bluuebunny/crossref_metadata_2025 huggingface dataset:
The Multi-Column Floater: A Dry-Tree Semisubmersible for Deepwater Offshore Brazil
Authors: Williams Neil , Tahar Arcandra , Finn Lyle
Published: June 2014

This paper presents the Multi-Column Floater (MCF), a dry-tree semisubmersible (DTS) platform concept appropriate for deepwater applications worldwide. The hull geometry is based on cell spar technology where each column consists of several individual vertical sub-columns (or cells). The use of multiple cells to provide column buoyancy results in a design flexible enough to be built anywhere in the world, and can be used to satisfy local content requirements. Hydrocarbons are produced from dry completion wells connected individually to well slots arranged in a rectangular pattern in a central wellbay. The key differentiator between the MCF and other proposed DTS solutions is that in the MCF design the drilling and production risers are supported from a vertically restrained well deck in the center of the MCF, termed the Multi-Riser Buoyancy Can (MRBC). The efficiency of the MCF design is demonstrated by configuring and analyzing the system for a hybrid development consisting of a wellhead DTS and an FPSO in 1,525 m water depth in the Campos Basin offshore Brazil.

Background

Selection of the optimal floating production system (FPS) for a given application depends on several factors, including reservoir characteristics, well-access requirements, payload, water depth and metocean conditions. In water depths greater than 1,500m (beyond the range of conventional TLP technology) a dry-tree semisubmersible (DTS) offers an attractive FPS solution. A semisubmersible hull can be configured for quayside/inshore hull-topsides integration, hook-up and commissioning, thereby eliminating the project risk associated with an offshore lift. Furthermore, dry-trees allow easier well management, reduced OPEX and superior recovery rates than a wet-tree solution. Also, compared to Spars, semisubmersibles provide safer, more efficient wellbay and topsides layouts, while offering similar mooring characteristics.

The development of the dry-tree semisubmersible concept has attracted significant attention from all the major engineering contractors, primarily those based in Houston [1 - 6]. The proposed concepts all support the drilling and production risers using long-stroke riser tensioners, and both hanging and ram style tensioners have been proposed. The design of a semisubmersible hull to support dry trees requires careful consideration of the allowable hull motions so that existing riser tensioner technology may be utilized, and requires integrating the design of the riser system into that of the hull and topsides. Acceptable motions are obtained by a combination of heave natural period control and a large operating draft. A review of current industry efforts and the design challenges associated with the development of a DTS concept may be found in [7].
Relative Permeability Effects on the Miscible CO2 WAG Injection Schemes Trough Compositional Simulations of Brazilian Small Scale Water-Wet Synthetic Pre-Salt Reservoir
Authors: Laboissiere Philipe , Mello Samuel Ferreira , Trevisan Osvair Vidal , Schiozer Denis Jose
Published: June 2014

The present study aims to deepen the investigations of a previous study, in order to rank which variables are more critical to CO2-WAG process Enhanced Oil Recovery and which injection schemes and parameters are more effective when capillary pressure and relative permeability are adapted to Brazilian pre-salt scenario. The methods compared were Water Alternating Gas (WAG) and Hybrid Water Alternating Gas, considering saturation dependent hysteresis modeled through Larsen-Skauge model.

A detailed and reliable Equation of State for oil with high pressure, and unusual natural carbon dioxide content (8.4%) was developed based in published data to match rheology and swelling measurements. The model was a small scale water-wet carbonate/stromatolite reservoir model with the same set of relative permeability and capillary pressure with hysteresis and entrapment data were modeled as basis for pre-salt Brazilian reservoir data. The optimization were analized including hysteresis and entrapment data from the literature.

The reservoir model well constraints for each strategy were meant to be as realistic as possible, the recovery was optimized using an optimization tool, and the cases were analyzed comparatively. The most important effects were ranked and the best injection scheme and parameters were determined for the studied case in order to clear conclusions about the importance of fluid and petrophysical mechanisms for miscible final oil recovery.

Among a series of petrophysical phenomena needing further investigations on their influence on oil recovery, relative permeability is of critical importance. Nonetheless, its representation in reservoir simulation is quite a complicated task. It may incorporate hysteresis effects (at least three different models that can be used), and it may present three-phase behavior (extrapolated from two phase relative permeability experimental data). Just like relative permeability hysteresis, there are at least four different models available to represent three phase relative permeability. In the present work, only Larsen and Skauge model was addressed.

As a consequence of all complexities involved, for some subtle changes in the injection scheme, such as the injector operating restraints, make recoveries sensitive to hysteresis and passive of improvement. Simulations indicated that an incremental oil recovery of about 11%, in both WAG and HWAG schemes when hysteresis was considered compared to no-hysteresis case.

