lead to hazardous situations.
6 MW HPHT Subsea Pump Development
Authors: Strikovski Andrei , Davalath Janardhan
Published: April 2016

The paper provides an overview of the value proposition for a 6 MW subsea pump unit in deep water subsea applications. 6 MW subsea pumps are needed for High Pressure High Temperature (HPTH) field developments, but they are not currently commercially available on the market. Development of a 6 MW subsea pump is based on the successful qualification of a 3.2 MW subsea pump. However, the technical challenges of almost doubling the shaft power, electrical current, maximum operating temperature and increasing the pressure rating to 15 ksi are successfully resolved. The paper also will describe any technology gaps and generally address how those gaps are closed.

The overview includes the steps taken to identify technical gaps and the methods to close them. The paper will provide an overview of the component qualification program.

Based on industry best practices, qualification testing and analysis is implemented to close identified gaps and provide confidence in successful completion of the subsea pump development. This is the first development of a subsea pump with a liquid filled motor rated to 6 MW shaft power. It is also the first subsea mudline pump rated to 15 ksi design pressure and 350 F temperature.
Numerical Modeling of Internal Waves and their Influence on Deepwater Floating Systems
Authors: Kurup N. V. , Shi S. , Jiang L. , Kim M. H.
Published: April 2016

Internal waves occur due to a combination of density stratification, bathymetry, and tidal effects and have been observed in many parts of the world. Recent discoveries of oil and gas reserves in areas where these phenomena are prominent have caused concern for field development. There have been several incidents where adverse effects were reported due to the effect of these waves on offshore platforms. This paper studies the effects of these waves on tension leg platforms (TLPs) and semi-submersible platforms within a coupled analysis framework. The physics is modeled by the second order Korteweg-de Vries (KdV) equation obtained by simplification and scaling of the Boussinesq approximation. A solution involving Jacobian elliptic functions coupled with a structure function that captures the effect of the pycnocline is utilized to model the wave. The model is implemented in a coupled analysis framework, and time domain simulations are performed to study the effects on a TLP and Semi configured to the developmental requirements and environmental conditions of an internal wave prominent area. Previous results showing the effects of internal waves on Spar platforms are also presented for comparison purposes. Two different internal waves with heights of 90m and 170m are utilized for the study. The impact of these waves on platform motion, tendon and mooring line tension are presented in this paper.

The study could provide guidance on platform selection in areas where the phenomenon is prominent.

In addition the model adopted in this study has the advantage of capturing temporal effects of internal wave trains making it an effective model for advance warning systems with real time monitoring.
Gulf of Mexico Lower Tertiary Development Wells - Cascade Field Case History
Authors: Moraes Flavio Dias De , Haddad Ziad , Becker Mauro Roberto , Nguyen Nhom
Published: April 2016

The Lower Tertiary (LT) play is the most recent production frontier in the deepwater of the Gulf of Mexico (GoM) in the United States. All LT discoveries in the area share common characteristics: deep reservoirs with low permeability, thick pay section, high initial reservoir pressures, Ultra-Deepwater depths, and long distances from flowline tie-ins. The Cascade field started producing in 2012 and has succeeded in proving the feasibility of the LT play as a new GoM producing horizon.

The Cascade Field is located in the GoM at 250 miles South of New Orleans, Louisiana and 165 miles from the closest position on the Louisiana coast. Its wells are placed at 8,200 ft. water depth in the Walker Ridge area. The LT reservoirs (Wilcox Fm.) are composed of many sandstone layers extending vertically for approximately 1,000 ft.

This paper will describe technologies applied in LT projects to deal with reservoir characterization and management, well construction, and production operations as a case history. Some of the topics addressed in this paper include: fracture design optimization, well completion design, pressure history, skin analysis, reservoir characterization, and technical limitation on production drawdown, artificial lift, and their impact on the formations.

