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A new polymer gel system developed for high temperature applications has been successfully employed on well H-43 of the Heather Field to isolate a high rate water production zone. The high temperature organic polymer gel system has demonstrated long-term stability when mixed with sea water at temperatures as high as 350 degrees F. Gel times can be delayed allowing a large volume of polymer gelant to be placed. The treatment increased oil production by 300 BPD and decreased water production by 2290 BPD. A production log run eight months later confirmed effective isolation allowing the lower Brent to produce.

The Wave Crest Sensor Intercomparison Study (WACSIS) was designed as a thorough investigation of the statistical distribution of crest heights. Measurements were made in the southern North Sea during the winter of 1997-1998 from the Meetpost Noordwijk in 18 m water depth. The platform was outfitted with several popular wave sensors. Buoys were moored nearby to obtain directional spectra. Two video cameras viewed the ocean under the wave sensors and their signals were recorded digitally. The data analysis focused on comparisons of the crest height measurements from the various sensors and comparisons of the crest height distributions derived from the sensors and from theories. The purpose of this paper is to give an overview of the project.

The statistical distribution of zero-crossing wave heights in mixed sea states is examined by analysing numerically simulated data. Nine different kinds of bimodal scalar spectra are used to study the effects of the relative energy ratio and the peak frequency separation between the low and high frequency wave fields on the wave height distribution. Observed results are compared with predictions given by relevant probabilistic models. Comparisons of the empirical data with relevant probabilistic models reveals that the Rayleigh model systematically overestimates the number of observed wave heights larger than the mean wave height except for one of the cases analysed. None of the models used to predict the observed exceedance probabilities is able to characterise adequately all the cases of bimodal sea states examined.

During offshore pipeline installations there is a possibility of pipe buckling which in turn could cause pipe fracture water ingress to the pipe and even loss of the pipe. The deeper and longer the pipeline the greater the likelihood of this happening. The Blue Stream Project is presented - two 24-inch pipelines from Russia to Turkey across the Black Sea a length of 390 kilometers. The Project is developing a repair system to be used as a contingency system in case of a buckle. The repair system will be capable of operating in water depths down to 2150 meters and in very soft soil. This system includes the Pipeline Recovery Head and assurance work to verify its fitness for purpose to function safely during the pipeline retrieval to surface. Photographs and diagrams appear on pages 13 to 19.

Bio-degradation of oil by micro-organisms is an important long-term process for removing oil from the environment. Bio-remediation is a technique which artificially accelerates this natural process to help remove oil pollution. Lack of information on the effectiveness and potential side effects of this technique has caused Australia to be unwilling to include it in oil spill response planning and operations. Now however the National Plan to Combat the Pollution of the Sea by Oil in conjunction with the Energy Research and Development Corporation has developed a research programme to look at bio-remediation as a clean-up tool. The history of the programme is outlined and its aims are highlighted. The potential value of the technique is discussed.

The container market has become one of the major shipping markets in the world but the demand pattern and the demand for ships in the future are being changed with the introduction of post Panamax container vessels feeder systems and a substantial increase in the reloading of containers (hub systems). Large operators are working through alliances aiming to integrate sea transport port services and land transport to their customers. More can be squeezed out of the liner industry in terms of lower transportation cost per unit and growing competitiveness with new participants likely to enter the scene from Latin America Middle East and Africa based on cheap second-hand tonnage services.

The problems associated with offshore and towage contracts are presented. Potential hazards are also addressed such as the Oil Protection Act 1990 (OPA 90). A brief statistical summary of the number and nationality of tugs entered is included. P & I insurers cannot cover for loss of or damage to wreck removal of the towed vessel or its cargo. There are areas of the world where there are no towage contracts and the tug is exposed to liability for damage caused to the tow. Jurisdiction often brings further problems. The salvor has traditionally sought insurance into the Lloyd's market for his liability as a salvor. However open cover facilities are becoming rare and costly as the Lloyd's market declines. The lobbying activities of groups like the Standby Ship Operators Association and the International Support Vessel Association are welcomed by the industry. There is concern that oil majors are placing unacceptable pressures on tug owners to accept onerous indemnities. The experience of Shipowner's Protection Ltd in personal injury crew towage and collision claims are discussed along with trends in the business. In the spheres of pollution and wreck removal the shipowner's liability is continually being expanded.

