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.

铀矿开采对加拿大的经济很重要，寻找更多的铀矿矿藏进行开采至关重要 这个行业的未来。加拿大的大多数铀矿位于萨斯喀彻温省北方的阿萨巴斯卡盆地。铀矿体位于地球表面以下数百米处，在深层基底岩石中的断裂带与基底岩石顶部的沉积岩之间的交界处。基底岩石中的这些断层带通常含有石墨，这使得它们与周围的岩石相比具有相对良好的导电性。电测和电磁测量对地下存在的这种导电特征很敏感，因此在阿萨巴斯卡盆地勘探新的铀矿体中发挥着重要作用。这些调查的数据包含有关石墨断层带的位置、深度、大小和导电性的信息。位置越好等等，通过这些勘测可以确定断层带的深度，所需的钻探越少，这可以显著降低勘探过程的费用。要从调查数据中得出这一信息，就需要使用计算机模拟和解释技术。然而，目前的技术不适合石墨断层带的尖锐，独特的性质，而是产生模糊，模糊的故障表示。该项目将扩大以前为重力和磁力数据开发的新的计算机解释方法，以包括电和电磁数据。这种新方法通过离散相邻岩石类型之间的界面来指定地下特征，然后移动和调整这些界面，使得针对该地下模型计算的地球物理勘测数据与勘测中测量的数据相匹配。这与当前的方法相反，当前的方法是将地下划分为许多小单元并找到所有单元中的电导率值，使得计算数据和测量数据之间的匹配良好，并且从一个单元到下一个单元的物理性质的变化是平滑的。