In this issue... Spring/Summer 2004

Transcription

1 Spring/Summer 2004 Evaluation of an Extendable Draft Platform. The Extendable Draft Platform (EDP) is a unique concept developed by Technip that offers the benefit of complete outfitting at dockside and minimal assistance during installation. Oceanic Consulting Corporation recently conducted an extensive model test program to evaluate the overall performance of the platform. Included in the program were tests to evaluate the stability and motions of the EDP under tow during pre-service transportation, as well as experiments to investigate vessel response during the 100-year hurricane and 1-year winter storm conditions when installed on site. In addition to a seakeeping evaluation, a structural load evaluation was conducted to investigate the forces and moments at the pontoon/column and deck/column interfaces. Measurements included motions and accelerations on the EDP, forces and moments at the column/deck and column/pontoon interfaces, as well as mooring and riser tensions. Further seakeeping and structural evaluations of the concept by Technip indicated a very good correlation with the model test results. The full program was conducted in the IOT 200 Meter Towing Tank and the Offshore Engineering Basin (OEB). The testing program provided some interesting technical challenges. In particular, the requirement to accurately measure the forces and moments at the interfaces of the main components. This was overcome through the use of some novel dynamometry design. Overall, the program was a success as Technip obtained valuble and reliable information that they can now use as they continue to enhance their concept and Oceanic increased its experience with novel deepwater platforms. Shawn Searle shawn_searle@oceaniccorp.com In this issue... Evaluation of an Extendable Draft Platform. Charting the Course: Spring/ Summer Preparing Sakhalin II for Mating. Flume Tank Aids Study of Vortex Induced Motions. Evaluation of a Mini Spar Concept. New Research in Escape, Evacuation and Rescue. Researcher Computes Ice Loads on Offshore Structures. Tandem Offloading Vessels and the Problem of Coordinated Control. Evaluation of Single Point Mooring Systems. Deepwater Moorings. Researching Vortex Induced Vibration. Journal Publications and Conference Papers. Personnel on National/ International Committees. MI 22 Meter Flume Tank Facility Specifications.

2 Charting the Course: Spring/Summer The Avalon Peninsula clings to the east coast of Newfoundland like a starfish holding a rock, with four legs stretched out into the Atlantic Ocean. The one connecting it to the rock called Newfoundland is the Isthmus of Avalon, and from that thin strip of land one can literally watch the Newfoundland offshore oil industry grow. On a clear day, you can see the first player in the industry, the North Atlantic Refinery in the small town of Come by Chance. Just beyond is the Whiffen Head transshipment terminal in Placentia Bay where crude oil is brought from the Hibernia and Terra Nova oil fields some 225 nautical miles away. As shuttle tankers travel up Placentia Bay, they pass the Cow Head Fabrication Site near Marystown where the SeaRose FPSO is being outfitted for operations at the White Rose oil field. Looking north, you can see Trinity Bay. The Hibernia gravity base structure was built at Bull Arm in the bottom of the bay. A few years later Terra Nova, Newfoundland s first FPSO, was outfitted at the same site. Unlike Placentia Bay with its year-round ice free water, Trinity Bay is exposed to the North Atlantic and for a good part of the spring is covered with pack ice and icebergs. What you can t see from the isthmus is what makes Trinity Bay most interesting. It is deep. Trinity Bay is so deep, in fact, that it is really an underwater canyon that leads out of the bay right to the Orphan Basin, likely the site of some of the most lucrative offshore oilfields in the western hemisphere. The Orphan Basin, with 2200 meters of water, 20 meter wave heights, 150 knot winds, multimillion tonne icebergs and substantial pack ice, is also likely to prove to be the most technologically challenging offshore site in the world. This newsletter demonstrates how Oceanic and its partner organizations, the Institute for Ocean Technology and Memorial University, are up for the challenge. On the cover you will read about our work for Technip Offshore in assessing its Extendable Draft Platform. On the facing page and in previous issues of Making Waves you will learn about flume tank evaluations of spars for the same company. Unique deepwater sites require unique solutions and Oceanic has been working with some of the world s leading experts in developing solutions for deepwater sites around the world. We