Optimization of well operating conditions and constraints (bottom-hole pressure of producers and injectors, gas and water rate limits) has a significant effect on oil recovery and production rates.
Severe Slugging in Catenary Risers - Simplified Modeling
Authors: Jian Su , Oliveira Junior Jose Vilani , Vaz Murilo Augusto
Published: June 2014

The objectives of this research are: to analyze the effects of the catenary shape during the occurrence of severe slugging and to develop a simplified but accurate mathematical model to calculate the main parameters of severe slugging in a flowline - catenary riser system.

Offshore exploration is achieving new records of ultra deep water petroleum production in subsea oil fields with multiple production wells at different flow rates, multiphase flow, high pressure gradients, and a wide range of flowlines and risers systems spread over the irregular seabed topography, which can lead to the occurrence of severe slugging. Severe slugging is an undesirable phenomenon.

Catenary riser is the most used geometry in the Brazilian offshore deepwater production scenario, and the catenary shape influence over the severe slugging is unknown.

The proposed model, which is based on Taitel´s model (1986), has been modified in order to take into consideration the geometric configuration of the riser in catenary. Therefore, new formulations for the residual liquid fallback have also been proposed and incorporated in the original models for the vertical riser. The developed model has been validated with experimental data of three test cases: being the first one of a vertical riser with 38.1m of length (case 1), the second one of a group of nine combinations of superficial speed of gas and liquid obtained from a catenary riser system with 9.886m height (case 2), and finally the third one being a real offshore system in production of a flowline-riser in catenary, operating in a water depth of 1,250m (case 3).

The obtained conclusion is that the catenary riser geometry has direct influence over the severe slugging cycle, the slug formation pressure, the liquid level inside the system, and the liquid fallback. It was also possible to verify the severe slugging cycle model sensibility to the top side riser angle, separator pressure, riser height, and liquid and gas superficial velocities.

Based on the comparison between the simulation results and the experimental data, it could be concluded that the proposed modified model for the flowline-riser system in catenary may be applied on the simulation of severe slugging with rather accurate precision.
Optimization of Corrosion Resistance and Weldability: A Challenge for Superduplex Filler Metals
Authors: Zinke D. , Hoberg Bernd , Gross Volker
Published: June 2014

The SDSS have been increasingly used in the offshore industry due to their excellent mechanical properties and corrosion resistance properties to the media they are exposed to. The SDSS are mainly used in subsea components such as Christmas Trees, Manifolds, BOP and also for Topside Modules in Platforms. A well balanced chemical composition guarantees the outstanding corrosion and mechanical properties of SDSS material. Ferrite forming elements such as Cr, Mo ensure a high resistance to chloride containing media as well as a high strength. Austenite forming elements Ni and Ni balance the microstructure to 50%. However, the thermal instability increases with the amount of elements and restricts the weldability compared to usual stainless weld metal of the 3xx series.

In particular the GMA-, and SA welding process asks for a specific approach to minimize the tendency to pore formation. This report describes the influence of a fine tuned chemical composition and welding parameters to achieve a sound weld metal along with an optimum in corrosion resistance.

1 Superduplex Stainless Steels

Superduplex Stainless Steels are materials characterized by a microstructure of austenite and ferrite, figure 1. Driven mainly by the offshore industry to increase the corrosion resistance and the mechanical properties enhancement of the conventional Duplex Steels has led to the so called Superduplex Stainless Steels. Main (Super) Duplex Steels are UNS 35750 and 35760. An overview of the chemical composition of usual Duplex steels is given in table 1. These steels are featured, compared to the conventional Duplex grades, by increased contents in Cr (22–25%), Mo (2–4%) and N (0,2 -0,35%), with possible additions of Cu and W. These increased contents lead to a higher corrosion equivalent (Pitting-Index PREN =% Cr + 3,3 % Mo + (0,5 % W) + 16 % N). This does not only improve the pitting (crevice) corrosion resistance in the as welded condition but is beneficial for a higher strength level as well.

Superduplex Stainless Steels show a PREn > 40. The heat affected zone (HAZ) was already experienced as the weakest part in conventional Duplex joints. A sufficient high N-content (> 0,20%) is badly required, to control embrittlement by grain grow and increased ferrite contents in the heat affected zone, even more for Superduplex Stainless steels.
Deepwater Floating Production Systems in Harsh Environment - a Look at a Field Development Offshore Norway and Need for Technology Qualification
Authors: Meling Trond Stokka
Published: June 2014

Deepwater field developments are regarded as standard technology in several areas of the world such as offshore Angola, Brazil and in Gulf of Mexico, but in very harsh environments no deepwater fields are put in production yet. When moving into harsher environment the extreme design loads becomes more challenging, but the increased fatigue loading may be just as important when selecting concept for field development. Especially riser and mooring solutions are vulnerable to the loading conditions in harsh environment. In the present paper key challenges for developing deepwater fields in harsh environment will be addressed. Development solutions that are working very well in more benign environments may not work as required in the deepwater harsh environments offshore Norway and Shetland. Careful reviews must be carried out to assess current technology status and applicability of selected technology in new environment settings. The Aasta Hansteen deepwater field development offshore Norway will be used to illustrate the drivers for the concept selection. Necessary steps to qualify the concept for sanctioning will also be highlighted.
Workflow For Wellbore Integrity Analysis During Reservoir Development
Authors: Fontoura Sergio , Lautenschlager Carlos Emmanuel Ribeiro , Righetto Guilherme Lima , Inoue Nelson , Albuquerque Rafael Augusto do Couto , Goncalves Clemente Jose , Alcure Marcos
Published: June 2014

