摘要
近來研究發現，新第三紀地層中的油氣來源並非局限在下部中新統之含煤地層。例如台南盆地在漸新世晚期開始張裂，而同張裂沈積產生的油氣就形成了F構造的油氣儲集。另外在北港高區南坡的A斷層之下，還有隱沒的H斷層在漸新世晚期形成地塹，而同張裂沈積產生的油氣亦沿著H斷層與A斷層移棲到北邊的八掌溪氣田。還有台西盆地在南日島脊旁邊，也有一個漸新世晚期形成的地塹，其同張裂沈積由潮汐河道運送到銅鑼向斜，經過深埋熟成以後，產生大量天然氣移棲到鐵砧山氣田。所以台西盆地有兩種石油系統，一為煤系地層的石油系統，廣佈在竹苗區陸海域，油樣類固烷以C29為主；二為同張裂沈積的石油系統，目前只發現鐵砧山氣田，油樣類固烷以C27為主。以往探勘太重視煤系地層，忽略了同張裂沈積，今後探勘應當聚焦在同張裂沈積的石油系統。台西盆地還有一些漸新世晚期生成的張裂盆地，能夠成為區域性生油中心，值得探勘人員注意。並且目前國內探勘處於低潮期，急需新觀念帶來新的探勘目標，所以追尋台西盆地新的探勘標的，實乃刻不容緩的事。再者，張裂盆地可由震測剖面辨認，能夠突破地球化學受鑽井位置以及分析岩樣的限制，擴大生油中心的尋找範圍，形成新的探勘觀念與方法，可以在台西盆地發現許多新的探勘目標。五里牌地塹本身就是晚漸新世開始的張裂盆地，不必藉助於潮汐河道，就有大量的同張裂沈積存在，並且深度亦達6000公尺以上，足夠提供成熟高溫，所以五里牌地塹產氣能力理當優於銅鑼向斜。可望找到像鐵砧山氣田同樣規模的大型油氣田。五里牌地塹實乃同張裂沈積探勘的首要目標。
並列摘要
After years of petroleum exploration, we have discovered a large amount of hydrocarbon deposits onshore and offshore in Taiwan. The hydrocarbon type of Paleogene is heavy oils while that of Neogene is natural gas or condensates. The petroleum systems of these sedimentary basins are quite different. The Paleogene basin was developed under independent and closed sedimentary environments while the Neogene under open environments. It is inferred that two different evolutional stages of the same basin providing the two hydrocarbon sources. The Neogene basin is purely sedimentary basin, not influenced by disturbance of tectonics. It is completely controlled by the sedimentary process so that most of the strata are marine faces. Therefore, the exploration target in the Neogene basin should be focused on the coal-bedded source rock.Recently, it is found that hydrocarbon in the Neogene reservoir is not only from the coal-bedded lower Miocene but also partly from the Late Oligocene and early Miocene. There appeared two petroleum systems in the Taichi basin. The first system significant with sterane C29 is the coal-bedded and distributed in Hsinchu-Miaoli area. The other system characterised by sterane C 27 in the synrift deposits of Tiechenshan area. The future exploration effort should focus more on the petroleum system of synrift hydrocarbon deposits.