A comprehensive in situ stress estimation is carried out in the fractured reservoir at the enhanced geothermal system development site in Pohang, South Korea. Various types of stress indicators were collected from the hydraulic stimulation data, drilling records, lost circulation records, well logs, seismic events, and the stress constraints from previously proposed stress models. The comprehensive comparison of the collected stress constraints was performed, and resulted in the possible stress magnitude range and corresponding limits on the range of possible friction coefficients. The resulting stress ratio is SV: Shmin: SHmax = 1 : 0.92–0.94 : 1.42–1.66 with the azimuth of SHmax in N101°E –N110°E range, based on the compilation of both direct and indirect stress information. The results also suggest a friction coefficient range of 0.35–0.38 that can best explain the involved stress constraints. The stress model suggested in this study can explain the characteristics of the Mw 5.5 Pohang earthquake in November 2017 in terms of reproducing the slip rake of mainshock and the slip tendency of the corresponding fault. Therefore, the result can be used for clarifying the causal mechanism of the Pohang earthquake, providing an insight for fault stability analysis or possible geo-energy application in the southeastern part of the Korean Peninsula. Comprehensive in-situ stress estimation method suggested in this study integrating extensive direct and indirect stress indicators can improve the credibility of the in-situ stress model at a fractured reservoir.

中文翻译：

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使用钻井数据、水力刺激和诱发地震活动对韩国浦项裂缝性地热储层进行全面的原位应力估计


在韩国浦项的增强型地热系统开发现场的裂缝储层中进行了全面的原位应力估计。从水力增产数据、钻井记录、丢失循环记录、测井、地震事件以及先前提出的应力模型中的应力约束中收集了各种类型的应力指标。对收集到的应力约束进行了综合比较，得出了可能的应力大小范围和可能的摩擦系数范围的相应限制。根据直接和间接应力信息的汇编，生成的应力比为 SV：Shmin：SHmax = 1：0.92–0.94：1.42–1.66，SHmax 的方位角在 N101°E –N110°E 范围内。结果还表明，摩擦系数范围为 0.35-0.38，最能解释所涉及的应力约束。本研究提出的应力模型可以从再现主震滑耙和相应断层的滑移趋势方面解释 2017 年 11 月 Mw 5.5 浦项地震的特点。因此，该结果可用于阐明浦项地震的因果机制，为朝鲜半岛东南部的断层稳定性分析或可能的地能应用提供见解。本文提出的综合原位应力估计方法，整合了广泛的直接和间接应力指标，可以提高裂缝性储层原位应力模型的可信度。