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.

铀矿开采对加拿大经济很重要，找到更多铀矿床来开采至关重要 为了这个行业的未来。加拿大的大多数铀矿床都位于萨斯喀彻温省北部的阿萨巴斯卡盆地。铀矿体位于地表以下数百米处，位于深层基岩断层带与基岩顶部沉积岩的交界处。基岩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。电学和电磁勘探对地下此类导电特征的存在很敏感，因此在阿萨巴斯卡盆地新铀矿体的勘探中发挥着重要作用。这些调查的数据包含有关石墨断层带的位置、深度、大小和电导率的信息。从这些勘测中可以更好地确定断层带的位置等，所需的钻探次数就越少，这可以显着降低勘探过程的费用。要从调查数据中获取这些信息，需要使用计算机建模和解释技术。然而，当前的技术不适合石墨断层带的尖锐、独特的性质，而是产生断层的模糊、模糊的表示。该项目将扩展以前为重力和磁力数据开发的新计算机解释方法，以包括电气和电磁数据。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，以便为此地下模型计算的地球物理测量数据与测量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分成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物理性质的变化从一个细胞到下一个细胞是顺利的。