In all European countries with shallow coastal waters and strong mean wind speed at the coast the planning and construction of offshore wind farms is on the way. Large parts of the North Sea and the Baltic are under investigation as to whether they are suitable for offshore parks. In this paper it is demonstrated how satellite images taken by spaceborne radar sensors can be used to determine mesoscale wind fields and thus help in the task of planning offshore wind farms. High resolution SAR images acquired by the European remote sensing satellite ERS 2 are presented which show single wind turbines. The derivation of high resolution wind fields from SAR images is explained and comparisons with numerical models are presented.

In order to move forward from the experimental phase the development of WIG craft must move from technology-led to market-led considerations. An economic model is provided to interpolate between the main cost elements of existing conventional boat and aircraft transport so as to explore the commercial expectations which WIG craft must satisfy. Several WIG craft and market scenarios are discussed. Obstacles to commercialism are considered together with the question of how these may change as both technology and market evolve. The commercial viability of the WIG concept is questioned and market entry and development strategy are discussed. Clear cost targets for designers to respond to are provided. (Appendices containing photographs tables and graphs appear on pages 261-262.)

The USCG's (US Coast Guard) current fleet of buoy tenders consists of about 40 cutters of the WLM and WLB classes. The majority of these vessels were built between 1942 and 1944 and have undergone numerous modifications overhauls and renovations in their 50-year service lives. In 1979 the USCG facing increasing costs associated with operating this aging fleet of buoy tenders and increasing pressure to control budget growth by operating fewer ships with fewer men embarked on an ambitious replacement program. This procurement approach resulting from the USCG initiative is discussed and the WLB and WLM designs which were selected for procurements are described. Also discussed are a number of the significant design trade-offs and design drivers and the rational for selection of both the overall ship configuration and specific shipboard systems for the two designs is provided.

This paper reports on a joint DSTO/CRC for Welded Structures (CRC-WS) program to investigate the feasibility and potential benefits and challenges of using API X80 Grade steel in warship construction. The work presented covers the following aspects of the work carried out so far: Phase I - development of a materials/welding technology package to validate fabrication of X80 steel in future RAN warship construction and also for industry demonstrator purposes. Phase II - installation of an X80 steel demonstrator panel in the Landing Craft Heavy HMAS Balikpapan. Phase III - FEA assessment of structural performance and possible weight savings gained through the use of X80 steel in RAN warship superstructures. The paper concludes by giving a brief description of the next steps to be taken in the program.

The Yemen LNG Company (YLNG) formed in order to produce and export LNG (by transporting feed gas from the Marib fields to a liquefying plant and to the Yemen gas Company) has selected a site at Bal-Haf on the Gulf of Aden coast for its LNG Plant a proposed layout is presented. Principle reports commissioned to enable the safe and reliable design of the marine facilities at Bal-Haf are discussed including: preliminary surveys (topographical bathymetric geophysical oceanographic); offshore soils investigation by seismic refraction and sampling (borehole PCPT and surface grab); and environmental baseline survey. Special consideration is given to the acquisition of weather data construction of weather databases and their processing by typical and specific analytical techniques details include: preliminary oceanographical survey; subsequent exhaustive data acquisition using advanced techniques of satellite measurement (altimeter scatterometer synthetic aperture radar) and survey; construction of offshore sea-state databases; achievement of the coastal transfer of the offshore sea-state databases; and correlation between offshore and local winds.