Oil wells are engineering structures that should last safe and sound for decades. Its integrity should be guaranteed not only during drilling but also throughout the life of the reservoir. Reservoir production generates stress changes within the reservoir as well as throughout the surrounding rocks. These stress changes cause displacements and strains around existing wells that may lead to undesired casing deformation and eventually to its failure. The aim of this paper is to describe the geomechanical workflow to deal with wellbore integrity during the life of the reservoir. The stress and displacement fields developed during reservoir production are evaluated through the use of a coupled stress-flow analysis. Since the stresses are defined within large volumes of rocks, a special workflow has to be followed in order to define the stress field at the scale of the wellbore. It is presented an application example of a real reservoir considering a blackoil model containing producer and injector wells. It was made a submodel analysis around the producer well, considering the results of two global models simulated using one and two-way partial coupling. The results showed the workflow applicability and the importance of employing a rigorous fluid mechanical methodology in well integrity analysis.

Introduction

Current challenges in the extraction of hydrocarbons include the exploration of deep reservoirs, which are often part of highly complex geological scenarios, as well as the drilling and completion of wells, in broad spectrum of directions, in such formations. From the geomechanical point of view, the problematic of wells and reservoirs is often distinctly addressed, mainly because of the scale difference between such entities. Although the system behaves in an integrated way, the association of the phenomena involved in the analysis of wells and reservoirs is frequently neglected. The wells are linear constructions whose geomechanical behavior is closely related to the stress state of the rock which is going through, to the fluid employed during drilling, to the drilling direction and to the casing type. By the activities performed through the well, the reservoir undergoes significant changes in its equilibrium configuration, once the production (or injection) of fluid in the porous medium causes significant variations in their pore pressure and therefore in its stress state. Nevertheless, the reactions of the reservoir to the effects of development are not concentrated only within its borders, but they spread through the adjacent rocks, many of which are crossed by wells that propel the geomechanical changes. Clearly, there is what may be called well-reservoir system, since the behaviors of entities involved are not independent of each other, mainly due to the aforementioned stress state morphology.
Arctic Operations Handbook JIP
Authors: Wiersema Ed , Lange Frank , Cammaert Gus , Sliggers Frank , Jolles Wim , van der Nat Clemens
Published: June 2014

The Arctic Operations Handbook Joint Industry Project (JIP) was set up in 2012 with a focus on the operational activities for transport and installation of fixed, floating and subsea units, as well as for dredging, trenching, pipe laying and floating oil and gas production in Arctic and cold weather conditions. The prime purpose of the JIP was to identify gaps in the existing standards and guidelines. Specific recommendations were subsequently proposed which will hopefully contribute to the development of internationally accepted standards and guidelines.

The project addressed safety and sustainability of offshore operations in the Arctic. This investigation into existing rules, regulations, standards and guidelines was intended to provide a common understanding for the offshore industries. Work groups were formed to execute work packages which were judged to be of prime importance.

Taking into account numerous aspects of the impact of the Arctic on various operations it was considered that the overall risk levels for such operations can be reduced by adopting the outline recommendations including, for instance, those related to weather monitoring and forecasting, environmental impacts, logistics, equipment preparation, vessel operations, training and health and safety management.
Quantile Regression as a Tool for Investigating Local and Global Ice Pressures
Authors: Spencer Paul , Morrison Tom
Published: June 2014

In the companion ATC 2014 paper by Morrison and Spencer, the quantile regression data processing technique was introduced. In the current paper, we use the technique to estimate the local pressure trend at various quantiles, namely 90%, 99% and 99.9% and to revise the recommendations in ISO 19906 (ISO International Standard. Petroleum and natural gas industries—Arctic offshore structures). In addition we make recommendations on the form and parameters of the random pressure distribution for use in Monte-Carlo methods. The quantile regression method is also used to analyse global pressure data for wide structures for both the Baltic ice measurements and the Arctic ice measurements and compare with the expressions provided in ISO. The alternative statistical analysis provided in this paper indicates that changes to the ISO formulations are required.

Introduction

In the companion paper (Morrison and Spencer, 2014) the quantile regression method of analysing data was introduced. The example data set was the local pressure for ice crushing failure (Masterson et al. 2007), who used least-squares regression along with binning of the data in deriving the design pressure guidelines. This result has been incorporated into an offshore structure standard (ISO, 2010). Using this data set it was shown (Morrison and Spencer, 2014) that a fuller picture of the data could be obtained using a method that does not require binning or grouping of the data. As was also demonstrated, the power-law fit parameters determined using the quantile regression are different from the recommendations contained within ISO (2010).

