Development of joint moving-interface inversion methodology for geophysical DC resistivity and time-domain EM data

地球物理直流电阻率和时域电磁数据联合动界面反演方法的开发

• 批准号: 543677-2019
• 负责人: Farquharson, Colin
• 金额: $ 4.08万
• 依托单位: Memorial University of Newfoundland
• 依托单位国家: 加拿大
• 项目类别: Collaborative Research and Development Grants
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=699046
• 关键词: Development; joint; moving; interface; inversion

Uranium mining is important to Canada's economy, and finding more uranium ore deposits to mine is critical to the future of this industry. Most uranium ore deposits in Canada are to be found in the Athabasca Basin in northern Saskatchewan. The uranium ore-bodies are located hundreds of metres beneath the Earth's surface at the junction between fault zones in the deep basement rocks and the sedimentary rocks which lie on top of the basement rocks. These fault zones in the basement rocks often contain graphite, which makes them relatively good at conducting electricity compared to the surrounding rocks. Electrical and electromagnetic surveys are sensitive to the presence of such electrically conductive features in the subsurface, and so play an important role in the exploration for new uranium ore-bodies in the Athabasca Basin. The data from such surveys contain information about the location, depth, size and electrical conductivity of the graphitic fault zones. The better the location, etc., of the fault zones can be determined from these surveys the less drilling is required, which can significantly reduce the expense of the exploration process. To derive this information from the survey data requires the use of computer modelling and interpretation techniques. However, current techniques are not suited to the sharp, distinct nature of the graphitic fault zones, producing instead fuzzy, indistinct representations of the faults. This project will extend a new computer interpretation approach, previously developed for gravity and magnetic data, to include electrical and electromagnetic data. This new approach specifies the subsurface features by discretizing the interfaces between neighbouring rock types, and then moving and adapting these interfaces so that geophysical survey data computed for this model of the subsurface match the data measured in a survey. This is in contrast to the current approach, which is to divide the subsurface into many little cells and to find the values of electrical conductivity in all the cells such that the match between computed and measured data is good and that the variation of the physical property from one cell to the next is smooth.

铀开采对加拿大的经济很重要，寻找更多的铀矿床是至关重要的 到这个行业的未来。加拿大的大多数铀矿床都可以在萨斯喀彻温省北部的阿萨巴斯卡盆地中找到。铀矿石体位于地面深地下岩石中的断层区与位于地下岩石顶部的沉积岩石之间的交界处的数百米处。地下室岩石中的这些断层区通常包含石墨，这使其与周围岩石相比在传导电力方面相对较好。电气和电磁调查对地下中这种导电特征的存在敏感，因此在探索阿萨巴斯卡盆地的新铀矿石体中起着重要作用。来自此类调查的数据包含有关石墨断层区域的位置，深度，大小和电导率的信息。断层区域的位置等越好，可以从这些调查中确定所需的钻孔，这可以显着降低勘探过程的费用。为了从调查数据中得出这些信息，需要使用计算机建模和解释技术。但是，当前的技术不适合石墨断层区的鲜明，独特的性质，而是产生模糊，模糊的断层表示。该项目将扩展一种新的计算机解释方法，该方法先前用于重力和磁数据，以包括电气和电磁数据。这种新方法通过离散相邻的岩石类型之间的接口来指定地下特征，然后移动和调整这些接口，以便为地下该模型计算的地球物理调查数据与调查中测量的数据匹配。这与当前方法相反，后者是将地下分为许多小单元，并在所有单元中找到电导率值，以使计算和测量数据之间的匹配是好的，并且从一个单元格到下一个单元的物理特性的变化是平稳的。