We present modelling of the geophysical data from the Newcastle area, west of Dublin, Ireland within the framework of the IRETHERM project. IRETHERM’s overarching objective was to facilitate a more thorough strategic understanding of Ireland's geothermal energy potential through integrated modelling of new and existing geophysical, geochemical and geological data. The Newcastle area, one of the target localities, is situated at the southern margin of the Dublin Basin, close to the largest conurbation on the island of Ireland in the City of Dublin and surrounds. As part of IRETHERM, magnetotelluric (MT) soundings were carried out in the highly urbanized Dublin suburb in 2011 and 2012, and a description of MT data acquisition, processing methods, multi-dimensional geoelectrical models and porosity modelling with other geophysical data are presented. The MT time series were heavily noise-contaminated and distorted due to electromagnetic noise from nearby industry and Dublin City tram/railway systems. Time series processing was performed using several modern D ow naded rom http/academ ic.p.com /gji/advance-articleoi/10.1093/gji/ggz530/5643919 by U niersity of Eeter user on 02 D ecem er 2019 robust codes to obtain reasonably reliable and interpretable MT impedance and geomagnetic transfer function “tipper” estimates at most of the survey locations. The most “quiet” 3-hour subsets of data during the night time, when the DC “LUAS” tram system was not operating, were used in multi-site and multivariate processing. The final 2-D models underwent examination using a stability technique, and the final two 2-D profiles, with reliability estimations expressed through conductance and resistivity, were derived. In the final stage of this study, 3-D modelling of all magnetotelluric data in the Newcastle area was also undertaken. Comparison of the MT models and their interpretation with existing seismic profiles in the area reveals that the Blackrock to Newcastle Fault (BNF) zone is visible in the models as a conductive feature down to depths of 4 km. The investigated area below Newcastle can be divided into two domains of different depths, formed as depth zones. The first zone, from the surface down to 1-2 km, is dominated by NE-SW oriented conductors connected with shallow faults or folds probably filled with less saline waters. The conductors are also crossing the surface trace of the BNF. The second depth domain can be identified from depths of 2 km to 4 km, where structures are oriented along the BNF and the observed conductivity is lower. The deeper conductive layers are interpreted as geothermal-fluid-bearing rocks. Porosity and permeability estimations from the lithological borehole logs indicate the geothermal potential of the bedrock, to deliver warm water to the surface. The fluid permeability estimation, based on Archie’s law for porous structures and synthetic studies of fractured zones, suggests a permeability in the range 100 mD – 100 D in the study area, which is prospective for geothermal energy exploitation.

中文翻译：

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都柏林盆地南缘膨胀带中的地热含水层

我们在 IRETHERM 项目的框架内展示了来自爱尔兰都柏林以西的纽卡斯尔地区的地球物理数据的建模。IRETHERM 的总体目标是通过对新的和现有的地球物理、地球化学和地质数据进行综合建模，促进对爱尔兰地热能源潜力的更透彻的战略理解。目标地区之一的纽卡斯尔地区位于都柏林盆地的南缘，靠近爱尔兰岛上最大的都柏林市及其周边地区。作为 IRETHERM 的一部分，2011 年和 2012 年在高度城市化的都柏林郊区进行了大地电磁 (MT) 测深，并描述了 MT 数据采集、处理方法、提出了多维地电模型和孔隙度建模与其他地球物理数据。由于来自附近工业和都柏林市电车/铁路系统的电磁噪声，MT 时间序列受到严重的噪声污染和失真。时间序列处理是使用几个现代 Dow naded rom http/academ ic.p.com /gji/advance-articleoi/10.1093/gji/ggz530/5643919 由 U niersity of Eeter 用户在 02 D ecem er 2019 鲁棒代码进行的，以获得在大多数调查地点，合理可靠和可解释的 MT 阻抗和地磁传递函数“倾斜”估计。当 DC“LUAS”有轨电车系统未运行时，夜间最“安静”的 3 小时数据子集用于多站点和多变量处理。最终的二维模型使用稳定性技术进行了检查，并导出了最后两个二维剖面，其中可靠性估计通过电导率和电阻率表示。在本研究的最后阶段，还对纽卡斯尔地区的所有大地电磁数据进行了 3-D 建模。MT 模型及其与该地区现有地震剖面的解释的比较表明，黑岩至纽卡斯尔断层 (BNF) 带在模型中是可见的，作为深达 4 公里的导电特征。纽卡斯尔下方的调查区域可分为两个不同深度的区域，形成深度带。第一个区域，从地表到 1-2 公里，主要是 NE-SW 定向的导体，这些导体与浅层断层或褶皱相连，可能充满了较少的咸水。导体也穿过 BNF 的表面轨迹。第二个深度域可以从 2 公里到 4 公里的深度进行识别，其中结构沿 BNF 定向，观察到的电导率较低。较深的导电层被解释为含有地热流体的岩石。来自岩性钻孔测井的孔隙度和渗透率估计表明基岩的地热潜力，可将温水输送到地表。流体渗透率估计基于阿奇定律对多孔结构和裂缝带的综合研究，表明研究区的渗透率在 100 mD – 100 D 范围内，具有开发地热能的前景。来自岩性钻孔测井的孔隙度和渗透率估计表明基岩的地热潜力，可将温水输送到地表。流体渗透率估计基于阿奇定律对多孔结构和裂缝带的综合研究，表明研究区的渗透率在 100 mD – 100 D 范围内，具有开发地热能的前景。来自岩性钻孔测井的孔隙度和渗透率估计表明基岩的地热潜力，可将温水输送到地表。流体渗透率估计基于阿奇定律对多孔结构和裂缝带的综合研究，表明研究区的渗透率在 100 mD – 100 D 范围内，具有开发地热能的前景。