| 摘要: | 台灣地區油氣資源開發肇始於苗栗出磺坑背斜構造，過去出磺坑地區油氣潛能相關研究甚多，但地化研究相對較少。本研究目的為藉由熱裂分析及總有機碳(TOC)測定，加入礦物組成對孔隙率影響及XRD等方法，綜合評估台灣西北部油氣資源生產潛能，據以探討出磺坑背斜下部中新統之石油系統，共使用30件出磺坑層、碧靈頁岩、木山層和五指山層井下樣本。本研究著重於(1)儲集層有機質富集度與成熟度，(2)儲集層孔隙率與滲透率，及(3)儲集層礦物組成。結果顯示，出磺坑層和碧靈頁岩礦物顆粒偏細，只有少量較完整的石英且褐色黏土質岩屑較多，推測這兩地層孔隙率不高。而木山層與五指山層樣本中石英的含量大多都在40%左右，顆粒較出磺坑層和碧靈頁岩樣本大且清楚，推測在木山層及五指山層樣本中，石英提供的受壓裂隙可使地層在深埋過程中孔隙率不致大幅下降。XRD結果亦顯示本研究區各層主要礦物都為石英，但木山層以及五指山層黏土礦物較少，孔隙率大約在4~6%，且與深度呈負相關。而TOC以及熱裂分析實驗數據顯示，大部分樣本TOC皆在2%以下，為貧乏級，但有一個五指山層樣本TOC超過4%，其Tmax達到492oC，達過成熟，以產氣為主，鏡煤素反射率結果趨勢亦與Tmax相同。熱裂分析之氫指數(HI: mg HC/mg TOC)顯示19件樣本為III型有機質，以產氣為主。綜合以上結果，評估五指山層最具油氣潛能，因其有機材料較富集且成熟度進入油窗。;Chuhuangkeng anticline is the first oil-producing structure in Taiwan, there are many studies of HC in Chuhuangkeng area in the past, whereas geochemical data are comparingly less than other geophysical and geological data. In this study, we try to evaluate the petroleum system of possible reservoirs in Chuhuangkeng anticline by using geochemical analysis, combined with the results of mineral composition and XRD analysis. 30 samples including Miocene Chuhuangkeng Formation, Piling Shale, Mushan Formation and Oligocene Wuchishan Formation were studied. There are three scopes in this study: 1) to evaluate the total organic carbon(TOC) and thermal maturity of reservoirs, 2) to evaluate the porosity and permeability of reservoirs, and 3) to observe the mineral composition of reservoirs. The results of mineral composition show that there are mostly fine-grained minerals in Chuhuangkeng Formation and Piling Shale, noticeable brownish clay minerals will result in the lowering of porosity for those two formations. On the other hand, quartz content is more than 40% in Mushan Formation and Wuchishan Formation with larger grain size minerals. Furthermore, the result of XRD also shows that quartz is the major mineral in samples studied. Clay mineral contents in Mushan Formation and Wuchishan Formation are relatively less than other formations. In addition, the porosities of Mushan Formation and Wuchishan Formation are 4-6%. and negatively correlated with depth. Finally, the results of TOC and Rock-Eval pyrolysis show that TOC of most samples are less than 2%, except sample No.14 with TOC content > 4% and Tmax 492oC. The result of Ro% exhibits the same trend with Tmax. Moreover, hydrogen index(HI) indicates that sample No.14 has type III kerogen, which is gas prone. In conclusion, we expect Wuchishan Formation has the highest HC potential among samples in this study, due to its good TOC content and thermal maturity. |
