To date, magnetotelluric monitoring of processes during reservoir engineering of geothermal systems have been carried out only at three sites world-wide. Here, we add a new survey at the Reykjanes peninsular (Iceland). The MT data acquisition at RN-15/IDDP-2 covered the last third of the drilling period and thermo-hydraulic stimulation. Drilling was accompanied by temporal total fluid losses of up to 60 L/s as well as randomly distributed induced seismicity. Our experimental results of a two-months magnetotelluric monitoring during the deepening of the RN-15/IDDP-2 well on the Reykjanes peninsular (Iceland) to 4’659 m are in line with earlier observations on decreasing resistivities at periods of a few s to about 20 s (or up to about 40 s) in conjunction with fluid injection. Simple models indicate however that it is not the fluid volume itself that causes the anomaly. Moreover, here, temporal decreases in the electric resistivities occur at 0.2-20 s with minima at periods of about 0.4 s 1-2 days ahead of clusters of seismic events with magnitudes up to M_L < 2. Unlike in the previous studies, where resistivity decreases occur on the component that is parallel to Shmin, here they in both components (XY and YX) of the MT data. At the Reykjanes peninsular, Shmin is oriented N120°E off the XY component (N0°E). Therefore, if we rotate our data in Shmin direction, the difference between both components would be slightly smaller than that for the non-rotated ones. The decrease in resistivity (on both components) extends over > 1 order of magnitudes over a short period range and is thus considered noise induced in the subsurface. This study aims at adding an essential dataset to the general discussion on MT monitoring of reservoir processes. The results show a temporal relation between decreasing apparent resistivity and (i) the geomagnetic field activity, (ii) the fluid losses up to 60 L/s, as well as (iii) mechanic processes occurring in the reservoir before clusters of induced seismicity on the other hand.

迄今为止，地热系统储层工程过程中的大地电磁监测仅在全球三个地点进行。在这里，我们在雷克雅内斯半岛（冰岛）添加了一项新调查。RN-15/IDDP-2 的 MT 数据采集涵盖了钻井周期的最后三分之一和热液增产。钻井伴随着高达 60 L/s 的时间总流体损失以及随机分布的诱发地震活动。我们在 Reykjanes 半岛（冰岛）的 RN-15/IDDP-2 井加深到 4'659 m 期间进行了为期两个月的大地电磁监测的实验结果与早期关于在几秒内降低电阻率的观察结果一致结合流体注射，持续至约 20 秒（或最多约 40 秒）。然而，简单的模型表明，引起异常的并不是流体体积本身。此外，在这里，电阻率的时间下降发生在 0.2-20 秒，最小值出现在大约 0.4 秒的周期内，在震级高达 M_升 < 2. 与之前的研究不同，电阻率降低发生在平行于 Shmin 的组件上，这里它们出现在 MT 数据的两个组件（XY 和 YX）中。在雷克雅内斯半岛，Shmin 的方向偏离 XY 分量 (N0°E) N120°E。因此，如果我们在 Shmin 方向旋转我们的数据，两个组件之间的差异将比非旋转组件的差异略小。电阻率的下降（在两个组件上）在短期范围内超过 1 个数量级，因此被认为是在地下引起的噪声。本研究旨在为油藏过程的 MT 监测的一般性讨论添加一个基本数据集。结果显示了降低视电阻率与 (i) 地磁场活动，(ii) 高达 60 L/s 的流体损失之间的时间关系，