In this paper we use the quantile regression approach to estimate what would be an appropriate probability distribution function for the ice crushing pressure at local scale and to produce new recommendations for local design pressure at a range of quantile, or equivalently a range of probabilities of exceedence. In addition we use the quantile regression method to analyse the data used in generating the Arctic global and the Baltic global pressure recommendations given in ISO (2010) and to compare with the ISO recommendations.
Arctic Offshore Islands - Lessons Learned
Authors: Hewitt Kevin
Published: June 2014

Five general categories of offshore structures incorporating granular material (‘islands’) have been utilized in the Beaufort Sea, primarily in the 1970's and 1980's. Although each concept has generally served its purpose, there have been many issues both during construction and during operations. This paper reviews the major issues by referring to three specific case histories.

Introduction

Five general categories of offshore structures incorporating granular material (‘islands’) have been utilized in the Beaufort Sea. Such ‘islands’ include sandbag retained islands, sacrificial beach islands, gravel islands (mainly in the U.S. Beaufort Sea), caisson retained islands and a water ballasted caisson on a berm. The majority of these structures, which total close to seventy, were constructed in the 1970's and 1980's. Apart from a few more recent production islands, these structures were primarily constructed to support exploratory drilling operations. Although the majority of these islands were in water depths less than 10 metres (approx. 30 feet) some hybrid islands have been successfully constructed in depths up to 31 metres (approx. 100 feet).
Magnetic Tomography Method (MTM) &ndash A Remote Non-destructive Inspection Technology for Buried and Sub Sea Pipelines
Authors: Kolesnikov I.
Published: June 2014

Magnetic Tomography Method (MTM) Technology is developed by R&D Center "Transkor-K" (Russia) for assessing safety and integrity of pressurized pipelines of any purpose made of ferromagnetic materials. Quality of assessment is not influenced by transported product (gas-, oil-, water-, or other). MTM is based on the inverse magnetostrictive effect (Villary effect) - the change of the magnetic susceptibility of a ferrous material when subjected to a mechanical stress. Method uses " natural" magnetization of the ferrous pipes by magnetic field of the Earth. MTM equipment remotely registers magnetic field from the pipe while moving along its axis. MTM does not measure the dimensions of geometric defects alone but instead it measures the stress caused by these defects and identifies their type, location and orientation in accordance with the location and orientation of the area of stress. MTM determines the comparative degree of danger of defects by a direct quantitative assessment of the stress-deformed state of the metal.
Station-Keeping in Ice – Normative Requirements and Informative Solutions
Authors: Pavel Liferov Pavel
Published: June 2014

The present paper addresses station-keeping in sea ice. Both design and operational measures are considered. Normative framework is reviewed and informative solutions to satisfy and document the requirements are presented.

Introduction

This paper concerns station-keeping in ice, with focus on design which relies on operational measures. Floaters in ice can generally be categorized as shown in Table 1, depending on how much ice and how many icebergs they are expected to meet during their operating life.
Opportunities and Challenges for Arctic Oil and Gas Development
Authors: _ _
Published: June 2014

As climate change renders the Arctic increasingly accessible, there has been a substantial uptick in industry interest in the region; it is believed an estimated $100 billion could be invested in the Arctic over the next decade. The Arctic contains vast oil and natural gas reserves—the U.S. Geological Survey estimates the Arctic could contain 1,670 trillion cubic feet (tcf) of natural gas and 90 billion barrels of oil, or 30 percent of the world's undiscovered gas and 13 percent of oil. Energy companies are certain to be at the forefront of Arctic development and investment.

Climate change has played an important role in expanding access to the Arctic region, although there have been fewer opportunities to access lower cost oil and gas plays. As conventional production has declined, industry has had to focus more on difficult-to-access and unconventional oil and gas plays throughout the world, including those in the Arctic. Exploration and development in the Arctic requires expensive, tailored technologies as well as safeguards adapted to the extreme climatic conditions. In the wake of the 2010 Deepwater Horizon incident, there have been additional costs associated with emergency response and containment requirements.
The Arctic Oil Spill Response Technology – Joint Industry Program
Authors: Mullin Joseph V.
Published: June 2014

