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Cold water corals, e.g. Lophelia pertusa and Paragorgia arborea, are found in several places in the Norwegian Sea where oil exploration and production activities are going on. The corals are expected to be vulnerable for sedimentation of particles and exposure to chemicals from drilling activities (drill cuttings and drilling mud) and for physical damage from e.g. anchor lines. How vulnerable they are for these disturbances is, however, not well known. Oil and gas licences licenses in the area are therefore obligated to map possible corals and to take measures to avoid harming them. These obligations have been strengthened in the Integrated Management Plan for the Norwegian Sea approved by the Norwegian Parliament in May 2009.Det norske oljeselskap has in 2009 drilled 4 exploration wells in the Norwegian Sea and carried out a number of activities to map corals, study the effects of drill cuttings and drilling mud, and apply technical and operational measures to reduce the effects. This includes:Mapping of corals around the drill site by use of side scan sonar, multibeam echo sounder and ROV mounted camera/video Measurement of particle size distributions in the discharges of cuttings and drilling mud Computer simulation of sea bed currents and sedimentation of discharged particles Analyses of particles from sediment traps and sea bottom core samples close to the drill site for verification of simulation models and evaluation of effects on corals Camera observation of corals before and after the drilling operation Recovery of all cuttings (also from the top hole) to the rig for possible disposal away from corals. Our experience shows that technology is available to handle drill cuttings and mud and control the discharges and spreading to avoid harming corals and other sensitive resources.

There has been much focus on possible acute toxicity of produced water and which natural components and chemicals contributes most to the toxicity. This paper describes a method for risk analyses of discharges to sea based on exposure dose instead of the more common method using concentration. Results are presented from such analyses for the produced water from 4 Norwegian oil/gas fields. A comparison of environmental effects of discharge and reinjection of produced water is also presented based on available methods for assessment of environmental impacts. Introduction Since new, strict regulations for oil content on drill cuttings were introduced in 1993, produced water has become the major contributor of oil to the sea from the Norwegian oil industry. As a consequence, there has been much focus on possible acute toxicity of produced water and which natural components and chemicals contributes most to the toxicity. The amount of produced water from the fields in the Norwegian part of the North Sea is steadily increasing as new fields come on stream and the water cut increases on older fields. Currently. the yearly discharge is approx. 30 Mm3, and is expected to increase to around 90 Mm3 by the year 2000. Typical discharge volumes are from 500 m3/day to 25,000 m3/day from one platform. Produced water composition Typical values for the most important components in the produced water are shown below. The concentration of the chemicals in the discharge water depends both on the amount used and how they follow the gas, oil and water phases. Spreading of produced water Field tests have shown that the produced water is more rapidly diluted than earlier anticipated. These field tests have been used to calibrate computer models. A simplified formula for calculating the spreading is: where c0 concentration of a component in the discharge c(x) concentration at distance x x distance from discharge point Q0 discharge volume pr time unit (flux) U current velocity Kz vertical diffusion coefficient (typically 0.01 m2/s) P. 471

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The Poseidon project aims at developing technology for subsea multiphase development of offshore oil and gas fields. This paper shows the potential of this technology through three synthetic North Sea field examples. The investment cost may be reduced by 10-40% using multiphase technology. Realizing this technology with an unmanned wellhead platform concept or a subsea (Poseidon) concept may give neglible cost differences. The main technical areas of concern are listed and some conclusions are drawn as to the future use of multiphase technology. THE POSEIDON PROJECT The Poseidon project was started in 1984 as a cooperation between Institut Francais du Petrole (IFP), Total and Statoil. The aim of the five year project is to develop the technology for subsea development of deepwater oil and gas fields. The concept, fig. 1 includes subsea wells, subsea multiphase pumps and long distance multiphase pipelines. In this project, IFP has developed a multiphase pump. An industrial prototype of this pump will be tested in a flow-loop, outside Lyon late 1988. Total has developed the subsea station and put main emphasis on full-scale test of an electric motor for the multiphase pump. This motor was tested in 150 meters of water outside the west coast of Norway in the autumn of 1987. Statoil's part of the work has been the pipeline system. A computer program for dynamic simulation of multiphase flow has been developed and used to study slugging phenomena and transient behaviour during start-up and shut-down of the pipeline. Moreover, numerous tests have been performed to study hydrate formation in flowing media as well as corrosion and erosion in the presence of oil, gas water and sand. Special consideration has been given to corrosion under sand beds and inhibitor efficiency in the roof of pipelines carrying mainly gas. Instrumentation for reservoir monitoring and control of pump inlet conditions have been studied. Finally, Statoil has headed the field concept studies in which also personnel from Total and IFP have taken part. This paper will present some of the conclusions from these studies. CONVENTIONAL OIL AND GAS FIELD DEVELOPMENTS Fig. 2 shows the functions included in a conventional field development. To arrive at new concepts it is necessary to consider if all these functions are necessary and where the accompanying equipment should be placed. Apart from the pipelines, the main part of the equipment and therefore also the investment and operating costs are connected to well control/manifolding, separation and pumping. Well control and manifolding are always necessary. The question is therefore whether the equipment should be placed on a platform or on the sea bottom. The equipment for separation and pumping is today always placed on a platform. Platforms for water depths of 70 to 500 meters, as in the Norwegian part of the North Sea, tends to be very large constructions, fig. 3. The Gullfaks C platform, which will be installed in 220 meters of water depths late this year, will cost in the order of 18 billion NOK.