螢光光譜評估源岩之生油動力學初步研究

摘要石油系統中，若能有效地掌握源岩產油的條件(埋藏深度、時間)，及分辨油氣生成先後，將能大大提升石油開採的經濟效益。有鑑於前人研究多以熱裂解(Rock-Eval Pyrolysis)方式分析源岩產油氣之總體潛能，而無法區分油氣生成的時間，因此，本研究嘗試利用鑽石的透光性，同時結合了生油岩裂解產生石油與天然氣時，唯石油有螢光反應的特性，針對有機物的熱裂解產油反應進行現場(in-situ)螢光光譜即時分析，並利用動力學原理計算反應活化能，進一步應用於已知深埋歷程的地層中，推估其產油的時間。實驗樣品包括不同沉積環境之生油岩：八個海相生油岩(TypeⅡ)，其中兩個為富含硫成份之樣品(TypeⅡS)，四個湖相生油岩，以及從腐植煤中分離出的殼質組(liptinite)，分別以五種加熱速率(1、3、8、25、50°C/min)，在300°C~600°C範圍內量測螢光或產油反應。實驗結果如下：(1) 不同沉積環境之源岩產生螢光之溫度區間以及光譜的變化不盡相同，例如達到最大螢光強度之溫度以海相476°C最低，湖相497°C次之，陸相之506°C為最高。同一樣品在五種升溫速率下之螢光強度變化，可做為計算生油反應動力學參數。(2)於設定頻率因子(A)的條件下，各生油岩之生油反應活化能(Ea)主要分布於每莫耳53~55仟卡(kcal/mol)之間。就單一樣品之活化能分布情形而言，皆集中於一至兩個值。(3)推算在每百萬年升高攝氏十度(10°C/my)之地質加熱速率下，各生油岩最高產油速率之溫度範圍為135°C ~167°C，若排除含藻煤之樣品，則各有機物之主要產油溫度區間則縮小至20°C左右的差距。(4)利用前人研究中已知頻率因子之相同樣品，求得產油反應活化能，結果發現log A對Ea作圖呈現與前人研究一致的線性關係，而活化能值則有些微差距，推測造成誤差的因素為前人實驗含有水的緣故，以及其萃取反應後浮在水面上的油進行分析，忽略了部份存在樣品中的油所致。這樣的結果顯示以螢光光譜之分析方法能有效辨識生油岩產油的時間並改善前人研究中無法代表自然界開放系統環境，另一方面，針對自然產油環境下，確實含有水分的存在，則是本研究未來需進一步探討的方向。

關鍵字

螢光光譜；產油動力學；生油源岩；鑽石砧裂解

並列摘要

Abstract In a petroleum system, if we can define the conditions, in particular, the relative timing when oil or gas was generated, we can greatly reduce the economic risk of exploration. Most conventional techniques for studying hydrocarbon generation, however, provide kinetic parameters for predicting only bulk hydrocarbon (oil + gas), and are unable to distinguish between oil and gas. The present study is developing a new technique using fluorescence spectroscopy to determine the kinetics for liquid petroleum(oil) generation in a closed system. The technique monitors in-situ the fluorescence response of oil newly generated from kerogen through an optical window of a diamond anvil cell during pyrolysis. Since the fluorescence response is proportional to the extent of oil generation only, the measurement can be used to calculate the kinetic parameters for oil generation and extrapolate to the source beds of known burial history for predicting the timing of oil generation. The starting samples include a variety of oil-prone source rocks from different depositional environments: six marine (Type II), two sulfur-rich marine (Type IIS), two lacustrine (type I) kerogens, one torbanite (boghead coal), and one liptinite separated from a humic coal. The pyrolysis experiments were conducted at five heating rates (1, 3, 8, 25, 50°C/min) at temperature from 300 to 600

並列關鍵字

fluorescence ； oil kinetics ； oil-prone source rock ； DAC pyrolysis

參考文獻

Barker, C., 1974. Pyrolysis techniques for source-rock evaluation. The American Association of Petroleum Geologists Bulletin, 58, No.11, pp.2349-2361.

Baskin, D. K., 1997. Atomic H/C ration of kerogen as an estimate of thermal maturity and organic matter conversion. The American Association of Petroleum Geologists Bulletin, 81, No. 9, pp. 1431-1450.

Bassett, W.A., 1979. The diamond cell and the nature of the earth’s mantle. Ann. Rev. Earth and Planetary Sci., 7, pp. 357-384.

Bassett, W.A. and Ming, L.C., 1972. Disproportionation of Fe2SiO4 to 2FeO+SiO2 at pressures up to 250 kbar and temperatures up to 3000˚C. Phys. Earth Planet. Inter., 6, pp. 154-160. Cited in, Bassett, W.A., 1979. The diamond cell and the nature of the earth’s mantle. Ann. Rev. Earth and Planetary Sci., 7, pp. 357-384.

Bassett, W.A., Shen, A.H., Bucknum, M.J. and Chou, I.M., 1993. A new diamond anvil cell for hydrothermal studies to 2.5 GPa and from -190 to 1200 °C, Review of Scientific Instruments, 64, pp. 2340-2345.

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螢光光譜評估源岩之生油動力學初步研究

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