A special modulation format derived from OQPSK (offset quadri-phase shift keying) is applied to digital transmission and a novel practical multichannel receiver architecture is proposed for its demodulation. The receiver is based on the standard adaptive DFE (decision feedback equaliser) which is extended so that both its multichannel feed-forward section and the feedback section operate fractionally spaced. A new decision rule is therefore introduced that exploits the structural properties of this signal type and allows the adaptive filters to be updated twice per symbol. This also enables the receiver to operate in a completely self- recovering or blind manner. To compensate for Doppler effects explicit non-data-aided timing recovery and decision- directed carrier recovery is performed. To demonstrate the performance of the proposed system the receiver is applied to experimental data for acoustic communication in shallow water where the information signal is both emitted by a fixed and a moving source. The modulation format is characterised (section 2). The applied timing recovery scheme is briefly described (section 3). The doubly-fractionally spaced DFE (DFS-DFE) is presented (section 4) where we also derive the decision rule. A short description of the data obtained from an underwater communication experiment is given (section 5). Results of the system’s application to experimental data are presented (section 6).

A common problem in video surveys in very shallow waters is the presence of strong light fluctuations due to sunlight refraction. Refracted sunlight casts fast-moving patterns which can significantly degrade the quality of the acquired data. Motivated by the growing need to improve the quality of shallow water imagery a method is proposed to remove sunlight patterns in video sequences. The method exploits the fact the video sequences allow several observations of the same areas of the seafloor over time. It is based on computing the image difference between a given reference frame and the temporal median of a registered set of neighbouring images. A key observation is that this difference will have two components with separable spectral content. One is related to the illumination field (lower spatial frequencies) and the other to the registration error (higher frequencies). The illumination field recovered by low-pass filtering is used to correct the reference image. In addition to removing the sun-flickering patterns an important advantage of the approach is the ability to preserve the sharpness in corrected image even in the presence of registration inaccuracies. The effectiveness of the method is illustrated in image sets acquired under strong camera motion containing non-rigid benthic structures. The results testify to the good performance and generality of the approach.

Existing simulation methods are not able to determine in detail the wave loads on a complex subsea structure when it is passing through the splash zone. To determine these loads model tests are necessary. Otherwise only simplified formulations or empirical relations for added mass and damping can be used. The iVOF (improved volume of fluid) method presented is a potential candidate for the better numerical prediction of the behaviour of a subsea structure in the splash zone. The iVOF method included in the ComFLOW program is summarised. Then results of simulations with a typical subsea structure in the splash zone are presented. A comparison is made with results of dedicated model tests with the same structure. The comparison gives good insight in the special capabilities of the method. However significant further development and validation is needed before a fully coupled simulation of a subsea structure and its lifting vessel in waves can be carried out. This possibility is also affected by the long simulation times required at the moment. As an intermediate step the method might be used to determine the wave loads and added mass in an uncoupled simulation.

Understanding the spatial and temporal structure of ambient noise is a critical factor for estimating the performance of active and passive sonar systems. This is especially true in warm shallow waters where snapping shrimp dominate the ambient noise spectrum over 6 octaves. A second reason for designing a compact high-frequency data acquisition system is to study dolphin echolocation. A compact high bandwidth (up to 5MSa/s) simultaneous quad channel general-purpose sampling data acquisition system has been developed. It is highly modular and easily reconfigured to suit different acquisition specifications. It permits 3D spatial beamforming on the data collected. Up to four sensors can be connected to the four synchronised input channels allowing the realisations of different arbitrary array configurations. The system is described and some sample data from the dolphin echolocation study is presented. The building blocks of the acquisition system are described together with their possible alternate modules-configuration in respective modules. The performance of the hardware setup used for the echolocation studies is briefly described. The discussion continues with two application examples followed by sample data collected from the dolphin echolocation study. In short the system is a highly modular general-purpose high-speed data recording system that is compact and low cost.

