地下流體與多孔隙介質礦物顆粒間產生地球化學反應，伴隨著孔隙率與水力傳導係數變化，此現象在科學、工程與工業領域皆為重要之研究議題。本研究進行一系列批次表面反應實驗及管柱流動實驗，進而瞭解流體流經碳酸鈣產生溶解與沈澱反應對孔隙率與水力傳導係數之變化。利用鹽酸HCl(aq) 及硫酸H2SO4(aq) 兩種溶液作為地下流體以加速反應速率。以測壓計測量水位，記錄管柱兩邊壓力差以達西定律計算水力傳導係數；測量出流水中鈣離子與硫酸根離子之濃度，以便計算孔隙率變化。管柱流動實驗結束，將管柱之碳酸鈣礦石填充床取出，進一步進行碳酸鈣微觀型態與礦物組成分析。研究結果發現碳酸鈣之粒徑與溶解/沈澱彼此競爭以致孔隙率與水力傳導係數有震盪的情形；SEM觀測得知石膏沈澱皆於進流口，以上現象皆與理論相符。 Investigation of chemical reactions between a fluid and the porous medium through which it flows, and of the subsequent changes in the medium porosity and hydraulic conductivity, is an area of interest for many scientific, industrial and engineering. Dissolution and precipitation are two of the most important processes affecting fluid chemistry, and they can significantly modify the physical and chemical properties of porous media. In this study, we investigate the effect of particle size of carbonate rock on temporal evolution of porosity and hydraulic conductivity induced by dissolution and precipitation by performing a series of laboratory surface reaction experiment and column flow experiment by injecting HCl/H2SO4. The temporal evolution of overall hydraulic conductivity is calculated by measurement of change in hydraulic head gradient and application of Darcy’s law. Variation in porosity is obtained by analyzing the effluent acid for Ca2+ and and invoking the law of mass balance. Furthermore, after each experiment, the column sample is retrieved and sectioned in order to study the micro-morphology and mineral composition. Results show that significant fluctuations in porosity and hydraulic conductivity occur due to competition between dissolution and precipitation. The patterns of fluctuations in porosity and hydraulic conductivity are influenced by particle size of calcium carbonate. SEM analysis shows that gypsum precipitates in the inlet of the column. These findings are in qualitative agreement with conceptual understanding of such phenomena.
