There has been considerable interest in deepwater opportunities offshore Newfoundland and Labrador (NL). The significant discovery of Mizzen, Harpoon and Bay du Nord fields by Statoil and partner Husky Energy, as well as the regional seismic data and metocean characterization projects by Nalcor, has generated industry interest in the area resulting in successful calls for bids in the deepwater region by the Canada Newfoundland Offshore Petroleum Board (CNLOPB) in 2014 and 2015. With the recent exploration license activity and significant deepwater discovery, the potential for further exploration and near-term development is rapidly approaching. There has been extensive operations experience and research and development within the shallow waters of continental shelf Jeanne d'Arc Basin over the past 40 years. With the progression of opportunities for exploration and development in deep water, the operations experience and applied research proven in shallow water can be utilized and adopted to deep water. The technical aspects of Remote Sensing, Ice Engineering, Ice Management and Geotechnical Engineering will be reviewed and discussed in the context of deepwater developments and opportunities for enhancement of technology will be presented.
A floating platform in deep water Eastern Canada is required to withstand iceberg loads and/or be disconnected and towed away only in the event of very large approaching icebergs, leaving the mooring lines and risers in-place, support large topsides and provide large quantities of oil storage in the hull. Additionally, the platform should provide low motion response to storm and ice loads to maximize the operational uptime and facilitate the use of a large number of different riser systems including steel catenary risers (SCR).
This paper presents the details of a Disconnectable Concrete Spar FPSO platform that has been configured to satisfy all the above requirements and is able to be constructed locally in Eastern Canada. The paper describes a number of key features of the Spar shaped hull, mooring and riser systems that are specifically designed to withstand large iceberg loads and other environment loads while maintaining the characteristic low motion response to storm environments. The design helps to minimize disconnection frequency due to approaching icebergs and disconnection may only be required for very large icebergs or ice islands. Additionally, the system has been designed to minimize disconnection and reconnection time.
An analytical approximate approach for determining periodic solutions and identifying parametrically nonlinearity of sheltered riser vessel (SRV) motion equations involving three degrees of freedom is investigated. The cubic stiffness and square damping involved nonlinearity describing both of sloshing and piston phenomena of SRV motion are taken into account in motion equations. The iteration scheme of motion is established by incremental harmonic based method. The nonlinear parameters are identified according to deduced iteration scheme, which shows good convergence with numerical solution. Utilizing the developed IHB based method, the nonlinear parameters involving in motion of SRV are identified. The developed parametrical identification methodology exhibits good computational effectiveness and can be utilized in strong nonlinear and multi degrees of freedom occasions.
This paper details two fatigue analysis approaches, that is, time history and spectral fatigue analyses for truss spar under in-place and trans-ocean dry tow environmental conditions. For the efficiency of in-place time history fatigue damage calculation, a method to condense the sea-states is introduced based on a closed form solution of the fatigue damage calculation. The typical fatigue hot-spot locations of the deepwater Truss-Spar are identified. The barge structural flexibility effect on the tow fatigue analysis results is summarized. A real Truss-Spar platform successfully installed and operated in the Gulf of Mexico (GOM) more than 10 years with water depth greater than 3000 feet is presented. Since this deep-water platform had successfully withstood the major hurricanes (e.g., Ivan, Katrina, Rita, and Ike) and is still operating subjected to under-water inspections as per the requirements of BSEE, it had been proved that the original fatigue analysis approaches are practically conservative and the fatigue strength of the platform is adequate.
Poll, Philip (Houston Offshore Engineering) | Park, Y.C. (Williams Field Services) | Converse, Robin (Williams Field Services) | Godfrey, Dan (Williams Field Services) | Gian, Michael (Gulf Marine Fabricators)
Historically, Spar hulls have been compartmented using both flats and radial bulkheads. These hulls were fabricated into quarter or half sections and joined into full cylinder sections then into the full hull length while in a horizontal orientation. This approach left considerable fabrication work to be performed after assembly, disadvantageously, due to the horizontal position.
