石油和天然气勘探中英文对照外文翻译文献

中英文对照外文翻译文献

(文档含英文原文和中文翻译)

OIL UNDER ICE DETECTION: WHAT IS THE STATE-OF-THE-ART?

Abstract. Since the exploration for oil and gas in the Canadian and US arctic commenced in the early 1970s, a need has been identified to develop technology to detect oil under ice. Both electromagnetic and acoustic sensors have been tried, but a practical field instrument has not been identified. Most proposed systems require that the equipment be operated from the ice surface in order to get adequate coupling and, for some systems, the snow must be removed from the ice. For many ice

situations, surface access is difficult and poses a severe safety issue. Two recent spills in Alberta used “high technology” ice augers to detect the presence of oil under the ice. Some potential new techniques are discussed and the basic principles of their operation described. Keywords: arctic, oil spill response, oil in ice, detection

1. Introduction

The detection of oil under continuous ice cover has presented one of the most difficult challenges to the oil-spill technological community for the past two decades and there is still no operationally proven system available. Dickins (2000) under the sponsorship of the US Minerals Management Service conducted an excellent review of the status of oil-under-ice detection and this paper complements this review with a more detailed analysis of some systems. Dickins identified many false start concepts, which will not be discussed in this paper. In order to determine the design of a suitable oil-under-ice detector, the various situations under which oil may be found under a continuous ice sheet need to be considered.

The oil must come from a sub-surface release since any surface release would either be on the ice surface or in a lead or other opening in the ice. Potential sources of sub-surface oil are a leak in a pipeline, the leakage from a submerged tank or vessel or a natural seep. Oil when trapped under ice does not spread rapidly or cover a large area due to natural

roughness of the ice-water interface (Rosenegger, 1975). The situation is analogous to oil spilled on land, rather than the more dynamic situation of oil on water. Unlike the oil-on-water situation, the probable location of the source of the oil can be well defined spatially, so the search for the oil is over a relatively small confined area. Depending on the time of year, the ice may just be forming, be in a rapid growth phase, be essentially static or in a break-up situation, so that the oil may be on the surface surrounded by ice floes, at the ice-water interface or in the sheet. In the first and last case, traditional remote sensing techniques can be used to detect the oil. When the oil is at the ice-water interface or incorporated in the ice sheet, new oil-under-ice detection systems are required. The basic mode of detection may be different for the two situations.

2. Existing Technology

The signal associated with the detection of oil under ice may be due to dielectric or acoustic impedance difference between the oil and the ice, or by a change in the surface roughness of the oil-ice interface. The rougher the interface, the more the probing signal is scattered and hence the weaker the signal returned to the receiver. This is the basis, for example, of the detection of oil-on-water using radar. The interface roughness has been directly measured using a mould system deployed by divers (Goodman et al., 1987) and found to be rough at spatial scales of meters and roughness values of several. The oil released under ice fills the