are now able to bring those lessons home to work on projects off our own coast. While our deepwater projects off the coast of Africa and in the Gulf of Mexico may not have ice problems, the work we do for the east coast of Russia does. Testing has been carried out in the IOT 90 Meter Ice/Towing Tank for a Single Buoy Moorings project off Sakhalin Island. Evaluating mooring loads in both ice and waves assists Oceanic in building a capability that can be integrated with our deep water work as we help our own industry in the Orphan Basin. Our research efforts are also helping to broaden our capability to support the growth of our industry. Efforts are being undertaken at MUN and IOT in escape, evacuation and rescue. Work at IOT is expanding our knowledge of ice loads on offshore structures. Working with IOT and MUN personnel, Oceanic is continuing to build its capabilities in modeling deepwater moorings. There is an expression in Newfoundland that says, What goes around comes around. It is usually used in reference to revenge on practical jokers, but it is also relevant here. Oceanic and its partners learned much about the offshore industry by working on Hibernia and Terra Nova. We took that experience and nurtured it on projects for Africa, the Gulf of Mexico, Sakhalin Island and Southeast Asia. Now we will need all those lessons for Newfoundland s Orphan Basin, and beyond. For Oceanic Consulting Corporation Best Regards, Dan Walker, Ph.D., P.Eng. President

3 Preparing Sakhalin II for Mating. An extensive, four phase test program has been completed for the transportation and float-over installation of a topsides unit for the Sakhalin II project. Phase 1 of the test program was conducted in the IOT 90 Meter Ice/Towing Tank to determine drag forces on the transportation barge. Using Oceanic s Planar Motion Mechanism (PMM), drag on the barge was tested in 15 increments for a full 180. Phase 2 of testing was conducted in the IOT Offshore Engineering Basin (OEB), in which the seakeeping properties of the transportation barge with topsides was evaluated in regular and irregular waves. After completion of the transportation tests, the next two phases of testing focused on the float-over and installation of the topsides. Phase 3 of testing was again conducted in the IOT 90 Meter Ice/Towing Tank to identify the effect of the GBS on the barge current drag loading. The drag of the transportation barge was tested in open water, and then in place on the GBS. Results of the tests were then used to determine the correct force vector to apply to the model to simulate current loading during the next phase of testing. The final and most extensive testing phase was conducted again in the OEB. The objective of Phase 4 was to determine the force interactions between the barge, topsides and GBS structures. The testing in this phase was broken into five stages. The first stage of these tests was designed to determine fender loads at the mating pull-in stage. To optimize the fender design, barge fenders were tested with three different spring rates. Starting at the pull-in stage, with the topsides supported wholly by the transportation barge and with clearance between the topsides and the GBS, the barge was ballasted in stages until the topsides were fully supported on the GBS, with clearance between the barge and topsides. The second, third and forth stages of testing investigated the interactions of the three bodies at different stages (0%, 50% and 100%) of load transfer from the barge to the GBS. At the fifth and final stage of this phase of testing, the topsides were fully supported by the GBS and there was clearance between the barge and topsides. A further series of tests were conducted on the same models in deeper water. The GBS structure was extended upwards and tests at two of the float-over conditions (pull-in and 100% load transfer) were repeated. Specialized mechanical devices were necessary to replicate the mechanical properties of the fendering, support and mating systems, and to accurately record force loading. In particular, to match the polymer materials of the leg mating system between the topsides and GBS, a system was designed with the specified non-linear spring properties. Tim Moore tim_moore@oceaniccorp.com Flume Tank Aids Study of Vortex Induced Motions. Testing of SPARs in the MI 22 Meter Flume Tank offers several unique opportunities for the study of Vortex Induced Motions (VIM). As the Flume Tank allows tests to be conducted for a long duration, phenomenon such as beat envelops in the VIM can be observed. In addition, the underwater viewing gallery of the tank provides a unique opportunity for flow visualization. Oceanic Consulting Corporation has recently completed a third set of SPAR VIM