濱海鹽水層二氧化碳地質封存移棲特性數值模擬評估

Numerical Assessment of the Migration Characteristics of CO2 Geological Sequestration in Deep Saline Aquifer

宋睿唐(Rui-tang Sung)

指導教授 ： 李明旭

國立中央大學/地球科學學院/水文與海洋科學研究所/博士(2014年)

摘要

為了因應全球暖化國際上逐年減少碳排放量的趨勢及壓力日增，台灣積極推動二氧化碳捕捉及地質封存研究。目前台灣地區二氧化碳排放量估計約為每年2.4億噸，主要的碳排放源為火力發電廠及工業生產(如煉鋼廠、水泥廠及石化產業)約各佔台灣年排放量1/3。因石化燃料須從國外進口加上冷卻用水取得方便等因素，故大多沿台灣北海岸和西海岸分布。而台灣西海岸地區存在廣大發展良好的沉積層環境，深具發展鹽水層二氧化碳地質封存的潛能。過去調查初步選出三個適合的區域，由北至南分別為觀音高地、台西盆地及台南盆地。其中彰濱工業區二氧化碳潛勢封存場址位在台西盆地東南側，附近主要碳排放源為台中電廠及麥寮電廠。
為瞭解封存場址特性，進行一系列地球物理探測及應用數值模擬工具進行評估。本研究以美國勞倫斯柏克萊國家實驗室發展的TOUGHREACT/ECO2N模式應用現有能取得的封存場址資料進行一系列的數值模擬評估。所推估之儲集層為桂竹林層、南莊層及觀音山砂岩上部，約400公尺厚，低滲透性蓋岩為錦水頁岩位在桂竹林層頂部。封存場址地層為傾斜層狀非均質地層，大致由東向西逐漸變淺，主要由砂頁岩互層組成。模擬範圍為11 km 11 km，採單井灌注評估，灌注口深度為2670公尺，二氧化碳灌注率假設為每年一百萬噸，灌注期為五十年，整個模擬期間為五百年。本研究主要針對二氧化碳灌注階段造成地層孔隙壓力上升、灌注期間二氧化碳的相變過程及灌注口孔隙水乾涸及伴隨NaCl沉澱，以及停止灌注後二氧化碳移棲範圍特性及其垂直剖面結構等，探討封存機制及評估是否有逸漏的可能，並針對不同模擬案例進行比較，如非加密或局部加密網格及考慮地化反應傳輸或物理傳輸機制等。
模擬500年結果顯示，考慮地化反應傳輸模擬案例，二氧化碳移棲對地層孔隙率的變化影響幅度很小(最大孔隙率改變減少1.84 10-3及增加7.43 10-4)，對側向移棲特性無顯著影響。局部加密網格有助於解析灌注井周遭灌注二氧化碳的相變過程及CO2 Plume在層狀非均質地層的空間分布特性。各模擬案例的二氧化碳最大移棲距離為2700公尺，主要朝台灣海峽方向移棲，而向陸地方向的最大移棲距離為2300公尺。

關鍵字

二氧化碳地質封存 ； 彰濱工業區封存場址 ； TOUGHREACT/ECO2N Simulator ； 局部加密網格

並列摘要

Reductions of CO2 emissions to mitigate global warming are an inevitable trend in the world. Taiwan government has been aggressively promoting the studies of carbon dioxide capture and carbon dioxide geological sequestration (CGS) to investigate the feasibility of such mitigation techniques. The annual CO2 emission in Taiwan was estimated as high as 0.24 billion tons. The majority of CO2 emission sources are the thermal power plants and industrial sectors (e.g., cement mills, steel mills, petrochemical industry etc.), and each contributed about one third of annual CO2 emissions in Taiwan. Due to requirements of fossil-fuel importation and cooling water acquirements, most of thermal power plants distributed along the North and West costal lines of Taiwan. Advantages of extensive and well-developed sedimentary formations along West costal area of Taiwan provide massive volume for CGS practices. Preliminary investigations showed that the Kuanyin Plateau, Taihsi Basin, and Tainan Basin are the potential area for CGS. The Changhua Coastal Industrial Park (CCIP) potential site was located in the southern part of the Taihsi Basin and near by the Taichung Power Plant and Mailiao Power Plant.
To evaluate the feasibility and risk of CGS practices in Taiwan, intensive geophysical explorations and numerical assessments are needed. In this study, we utilize the TOUGHREACT/ECO2N simulator to perform a series of numerical simulation and assessment for CGS at the CCIP Site. Objective reservoir was located from Kueichulin Formation, to upper part of Kuanyinshan Sandstone with thickness of 400 meter and beneath the low permeability caprock by the Jinshui Shale. Sloping and layered heterogeneous formations were composed of interbedding sandstone and shale that became thinner from East to West. Simulation area is 121 km2 (11 km 11 km) with single injection well in the center and injection point at -2674 meter. Injection of CO2 is assumed with a constant injection rate of 1 Mt/year for the first fifty years and total simulation period is 500 years. Characteristics of pore pressure differences, phase change of injected CO2, pore water drying-out, and subsequent halite precipitation during CO2 injection period and migration behavior of CO2 plume, pattern of cross-sectional CO2 plume, and trapping component analysis are simulated and analyzed with several simulation studies (e.g., cases of the non-refined grids and local refined grids, physical transport and reactive-transport).
At 500 years, simulation results show that the effects of porosity differences are minor to the lateral migration of CO2 Plume. The simulation cases with local refined grids can improve on phase change evolution of injected CO2 and the spatial distribution pattern of CO2 plume in sloping and layered heterogeneous formations. The maximum migration distances of CO2 plume are 2700 meter and 2300 meter toward upslope direction of formation below the Taiwan Strait and toward downslope direction of onshore area, respectively.

並列關鍵字

CO2 Geological Sequestration ； Changhua Coastal Industrial Park Site ； TOUGHREACT/ECO2N Simulator ； Local Refinement Grids

參考文獻

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