Various applications of applied controlled source airborne electromagnetic methods
Controlled source airborne electromagnetic (AEM) systems were developed about 60 years ago to explore for mineral deposits. Electromagnetic systems primarily respond to the conductivity (or the resistivity) of material in the earth. Their primary success has been for discovering highly conductive massive sulphide bodies located in areas such as the Canada and Fennoscandinavia. Recent examples are the Storliden deposit in Sweden and exploring for uranium in Canada.Recently, the systems have been modified to respond to subtle changes in conductivity, allowing the systems to be used to map stratigraphic features -- both near the surface and at depths down to a few hundred metres. This means that airborne electromagnetic methods have been used to assist in the search for groundwater. In an example from the USA, different porosities have been identified and in an example from Denmark, the thickness of an aquifer has been mapped. AEM systems have also been used in Australia to map salinity.AEM methods have also been used for hydrocarbon exploration. Some surveys were acquired over known oil fields and in some cases there was a good correlation between the near-surface conductivity and the surface projection of the oil field. In this case the AEM was believed to be mapping a near-surface alteration zone associated with a hydrocarbon chimney.In the last few years, a number of surveys have been flown to map shallow, electrically resistive, paleochannels. These channels can be low-pressure gas reservoirs, but have a very high permeability that means they can be exploited very quickly and economically. Knowledge of the location and depth of inter-till channels may also be useful for drilling hazard evaluation.Use of airborne electromagnetics has also been made to map the bituminous sands in northern Alberta. This data can be used in exploration or to provide important information for environmental due diligence and engineering reports. Airborne EM is moderately successful where the sands are close to the surface. Where the sands are deeper and covered by conductive shale, it is more difficult to map subtle changes in the resistivity caused by variations in bitumen quality. However, the continuity of the seal above the reservoir can be imaged and this information is useful for planning in-situ recovery.
airborne electromagnetic methods mineral groundwater hydrocarbon exploration.
Richard Smith
Fugro Airborne Surveys, Ottawa, Canada
国际会议
The 19th International Workshop on Electromagnetic Induction in the Earth(第十九届国际地球电磁感应学术研讨会)
北京
英文
379-384
2008-10-23（万方平台首次上网日期，不代表论文的发表时间）