Modelling of steady-state vs transient heat transfer in the COSC-1 drillhole, Central Sweden

这一建议与ICDP资助的斯堪的纳维亚加里东尼德斯碰撞造山运动（COSC）项目有关。COSC-1于2014年在瑞典中部Åre镇附近钻探并完全取心。达到垂直深度约2.5 km，岩心采收率接近100%。该项目是由申请人领导的中cosc地热集团资助的，本提案的目的是申请第三年的资助，以完成博士项目。我们希望对前寒武纪盾的地热机制有所贡献。在这样的地质环境中，很少有深的科学钻孔。迄今为止，只有两个钻孔提供了有关深克拉通地壳平流影响的详细分析，得出了相反的结论。因此，一个主要的目标是表征瞬态平流热流的相对贡献。我们假设裂缝渗透率足以促进前寒武纪盾层的显著平流。然而，在一般情况下，地形头是不存在的，这意味着一个（准）稳态地热制度。COSC-1钻孔位于稳定的前寒武纪地盾的山区，将为验证我们的工作假设提供最佳数据。为了实现这一具体目标，我们计划在项目的前两年开展以下任务：(1)测量100个岩心样品的热性质；(2)分析钻孔测井以构建岩性/岩石学剖面；(3)计算COSC-1的热流密度剖面，并分离最终的瞬态信号，包括平流和古气候信号。对于第三年（即本提案），我们建议基于获得的数据建立一个3D地热模型，并限制COSC-1井周围的地热状况。

This proposal is linked to the Collisional Orogeny in the Scandinavian Caledonides (COSC) project funded by ICDP. COSC-1 was drilled and fully cored near the town of Åre, Central Sweden in 2014. Reached vertical depth was ~2.5 km and core recovery nearly 100 percent. This project is a contribution from the COSC Geothermal Group, led by the applicant and the aim of this proposal is to request a 3rd year of funding in order to complete the PhD project. We wish to contribute to knowledge on geothermal regimes of Precambrian shields. Deep scientific drillholes in such geological environments are very seldom. To date only two drillholes have delivered detailed analyses with opposite conclusions concerning the impact of advection in deep cratonic crust. Hence, a major objective is to characterise the relative contribution of transient advective heat flow. We postulate that fracture permeability is sufficient to promote significant advection in Precambrian shields. However, topographic heads are absent in the general case, implying a (quasi) steady-state geothermal regime. Being located in a mountainous area of a stable Precambrian shield, the COSC-1 drillhole will furnish optimal data to test our working hypothesis. In order to reach this specific goal we planned to carry out the following tasks during the first two years of the project: (1) to measure thermal properties on 100 core samples, (2) to analyse borehole logs in order to construct a lithological/petrological profile and (3) to calculate the heat flow density profile for COSC-1 and isolate eventual transient signals, including advective and paleoclimatic ones. For the 3rd year (i.e. this proposal) we propose to build a 3D geothermal model based on the acquired data and to constrain the geothermal regime around the COSC-1 well.