tests in the MI 22 Meter Flume Tank and the IOT 200 Meter Towing Tank. A control set of test runs was conducted in both tanks, the results of which indicated a good correlation between the tests conducted in the two facilities. The Flume Tank also offers the possibility of creating sheared flow profiles for testing deep draft vessels in wind generated currents. Phase 1 of the testing, involving the creation of sheared flow profiles, has shown promising results and Phase 2 of development is scheduled for March The primary focus will be to investigate simple methods of producing various shear flow profiles. Once completed, Phase 2 of the shear flow development should provide Oceanic with sufficient information to produce wind generated surface currents with relative ease. A secondary focus for Phase 1 was placed on increasing the efficiency of the uniform flume flow. Several minor inefficiencies were identified during this phase of testing and improvements were implemented during the regularly scheduled annual maintenance. John Monk john_monk@oceaniccorp.com Tim Moore tim_moore@oceaniccorp.com

4 Evaluation of a Mini Spar Concept. In a recent test program, Oceanic Consulting Corporation evaluated a proposed Mini Spar for SparTEC Inc. The Mini Spar is a floating production platform designed to support a marginal, deepwater field development with topside payload in the range of s. tons. The experiments were conducted with a spar model moored in the upright position while the model was subjected to simulated environments for various headings. During testing, measurements included spar motions, deck accelerations, air gap, green water occurrence, global shear force at the structural interface between the topside and the mid-body and mooring line tensions for each of the environmental conditions investigated. In addition to the in-place testing, a series of Vortex Induced Motion tests (VIM) were performed in the 200 Meter Towing Tank. The environmental conditions included regular and irregular waves, current and wind. In total, four different stroke configurations were examined for intact and damaged moorings, as well as for intact and flooded hull compartments. Vessel responses during the wave testing were proportional to the environment being tested. The hurricane environments were most severe with larger, more frequent motions experienced. The ten-year winter storm had some moderate vessel responses but the magnitudes were significantly reduced, while the one-year storm produced little significant vessel motion. John Monk john_monk@oceaniccorp.com New Research in Escape, Evacuation and Rescue. A multi-year, multi-partner collaboration on escape, evacuation and rescue (EER) is forging ahead with model test programs, numerical models and field trials. The project is managed by NRC s Institute for Ocean Technology and Memorial University s Engineering Department, with stakeholders in industry, government, training centres and regulatory agencies. The EER team is embarking on experimental testing related to life-craft survivability and rescue in different weather conditions. Of particular interest are the basic motion characteristics and ability of the life-craft to execute maneuvers related to rescue. The more recent experimental work, together with numerical modeling, will be incorporated in the Survival Craft Simulator being developed at the Centre for Marine Simulation. The project moved a step closer to the prototype stage when funding was received in January from NSERC under the i2i (idea-to-innovation) program. Several months ago, the EER team conducted full-scale trials of lifeboat deployments at the Offshore Safety and Survival Centre in St. John s. That data, along with data from previous physical model experiments, was used to validate the 3-dimensional numerical model developed for the same systems. In January 2004 the EER team boarded the drilling rig Galaxy II for time trials in the launch of the vessel s lifeboats. Over the last year the team conducted a comprehensive set of experiments on the freefall lifeboat system in order to benchmark its performance in a range of weather conditions. EER personnel also examined lifeboats in ice-covered waters and waves in order to establish basic performance limits and the effects of additional power on the lifeboats operations. All of this information is being added to the project s database, which continues to be developed and upgraded by NRC s Canadian Institute for Scientific and Technical Information. The information gathered will be used to formulate guidelines for government and industry approval of safety equipment. The database is available at Antonio Simoes Re antonio.simoes_re@nrc-cnrc.gc.ca Brian Veitch bveitch@engr.mun.ca