Sea ice thickness is one of the most important parameters for ice engineering problems and climate studies. Apart from IPS (ice profiling sonar) measurements EM (electromagnetic induction) thickness sounding has become an accurate and efficient method for thickness profiling and can be operated on the ice from ships or from structures like lighthouses or oilrigs. However EM sounding is most powerful when operated from helicopters or from fixed-wing aircraft. The accuracy of EM thickness sounding increases with the salinity of the water below the ice. Unfortunately in many key regions for ice-engineering activities the salinity of the water is very low for example in the brackish waters of the Baltic and Caspian Seas. An example of EM thickness measurements in the shallow water of the Bay of Bothnia (northernmost Baltic Sea) is shown using a small helicopter EM sensor and some model results. These demonstrate the particularities of EM sounding in brackish water. It is also shown that accurate ice thickness measurements are still possible with very low salinities of 3 ppt. In addition it is shown by means of model calculation and data that EM ice thickness measurements in shallow water less than 10 m deep are possible with instruments using high frequencies.

It is foreseen that the logistics will be one of the important services in Hong Kong for the next economic evolution. The role of the sea transportation becomes more and more important; it is not only to serve the re-export of the Pearl delta but a key nodal of the sea transportation chain in southeast China. nowadays when the emission from other sources is under control the contribution from marine becomes significant. Currently the local marine emission inventory estimation is following the reference issued in Europe and the United States and no work has been done to verify the accuracy of these approaches in Asian countries. in the last two years preliminary study has been carried out which included a survey of marine activities engine power of vessels and the measurement of ambient pollutants at Tsing Yi area. The result of survey and measurement could show a weak correlation of the concentration of pollutants and the maritime activities globally in Hong Kong region and also locally in Kwai-Tsing region. An alternative method is proposed for estimation of emission inventory using a systematic database of individual engine power of ocean-going container vessels. The result provides additional information on the martime emission to assist and refine the estimation/prediction of the emission inventory of the seagoing container vessels. Furthermore it can assist in the assessment of environmental impact from maritime activities. Better estimation of the marine emission inventory could improve the pollution prediction town planning as well as to enhance theX40694

A behaviour-based scheme for the high-level control of AUVs (autonomous underwater vehicles) is proposed. Two main characteristics are highlighted in the scheme. Firstly behaviour co-ordination is carried out through a hybrid methodology which takes advantage of the robustness and modularity in competitive approaches as well as the optimised trajectories in co-operative ones. Secondly behaviour state- action mapping is learnt by means of RL (reinforcement learning). A continuous Q-learning algorithm implemented with a feed-forward neural network is used. The behaviour- based scheme attempts to fulfill simple missions in which several behaviors (tasks) compete for the vehicle’s control. The feasibility of the scheme is shown with a target following mission designed to be carried out in a pool with the AUV ODIN. Simulation results show the good performance of the hybrid method on behaviour coordination as well as the convergence of the RL-based behaviours. The proposed hybrid co-ordination system is described (section 2). The continuous Q-learning algorithm used for behaviour learning is introduced (section 3). The target following application to test the hybrid co-ordination method is detailed (section 4). Simulation results are presented (section 5). Finally conclusions and future work are presented (section 6).

In offshore construction knowledge about sediment transport dynamics is essential and the quantification of SPM (suspended particulate matter) is of great importance. The Laptev Sea shelf is one of the largest Siberian shelf seas and ice-covered for about nine months a year. In order to use indirect measuring devices for the quantification of SPM concentration on the Laptev Sea shelf optical (turbidity meter) and acoustic (ADCP) (Acoustic Doppler Current Profiler)) backscatter sensors were compared to assess their potential for the investigation of SPM dynamics in an arctic environment. To estimate SPM concentrations from optical backscatter signals these were converted using the linear relation between the backscatter signals and SPM concentrations derived from water samples. By applying the theoretical interaction of sound in the water with SPM the acoustic backscatter signals were transformed adapting a previously established approach. SPM concentrations estimated from the backscattered signals of both sensors showed a close similarity to SPM concentrations obtained from filtered water samples. While the ADCP offers distinct advantages over the turbidity meter in that it allows measurement of the complete concentration profile bottom location and currents co-deployment of both sensors are recommended for improved SPM measurements.