岩石物理模拟应用於台湾西南部上新-更新世前陆盆地之定量油气潜能评估  

Rock Physics Modeling Applied to Quantitative Evaluation of Shallow Gas Potential of Plio-Peistocene Foreland Basin, Southwestern Taiwan

作  者:傅式齊(S. C. Fuh) 張資宜(S. C. Liang) 梁守謙(T. Y. Chang) 巫國華(K. W. Wu) 周定芳(T. F. Chou) 楊育良(Y. L. Yang) 林人仰(J. Y. Lin) 陳佑吉(Y. J. Chen) 

出  处:《石油季刊》

摘  要:台湾西南部上新/更新世前陆盆地地层之油气潜能,与震测逆推声波阻抗、振幅支距异常、振幅亮点、振幅A/B分析等震测特性分析结果之关联性相当高。但陆域震测资料杂讯能量高,各项反应油气的震测特性,在不同井位其异常值的大小,极可能差异不小,以致在运用震测特性异常来评估油气潜能时,造成困扰及模糊空间。基於此,近两年施测的官田三号及永康一号之密度、P-Sonic、及S-Sonic等测录,被应用於岩石物理模拟及孔隙流体替换,预测储集岩各种含水饱和率之测录特性,并建立井测为依据之AVO油气异常类型及A/B油气异常量化标准。将传统的定性油气潜能评估,改进为定量油气潜能评估。研究结果发现,官田地区埋深700余公尺二重溪目标层,上倾方向储集岩之A/B与下倾方向水层之A/B比值,在1.78以上方具高油气潜能。合成P-G交又图分析结果显示,第三类型AVO异常的确为二重溪目标层之油气指徵。永康地区埋深1,700余公尺的崁下寮顶部目标层,上倾方向储集岩之A/B与下倾方向水层之A/B比值,在1.41以上方具高油气潜能。合成P-G交又图显示,第四类型而非预期的第三类型AVO异常,为崁下寮顶部目标层之油气指徵。依据这些标准,油气封闭综合评估的结果显示,永康构造西侧约5公里处为二重溪海底峡谷所切蚀之崁下寮顶部残留地块地层封闭,地质条件、A/B振幅特性及AVO异常,均显示油气潜能高的可能。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 region. 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.

关 键 词: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 

 

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