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臺西盆地模擬及油氣生成潛能評估

Basin Modeling and lts Application to the Assessment of Hydrocarbon Generation Potential of the Taihsi Basin

摘要


本研究針對臺西盆地中新世以後十個地層層序進行一維及擬近三維盆地模擬,分析臺西盆地不同地質年代區域性之沈積基盤熱流分佈、單位面積累積油氣生成量分佈、單位面積油氣排放量分佈,據以估算臺西盆地累積油氣總生成量及排放量,並評估海域油氣探勘潛能。 根據一維盆地模擬結果,A1井之碧靈層約在4 Ma入油窗;C1井之石底層約在3-4 Ma間進入油窗;D1井之五指山層約在3 Ma進入油窗,木山層則約在1 Ma進入油窗;E1井之五指山層約在1 Ma進入油窗;K14井之五指山層約在13 Ma進入油窗,木山層則約在9 Ma進入油窗,石底層約在4 Ma間進入油窗;L5井之五指山層約在9 Ma進入油窗,木山層則約在4-5 Ma進入油窗;N1井之五指山層約在5 Ma進入油窗,木山層僅底部約在3 Ma進入油窗;W之五指山層約在14 Ma進入油窗早成熟期,木山層則約在12 Ma進入油窗早成熟期;P井之碧靈層約在4 Ma進入油窗早成熟期。火成作用可能是造成K14井甚早進入油窗的原因。除W井之五指山層在3-4 Ma時進入油窗中成熟期外,甚餘各井生活地層均保留在早成熟期。 擬近三維臺西盆地模擬結果顯示:以加權平均法估算海域D、E、K等構造煤屑富集帶的TOC值,可獲得較合理之S1擬合。各地質年代沈積物基盤古熱流分佈趨勢與早中新世以後各地層向東增厚的趨一致,亦向東增加;但同一地點,基盤古熱流卻顯示隨地質時間冷卻之現象。相較於台南盆地油氣累積生成總量,台西盆地油氣生成潛能相對小許多。

並列摘要


By using the 1D BasinMod and the 2.5D Basin View computer soft-wares,geological and geochemistry data of eleven wells and ten interpreted post-Miocene seismic sequences in the Taihsi Basin were integrated to model the evolution of the basement heat flow as well as the temporal and special histories of the maturity, the hydrocarbon generation and the expulsion of the source rock. According to 1D modeling results, the onsets of hydrocarbon generation of the Shiti formation in the C1 and the K14 wells are 3 and 4 Ma, respectively. Those of the piling formation in the A1, the K14 and the P wells are 4, 5.5, and 4 Ma, respectively. Those of the Mushan formation in the Dl, the K14, the L5, the N1, and the W wells are 1, 9, 4-5,3 and 12 Ma, respectively. Those of the Wuchishan formation in the D1, E1, the K14, the L5, the N1, and the W, are 3, 1, 13, 9, 5, and 14 Ma, respectively. The Modeled S1 based on the weighted average TOC values, which honor the coal seams contribution to hydrocarbon generation, can fit the measured S1 better than that excluding the coal seams. According to 2.5D modeling results, the basement heat flow in the eastern flank of the basin was higher than that of the western flank through all geological time. Yet for the same location, the basement heat flow decreased with the decreasing geological time. A rifting center was inferred to having been existed in the Taihsi basin and the basement has been cooling down since early Miocene after the rifting center shift further eastward. The assessed volumes of the hydrocarbon generation and the expulsion of the source rock were concluded to be much smaller than those of the Tainan basin. The offshore exploration potential would be flourished only if the hydrocarbon generated in onshore Taiwan basin is abundant or offshore pre-Miocene source rock is available.

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