An enormous body of scientific research and testing has been conducted in the past 50-years on the techniques and technologies available for responding to oil spill in icy conditions, including spills in the Arctic. To build on this existing research and continue improving the technologies and methodologies for Arctic spill response, nine international oil and gas companies (BP, Chevron, ConocoPhillips, Eni, ExxonMobil, North Caspian Operating Company (NCOC), Shell, Statoil, and Total) established the Arctic Oil Spill Response Technology - Joint Industry Programme (JIP). The goal is to advance arctic oil spill response strategies and equipment as well as to increase understanding of potential impacts of oil on the marine environment. This JIP has brought together the world's foremost experts on oil spill response research, development, and operations from across industry, academia, and independent research centres to undertake the technical work and scientific studies. Research projects are being conducted in six key areas: Dispersants, Environmental Effects, Trajectory Modelling, Remote Sensing, Mechanical Recovery, and In Situ Burning (ISB). Solid progress has been made with technology assessments identifying and summarizing the state-of-the-art in dispersants, remote sensing and ISB being completed.
Simultaneous Dual Vessel Marine 3D Seismic Acquisition in Baffin Bay, Greenland
Authors: Makhorin M. , Fontana P. , Podshuveyt N. , St. Peter, D. , Smit Polarcus F. , Williams T.
Published: June 2014

Amongst the many challenges confronting the acquisition of towed streamer marine 3D seismic data in arctic regions is the limited operational time windows afforded by poor weather conditions, sea ice conditions, and restricted periods of air gun operations due to environmental regulations.

During the summer of 2012, a large 3D towed streamer survey was undertaken in Baffin Bay, West of Greenland. The full desired survey area was approximately 8,650 km2 and was located in water depths ranging between 280 and 820 meters. Due to environmental restrictions related to the Greenland Narwhal whale migration period, the survey was permitted for only 76 days of air gun operations. During that period the area was infested with icebergs and berg remnants.

Given the time restrictions and expected challenges of towing streamers in proximity to moving icebergs, a number of seismic data acquisition techniques designed around the use of two streamer vessels were combined to maximize the 3D seismic coverage over the primary pre-plot area within the short acquisition window.

In this paper, we will describe the dual vessel acquisition geometry, the techniques used to mitigate seismic interference between the two vessels, and the ice management techniques used to ensure the safety of the vessels and the towed equipment while maximizing acquisition time. These techniques proved very effective in that 7,175 km2 of 3D data was acquired over the priority areas at average production rate of just over 94 km2 per day.

This experience demonstrates that similar techniques may be applied in other geographical locations with short time windows available for marine seismic data acquisition, especially where free movements of streamer vessels are limited due to floating ice.
Next Generation to Break the Ice -The Oblique Icebreaker
Authors: Hovilainen M. , Uuskallio A. , Romu T.
Published: June 2014

In the early 1990's Russia was looking for the possibility to build a new oil export channel from the Timan — Pechora area through a pipeline to a port located in the Gulf of Finland. Various port options were studied and the final export harbour location was decided to be in Primorsk, Russia in the Eastern end of the Gulf of Finland. From Primorsk the crude oil would be shipped to commercial markets by tankers

Already at that time it was seen that the increased oil transportation in the Baltic Sea would mean larger size tankers. This led to new requirements for the of icebreaking operations to assist the vessels, which are wider than the assisting icebreakers. With the existing icebreaker fleet two icebreakers are needed to create wide enough channel for one tanker.

To avoid using two icebreakers and reduce the operation cost, one vessel would need to be able to make both wide and narrow channel. The oblique icebreaker concept was developed in the mid 1990's by Aker Arctic (at that time Kvaerner Masa Yards Arctic Research Centre - MARC). The idea is to use one single vessel with two operational modes; normally bow / stern ahead or in an oblique angle. This would enable the vessel to create both narrow and wide channel.

The oblique operation would mean that the ship hull is not symmetric. The general requirements in asymmetric ship design has forced to new thinking also in other areas, which in turn has re-opened the commonly used solutions and designs. The new unconventional concept has opened wide range out-of-the-box possibilities also in other areas, such as oil spill combatting, ice management in harbours and offshore.

The novel concept has seen many stages of development and now it is becoming reality as Russian Ministry of Transportation decided to order the first oblique icebreaker in 2011 for Baltic operations. The first vessel (NB508 at Arctech shipyard) is under construction, when this paper is being written. The operation of the new concept will also be a learning process for the captains and will in time further reveal new possibilities for the vessel use.

Experience from the design of the Baltic version is used to further develop the concept for Arctic use. The Arctic version was introduced to public in May 2013.

This paper shows the technology behind the vessel under construction and also shows major principles of the concept and introduces the new possibilities of the oblique ship concept.
Discrete Element Method Helps Determine Load Levels for Ice-Capable Jackups
Authors: Di Shaocheng , Ji Shunying , Liu Jiancheng (Jessie) , Yu Han-Chang
Published: June 2014

Ice-capable jackups can offer mobility and efficiency while drilling in shallow, ice-infested waters. However, the industry has limited experience operating jackups in ice environments, and technology gaps and uncertainties remain when assessing ice loads on multi-legged jackup units.

The Graphic Processing Unit (GPU)-based Discrete Element Method (DEM) can be applied to investigate the degree of ice effects on multi-legged jackup units. In previous applications, the DEM method was used to simulate ice interaction with structures, but computations were limited to simple interactions. Introducing a GPU platform enables a substantial increase in the number of elements characterized so that the interaction of multi-legs and ice can be modeled with greater efficiency. For example, level ice modeled with 3-D bonded spherical elements can address the buoyancy, current effects and drag force encountered in harsh environments. Additionally, the parallel bonding approach and de-bonding criteria are used to model level ice freezing and breakage.

