Ocean Management最新文献

This paper reviews the impact of the laying and maintenance of offshore pipelines on the marine environment of the North Sea, with an emphasis on the interaction between the offshore oil and gas industry and the fishing industry. The paper describes the coating, laying, burying and surveying of pipelines. Both natural hazards (water movement, corrosion, sediment movement) and man-made hazards (anchors, fishing activities) are discussed. A case history of a pipeline floatation is given in more detail.

Further items are: fishery damage attributed to offshore activities, fishing activity in relation with pipelines, improvements of fishing gear to reduce the impact on pipelines and the biological effect of introducing structures on the bottom.

It is suggested to base the requirements for each new projected pipeline on a combination of considerations and to assess these requirements case by case instead of applying standard requirements on e.g. burial depth, trenching, etc.

The 200-mile exclusive economic zone for fisheries management is criticized by some as being inconsistent with demands for a New International Economic Order. This paper examines the implications of the new fisheries regime for the developing countries. While the regime is no panacea, it will improve the allocation of resources and the bargaining leverage of developing countries. Their long-term success in achieving nutritional, employment and commercial benefits will depend upon availability of infrastructure and venture capital for processing and marketing of the catch, sea-orientation among the peoples and the pattern of internal economic concentration.

Barites often contain trace metal impurities. Oil exploration in the Beaufort Sea will require barite as a major component of drilling fluid, most of which will be disposed after drilling. The trace metal impurities Hg, Pb, Zn and Cu have been examined by considering the natural budget and residence time of these elements for the Beaufort Shelf compared to projected scale of barite disposal. The form of metal, its solubility and bioavailability, and dispersion during ocean disposal have also been considered. Measurable effects of trace metals on the water column are not likely to extend much beyond hundreds of meters from the disposal. Elevated metal concentration in sediments will be most noticeable within about 100 m of disposal but detectable to perhaps 1 km depending on currents, sedimentation, and time since disposal. It is unlikely that much of the metal will enter the biosphere, and effects on the biota are more likely to arise from smothering or from other components used to make drilling fluid. Options such as land disposal or extraction of trace metal impurities from barite may not improve the overall environmental aspect of disposal.

The progression from exploration to development of the hydrocarbon reservoirs in the North Sea has necessitated the introduction of many innovative engineering techniques, such that the North Sea has remained at the forefront of oilfield technology for several years.

Obviously it was the water depths and weather conditions which originally made the North Sea quite a unique area, but it should also be remembered that some of the North Sea fields are noted for their high productivities of light oil sometimes with a high G.O.R. This latter aspect of high flow-rates can necessitate the use of specially designed well completions and completion equipment.

In view of the fairly small geographical area and the presence of many of the major oil companies, a unique opportunity exists to review and compare the well completions being used for a large number of fields.

The authors have concentrated their review mainly on the practices prevailing in the northern North Sea operations; however, certain aspects of the completions in the southern North Sea gas fields have also been included.

Since the development of many of the fields has reached an advanced stage, the intentions regarding well stimulation and workover practices have also been investigated.