綜合許多提出CO2封存技術的研究中，因地質封存具有巨大潛在的儲存量，因此將CO2注入地底封存為最有遠景的方式。然而評估保護井孔的油井水泥在長期的封存下是否能安全且有效的封存CO2為我們必須做的一項課題。CO2注入到深層的地質結構中通常伴隨著含水層或鹽水層，CO2與水會結合形成碳酸(H2CO3)並且使水泥鹼性降低、抗壓強度降低、滲透率增加，這些可能會造成CO2從井孔洩漏的風險。
本研究試圖研究不同配比的API G級水泥在CO2環境下(常壓、70℃)對其力學性質、化學組成、微觀結構之影響。添加物包含飛灰、膨潤土、矽粉及重晶石。連續反應28天後進行試驗，力學試驗部分包括抗壓強度、彈性參數，微觀結構分析包括XRD、SEM、EDS，也觀察記錄了試體的碳化深度。本研究發現添加飛灰的API G級水泥有最佳的抗壓強度且有最深的碳酸鈣堆積層，添加膨潤土的API G級水泥因水灰比較高所以其抗壓強度最弱且碳酸鈣堆積層深度較淺。

Among commonly proposed CO2 storage techniques, injection of anthropogenic CO2 underground is promising due to their large potential storage capacity and geographic ubiquity. However, the long-term wellbore integrity of the cement sheath should be carefully evaluated to ensure the safe and efficient storage of CO2. Injection of CO2 into the deep geological formations often encounters the aquifers or deep saline aquifers. CO2 reacting with water will become the carbonic acid (H2CO3) and it will make cement more alkaline, lower in compressive strength, and increasing in degree of saturation. The well integrity will be weakened by the increase in the degree of carbonization. It will result in the reduction in service life of the well and possible leakage of CO2 from the wellbore.
This paper attempts to study the mechanical properties, chemical compositions, and microscopic structures of API G cements with different additives in the saturated-CO2 condition (atmospheric pressure, 70℃). The additives under investigation include fly ash, bentonite, and barite with silicate. The evolution of the mechanical properties including compressive strength, deformation modulus, and microscopic structure analysis including XRD, EDS, and SEM, were recorded over a period of 28 days. The carbonized depths of the samples over time were also observed. This study finds that the API G cement with fly ash displays the best compressive strength with deepest penetrating depth of carbonization. The API G cement with bentonite with higher water content has the lowest compressive strength with shallowest penetrating depth of carbonization.

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