溶解反應對碳酸岩孔隙率與水力傳導係數之影響

Evolution of Porosity and Hydraulic Conductivity Induced by Dissolution in Carbonate Rocks

張星悅(Hsing-Yue Chang)

指導教授 ： 陳瑞昇

國立中央大學/地球科學學院/應用地質研究所/碩士(2008年)

摘要

地下流體流經多孔隙介質會帶動化學物種遷移，並伴隨發生地球化學反應，由於多孔隙介質礦物固體材料之溶解或沉澱反應，使得多孔隙介質之孔隙率改變，進而改變多孔隙介質之水力傳導係數。本研究目的是探討地下流體流經碳酸岩之溶解反應，對孔隙率與水力傳導係數之影響。
藉由實驗室批次與定流量管柱實驗，分別了解碳酸鈣表面的溶解速率，以及流體流經管柱時所發生之溶解反應所導致之孔隙率與水力傳導係數的變化。定流量管柱實驗中分別在不同流量、濃度、粒徑的條件下，觀察流體流經碳酸岩溶解反應對孔隙率與水力傳導係數之變化。結果顯示批次實驗裡CaCO3固體之溶解速率隨HCl溶液濃度增加而增加。定流量管柱實驗時，HCl溶液濃度愈高與流量愈大，皆會導致Ca2+生成量增加，反之HCl溶液濃度愈低與CaCO3固體顆粒間溶解反應較為完全，但Ca2+生成量相對增加趨緩。本研究所選定的CaCO3固體顆粒粒徑差異太小，使得CaCO3固體顆粒對孔隙率與水力傳導係數變化並未有顯著影響出現。本研究中流體流經管柱中CaCO3固體顆粒以SEM掃描發現，CaCO3固體顆粒產生溶解反應後，而產生CaCO3再結晶於CaCO3固體顆粒表面。

關鍵字

孔隙率 ； 溶解反應 ； 水力傳導係數 ； 碳酸岩

並列摘要

While flowing through a porous medium, migration of solute causes mineral dissolution and precipitation, thus modifying porosity and hydraulic conductivity. This study investigates the evolution of porosity and hydraulic conductivity induced by dissolution of carbonate rocks.
Batch experiments were carried out to understand the dissolution rates of CaCO3. Column experiments with constant flow rate were subsequently executed to investigate the evolution of porosity and hydraulic conductivity affected dissolution in carbonate rocks. Evolution of porosity and hydraulic conductivity induced by dissolution under different conditions of flow rates, HCl concentration and particles size were examined. Results show that higher HCl concentrations cause a faster CaCO3 dissolution of the porous medium in batch experiment. Moreover, higher HCl concentrations and larger flow rates cause faster increments in porosity and permeability. The size of CaCO3 particle has insignificant influences on the evolution of porosity and permeability. Additionaly, re-crystallized CaCO3 particles were found in SEM.

並列關鍵字

dissolution ； carbonate rocks ； hydraulic conductivity ； porosity

參考文獻

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