In this investigation, the global ice loads on a jackup unit's single leg are analyzed to determine the effects of ice thickness, ice strengths and drifting velocities. The estimated ice loads are validated against full-scale data acquired from one application in Bohai Bay. Further, the mechanism of the interaction between the multiple legs and level ice is analyzed using the large-scale GPU-based simulation, the effects of sheltering and jamming are investigated and the ice loads simultaneously acting on the multiple legs are estimated to determine the total shear force and overturning moment.
Numerical Simulations of Ice Forces on Moored and Thruster-Assisted Drillships
Authors: Sayed Mohamed , Kubat Ivana , Wright Brian , Millan Jim
Published: June 2014

The present work examines the loads on moored/DP-assisted drillships and their responses in managed pack ice. Numerical simulations are used to determine deformations and stresses within the ice cover and the movements of the vessel. The results give ice forces and moments on the vessel, as well as its surge, sway and yaw responses. The drillship assumed in this simulation work has a length of 230 m, a beam of 42 m, and a mass of 100,000 Mt. Simulations examine a case representing a moored vessel in a managed ice field consisting of 50 m floes that are 1 m in thickness, moving at a constant speed of 0.3 m/s. For ice moving along the surge direction, the peak surge force was approximately 2 MN. The corresponding maximum surge was 1.5 m. A parametric study further examines several aspects of ice interaction with the vessel. The results quantify various effects of ice management (the role of floe size), ice thickness and drift speed, the direction of ice movement, and stiffness of the mooring system. A case of combined mooring and thruster-assisted mooring is also examined. The additional contribution of the thrusters (or control of the DP system) is shown to somewhat reduce the offsets of the vessel. The work presents a methodology for evaluating the stationkeeping performance of vessels in managed pack ice and quantifying the role of the mooring/DP system characteristics.
A Decision-Support System for Ice/Iceberg Surveillance, Advisory and Management Activities in Offshore Petroleum Operations
Authors: Tiffin S. , Pilkington R. , Hill C. , Debicki M. , McGonigal D. , Jolles W.
Published: June 2014

Seismic, coring, drilling, and supply operations in ice- and iceberg-infested zones require large quantities of environmental and operations related information which should be available quickly and conveniently to the operations and ice advisory personnel. Specialized software is available to support ice advisory work, generate ice charts, and ice and iceberg drift forecasts. Specialized instruments are available for ice hazard tracking and the safe deployment of these instruments by aircraft and UAVs. This paper describes a toolkit that is being developed to bring together currently available systems into one convenient package. This will assist a ship or rig's OIM and officers and ice advisory team members by providing clear displays of the current situations with respect to the location and movements of ice in the proximity of the operations site. The system will improve the response time of forecasts, efficiency of work and quality of decision-making by OIM and their support personnel. This toolkit will be a decision-support system, which will forecast ice, keep track of hazardous ice features, provide alarms for any and all environmental conditions that might threaten the operation, and assist in planning of new operations. The paper describes the need for such a system, best practices in Ice Observation and Advising, the key system design criteria; main system components, inputs and outputs; the stages of development, the modes of application that will achieve acceptance in the field; and finally, the benefits. Experiences of ice advisory projects undertaken in the Beaufort Sea, Baffin Bay, Sea of Okhosk, and the Caspian Sea are described.

Rather than simply describe Ice Advisory work in the field, the paper casts current practice into the framework of standardized and best practices, and indicates how software, communications and instrumentation technological advances can be applied to support better decision making by expert teams that are distributed in space and involve people from different job functions and skill sets.
The MARENOR Project – Maritime Radio System Performances in the High North
Authors: Kvamstad B. , Bekkadal F. , Grythe K. , Jensen I. , Haakegaard J.E. , Behlke R.
Published: June 2014

This paper describes the main objectives and early achieved results from the MARENOR project. MARENOR is financed by the Research Council of Norway as well as Norwegian industry partners from oil and gas (EM survey company EMGS), fisheries (shipping company and shrimp trawler Remoy), positioning and navigation suppliers (Kongsberg Seatex and Polar Science Guiding) and telecommunication service suppliers (Telenor Satellite Broadcasting). Academic partners are MARINTEK, SINTEF ICT, University of Svalbard from Norway and Wroclaw University of Technology from Poland. MARENOR was kicked off in February 2012 and will end in February 2015. Test equipment for measuring system performance of navigation and communication systems in the High North has been installed at two vessels (Atlantic Guardian and Remoy) and at Kjell Henriksen Observatory at Svalbard. The data to be measured include performance parameters from navigation and communication systems, ionospheric parameters, atmospheric parameters, ship movements and positions.
Arctic Port – Relocatable
Authors: Lewis James C.
Published: June 2014

