台西盆地的三種石油系統與探勘前景

New Play and Petroleum Systems in the Taichi Basin

李長之(Chang-Jie Lee) ； 吳素慧(Su-Huei Wu) ； 王佳彬(Jar-Ben Wang)

《石油季刊》 47卷2期 (2011/06) Pp. 21-54

https://doi.org/10.30128/JP.201106.0003

摘要

台西盆地有三個石油系統，其油樣之碳十三穩定同位素與Pristane/Phytane對比的關係都不相同，分成三個群聚。（一）潮汐三角洲生成竹苗區陸海域各油氣田新竹苗栗陸海域各油氣田之油氣生產為天然氣帶凝結油，主要生產層包括中新統打鹿層、南莊層、石底層、木山層及漸新統五指山層。氣油比(GOR)高，屬熱成熟生成氣，成熟度估計為0.7~0.9%，為中度成熟。油比重之API 約為31~62，Pristane/Phytane約為4~10。(二)河流三角洲生成CBD構造的油氣CBD構造於CBD-1號井木山層鑽獲天然氣及凝結油。天然氣C2(上標 +)約10%，CO2含量高達32%，凝結油比重為API 52 ，正烷烴以低碳數為主，Pristane/Phytane比值高接近10。與新竹苗栗陸海域各油氣田的油樣成份相異。(三)同張裂沉積生成的CBE構造的油氣CBE構造於CBE-2號井北寮層鑽獲天然氣與API 37 Pristane/Phytane 5.53的凝結油，以及木山層鑽獲API 10 Pristane/Phytane 13.66的重油。其木山層油樣與新竹苗栗陸海域各油氣田的油樣成份相異，也有比CBD-1井更高的類萜烷／類固烷比值。（四）無論潮汐三角洲內潟湖與潮汐沼地之大量植物生成煤層，或觀音高區南側CBD凹地沖積的煤層，其深度都不深，使得沉積當地生成的煤層，因為地溫太低造成油氣成熟度不足，難以生成大量油氣。必須靠潮汐三角洲系統將其搬運到東邊的低區，才能到達足夠的成熟溫度，產生大量的油氣形成區域性的生油中心。但竹苗區陸海域諸多油氣田，都屬於煤系地層的石油系統，因此在多年探勘後，要再找到源自煤系地層的新油氣田，實屬非常困難。從局部張裂盆地來尋找區域性生油中心，為新的探勘觀念與方法，可以突破傳統地化受限於鑽井不足以及生油中心沒有鑽井等種種不利限制，而精準地在震測剖面找到生油中心。增加了台西盆地許多新的探勘目標，實為台西盆地繼續探勘的前景所在。

關鍵字

台西盆地 ； 石油系統 ； 同張裂沉積

並列摘要

In this study, it has been found that hydrocarbons in the Neogene reservoir are not only from the coal-bedded lower Miocene, but also partly from the Late Oligocene and early Miocene. For example, the Tainan Basin extended initially in the late Oligocene. The synrift deposits have become the source rock in the F Field, Kaohsiung offshore. The other example was happened in the souther side of ”A” Fault. The blind ”H” Fault with a graben formed in late Oligocene. The hydrocarbons in these synrift deposits migrated to the Pachungchi Gas Field along the H Fault and A Fault. Furthermore, there is a graben located in Taichi's Basin nearby the Nanjihtao Ridge. This graben was also formed in the late Oligocene. Their synrift deposits were transported to the Tunglo Syncline by tidal delta. After deep burial, large amount of hydrocarbons migrated to Tiechenshan Gas Field. There are two major kind of petroleum systems in the Taichi Basin. The first system with sterane C29 is the coalbedded, distributed in Hsinchu-Miaoli area. The other system was characterised by sterane C 27 in the synrift deposits of Tiechenshan Gas Field. In the past, we were paid so much attention to the study on coal-bedded formations and neglected the synrift deposits. The better way for future exploration is to focus on the petroleum system of synrift deposits.There are still some existing extension basins occurred in the late Oligocene in the Taichi Basin. It is worthy to pay attention to this kind of rift basin. At present, the domestic exploration is in the low atmosphere. It is necessary to bring new exploration targets and focus on the Taichi Basin.

並列關鍵字

Taichi Basin ； Petroleum System ； Synrift Deposits