The configuration of the Gulfstar FPS reduces the number of radial bulkheads by locating the flats closer together, thus opening up the option to fabricate full cylindrical sections upright with open tops for ventilation and access during fabrication. Rotating each cylindrical section for final assembly was not required until all possible work, inside and out, on each section had been completed. This fabrication plan leaves only structural and systems tie-ins between sections once blocks are rotated and set in place.
Vertical fabrication of sections starts an overall structural arrangement philosophy to develop a configuration that is not only repetitive and efficient but also "fabrication friendly." The idea for improving constructability permeated other aspects of structural design. The purpose of this paper is to summarize some of the ways in which the Spar structure was arranged to improve fabrication and to evaluate the expected improvement with actual fabrication experience. This paper presents the genesis of the basic framing then culls out and discusses some notable lessons learned.
The information and results presented in this paper are applicable to engineers, designers and fabricators when evaluating structural arrangements and fabrication options for stiffened plate hulls, particularly Spar hulls. Cost and schedule benefits can potentially be achieved by incorporating some of the lessons learned presented in this paper.
Decent profit margins enjoyed by the oil industry are mainly due to inexpensive wells of the past. Exploration, development, and production costs have escalated to a level where small to medium size offshore fields are challenged to be economically developed. Each opportunity comes with its own unique constraints requiring adaptive and flexible applications from a variety of processes and systems. The art of field development engineering requires linking interactive and integrated flow of information, best practices, lessons learned, and risk management across all disciplines. This starts with reservoir evaluation and development through surface facilities and transport systems, and production management. Further considerations include finance, procurement and contracting strategy, equipment standardization, and decommissioning. Success of economically challenged field development depends on an experienced team with deep understanding of each respective domain and appreciation in interfacing disciplines. Such a team using a systematic approach challenging each constituent system and process in the field development procedure chain will help identify an optimum development plan.
In this paper, the strategy, technology, and step changes necessary for successful development of economically challenged fields are identified. The inter-dependence between sub-surface, drilling and completion, and surface facilities including production and operations are established in relation to cost, safety, and risk management. This paper will discuss a systems approach for prudent selection of all surface facilities and drilling and completion design taking due account of reservoir uncertainty.
The primary focus of this work is deep water fields of Gulf of Mexico (GOM) with strong analogs for application in other regions of the world including regional socio-political impact. High level discussion on the main drivers of the selection of deep water platforms, subsea architecture, and risers are presented.
Between 2005 and 2010, three major events led to a significant increase in design demands of deepwater field developments in the Gulf of Mexico (GoM): Category 5 hurricanes Katrina and Rita (2005), The Macondo well blowout (2010), and The development of deeper, tighter, more remote reservoirs
Category 5 hurricanes Katrina and Rita (2005),
The Macondo well blowout (2010), and
The development of deeper, tighter, more remote reservoirs
These events have resulted in increased metocean criteria, new safety regulations and functional requirements associated with producing deeper, higher pressure and lower porosity reservoirs. This paper will examine and contrast the design impacts on Tension Leg Platform (TLP), Semi-submersible and Spar floating platforms before and after these events. The overall impact of these new requirements on topsides, hull, station-keeping and riser systems of recently sanctioned TLP, Semi-submersible and Spar platforms will be compared with pre-2005 sanctioned platform analogues to demonstrate the resulting impacts on platform size and cost.
Increased demands of post-2005 sanctioned GoM floating platforms have resulted in higher deck elevations, greater topsides payload, more robust station-keeping systems and larger hull displacements. Further, the feasibility of proven risers and well systems is challenged by the higher wave induced motions associated with greater design and survival sea-states and high pressure reservoirs. The design impacts of pre- and post-2005 sanctioned TLPs (Mars A, Olympus), Semi-submersibles (Atlantis, Jack St. Malo) and Spars (Tahiti, Lucius) on topsides, hull, station-keeping and riser systems will be compared and differences explained.