5 Researcher Computes Ice Loads on Offshore Structures. With increased oil and gas activity off the coast of Newfoundland and Labrador, the risk for collisions of ships, offshore structures and marine installations with ice is real. The probability for a severe accident (with significant environmental, human and capital liabilities) is increased by the fact that the environment off the Canadian East Coast is harsh and hazardous, with heavy sea states, wind and fog. Designing offshore structures and ships to withstand impact ice forces is a major concern for structural engineers and naval architects in the arctic and sub-arctic regions. In nature, there are various discrete ice masses, such as bergy bits and growlers, and there are various continuous ice features, such as sea ice sheets, pack ice and ice ridges. At some point all of these interact and contact offshore structures, marine installations and ships. The dynamic response of a structure to a collision with a discrete ice mass is considerably different than its response when interacting with an ice sheet at low indentation speed. Dr. Ahmed Derradji of the NRC s Institute for Ocean Technology has developed what he calls the universal failure theory for ice. The theory was developed after analyzing the results of over 500 tests on ice involving sea ice, iceberg ice, fresh water ice and laboratory grown ice. These test results were obtained from the open literature and included the work of ice researchers in various laboratories in North America and Europe over the last 30 to 35 years. In a way, Dr. Derradji s theory is an extension of the traditional failure criteria developed for metals and geo-materials (rocks and soils) over the last 200 years. The universal theory has been implemented into ANSYS, a commercially available finite element analysis code. It has been validated against measurements of ice loads on the piers of the Confederation Bridge to PEI and on the Kemi-I lighthouse in the Gulf of Bothnia, between Finland and Sweden. In both cases, the capability of the universal model to predict actual ice loads was proven. Dr. Derradji has also investigated ship-ice collision forces and ice ridge impact forces on a cylindrical GBS destined for the waters around Sakhalin, Russia. He is also involved in an effort to secure collaboration and funding to study the effects of ice on a proposed fixed link between Newfoundland and Labrador. Ahmed Derradji ahmed.derradji-aouat.@nrc-cnrc.gc.ca Tandem Offloading Vessels and the Problem of Coordinated Control. Researcher Jim Millan has been discussing with FPSO operators the problem of controlling tandem offloading vessels. The difficulty lies with moored, dynamically positioned FPSOs offloading to similarly positioned shuttle tankers. The operation poses risks due to the close proximity of the two large vessels. Any number of factors can disrupt the offloading procedure, including excessive motion of the shuttle tanker, dynamic positioning operator error and abnormal interaction between the positioning and power management systems, to name a few. The NRC s Institute for Ocean Technology researcher says the consequences of these problems can vary from excessive fuel consumption to incidents that could endanger life, the environment or the vessels. The solution, he believes, lies in increased automation through the use of a supervisory controller to coordinate the control systems on the two vessels. Also required is an improved method of analyzing and validating the entire control framework. Millan has devised three approaches to the investigation, beginning with numerical analysis and the development of software tools. The second is scale-model testing to explore the efficacy of supervisory control systems versus independent controllers. The third approach is full-scale trials, now under discussion with offshore operators. Here, data will be collected from ships operating in multi-vessel systems and then compared with the model-scale results and numerically implemented systems. The research has potential benefits for a number of groups, Millan says. They include control equipment manufacturers, vessel operators and regulatory agencies. Jim Millan jim.millan@nrc-cnrc.gc.ca