The current low oil price market forces operators to become more efficient and creative in reducing the overall capital expenditure to develop the LT play. This paper will suggest potential future enhancements in well design to make the wells more efficient and improve project economics.
Calculation and Application of Safe Mud Density Window in Deepwater Shallow Layers
Authors: Deng Song , Fan Honghai , Tian Deqiang , Liu Yuhan , Zhou Yuyang , Wen Zixiang , Ren Weiyan
Published: April 2016

In this paper, based on the geologic features in deepater shallow, we optimize the calculation method of the overburden pressure (four parameters regression method), pore pressure (comprehensive interpretation method), collapse pressure (Mol-coulomb criterion) and fracture pressure (pressure coefficient method) through investigation and onsite application, therefore, we can determine the safety window of mud density in shallow. Additionally, the riser setting depth is given on the basis of safe density window; Furthermore, we seek out the gradient model of the multi gradient drilling (MGD) applicable for narrow density window on the condition of simplifying casing program. An example in the South China Sea is illustrated. In the paper, we gather the geological feature and well logging data. According to the method given above, the depth of conductor is suggested. Meanwhile, compared with the safe mud window previous, the MGD gradient model can largely the thin window before as the more simple structure of well can be applied.
Fuel Efficiency on Floating Production Systems
Authors: Bronneberg Jos
Published: April 2016

This paper assesses the benefits of using a cold heat sink to dissipate the inefficiencies of the various process functions on board an offshore deep water Floating Production System (FPS). Rather than using the customary surface water or air as the heat sink, this paper proposes to use cold water from the deep sea. The use of cold seawater not only improves the efficiency of various processes but also provides constant conditions compared to the temperature fluctuations caused by the annual seasons and day-night effect on surface water and ambient air.

Compared to other approaches to increase the fuel efficiency such as the use of (Organic) Rankine Cycles, (Adsorption, Absorption or Refrigerant based) Chilling units, etc., the use of cold seawater from deep sea requires less additional equipment and footprint, and it is abundant for Production Units located on deep water fields.

In some cases the use of cold sea water can reduce the number of Gas Turbine drivers, where the CAPEX and OPEX savings more than compensate for the required Cold Water Pipe in this concept. In addition to the cost benefits, it has the potential of making the plants smaller as some functions are reduced in size and/or number. This is particularly the case where central power generation concept (all electric Production Facility) is applied. In such case the main generators are all of the same (frame) size, which allows for tailoring the number of units to the power consumption needs.
Design Case Study for a 4 MTPA FLNG System for Severe Metocean Conditions
Authors: Shivers Robert M. , Michel Richard P. , Kolb Norman P.
Published: April 2016

Floating LNG is gaining acceptance as a viable alternative to conventional land based LNG plants. In the past few years, several FLNG projects have become commercial and reached FID. However, most FLNG systems designed to date remain complex, costly and operationally limited to areas with benign to moderate metocean conditions that allow side-by-side offloading of the LNG. This paper describes a "Split Process" FLNG design where primary production and gas treatment functions are provided on a host platform while liquefaction occurs on a separate vessel(s). The arrangement works in moderate to severe metocean operating conditions, such as offshore Western Australia or the Grand Banks of Eastern Canada, and is scalable from 1 – 6 MTPA.

The design and features of a 4 MTPA, deepwater case study are described. Salient features of the concept include: Segregation on separate facilities of gas processing/condensate storage from liquefaction/LNG storageImproved safety, constructability and overall project scheduleUse of existing, standard hull designs for host facility and liquefaction vesselsPre-cooled Dual N2 expansion liquefaction for safety, simplicity and operabilityDual fuel diesel electric (DFDE) power to improve fuel efficiencyNo offloading of LNG in open water; all offloading takes place in sheltered water

Process improvements have been made to the Dual N2 expansion liquefaction (DNX) process to reduce the unit liquefaction power. Fuel consumption for liquefaction is further reduced by the higher efficiency DFDE prime movers over gas turbines. The system offers lower capital cost and improved operability over conventional, integrated designs. Eliminating offshore LNG transfer and achieving fuel efficiency on N2 liquefaction similar to mixed refrigerant (MR) processes contribute to reliable/cost effective operations.

