岩石物理模擬應用於台灣西南部上新－更新世前陸盆地之定量油氣潛能評估

台灣西南部上新／更新世前陸盆地地層之油氣潛能，與震測逆推聲波阻抗、振幅支距異常、振幅亮點、振幅A/B分析等震測特性分析結果之關聯性相當高。但陸域震測資料雜訊能量高，各項反應油氣的震测特性，在不同井位其異常值的大小，極可能差異不小，以致在運用震测特性異常來評估油氣潛能時，造成困擾及模糊空间。基於此，近兩年施測的官田三號及永康一號之密度、P-Sonic、及S-Sonic等測錄，被應用於岩石物理模擬及孔隙流體替換，預測儲集岩各種含水飽和率之測錄特性，並建立井測為依據之AVO油氣異常類型及A/B油氣異常量化標準。將傳統的定性油氣潛能評估，改進為定量油氣潛能評估。研究結果發現，官田地區埋深700餘公尺二重溪目標層，上傾方向儲集岩之A/B與下傾方向水層之A/B比值，在1.78以上方具高油氣潛能。合成P-G交又圖分析結果顯示，第三類型AVO異常的確為二重溪目標層之油氣指徵。永康地區埋深1,700餘公尺的崁下寮頂部目標層，上傾方向儲集岩之A/B與下傾方向水層之A/B比值，在1.41以上方具高油氣潛能。合成P-G交又圖顯示，第四類型而非預期的第三類型AVO異常，為崁下寮頂部目標層之油氣指徵。依據這些標準，油氣封閉綜合評估的結果顯示，永康構造西側約5公里處為二重溪海底峽谷所切蝕之崁下寮頂部殘留地塊地層封閉，地質條件、A/B振幅特性及AVO異常，均顯示油氣潛能高的可能。

關鍵字

岩石物理模擬；振幅－支距分析；震測逆推； A/B振幅特性；海底峽谷；深切谷；地層封閉

並列摘要

Due to lack of measured S-Sonic, shallow gas evaluation of Plio-Peistocene foreland basin underneath southwestern Taiwan plain area was mainly done qualitatively by utilizing seismic attributes such as A/B, full stack inverted impedance and AVO anomaly. Based on the previous exploration experience, AVO anomaly of Class Ⅲ was used as a direct hydrocarbon indicator for detecting shallow gas of Plio-Peistocene foreland basin in the southwestern Taiwan area. Based on this experience, the YK-1 well targeting at the top of the Kanhsiaoliao formation of Plio/Pleistocene was drilled in 2007 and failed. Realizing the importance of quantification of seismic response to reducing the uncertainty of well evaluation, rock physics modeling and fluid substitution were applied in this study to verify the type of log-based AVO anomaly and to quantify the threshold of A/B seismic amplitude anomaly for detecting gas sand. Based on the rock physics modeling and fluid substitution results, log-based AVO anomaly of class Ⅲ was confirmed for detecting gas sand in Plio-Pleistocene foreland basin buried shallower than 1,000 meters. As sand buried deeper than 1,700 meters, an AVO anomaly of class Ⅳ was verified as the indicator of potential gas sand. The quantified threshold value of A/B, seismic amplitude ratio between up-dip target sand and down-dip brine sand, for detecting gas sand buried shallower than 800 meters and deeper than 1,700 meters were concluded in this study to be 1.78 and 1.4, respectively. Re-examining the A/B amplitude curve of line 75PCCD5, the ratio (about 1.67) between the A/B level of the stratigraphic trap, located about 5 kilometers to the west of YK-Ⅰ well, and that of the brine saturated sand drilled in the YK-1 well is greater than the threshold value. High gas potential was also relected in the seismic based AVO analysis of this, which is consistent with the log-based AVO analysis.

並列關鍵字

Roch Physics Modeling ； AVO ； A/B ； Foreland Basin ； Shallow Gas

國際替代計量

岩石物理模擬應用於台灣西南部上新－更新世前陸盆地之定量油氣潛能評估

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