Abstract South Africa has long been dependent on coal and other fossil fuels for cheap electricity generation. While there has been an increase in utilising renewable energy over the last two decades, the main focus has been on solar and wind, which are intermittent, with geothermal energy not even considered. With advances in technology that harness geothermal energy, geothermal resources as low as 85 °C have been reported attainable when using low-enthalpy technologies as such binary systems. This makes geothermal energy a reality for regions in South Africa where moderately high geothermal gradients exist. The initial high level assessment of the geothermal potential of the Cape Fold Belt region was done through accessing eight hot springs found to have the highest temperature from previous studies. Temperature measurements were taken as close to the source as possible as well as collection of water samples for ICP-AES analysis for major cations. The cation concentrations from the ICP-AES analysis (completed with the Thermo ICap 6200 ICP-AES) allowed for geothermometry calculations to be conducted which gave the minimum temperature estimates of the reservoirs of each hot spring. Both the surface temperature measurements and the estimates of the reservoir temperature resulted in two locations that were in the top three for both measurements. These two locations were Calitzdorp and Caledon, having water temperatures of 47 °C and 45 °C at surface and estimates of the reservoir temperatures of 117 °C ± 13 °C and 108 °C ± 21 °C respectively. The hydro-geological analysis of the Oudtshoorn region, where the Calitzdorp hot spring is located, was conducted using published geophysical data in the form of magneto-telluric (MT) survey that was carried out in 2005 by the Agulhas-Karoo Geoscience Transect project. The MT data was presented in a paper by Weckmann et al. (2012) as a cross sectional profile from Mossel Bay to Prince Albert to a depth of 30 km, where a large region of low resistivity was found below the Oudtshoorn basin. The Calitzdorp hot spring is positioned at the surface above this region. The geological cross sections and regional interpretation presented in this study infers that a major syncline of the Cape Supergroup exists below the basin, potentially as deep as 10 km, and covers the low resistivity area shown in the MT profile. This led to the inference that the large region of low resistivity is most probably due to a large water reservoir. This potential reservoir is about 40 km in length with a depth of 2.5 km–7 km at its thickest, tapering out towards the edges. The depth to the top of the potential reservoir and the estimated reservoir temperature from the geothermometry results in a geothermal gradient of 39 °C/km ±4.3 °C/km. Thus Calitzdorp was identified as a promising location for further exploration, ideally deep boreholes or more geophysical surveys, to validate the existence of a reservoir and take down-hole temperature measurements. The depth and size of this potential reservoir would make it a favourable candidate for a pilot low-enthalpy geothermal power plant within the Cape Fold Belt and South Africa.

中文翻译：

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探索开普褶皱带低焓地热发电厂的潜力

摘要 南非长期以来一直依赖煤炭和其他化石燃料来廉价发电。虽然在过去的二十年中，可再生能源的利用有所增加，但主要关注的是太阳能和风能，它们是间歇性的，甚至没有考虑地热能。随着利用地热能技术的进步，据报道，当使用低焓技术（如二元系统）时，可实现低至 85 °C 的地热资源。这使得地热能成为南非地热梯度中等偏高的地区的现实。对开普折叠带地区地热潜力的初步高水平评估是通过访问先前研究中发现温度最高的八个温泉来完成的。温度测量尽可能靠近源进行，并收集水样用于主要阳离子的 ICP-AES 分析。来自 ICP-AES 分析（使用 Thermo ICap 6200 ICP-AES 完成）的阳离子浓度允许进行地热计算，从而给出每个温泉储层的最低温度估计值。地表温度测量值和储层温度估计值都产生了两个测量值均位于前三名的位置。这两个位置是 Calitzdorp 和 Caledon，地表水温分别为 47 °C 和 45 °C，估计储层温度分别为 117 °C ± 13 °C 和 108 °C ± 21 °C。Calitzdorp 温泉所在的奥次颂地区的水文地质分析，使用已发表的地球物理数据以大地电磁 (MT) 调查的形式进行，该调查由 Agulhas-Karoo Geoscience Transect 项目于 2005 年进行。Weckmann 等人在一篇论文中介绍了 MT 数据。(2012) 作为从莫塞尔湾到阿尔伯特王子港深度为 30 公里的横截面剖面图，在奥茨胡恩盆地下方发现了大面积的低电阻率区域。Calitzdorp 温泉位于该地区上方的地表。本研究中的地质剖面和区域解释推断，海角超群的主要向斜存在于盆地下方，可能深达 10 公里，覆盖了 MT 剖面中显示的低电阻率区域。这导致推断低电阻率的大区域最有可能是由于大型水库。这个潜在的水库长约 40 公里，最厚处为 2.5 公里至 7 公里，向边缘逐渐变细。潜在储层顶部的深度和根据地温测量估计的储层温度导致地温梯度为 39 °C/km ±4.3 °C/km。因此，Calitzdorp 被确定为进一步勘探的有希望的地点，最好是深钻孔或更多地球物理调查，以验证储层的存在并进行井下温度测量。这个潜在水库的深度和大小将使其成为开普折叠带和南非内试点低焓地热发电厂的有利候选者。潜在储层顶部的深度和根据地温测量估计的储层温度导致地温梯度为 39 °C/km ±4.3 °C/km。因此，Calitzdorp 被确定为进一步勘探的有希望的地点，最好是深钻孔或更多地球物理调查，以验证储层的存在并进行井下温度测量。这个潜在水库的深度和大小将使其成为开普折叠带和南非内试点低焓地热发电厂的有利候选者。潜在储层顶部的深度和根据地温测量估计的储层温度导致地温梯度为 39 °C/km ±4.3 °C/km。因此，Calitzdorp 被确定为进一步勘探的有希望的地点，最好是深钻孔或更多地球物理调查，以验证储层的存在并进行井下温度测量。这个潜在水库的深度和大小将使其成为开普折叠带和南非内试点低焓地热发电厂的有利候选者。验证储层的存在并进行井下温度测量。这个潜在水库的深度和大小将使其成为开普折叠带和南非内试点低焓地热发电厂的有利候选者。验证储层的存在并进行井下温度测量。这个潜在水库的深度和大小将使其成为开普折叠带和南非内试点低焓地热发电厂的有利候选者。