The liquefaction vessel is derived from a standard DFDE Moss LNG carrier which is extended 42 ft. at the bow to add a liquefaction module, switchgear and disconnectable turret mooring. Additional power generation is added to drive the 2 MTPA liquefaction unit. The liquefaction vessel disconnects when full and transits to a transfer jetty in sheltered water to offload. A fleet of 3 × 2 MTPA dedicated liquefaction vessels provides continuous operation and total system capacity of 4 MTPA. A host platform, determined by site specific considerations, handles primary production, condensate storage/offloading and treats the gas to an LNG inlet specification. The host may be an FPSO, TLP or fixed platform/FSO depending on upstream field development requirements.

The FLNG concept described offers both schedule and cost advantages through the use of standardized hull forms and repetitive, standardized design.
Improved Binning Criterion for Developing Scatter Diagram of Loop Current and Eddies
Authors: Agarwal Puneet , Forristall George
Published: April 2016

Loop Current and Eddies (LCE) occur in the Gulf of Mexico and can cause fatigue of tubular systems such as drilling and production risers and wellhead/casing systems by vortex-induced vibrations (VIV). It is a standard practice to perform a cumulative fatigue assessment of risers and wellhead/casing systems using a site-specific scatter diagram of LCE. A scatter diagram consists of a number of full-depth current speed profiles and associated probabilities of occurrence for each profile. Scatter diagrams often consist of too many current profiles, which can make the VIV analysis computationally very expensive and intractable. On the other hand, if the higher-order modes are excluded in order to reduce the number of profiles, fatigue estimates may be inaccurate and sometimes unconservative.

In this paper, a more efficient binning procedure is presented for deriving the LCE scatter diagram using 1000 years of simulated data from the GEM42 hindcast model. The hindcast data consist of mode shapes and amplitudes of the first three empirical orthogonal functions (EOFs) of the LCE. The statistics of the amplitudes of the three EOF modes are carefully investigated to find relevant trends that guide the binning procedure. It is first shown that using all three modes is required since reconstructing current profiles with only two modes results in significant speed errors. Further, VIV fatigue analysis of a wellhead/casing system shows that using only two modes can result in significantly unconservative fatigue life estimates. The joint distribution of the last two mode amplitudes is analyzed and found to be polar. Therefore, the three mode amplitudes are mapped to a cylindrical coordinate system, and it is found that cylindrical binning is more efficient, by a factor of more than 2, as compared to traditional binning in the Cartesian coordinate system. Finally, cumulative VIV fatigue analysis of a drilling riser and wellhead/casing system is performed to investigate the effect of different binning choices (i.e., bin widths, coordinate system, and number of modes) on the end result, i.e., fatigue estimates. Fatigue life results show that cylindrical binning can be significantly more efficient without losing accuracy.
Novel Methods for Asset Integrity Management in a Low Oil-Price Environment
Authors: Rosen Jeremy , Potts Andrew , Sincock Paul , Carra Chris , Kilner Andrew , Kriznic Peter , Gumley Jonathan
Published: April 2016

The most cost-effective solution to ongoing production in a low oil price environment is often to extend the life of ageing producing assets past the original design intent. The offshore oil and gas industry therefore faces the challenge of extending the useful production life of ageing assets whilst ensuring their integrity. The challenges to increased life include ensuring integrity given potential modifications to the floating or fixed assets, modifications to the loading design conditions over their service life, as well as the cumulative effect of fatigue loading on key structural components. Operators and designers increasingly have access to relatively low-cost, high-accuracy instrumentation systems that can be used to monitor the loading and dynamic response of FPSOs and offshore platforms. This paper details a suite of cost-effective ongoing health monitoring measures that can be used to extend the life of producing assets. A design verification process is envisaged to validate original design assumptions and update them against more detailed local site knowledge. Instrumentation can supply health-monitoring data that can be analysed in close to real-time, and which can signal to operators the advent of elevated risk scenarios requiring a higher level of intervention and inspection. This facilitates a methodology for applying risk-based inspections to key components, under which production can be extended while relatively riskier locations are targeted for priority inspections and, if necessary, repair or modification. The technologies investigated here provide cost-effective methods for implementing the concepts of Mooring Integrity Management (MIM) recently expounded by DeepStar®, as well Risk-Based Inspections (RBI). Use of these procedures can allow safe, extended operation of productive assets beyond their original design life at minimum ongoing cost. The techniques will be of significant benefit to offshore operators with ageing assets, as well as to FPSO and fixed platform designers and contractors.
Metocean Design Criteria in Tropical Cyclone Prone Areas: the Mozambique Channel
Authors: Terrile E. , Guida B.
Published: April 2016

Tropical cyclones represent one of the most catastrophic examples of Natural Hazard. The effect of such events on the environment and human activities is a foregone conclusion.