This paper will enable Operators and platform designers to: Appreciate the magnitude of impact on size and cost of floating platforms of post-2005 requirements, Understand the relative impacts on the three major hull types commonly used for GoM developments, and Update analogues and norms used in benchmarking and concept selection
Appreciate the magnitude of impact on size and cost of floating platforms of post-2005 requirements,
Understand the relative impacts on the three major hull types commonly used for GoM developments, and
Update analogues and norms used in benchmarking and concept selection
This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 24511, "Deepwater Floating Production Systems in Harsh Environments: A Look at a Field Development Offshore Norway and the Need for Technology Qualification," by T.S. Meling, Statoil, prepared for the 2013 Offshore Technology Conference Brasil, Rio de Janeiro, 29-31 October. The paper has not been peer reviewed. Copyright 2013 Offshore Technology Conference. Reproduced by permission.
Deepwater field developments are regarded as standard technology in several areas of the world, but in harsher environments, extreme design loads and increased fatigue loading become more challenging. In particular, risers and mooring solutions are vulnerable to loading conditions in harsh environments. Development solutions that work well in more-benign environments may not work as required in deepwater harsh environments such as those offshore Norway.
Floating production systems in harsh environments have long been in operation, but have been limited to water depths of 400 to 500 m. Deepwater floating production systems have been in operation in benign environments such as offshore Brazil, west Africa, and the Gulf of Mexico (GOM) for almost 2 decades. After Hurricanes Katrina and Rita, the design level for the GOM has been increased, and one can argue that the GOM is no longer considered a benign environment. But tropical-storm areas such as the GOM have significantly less dynamic loading in general than harsh-environment areas such as offshore Norway.
Currently, Statoil and its partners OMV and ConocoPhillips have sanctioned the gasfield development Aasta Hansteen in 1300-m water depth in the Norwegian Sea. Field developments are moving into deeper waters in some of the harshest conditions in the world.
Concept Selection: Deepwater Floating Production in Harsh Environments
Aasta Hansteen is a rich gas field located 300 km from shore. It consists of three reservoirs, and the drainage strategy is pressure depletion. Dry trees offer no benefits; therefore, the field will be developed with subsea trees, seven in total, tied back to a floating production facility. There is also a limited amount of condensate present.
The plant processing capacity is higher than needed because the development opens a new area; the production facility will be used as a hub. The treated gas will be exported through a new approximately 500-km-long pipeline to Nyhamna for final processing and further export (Fig. 1), and the produced water will be cleaned and disposed of at sea. However, the small volumes of condensate caused some challenges for concept selection. Economically, the condensate is more of a burden than a value because a solution is required for the limited production. Export through the pipeline was not feasible from a flow-assurance standpoint; and, because the closest existing facility with storage capacity is 150 km away, a separate condensate- export pipeline was not attractive either. Therefore, local storage of 25 000 m3 of condensate and offloading was required at the lowest possible cost.
This paper explores and discusses the interplay between field development and lifecycle reservoir management and the selection and operation of dry or wet tree host systems for the development and production of deepwater oil and gas fields. Drawing on insights from recent Shell deepwater projects, the selection criteria related to development and reservoir management are highlighted and discussed to portrait the advantages and limitation of the two different host concepts. The paper does not attempt to expand on the engineering and construction elements of either option.
With Pre-salt area being a massive new offshore oil frontier, there is a high demand for deepwater floaters for both drilling and
production. There are some unique challenges related to the ultra-deepwater (water depth beyond 1500m) and the Brazilian
environment for the pre-salt area. Various floater concepts have been evaluated with specific focus for Offshore Brazil
This paper provides an overview of the current technology related to dry tree solutions as well as discussion of the pros and cons
of various concepts. The paper also discusses some new concepts emerging in the industry attractive for Offshore Brazil.
A dry tree solution has the advantage of direct access into reservoirs from the floaters. This allows the operators to drill, complete
and workover the well directly from the same hosting unit. The result could be increased reserves and productions in Offshore
Brazil as well as significant cost reduction. Proper validation of the concepts and technology qualification of all the
systems/components associated with novel technology, establish the basis for a safe and successful project implementation while
reducing potential risk to personnel, environment and property.
DNV has established processes to systematically evaluate new concepts and new technologies, e.g. Approval in Principle (AiP)
and Technology Qualification (TQ). A brief introduction to these processes is included in the paper and how they support the
development of these new concepts.