Temporal Changes in Seismic Velocity and Attenuation at The Geysers Geothermal Field, California, From Double‐Difference Tomography
Temporal Changes in Seismic Velocity and Attenuation at The Geysers Geothermal Field, California, From Double‐Difference Tomography
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DOI：
10.1029/2021jb022938
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发表时间：
2022-05
期刊：
影响因子：
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通讯作者：
Hao Guo;C. Thurber
中科院分区：
文献类型：
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作者：
Hao Guo;C. Thurber
注水和增强型地热系统（EGS）技术已被用于开采地热储层的热能资源。检测储层物理性质的时空变化对于监测因注水和EGS导致的储层状况变化非常重要。在此，我们利用双差地震波速和衰减层析成像技术，确定了2005年至2011年间加利福尼亚州盖瑟斯地热田西北部三维P波速度和衰减（Vp和Qp）结构随时间变化的高分辨率模型。盖瑟斯西北部有一个浅层常温储层（NTR），其下方是一个高温储层（HTR），该高温储层拥有大量未充分利用的热能资源，但未来可能通过EGS得到更充分的利用。然而，在盖瑟斯西北部的东南部，EGS已经成功但无意地应用了至少50年，因为注入NTR的水一直流入HTR。我们的模型在该区域有很好的分辨率，并且表明NTR和HTR对注水有不同的地震响应（地震活动、Vp和Qp），这可以通过注水引起的破裂和饱和度差异来解释，而这些差异可能与它们的地质特性有关。我们的研究结果表明，对地震活动、速度和衰减变化的联合分析对于描述储层破裂和饱和度状况的变化是有价值的。我们的研究结果还表明，高渗透率区域和/或预先存在的渗透性断层区域对于盖瑟斯以及其他潜在地热系统中EGS的成功至关重要。
Water injection and Enhanced Geothermal System (EGS) technologies have been used to exploit heat resources from geothermal reservoirs. Detecting spatial and temporal changes in reservoir physical properties is important for monitoring reservoir condition changes due to water injection and EGS. Here, we determine high‐resolution models of the temporal changes in the three‐dimensional P wave velocity and attenuation (Vp and Qp) structures between the years 2005 and 2011 in the northwestern part of The Geysers geothermal field, California, using double‐difference seismic velocity and attenuation tomography. The northwest Geysers has a shallow normal temperature reservoir (NTR) underlain by a high temperature reservoir (HTR) that has substantial underutilized heat resources but may be more fully utilized in the future through EGS. In the southeastern part of the northwest Geysers, however, EGS has been successfully but unintentionally applied for at least 50 years because the waters injected into the NTR have been flowing into the HTR. Our models are well resolved in this area and show that the NTR and HTR have different seismic responses (seismicity, Vp, and Qp) to water injection, which can be explained by the injection‐induced differences in fracturing and saturation that are likely related to their geological properties. Our results indicate that the joint analysis of changes in seismicity, velocity, and attenuation is valuable for characterizing changes in reservoir fracturing and saturation conditions. Our results suggest that high‐permeability zones and/or pre‐existing permeable fault zones are important for the success of EGS at The Geysers and potentially other geothermal systems.