Metocean design criteria are usually defined using databases of historical tropical cyclone tracks characterized by wind and central pressure values. From these historical databases wind and wave maxima are subjected to extrapolation in logarithmic space. In order to correctly evaluate the required return period (up to 1 on 10,000 years) extrapolating the tail of the distribution from historical database provides highly uncertain estimates, therefore, a synthetic tropical cyclone database is needed.

The present work describes step-by-step the setup of a synthetic tropical cyclone database valid for the Mozambique Channel area and finalized at the definition of metocean design criteria in area characterized by such events. The synthetic tropical cyclone database, statistically consistent, has been build-up using an autoregressive model for increments in track speed, direction and maxima cyclone winds. Moreover the used methodology involves application of a physically based wave model in order to catch a correct representation of the main processes: wave shoaling/refraction, trapped fetch effects, wave breaking, correct representation of offshore islands, etc.

In order to reduce the computational time without reducing the benefit of the wave modeling phase, the proposed methodology considers a track pre-selection step allowing wave simulation only for tropical cyclone tracks characterized by the higher waves at point of interest. In such way the tail of the distribution, obtained from the synthetic database and characterized by higher return periods (i.e. 1,000, 5,000 and 10,000 years), is effectively simulated by the wave numerical model allowing a correct definition of the corresponding metocean design criteria. Furthermore, fitting modeling results with an extreme distribution function (e.g. Weibull, Pareto, etc.) allows definition of extreme values at lower return periods (i.e. 100, 200 and 500 years).
Drillship Moonpool Design to Reduce Added Resistance for Fuel Saving
Authors: Ma Peifeng , Xing Xiuqing , Yan Deguang , Chien Hung-Pin , Lee Sing-Kwan , Gu Hai , Xu Haihua , Choudhary Ankit , Hussain Anis , Merchant Aziz Amirali
Published: April 2016

During transit, a drillship moonpool creates added resistance that can be more than 50% of the total resistance and hence significantly increase the fuel consumption. This paper reports a real case study for reducing moonpool added resistance by model tests and Computational Fluid Dynamics (CFD) simulations. Model test data show that, unlike conventional ships that experience nearly constant resistance, a drillship resistance presents largely fluctuating behaviour. In CFD validation, the physics based CFD best practices are applied for resistance predictions. The largely fluctuating resistance is well captured in simulations. It is found from flow visualizations of the large amount of CFD simulation results that the high moonpool induced added resistance is mainly attributed to the vortices shed from the moonpool front wall, which enter into the moonpool and impinge on the rear wall. The CFD predicted mean resistance are in good agreement with the model test data, within 3% difference for a wide range of speeds. The well validated CFD tool is applied to study the effects of moonpool dimensions on the added resistance. The results of parametric study reveal a design principle that smaller moonpool dimension results in smaller added resistance. Through comprehensive CFD parametric study, a universal design principle and CFD best practice are established for industry applications.
Design and Installation of an Innovative Tension Leg Platform for 2 MW Offshore Wind Turbine at Baltic Sea
Authors: Dahlhaus Frank , Großmann J.
Published: April 2016

