深部地層流體注入觸發地震的力學模擬技術初步研究

燃煤發電結合碳捕集、封存、再利用（CCS或CCUS）技術，向來為產官學研所屬各研究單位紛紛投入研發的新領域，也是目前國際社會倡議為控制全球升溫少於1.5°C，達成2050年淨零排放，實現碳中和目標所不可或缺的減碳方法。然而，碳封存期間對儲集地層安定性之影響，一直是環保人士或懷疑論者不斷質疑之處，其中對於流體注入是否會觸發或誘發地震，是其中最受矚目的爭議。為釐清注儲與觸發地震的關聯性，本研究初步以FLAC3D程式建置水力學－力學（H-M）耦合分析模式，探討深部地層之流體注儲行為，並導入震波模擬技術，以量化地震可能的影響潛能。經初步分析，彰濱工業區下方儲集層假設以單井每年百萬噸灌注，並假設斷層距注入井500公尺，其灌注壓力皆未能使斷層產生錯動。進一步進行最壞狀況情境分析（每日約5.5萬噸），方可能觸發斷層發生滑動破壞。在此假設情境下，對於距3.3公里之觀測點（台灣玻璃館附近）可能產生最大東西向約5.55 gal，及6.3公里外之觀測點（鹿港鎮附近）產生最大南北向約0.82 gal之地動反應，引發震度均為二級或以下。未來，本研究將進一步以TOUGH2取代模式中的水力學模式，以準確地模擬二氧化碳注儲行為，提供更為完整的評估技術與流程，以作為國內未來相關作業之評估參考與科學化論證數據。

關鍵字

碳封存；觸發地震；耦合分析模式； FLAC3D

並列摘要

Coal-fired power generation combined with carbon capture, storage, and utilization (CCS or CCUS) has recently became an indispensable carbon reduction method to achieve carbon neutrality and net zero emissions by 2050. However, the adverse impact of CCS where large amount of carbon dioxide will be injected into deep saline aquifer has been a constant source of questioning among environmentalists and skeptics, with the most high-profile debate over whether fluid injection can trigger or induce earthquakes. In order to clarify the correlation between carbon storage and triggering of earthquakes, this study aims at establishing a hydraulic-mechanical (H-M) coupled analysis model with the FLAC3D program to explore the behavior of fluid injection and storage in deep formations. In addition, shock wave simulation technology is also introduced to quantify the potential of earthquakes under inferior injection condition. Preliminary numerical analysis in this study shows that the sandstone reservoir deep down below Zhang-bin Industrial Park close to the western coast in central Taiwan, as a scenario example, is injected by water with a fluid injection rate of one million tons per year via a single deep well. In the start-up simulation, it is assumed that a given fault is 500 meters away from the injection well, and the induced injection pressure cannot cause any damage to the fault in such case. However, in a worst-case scenario analysis (about 55,000 tons injection amount per day), it is noted that a slip failure of the fault would be triggered. Under this hypothetical scenario, the observation point 3.3 kilometers away (near a Glass Museum) may sense a maximum seismic movement in east-west direction of about 5.55 gal, and the observation point 6.3 kilometers away (near Lu-kung Town) may have a maximum north-south movement of about 0.82 gal. The induced seismic intensities are ranked as Scale 2 or less. The subsequent research will extend the hydraulic model in the model with TOUGH2 to simulate the carbon dioxide injection and storage behavior in a more realistic manner, and provide a more sophisticate evaluation process. It is believed that the studies can be used as evaluation reference and scientific demonstration data for future domestic CCS operations.

並列關鍵字

carbon storage ； triggered earthquakes ； coupling model ； FLAC3D

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