The purpose of this paper is to introduce various offshore platform conceptsthat can be employed in ice infested waters, particularly shallow waters,depths varying from 65 ft to 500 ft. The paper illustrates five innovativeplatform concepts that for arctic drilling. The proposed platform conceptswould have ability to withstand extreme ice, wind, wave and temperatureconditions to extend the drilling seasons either near to winter sever storm orfor round the year operation. The platforms are designed to operate indifferent water depths in different part of the arctic by accommodating thedrilling structures and equipment on the deck. The emphasis is on theefficient of breaking, moving ice sheets around the structure and withholdingthe topside loads. Some of the platform concepts are fixed and others aredeveloped from the floating solution and the technical details are presented inthis paper.
Producing and delivering North West Australia (NWA) deepwater gas reserves to LNG plants poses unique challenges. These include extreme metocean conditions, unique geotechnical conditions, long distances to infrastructure and high reliability/availability requirement of supply for LNG plants. A wet or dry tree local floating host platform will be required in most cases. Whereas semisubmersible, TLP, Spar and floating LNG (FLNG) platform designs all have the attributes to be a host facility, none has been installed in this region to date.
This paper will address important technical, commercial and regulatory factors that drive the selection of a suitable floating host platform to develop these deepwater gas fields off NWA. Linkages between key reservoir and fluid characteristics and surface facility requirements will be established. A focus will be on the unique influence of regional drivers and site characteristics including metocean and geotechnical conditions, water depths and remoteness of these fields.
There have been 17 FPSOs producing oil in Australian waters. These facilities have been chosen because of the remoteness of the fields and the lack of pipeline and process infrastructure. Storing oil on the FPSO for offloading and shipping from the fields becomes an obvious solution. Semisubmersible, TLP or Spar platforms show little advantage in such developments.
For deepwater gas developments, the product has to be processed, compressed and piped to shore for liquefaction. As host processing facilities, Semisubmersible, TLP and Spar platforms have clear advantages over FPSOs because of their superior motion performance in the harsh Australian metocean environment and other benefits such as facilitating drilling, dry tree completion and well services. FPSOs or FSOs may be applied for storage of associated oil and condensates. For marginal and remote gas field developments, an LNG FPSO (FLNG) may be an attractive option as it eliminates long pipelines and land-based liquefaction plants.
As discussed by Dorgant and Stingl (2005), a deepwater field development life cycle following discovery usually involves five distinct phases, Figure 1. The "select?? phase occurs after a discovery has been appraised sufficiently to further evaluate it for development. It consists of evaluating multiple development concepts and scenarios and selecting the one that will most likely achieve the identified commercial and strategic goals. Selecting a floating platform and its functions for a deepwater development is an important subset of the select phase and the overall field development planning.
The process of field development planning involves a complex iterative interaction of its key elements (subsurface, drilling and completions, surface facilities) subject to regional and site constraints (D'Souza, 2009). The objective is to select a development plan that satisfies an operator's commercial, risk and strategic requirements. It entails developing a robust and integrated reservoir depletion plan with compatible facility options. The selection occurs while uncertainty in critical variables that determine commercial success (well performance, reserves) is high. One of the challenges is to select a development plan that manages downside reservoir risk (considering the very large capital expense involved) while having the flexibility to capture its upside potential.
Hong, Sa Young (Maritime and Ocean Engineering Research Institute (MOERI)) | Kim, Jin Ha (Maritime and Ocean Engineering Research Institute (MOERI)) | Kim, Hyun Joe (Daedeok Ship R&D Center, SSMB, Samsung Heavy Industries, Co., Ltd.)
Lu, Haining (School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Xiao, Longfei (School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Li, Xin (School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Xie, Wenhui (China National Offshore Oil Corp. Research Center)
Cargo-transfer and underway replenishment are essentially important in long-term naval operations. The Office of Naval Research (ONR) initiated a technology development program in 2007 called STLVAST (Small to Large Vessel At-Sea Transfer). The goal of this program is to develop ‘enabling capabilities’ in the realm of logistic transfer (i.e. stores, equipment, vehicles) between a large transport vessel (e.g., the USNS Bob Hope) and a smaller T-craft ship, using a Deep Water Stable Crane (DWSC) spar between them. The DWSC spar consists of two entities, a catamaran craneship and a detachable spar. In this paper, a new numerical scheme to simulate time-domain motion responses of floating systems has been successfully proposed and applied to the motion response control of the DWSC spar. The equation of motions using the Impulse Response Function (IRF) is initially discretized into a new state-space model, where the first order and second order waves loads transfer functions are calculated from WAMIT. Two time steps affect the construction of this state-space model: the time step Δτ used to estimate the IRF, and simulation step Δt. The LQR method is selected in this study. Firstly, the effects of both time step on the controlling efficiency is studied. Then various weighting factors (Q,R) for the LQR controller are further considered to study the robustness of the LQR method. INTRODUCTION The Cargo-transfer and underway replenishment are essentially important in the long-term naval operations. The Office of Naval Research (ONR) initiated a technology development program in 2007 called STLVAST (Small to Large Vessel At-Sea Transfer). The goal of this program is to develop ‘enabling capabilities’ in the realm of logistic transfer (i.e. stores, equipment, vehicles) between a large transport vessel (e.g., the USNS Bob Hope) and a smaller T-craft ship, using a Deep Water Stable Crane (DWSC) spar between them.
Jameel, Mohammed (Department of Civil Engineering, University of Malaya) | Khaleel, M. (Department of Civil Engineering, University of Malaya) | Saiful Islam, A.B.M. (Department of Civil Engineering, University of Malaya) | Ahmad, Suhail (Department of Applied Mechanics, Indian Institute of Technology Delhi)
Hong, Sa Young (KORDI Daedeok Branch, Korea Ocean Research & Development Institute) | Kim, Jin Ha (KORDI Daedeok Branch, Korea Ocean Research & Development Institute) | Hong, Seok Won (KORDI Daedeok Branch, Korea Ocean Research & Development Institute) | Kim, Hyun Joe (Daedeok Ship R&D Center, SSMB, Samsung Heavy Industries, Co., Ltd.)
The Spar platform has developed into a well functioning solution for Gulf ofMexico environment. Considering use of this solution in the North Atlantic, themetocean conditions differ by long period swell and fatigue induced by normaloperational seas.
In order to meet these challenges, it is desirable to consider a classic Sparthat is more fatigue redundant than a truss, but the swell requires highnatural periods, to avoid parametric heave-pitch resonance.
A new version of the Spar in response to these requirements is the Belly Spar.It can be considered as a classic Spar with a Belly; starting below the wavesurface and extending down to the hard tank depth. A concrete Spar concept withreduced waterline diameter has also been developed by Aker Solutions for arcticapplication. This concept had the dual benefit of increasing the natural periodin heave as well as reducing the ice load from sea ice
The concept has been developed for a field in the Norwegian Sea, in water depthof 1,200m (4,000ft). The hydrodynamic analyses show excellent performance,however contain assumptions on damping. The design has been by model testing ofthe design in wave and current combination representing 10,000yr events, asshown by results and correlations in the paper.
The design opens up new areas for the Spar platform, with good motions that canaccommodate steel catenary and top tensioned risers. As for previous Sparconcepts, the application is in deepwater and ultradeepwater.