The Offshore Wind Resources in deep water, but also the currently experienced issues with conventional foundations, are driving the solution requirements for new offshore wind power platforms. The latest monitoring results of German offshore wind farms show the challenges the industry is facing. Ecological impacts as well as foundation technology issues are forcing the sector to look for alternatives. The presentation will introduce a technology of a floating TLP-structure with a specific mooring line configuration as an innovative foundation concept for offshore wind turbines suited for water depths greater than 30 meters. The unique aspect of the GICON TLP is its modular, frame-work structure which allows buoyancy and load transfer functions to be decoupled from each other and instead be applied to the specific structural elements. In contrast to classic TLP designs and semi-submersible floaters, additional stabilizing effect achieved by this additional bracing minimizes the movement of the entire system. Due to this stable behavior of the TLP standard offshore turbines as currently available in the market should be usable for this platform. Furthermore results from model basin tests will be described. Also the comparison of calculated and experimental data obtained by extensive tank experiments with a scale model of an offshore turbine at Maritime Research Institute Netherlands (MARIN) in summer 2013 will be presented. These experiments include wind and wave loads that represent different sea states of the proposed location for the full scale prototype. In numerical simulations the dynamic behavior of the TLP under linked hydrodynamic and aerodynamic loading is taken into account also regarding different geometric configurations of the mooring line system and various types of anchorage systems at the sea floor. Using characteristic Campbell-diagrams structural stiffness of each component is optimized aiming at a soft-stiff design of the TLP-structure. The results of the scaled tests at MARIN have confirmed that a superposition of internal forces of the moored structure in operation for wind and wave loads can be assumed. Numerical modeling validation is confirmed by tank tests. Data and video from the tank tests will be shared as part of the presentation. GICON researchers plan to install a full-scale pilot plant in the German Baltic Sea in 2016.
Method for Driving Multiplexed Downhole Control Systems
Authors: Garcia Elias , El Mallawany Ibrahim
Published: April 2016

The paper presents a method for driving multiplexed downhole control systems employed as part of an intelligent completion, and provides a comprehensive analysis of the data collected as well as conclusions and results of the presented methodology. The content presented in this paper is based upon theoretical, design, and field data obtained at different stages of a product's development lifecycle.

This paper identifies a specific application where charlieplexing is used to control downhole intelligent completion systems. Charlieplexing allows the selective engagement of solenoid valves at great lengths of distance with a minimum number of electronic components. When paired with existing hydraulic systems, charlieplexing allows selective channeling and remote operation of hydraulic fluid to interval control valves in a well. Protection of the system's electrical conductors is provided through a hydraulic fluid-filled tubing encased conductor (TEC), which increases the overall reliability and longevity of the entire system. In addition, the paper details the components that make up the system and the associated testing to validate the theory presented.

Using a charlieplexing methodology for the development of a downhole control system proved to be an effective way to engage up to 12 solenoid operated valves with the use of a fluid-filled TEC. This methodology has been proven through component reliability testing, system integration testing, and field testing. The charlieplexing methodology is different from other methodologies used in existing downhole control systems. Charlieplexing facilitates the use of passive electrical components to achieve selective control of solenoid operated valves. Because of its inherent architecture, the charlieplexing methodology does not require a communication protocol to selectively engage components, thereby minimizing the total amount of components in the system. Ultimately, this component reduction makes charlieplexing inherently more reliable as it has fewer failure points. Test data is presented to support this conclusion.

This paper introduces the idea of using charlieplexing as a means for driving downhole control systems when paired with downhole intelligent completions equipment. The paper also highlights the use of a nonconductive, hydraulic fluid-filled TEC to prevent wellbore fluid ingress.
Collaboration with Client: Industry's First Open- Head, Full Rotating High-Torque Bucking Unit Enables Makeup of Tubulars on Pipe Deck
Authors: Hulke Markus , Habetz Jeff
Published: April 2016

The prevailing drive to develop innovative solutions to reduce rig time and associated costs, coupled with enhancing safety and optimizing operational efficiency, prompted a major Gulf of Mexico operator to request a customized solution to allow make/break of drillpipe triples and casing doubles on its space-restricted deepwater production installation. Specifically, the operator sought a sustainable solution that would reduce operational costs by minimizing the online running of drill pipe, casing and tubing, while also reducing logistical hurdles and rig-floor hazards.

This paper describes the collaborative initiative that resulted in the engineering of a purpose-built pipe deck, which drove the development and deployment of the industry's first open-head bucking unit and bespoke pipe transfer system designed to enable fingertip make-up and breakout of drill pipe triples and doubles of casing and tubing. At the onset, a number of challenges had to be addressed to meet the operator's objective to vertically integrate the bucking and hands-free pipe transport system into the rig, which comprised a single-activity derrick with limited rack back capabilities. The authors will discuss the cradle-to-grave design process, which featured a cantilevered pipe bridge off of the rig floor to house the new bucking unit and pipe transfer system. Furthermore, owing to challenging well designs with increased risk of differential pipe sticking, the paper discusses the complementary design of positioning systems that deliver record vertical lift and horizontal tong movement of 13 ft (4m).

