Repurposing a Geothermal Exploration Well as a Deep Borehole Heat Exchanger: Understanding Long-Term Effects of Lithological Layering, Flow Direction, and Circulation Flow Rate
Repurposing a Geothermal Exploration Well as a Deep Borehole Heat Exchanger: Understanding Long-Term Effects of Lithological Layering, Flow Direction, and Circulation Flow Rate
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将地热探井改造为深井热交换器：了解岩性分层、流向和循环流量的长期影响
DOI：
10.3390/su15054140
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发表时间：
2023-02
期刊：
影响因子：
3.9
通讯作者：
I. Kolo;C. Brown;G. Falcone;D. Banks
中科院分区：
文献类型：
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作者：
I. Kolo;C. Brown;G. Falcone;D. Banks
为了实现净零碳排放，供暖脱碳至关重要。这可以通过地热能源来促进，但是钻地热威尔斯井具有高风险和高成本。使用预先存在的威尔斯井（例如，耗尽的碳氢化合物威尔斯井或失败的地热勘探钻孔）抵消了这一成本，同时潜在地将负债转化为资产。纽卡斯尔科学中心深地热钻孔（NSCDGB）是一口地热勘探井，其钻探目标为1418.5至1795 m深的石炭纪Fell砂岩地层。然而，低水力传导率阻止了作为传统的“湿”地热提取井的开发;因此，正在探索新的替代开发方法。这项工作研究了将NSCDGB重新用作深埋管换热器（DBHE），重点是通过采用旨在为当地建筑物或热力网络做出贡献的恒定热负荷，长期实现系统的可持续运行。使用OpenGeoSys软件进行了数值建模，以分析系统的热和水力性能。均质和非均质模型的开发，比较岩性分层的影响，在一个均匀的（非分层）地下地质模型。从均匀模拟DBHE建模的深度为922米的结果表明，50千瓦的热负荷可以支持的寿命为25年。这相当于一个65千瓦的建筑负荷时，耦合到热泵的性能系数为4.33。因此，DBHE可以满足邻近城市科学大楼高达72%的热量需求。而不是一个纯粹假设的案例研究，这项工作考虑了一个真实的现有的钻孔，毗邻的建筑群，可以利用地热。在NSCDGB站点首次考虑的异质结，与同质模拟结果相比，其影响较小。流动方向和质量流率也表现出对系统性能的小的影响，而如果勘探井可以改变用途，以增加深度，热负荷可以增加。这是第一次研究同轴DBHE在NSCDGB网站考虑长期影响的质量流率，异质性和流动方向。该研究评估了将英国的一口地热勘探井重新利用为DBHE的可行性，DBHE可用作空间供暖的低碳热源，从而将负债转化为潜在的“绿色能源”资产。
In the drive to achieve net-zero carbon emissions, decarbonisation of heating is essential. This can be facilitated by geothermal energy, but drilling geothermal wells is associated with high risks and costs. The use of preexisting wells (e.g., exhausted hydrocarbon wells or failed geothermal exploration boreholes) offsets this cost while potentially turning liabilities into assets. The Newcastle Science Central Deep Geothermal Borehole (NSCDGB) is a geothermal exploration well that was drilled to target the Carboniferous Fell Sandstone Formation at 1418.5 to 1795 m depth. However, low hydraulic conductivities prevented the development as a conventional “wet” geothermal abstraction well; therefore, new alternative methods of development are being explored. This work investigates the repurposing of the NSCDGB as a deep borehole heat exchanger (DBHE), focusing on the sustainable operation of the system in the long term by employing a constant heat load designed to contribute to local buildings or a heat network. Numerical modelling was undertaken by using OpenGeoSys software to analyse the thermal and hydraulic performance of the system. Both homogeneous and heterogeneous models were developed to compare the influence of lithological layering in contrast to a homogeneous (nonstratified) subsurface geological model. Results from homogeneous simulations modelling the DBHE to a depth of 922 m show that a 50-kW heat load can be supported for a lifetime of 25 years. This corresponds to a 65-kW building load when coupled to a heat pump with a coefficient of performance of 4.33. Thus, the DBHE could meet up to 72% of the heat demand of the adjacent urban sciences building. Rather than being a purely hypothetical case study, this work considers a real existing borehole, adjacent to a building cluster which could make use of the geothermal heat. Heterogeneity, which has been considered for the first time at the NSCDGB site, exhibits a minor impact in comparison to homogeneous simulation results. Flow direction and mass flow rate also exhibited small effects on the system performance, whereas if the exploration well could be repurposed to increased depths, the heat load could be increased. This is the first study of a coaxial DBHE at the NSCDGB site considering long-term effects of mass flow rate, heterogeneity, and flow direction. The study evaluates the feasibility of repurposing an exploratory geothermal well in the UK as a DBHE that can be used as a low-carbon heat source for space heating, thus converting liabilities into potential “green energy” assets.