Abstract: Arctic Port – Relocatable

The requirements for deep water Arctic Marine Port are undeniable. It is possible to provide safe harbor and configure the port to fit the requirements of the endeavor. For Arctic offshore drilling and development operations, this port can be designed to provide safe harbor and be re-locatable. By a system of ship-like rectangular GBS type structures, a safe area can be constructed so that there is no ice movement and shelter from large wind storms. The structures would be constructed in the Pacific Rim and towed to the site of the new port. They would then be ballasted into position. The units would be designed to accommodate the shallow waters of the near shore Arctic seas. In addition, the individual units could be configured to serve multi-functions in the exploration and development of offshore hydrocarbon fields
Qualification of Flexible Fiber-Reinforced Pipe for Ultra-deepwater Applications - Update on Phase 1 Engineering and Phase 2 Prototype Testing
Authors: Salimi A. , Kalman M. , Yu L. , Liu J. , Joshi R.
Published: June 2014

This paper presents the result of the Phase 1 engineering study for a RPSEA sponsored project to develop, qualify, and field deploy flexible fiber reinforced pipe (FFRP®) for ultra-deepwater applications. In addition, the Phase 2 qualification testing scope of work is presented. FFRP is unbonded flexible pipe with composite reinforcement layers which has the advantages of light weight, high flexibility, and corrosion resistance. Due to these advantages, a simple, low top tension riser configuration is enabled. The design basis is a 7-inch ID, 690 barg design pressure, 120°C design temperature, 3048 meter design water depth production riser for a Gulf of Mexico application. The Phase 1 Engineering Study confirmed the product and system design to be employed in the subsequent phases. In Phase 2, a prototype pipe will be manufactured, and qualification testing will be conducted in accordance with API RP 17B recommendations. With successful testing, and subject to approval via a Phase 2 decision stage gate, Phase 3 will be an actual field deployment of the riser system with six months of performance monitoring.

Included in the paper is a summary of the Phase 1achievements and task deliverables. Due to its high level of importance, a relatively large portion of the paper is dedicated to the design of the FFRP structure and system, covering final pipe cross section arrangement, the riser system configuration and the results of analyses to provide a reliable prediction of the product's behavior in various working conditions. In addition, a review of the Phase 2 plan is presented. The outcome of the on-going phase 2 qualification testing will be utilized to calibrate the design models and to confirm the suitability of the pipe design, and the riser configuration.
HPHT Formation Evaluation : Planning For Success via a Structured Approach
Authors: Owens J.
Published: June 2014

Successfully delivering HPHT well information objectives can be achieved through a robustly planned formation evaluation programme by applying the principles of a project maturation process. The following discussion outlines a pragmatic approach that compliments many existing corporate project planning systems which adopt a front end loaded philosophy. The goal is to deliver maximum value in a safe manner through a structured planning, execution, application and learning cycle (PEAL).
Wax Deposit Surface Characteristic under Single-phase and Water-in-Crude-Oil Flow Conditions
Authors: Panacharoensawad Ekarit
Published: June 2014

The deposit surface roughness has a direct impact on the pressure drop of turbulent flow in flow lines. Currently, an arbitrary roughness value for the deposit roughness, typically the pipe roughness value, or reference measured pressure gradient is used in deposit thickness calculation models. During the process of wax deposition the topology of the deposit surface is expected to change. Therefore, the assumption of a constant pipe roughness for the deposit interface can result in inaccurate deposit thickness estimation. This paper presents the results of an experimental study on the surface characteristic of the single-phase and two-phase dispersed water-in-oil flow wax deposits. South Pelto crude oil was used for the deposition test. The tests with water cuts of 0, 16, and 35% were conducted. The general observation from the turbulent flow tests is that the deposit near the test fluid inlet side exhibited a patchwork pattern and the deposit sloughing occurred due to undeveloped flow. However, under the fully-developed flow conditions the deposit surface was found to be visually smooth in most cases. Specifically, the deposit surface of (1) the single-phase fully-developed flow cases where 3300 = Reini = 4300 and (2) the fully-developed flow region in all 16% water cut cases was found to be visually smooth. The deposit surface for laminar emulsion flow with 35% water cut displayed many stream-like grooves.
Deepwater Construction Vessel ‘Aegir’ Shifting the Frontiers of Reeling
Authors: van der Graaf Jan , van Zandwijk Kees
Published: June 2014

Description of the material

In the coming decades a significant rise in ultra-deepwater developments is expected. In 2013, Heerema Marine Contractors brought its multi-purpose Deepwater Construction Vessel ‘Aegir’ in operation with the aim to maintain and extend its position in this rapidly expanding market. The paper will focus on the novel concept of the vessel with a fully revised view on pipe reeling logistics.

