An exhaustive review of the available data related to the reservoir of the volcano-hosted Copahue geothermal system is presented. Reservoir interpretation to date suggests a vapor-dominated nature. However, the review provided reveals the limitations of this model, regarding the transition from shallow argillic to deep propylitic alteration zones, gas geothermometers calibrated to near-neutral pH environment, production tests, and low recharge of the feed zone, among the other features. We propose that a layered model with a shallow vapor zone above a fluid pressurized reservoir better accounts for the known features of the geothermal reservoir. Temperature profiles define the 800-m-thick upper thermal boundary that includes the impermeable clay cap. An argillic alteration layer (smectite + chlorite + illite + kaolinite) with low electric resistivity response, consistent with the presence of smectite, composes the clay cap. A shallow steam cap develops immediately below the impermeable layer. This vapor zone has 200–215 °C, low seismic activity, and high electrical resistivity, and is highlighted by the isothermal segment of the well logs. The bottom part of the reservoir is subjected to controversy because of the lack of direct measurements. The deep liquid-dominated reservoir has a temperature of ~ 280 °C, develops below 1500 m depth under near-neutral pH condition, and probably has a pervasive propylitic alteration, and wairakite + laumontite + chlorite + epidote + prehnite + actinolite is the likely mineral assemblage. Pressure collapse might trigger the development of the shallow steam cap during deflation–inflation volcanic cycles or Pleistocene-to-recent tectonic deformation. This work points out the main weak points of the previous conceptual model, providing an alternative one based on the first comprehensive compilation of data of the Copahue reservoir. Further research, including a deep exploration drilling stage, is required to establish the physicochemical reservoir state precisely and to validate the proposed layered model.

中文翻译：

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阿根廷Copahue地热储层的分层模型

本文详尽地回顾了与火山喷发的Copahue地热系统储层相关的可用数据。迄今为止，对储层的解释暗示着一种以蒸气为主的性质。但是，所提供的评论揭示了该模型的局限性，包括从浅的阿耳吉尔酸蚀变区到深的丙炔酸蚀变区的过渡，已校准至接近中性pH环境的气体地热仪，生产测试以及进料区的补给量较低等。我们提出，在流体加压储层之上具有浅层蒸汽带的分层模型可以更好地说明地热储层的已知特征。温度曲线定义了800米厚的上部热边界，其中包括不透水的粘土盖。具有低电阻率响应的绿泥石蚀变层（绿土+绿泥石+伊利石+高岭石）与绿土的存在一致，构成了粘土盖。在不透水层的正下方会形成一个浅层的蒸汽帽。该蒸汽带的温度为200–215°C，地震活动低，电阻率高，并且在测井曲线的等温段中突出显示。由于缺乏直接测量，储层底部存在争议。深液占主导地位的储层温度约为280°C，在接近中性pH的条件下可发育至1500 m以下，并且可能具有普遍的质变，并且可能有wairakite + laumontite +绿泥石+附子+ prehnite +阳起石。矿物组合。压力崩溃可能会在放气-膨胀的火山循环或更新世至最近的构造变形期间触发浅层蒸汽盖的发展。这项工作指出了先前概念模型的主要弱点，并基于对Copahue水库数据的首次综合汇编提供了一个替代模型。需要进行进一步的研究，包括深探钻探阶段，以精确建立理化储层状态并验证所提出的分层模型。