6 Evaluation of Single Point Mooring Systems. Oceanic Consulting Corporation recently completed a test program to evaluate the proposed Single Point Mooring (SPM) system for installation in Aniva Bay, Sakhalin Island, under the Sakhalin II Phase 2 Project. The SPM consisted of a Tanker Loading Unit (TLU) to which a generic Suezmax Tanker was moored. Phase 1 included the evaluation of the tanker motions and TLU response to open water environmental conditions. Current, wind and waves were simulated for a range of operating environments, from normal operations to greater-than-maximum design conditions. Testing in the IOT Offshore Engineering Basin (OEB) allowed for wind and waves to be modeled at various directions relative to current. During OEB testing, measurements included motions at the tanker CG, summer and winter oil offloading manifolds, as well as yaw response of the rotating TLU head and mooring hawser loads. During one test, a simulated tug load was also Deepwater Moorings. applied to the stern of the tanker to examine its effects on tanker directional stability. Phase 2, conducted in the IOT 90 Meter Ice/Towing Tank, evaluated the performance of the TLU and tanker in ice conditions typical of the installation area. Ice floes ranging from 60 Meters - 7/10 coverage to 300 Meters - 9/10 coverage and level ice were all examined for ballast and loaded tanker conditions. Qualitative and quantitative evaluation of tanker motion, TLU ice loading, and interaction between hawser and offloading hose was undertaken. With the TLU attached to the Planar Motion Mechanism (PMM) of the Ice Tank carriage, specific ice drift patterns were simulated. Modeling of straight-ahead, gradual (30 ) and sudden (90 ) ice drift shifts allowed for force and motion analysis as well as identification of specific operating issues. The tests demonstrated that the proposed SPM system is capable of operating in the environmental conditions identified for the installation location. Paul Herrington paul_herrington@oceaniccorp.com Physical modelling of floating structures moored in deepwater poses unique challenges in the representation of the mooring lines. Limitations of basin depths require that either the model scale must be very small, or that a full depth model mooring must be replaced with a mooring system offering an equivalent response but requiring less basin depth. Ultra-small scale models (1:150 and less) are restrictive in the level of detail and instrumentation that can be used. Wave making at these scales is generally restricted to survival sea states, and does not allow fatigue testing. Larger model scales (1:30-1:60) allow greater detail, range of instrumentation and sea states, but require an equivalent mooring system that will react in the same manner as a full depth system. an equivalent mooring system developed by Noble Denton Europe. Noble Denton used a numerical modelling program to develop mooring and Steel Catenary Riser systems in 2000ft and 3000ft depths that have an equivalent response to the design systems in 10,000ft. Oceanic built physical models of the 2000ft and 3000ft moorings and SCRs at two model scales. These lines were then tested with identical top connection point motions and the response was compared. The tests verified that the systems in shallower water did produce equivalent force responses at the top connections, invariant of scale or depth. Some challenges still remain in understanding and matching the unique material properties of synthetic (polyester) mooring lines. As part of the DEEPSTAR ( research project, Oceanic has recently tested Don Spencer don_spencer@oceaniccorp.com

7 Researching Vortex Induced Vibration. Oceanic Consulting Corporation has researched vortex induced vibration (VIV) of risers for the DEEPSTAR and VIVArray Joint Industry Projects (JIP). A number of areas for improvement were identified after initial testing and were addressed in Phase 2 to make a more versatile and reliable apparatus for general high Reynolds number VIV research. For instance, the stroke was increased to allow larger amplitude ratios, and forced VIV testing of a cylinder with amplitude ratios of 1.1 was recently completed. Significant improvements were also made in the free vibration setup including higher amplitudes, a better two degree-of-freedom setup, and lower overall system damping. The towing linkages were redesigned to minimize cylinder rotation induced by the vertical motion of the cylinder and tests confirmed the same response for towing and pushing directions. Improvements have been made to the control system allowing better control of damping and smoother forced oscillations. As well, pre-assembly of major subsystems has streamlined installation, shortening basin time and reducing costs. Journal Publications and Conference Papers. Mukhtasor, Husain, T., Veitch, B., Bose, N. (2004). An ecological risk assessment methodology for screening discharge alternatives of produced water. Accepted for publication by J. Human and Ecological Risk Assessment. Sadiq, R., Husain, T., Veitch, B. and Bose, N. (2004). Evaluation of generic types of drilling fluids using a risk-based analytical hierarchy process (AHP). Environmental Management (In press). Niu, H., Husain, T., Veitch, B., Bose, N. (2003). Transport properties of offshore