台湾地区的油气储集断层封闭

Fault Sealing and Hydrocarbon Accumulation in Taiwan region

台湾地区的油气除少部份分部在非褶皱带外，大部份的油气恉出现在台湾西北部麓山区的背斜中，而不论是在何种构造带中由於断层的无所不在，大部份的油气之储聚均与断层封闭有关。但较大量且具高经济价值的油气则储集於断层落差较小的背斜褶皱中，至於褶皱带与非褶皱带的油气之可采蕴藏量其差距达六倍以上，同样的破碎的背斜，在褶皱带的背斜其油气储量是非褶皱带的两倍以上。以新近发展的断层封闭分析方法：页岩断层泥比值(Shale Gouge Ratio)与页岩涂敷因子(Shale Smear Factor)分析现有台湾地区储集层与断层的关系，结果显示铁砧山与台南外海Ｆ构造的SGR值绝大部分小於0.2，前者已证实储集层是连通的。除上述二者外其余地区储集层之SGR值大都落於0.3以上，大部份出在0.4－0.6之间，少部份则可达0.8，但最高的SGR值分布区0.6－0.8的油气储集数量并不高，与已知SGR愈大封闭效果愈佳并不一致，其原因在於愈大的断层落差能储集油气的地层愈薄，而较大断层落差亦显示，断块经历过的断层活动次数较多或时间较久，故较不利於油气的持续积聚。至於SSF的分析值显示除铁砧山与台南外海Ｆ构造外之储油气层的SSF值均落在20以下，与已知SSF值大於7则页岩断层泥分布开始不连续，即断层面封闭较差之前人研究结果并不一致。若就高经济价值油藏的断层封储特性而言除了需较高的SGR外，另外就是断层落差不能太大的背斜中之侧贴封闭。

Most of the hydrocarbons distribute in the northwestern foothill of Taiwan. Only small amount of hydrocarbons were discovered in the tension fault zone. Wherever hydrocarbon accumulate, almost all hydrocarbon trapped by fault sealing for laking unruptured fold. Two methods, Shale Gouge Ratio(SGR) and Shale Smear Factor(SSF), were used to analyze the sealing effects of fault for production zones in this area. More than half of SSF are over 7. Which means shale gouge become discontinuity, and sealing could be failed. SGR range from 0 to 0.8. Most of SGR distribute between 0.4 to 0.6. A few of them are higher than 0.6, even up to 0.8. Only values of two fields are lower than 0.2, which means no sealing effect forfault plane. One of it has been proven that sand beds are connecting across the fault plane. SGR increase with decreasing recoverable volume of hydrocarbon, though higher SGR means higher colume of hydrocarbon could be trapped. Higher SGR also accompany with higher fault throw. The principal volume of recoverable hydrocarbon were trapped in sand bed of anticline by Juxtopose to thick shale bed with lower fault throw.