The development of the hands-free bucking unit and integrated pipe transport system clearly illustrates the intrinsic economic value of multi-party collaboration in creating operational efficiencies to reduce pipe process time, minimize or eliminate non-productive time (NPT), and deliver repetitive and predictive outcomes.
Application of an Advanced Data Analytics Methodology to Predict Hydrocarbon Recovery Factor Variance Between Early Phases of Appraisal and Post-Sanction in Gulf of Mexico Deep Offshore Assets
Authors: Gupta S. , Saputelli L. A. , Verde A. , Vivas J. A. , Narahara G. M.
Published: April 2016

Estimated Ultimate Recovery (EUR) is the expected amount of hydrocarbons that can ultimately be produced from a reservoir or group of reservoirs (oilfield) given certain subsurface characteristics and technologies. Usually, the EUR is estimated at different phases during the lifecycle of an E&P asset for a continuous economic assessment. Reduction in uncertainity in EUR estimation due to acquisition and analysis of data during early phases of exploration and appraisal would enable effective decision making process during later phases of development and production. Being able to predict EUR effectively early on in the field lifecycle would improve project viability and enable higher quality investment decisions during latter phases. In this study, EUR variance (?EUR) is computed between the EUR at pre-sanction and the EUR at post-sanction after first oil production. EUR variance is frequently overestimated as several reservoir parameters are unknown or less certain during appraisal phase. This paper presents a novel data-driven methodology to accurately determine ?EUR using known EUR at appraisal phase and data associated to oilfield characteristics, complexity and definition level. The methodology employs multi-variate statistical techniques and optimization procedure to construct a robust EUR estimation model and to identify key drivers that impact ?EUR. The analytical methodology was successfully validated and tested using real data from over 50 large operating assets of the Deepwater Gulf of Mexico (GOM) oilfields. Numerical case studies show the methodology was able to satisfactorily predict ?EUR and potential project train-wrecks with 73 and 85 percent of accuracy, respectively, as well as to identify, rank, and classify those key parameters responsible for both under- and over-estimating the EUR. The proposed model creates opportunities to reduce "appraisal gaps" between pre-sanction and post-sanction EUR and improve the field development planning process in a cost-effective manner. This data-driven methodology has immense potential in deepwater oilfields and other hydrocarbon plays to improve field appraisal and development strategy and also assess other risks in hydrocarbon management.
Europa Umbilical Retermination
Authors: Levar Jason , Seah Han Hsien
Published: April 2016

The Europa Chemical Injection (CI) umbilical was installed at the Mars platform in 1999. Over the past 16 years, many of the umbilical tubes were taken out-of-service due to leaks in the topside termination assembly. The umbilical was reterminated from the Mars platform during July and August of 2015. As a result, 6 out-of-service tubes were restored and the life and functionality of the umbilical was extended. In addition to the operational gains, the effort provided significant savings by mitigating the need for a replacement umbilical and simplifying a future abandonment operation. This is believed to be the industry's first ever topside retermination of an in service, steel tube umbilical.

The success of this offshore operation is significant to Shell and the greater operations community due to anticipated maintenance of aging, steel tube umbilicals like the Europa umbilical. Shell has several other umbilicals which were manufactured and installed in this same time period which may benefit learnings from this activity. It is believed based on engagement with the Europa operating partners that the learnings from this operation may also benefit other deepwater operators.

This first-of-its-kind operation established a best practice procedure to conduct a retermination of an aging umbilical from the platform. A new friction/squeeze clamp design was developed and qualified to 3 times the design load. The allowable squeeze limit of the umbilical was well above the calculated and recommended values. A unique chemical displacement strategy was utilized to partially displace the umbilical to accommodate cutting and welding activities. This strategy utilized S-traps along the umbilical route to prevent chemical backflow which drastically reduced the displaced volume of chemical.

In the current economic climate, operators are looking for ways to prolong the life of their aging assets. This operation is an example of a unique, cost-effective solution to maturing brownfield assets.