核磁共振與鑽石砧熱裂在油母質生油潛能之評估

Application of 13C NMR Spectroscopy and DAC Pyrolysis to the Study of Oil Potential of Kerogens

莫慧偵(Hui-Jane Mo)

指導教授 ： 黃武良

國立臺灣大學/理學院/地質科學研究所/博士(2009年)

https://doi.org/10.6342/NTU.2009.10521

摘要

油母質種類的不同以及成熟度的高低皆會在化學成分以及分子結構中顯示出差異。本研究使用波蘭地區石炭紀的煤素質樣品，利用鑽石砧熱裂解（DAC pyrolysis）直接觀察樣品受熱而裂解的過程、生油型態、與油氣潛能，再以固態核磁共振（Solid-state 13C CP/MAS NMR）去鑑定樣品在分子結構上的特性，同時也搭配其他非破壞性之光譜分析儀器電子顯微鏡（SEM）、紅外線（IR）、X光（XRD）、以及螢光（DAC-FS）等分析方法加以輔佐對比。在熱裂解實驗觀察出膜煤素產出大量顏色透明、流動性強的油，偶爾也伴隨一些氣泡的出現，熱裂解過程中產油速率最大那一刻的溫度Tpeak範圍是453~475℃；本研究使用含氫量一般的鏡煤素，這之中也有部分樣品能產出相當可觀的油量，這些油的顏色較深、質地較濃，Tpeak範圍是465~540℃，這結果顯示著並不是只有高氫量的鏡煤素（perhydrous vitrinite）才有產油潛能；惰煤素樣品在整個熱裂解過程中都沒有任何油或氣體的生成被觀察到；NMR的芳香環化指數（fa）是以惰煤素最高、膜煤素最低，芳香環指數之對數參數（logArNMR）與樣品自身成熟度（%Ro）顯示高度線性相關性，其餘光譜學分析結果也與以上這些煤素質的生油特性相當一致。另外，在探討成熟度對油母質生油潛力之影響上，研究樣品還包括三個不同沉積環境（湖相、海相、陸相）低成熟度的源岩，經由人工加熱至四個不同成熟度（Ro=0.79 /0.95 /1.10 /1.34%），經由光譜所呈現的化學分子結構探討個別煤素質及油母質的生油潛能。NMR結果顯示源岩樣品的脂肪烴結構明顯地隨著成熟度增加而大幅減少，fa隨成熟度增加而增加，其增加速率在低成熟度比較快，當Ro>1.1%之後的fa值則變化不大，對其作log（ArNMR）vs. %Ro圖，分別可得出三條線性趨勢線，然而相關性不如煤素質樣品那樣高。鑽石砧熱裂解的觀察中海相樣品在低成熟度下沒有生油的反應，推測其一原因可能是海相樣品會產生類似瀝青的中間產物，而在萃取固體粉末的過程中就被酸溶掉；另一可能原因是我們的這個海相樣品的組成有機物包含大量鏡煤素，因此熱裂解過程中沒有生油反應。

關鍵字

核磁共振 ； 鑽石砧 ； 油母質 ； 成熟度

並列摘要

A variety of maceral samples were characterized by the solid-state 13C CP/MAS NMR spectroscopy and their oil and gas generative potentials were evaluated by in-situ visual observations in a diamond anvil cell. The results show that exinite generated large amounts of visible oil-like liquid along with some gas, while fusinites generated no visible liquid and gas. The liquid (oil) from exinite appears light in color and less viscous. Some non-perhydrous vitrinite unexpectedly generated large amounts of visible liquid, although the liquid is darker and thicker than that from exinite, indicating that the oil potential of vitrinites is not limited to its perhydrous nature. The visual peak temperatures (Tpeak) of maximum rate of liquid petroleum generation for vitrinite (465-540°C) are generally higher than those for exinites (453-475°C). The results from NMR show that the aromaticities（fa） of macerals, which are the lowest in exinite and highest in fusinite, are inversely related to their oil generative capacities, which exhibits the highest oil generation potential for exinite. The observed linear relationship between the logarithms of fa values vs. %Ro suggests a potential maturity indicator. The dependence of NMR spectroscopy on organic maturity was further studied by artificially maturing two immatured keorgens from Green-River and Barnett shales and terrestrial coal. Isolated kerogen samples were pyrolyzed at 320°C in durations, equivalent to four levels of maturities（Ro = 0.79 , 0.95 , 1.10 , 1.34%） using confined-pressure (gold-tube) pyrolysis. Similar to those observed from macerals, the results show that the aliphatic groups in the matured kerogens decrease while aromatic groups increase significantly with increasing maturities. The fa values are positively correlated with the maturities among which the Green-River kerogen exhibited the highest effect. However, the fa values increase only subtle beyond a maturity equivalent to 1.1 %Ro for all three kerogens. The DAC pyrolysis of the matured samples reveals significant decrease in oil generation potential with maturity, particularly for the Barnett kerogen.

並列關鍵字

13C NMR ； diamond anvil cell ； kerogen ； maturity

參考文獻

莫慧偵，2004，有機物之生油潛能評估:鑽石砧熱裂解及紅外線光譜分析，國立台灣大學地質科學系研究所碩士論文。

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