discharged synthetic based drilling cuttings. Oceans 2003, San Diego. Sadiq, R., Husain, T., Veitch, B., Bose, N. (2003). Distribution of arsenic and copper in sediment Commercial and fabricated strakes have been tested in free vibration mode, in forced mode, and in free vibration with inline as well as cross flow compliance (two degree-of-freedom). For free vibration testing, two turbulence grids are available giving approximately five and nine percent turbulence. Some of the most interesting results have come from forced VIV tests with bare cylinders at different roughness heights. The tests indicated that roughness was a very significant parameter in determining the response of a bare cylinder. As part of the VIVArray JIP, the first forced tests with a straked cylinder have been completed mapping out areas of high damping at large amplitude ratios. Under the DEEPSTAR JIP the same strake was examined in free motion with two degree-of-freedom compliance. Experiments with a rough cylinder with two degree-of-freedom compliance showed a significantly different response than those with the in-line motion constrained. The new extended data sets show good correlation with the previous DEEPSTAR Phase 1 results. Don Spencer don_spencer@oceaniccorp.com pore water: an ecological risk assessment case study for offshore drilling waste discharges. Risk Analysis, Vol. 23, No. 6, Sarkar, S., Bose, N., Gosine, R., Walker, D., Sarkar, M. (2003). Design and development of autonomous submersible dredger/miner. International Conference on Coastal and Ocean Technology, National Institute of Ocean Technology, Chennai, India. Thanyamanta, W., Hawboldt, K., Husain, T., Bose, N., Veitch, B. (2003). Evaluation of offshore drilling cuttings management technologies using multi-criteria decision making. Environmental Management (in press). Personnel on National/International Committees. Institute for Ocean Technology Bruce Colbourne, Senior Research Officer Chair, Sea Operations Group, Canadian Standards Association Chair, ITTC Ocean Engineering Committee Groups SC7 and SC7/SC9 of the ISO (Marine Operations) Ahmed Derradji, Research Officer Chair, ITTC Ice Committee Pengfei Liu, Research Officer ITTC Azimuthing Podded Propulsion Committee David Molyneux, Senior Research Officer Technical Committee/Canadian Advisory Committee for ISO TC67/SC7 Chair, Organizing Committee, 27th American Towing Tank Conference David Murdey, Director Facilities Chair, ITTC Advisory Committee Chair, 27th American Towing Tank Conference Chair, Host Committee, 25th Symposium on Naval Hydrodynamics Rob Pallard, Technical Officer International Technical Committee of the Offshore Racing Council Eric Thornhill, Research Officer Secretary of the Board, CFD Society of Canada Mary Williams, Director General Chair, NSERC Faculty Awards Selection Committee Chair, Multidisciplinary Committee, Canadian Foundation for Innovation Memorial University Neil Bose, Canada Research Chair in Offshore and Underwater Vehicles Design Chair, ITTC Specialist Committee on Powering Performance Prediction NSERC panel for evaluation of Strategic Projects Chair, Canadian Atlantic Branch of RINA Brian Veitch, Associate Professor SNAME Education Committee ITTC Specialist Committee on the Assessment of Ocean Environmental Issues Oceanic Consulting Corporation Dan Walker, President Atlantic Innovation Fund Canada s Shipbuilding and Industrial Marine Advisory Committee SNAME Planning Committee

8 MI 22 Meter Flume Tank Facility Specifications: Length Width Depth Max. Water Velocity at Max. Water Depth Max. Velocity of Moving Ground Plane 22m 8m 4m 1m/sec 1m/sec Debris Screen Fishing Net Undergoing Testing Underwater Video System 20m x 3m Observation Window Remotely Operated Towing Masts 4.7 Tonne Crane Net Loft Tank Filtration System Electric Drive Motors Impellers and Diffusers Moving Belt Ground Plane Wave Damper Flow Straightening Screen Water Turning Vanes Flow Straightening Devices Tests Performed: Flow Visualization of Submerged Bodies Hydrodynamic Force Measurement Assessment of Fishing Gear Configuration Vortex Induced Motions Directional Stability Spar Motions Towed Vessels Specification Sheets are Available for all Major Facilities, Including: IOT Offshore Engineering Basin IOT 200 Meter Wave/Towing Tank OERC 58 Meter Wave/Towing Tank IOT 90 Meter Ice/Towing Tank IOT Cavitation Tunnel MI 22 Meter Flume Tank MI Centre for Marine Simulation Specification sheets can be obtained from the Oceanic website or by contacting our office. Meet us at: 95 Bonaventure Ave., Suite 401 St. John s, Newfoundland A1B 2X5, Canada Phone: (709) Fax: (709) oceanic@oceaniccorp.com May 3-6, 2004 Offshore Technology Conference (OTC) Booth 1633 June 2-3, 2004 Offshore Newfoundland Petroleum Show Booth 613