Application

The vessel is equipped with exchangeable reels, a concept enabling to keep the pipelay vessel in the field during its pipeline reeling operations. This efficiency gain will induce a step change in the economics of reeling. The presentation will illustrate how the functional requirements were translated into the specific lay-out of the vessel and how the requirements of the reeling system played a dominant role in this.

Many of the future deepwater oil and gas fields will be in open ocean waters. A number of novel features have been included in the design to ensure a good workability of the conventional hull-shaped Aegir in long ocean swells, in particular where it concerns the lifting of reels on board the vessel, in order to ensure continuous reeling operations.

Introducing the new pipelay concept with exchangeable reels required the design of new industrial processes for filling the reels at a spoolbase and transporting them to the Aegir. The separation of the reel spooling and transport from the pipelay vessel offers new opportunities for tuning the logistics process to specific project needs.

Results, Observations and Conclusions

The paper will discuss the properties of the vessel and the pipe lay system, the test results, performance of the off-line spooling process and performance in the field.

The market shows appetite for the new reeling concept: meanwhile, two major subsea construction projects have been landed for the Aegir, both making use of exchangeable reels. It will be illustrated how the different settings of these projects lead to different logistic concepts.

The paper will also touch upon the first in field experience with Aegir.

Significance of Subject matter

Subsea Field development, in particular the ultra-deep, HP/HT fields require Game changing Vessel concepts like Aegir to be able to serve the operators. Also when they decide to move to water depths beyond 10,000' with flow lines requiring top tension lay-capacity of 2000tn in remote areas of the world.
Study of the Effect of Condensate Tie-back on Wax Deposition in an Indonesian Offshore Crude Oil Pipeline
Authors: Singh A. , Lee H. , Singh P. , Sarica C.
Published: June 2014

A gas condensate field was tie-backed to an existing subsea pipeline transporting paraffinic crude oil from an Indonesian offshore production system where wax deposition was a primary flow assurance challenge. As expected, condensate addition did alleviate the challenge of both wax deposition and waxy oil gel restart of the commingled pipeline. Pipeline operating data including pigging frequency, transient flow rate and pressure drop were analyzed to estimate average wax deposit growth rates for the condensate line and the commingled line for various blends of oil and condensate liquids.

Flow rate, pressure drop, inlet and arrival temperatures, and seabed temperature data were used to validate thermo-hydraulics of the system. A numerical scheme was developed to eliminate noise in the data and calculate deposition rates between two consecutive pig runs for condensate and commingled pipelines for various blends of the condensate and oil. Detailed laboratory analysis of fluids was performed for their wax deposition potentials (including high temperature gas chromatographic, wax appearance temperature, wax content, density and viscosity). Wax characteristics have been used in an in-house Wax Deposition simulator to predict the wax deposition rate under various operating conditions.

For the condensate liquid, wax deposit surface roughness was found to significantly contribute to the pressure drop increases, and therefore, increase in the measured pressure drop cannot be solely attributed to deposit thickness increase. For the commingled fluid system, the simulator predictions using the Film Mass Transfer Model (FMTM) with aging reasonably matched the deposit thickness obtained from the field data. For the condensate liquid system, both FMTM and Equilibrium Model (EM) were assessed and it was confirmed that the predictions from the two models bound the wax deposition rate calculated from the field data.
Lessons Learned - Counter-acts Used To Install Pipelines Offshore In Very Soft Clay
Authors: Olsen Christian , Brown Neil , Rosborg Anne , Sørensen Carsten S.
Published: June 2014

As part of the Ormen Lange Northern Field Development, 36 large diameter steel cylinders were used as counter-acts to ensure pipeline stability during pipe-lay along route curves. The Ormen Lange field is situated 120 km off the mid-Norwegian coast of the Norwegian continental shelf at the base of the Storegga landslide. Due to the Storegga landslide, the soil conditions vary significantly with a stratigraphy characterized by very soft Holocene clay overlying very stiff clay till. Locally, the clay till outcrops at seabed level. The water depth is in excess of 800 m and the seabed topography is highly irregular. This makes the development of the Ormen Lange field very challenging. Ormen Lange came on stream in 2007, and the operator is A/S Norske Shell. Ormen Lange is the second biggest offshore gas field and the deepest subsea production facility in Europe. The gas is exported through one of the world's longest pipelines, and the gas-export in peak production equivalents 20% of the UK's gas demand.

The chaotic seabed topography and variable stratigraphy presented several unusual geotechnical design challenges. Stability charts were constructed based on a parametric study considering slope gradient, counter-act inclination and penetration of the skirt plate. With use of these design charts, decisions were made offshore to relocate, install additional counter-acts or increase the pre-load the counter-acts with use of a steel clump weight. The counter-acts were designed with an internal lifting mechanism, which allowed for safe installation in the harsh environment. Furthermore, optimization of counter-act locations removed the requirement for a costly subsea rock installation campaign. The methodology proved to be robust and this paper presents lessons learned for design, installation and retrieval of counter-acts in harsh environments on a soft seabed.