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 icesituations, 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, detection1. IntroductionThe 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 naturalroughness 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 TechnologyThe 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 theroughness features and generates a smooth inter the water, which can be detected using either acoustic or electromagnetic sensors.2.1. MECHANICAL SYSTEMSThe only proven and widely used technology is to drill a hole in the ice using an ice auger, a chain saw or similar mechanical system. While this is time consuming and is a single point measurement, it works. In order to increase the productivity of such units, they can be mounted on a small snow vehicle to increase their coverage, but consideration must be given to the additional safety concerns of using such equipmenton ice sheets of unknown thickness. Using hand-held systems, ice thicknesses greater than about a meter and a half are difficult.Some experiments (Dickins et al., 2005) have been conducted on the detection of the vapour from the oil that would permeate through the ice and be trapped on the surface. While this system worked well in the laboratory environment, it would be very difficult to implement in a typical cold weather environment. This system is very time consuming to install and the time for each measurement took several minutes. There is some evidence from field experiments that very little evaporation occurs under an ice sheet, so the presence of vapours in the laboratory experiment may well be an arte fact of the experimental situation .The electromagnetic band extends from long-wavelength radio waves to X-rays, and includes the visible band and radar. Various parts of theelectromagnetic spectrum had been tried for the detection of oil under ice, including low-frequency systems at about 100 kHz, various forms of radar from 100 to 1,000 MHz, and the visible band either directly or by detecting the fluorescence of the oil. While there is some variation of the dielectric constant with frequency, the values of Table 1 are typical. It is easy for electromagnetic radiation to be transmitted from the air to either the ice or the oil.The reflection at the oil-ice interface will be weak, but easily detected provided the sensor has an adequate dynamic range. There will be a strong reflection at the interface with the water. As with any sensing package, the spatial resolution depends on the wavelength (and pulse length for pulsed systems).There are a number of low-frequency electromagnetic systems, which use induction to detect surface and sub-surface anomalies .These systems typically operate at frequencies below 100 kHz (wavelengths of greater than 3,000 m). At these large wavelengths the spatial resolution is poor and while such systems have been proven useful for sea-ice thickness measurements, it is unlikely that this group of sensors would detect oil either in ice or at the ice-water interface (Kovacs et al., 1995)Ground penetrating radar (GPR) systems are routinely used to determine sub-surface structures and operate at frequencies between 300 and 1,000 MHz . In order to achieve good spatial resolution, most GPR systems usea high bandwidth antenna (low Q) and produce a short chirp signal (Moorcroft and Tunaley, 1985). Most of the currently available GPR systems are surface based and require good coupling between the unit antennae and the ice. Since such systems are routinely commercially available, they are very attractive to be used as an oil-under-ice detector. There have been a number of experiments, both in test basins and in the field to test the ability of these systems to uniquely detect oil-under-ice. The main problem is both signal strength and dynamic range, since, depending on the value of the dielectric constant of the oil, the reflected signal difference between oil and ice is 0.5–7% as opposed to the nearly 100% at the ice-water interface. Thus, the receiver must be sensitive to small variations in signal strength to see the oil-ice interface, while not being overloaded by the return from the water. Older systems lacked this. dynamic range and the ice-oil signal was masked by the water return. The electronics used by more recent designs have a better dynamic range, and Dickins et al. (2005) have recently used such a system to evaluate an oil-under-ice detection in a test basin using urea ice, and subsequently (Brandvik et al., 2006) in an experiment in the Norwegian Arctic. The test basin experiments used extensive signal analysis in order to identify the presence of oil under ice, which obscures what properties of the interface are actually being detected. The use of urea ice, whose electrical properties are different from natural ice, further complicates theinterpretation. The field data from 2006 is still being analyzed.For more than a decade, radio-echoing sounding systems operating in the same frequency band as the GPS have been used to measure glacier ice thickness from an airborne platform (Figure 7). These systems have a much narrower bandwidth and beam width than a typical GPS system, but offer the potential to remotely detect oil under ice. Since these systems have a much lower spatial resolution than the GPS, a larger area of oil-under-ice would be required for a reasonable test of the units’ capability. No such field studies have been undertaken.石油冰下检测:什么是最先进的?摘要：在二十世纪七十年代早期，石油和天然气勘探在加拿大和美国的北极开始需要被确认开发技术来检测油冰下。