基于谱分解的气藏识别技术与应用

Spectral decomposition based gas reservoir identification technique and its application

地震波传播穿过含油气砂岩时,高频能量发生明显衰减,研究地震波的这种衰减特征可以为油气检测提供有效信息。本文利用三类含气砂岩模型,针对完全弹性介质和盖层为弹性介质、储层为衰减介质两种情形,利用基于波动理论的反射率法分别正演模拟其相应的叠前地震记录,并利用广义S变换对模拟记录进行分频处理,分析不同频率时AVO特征。研究表明,弹性介质条件下AVO响应曲线不受频率影响;盖层为弹性介质、储层为衰减介质时不同频率的AVO响应曲线不同,随频率增加地震波衰减增大。据此对S油田实际资料进行分析,结果表明含气层表现出异常高衰减特性,利用谱分解技术可以有效预测气层的分布。

When seismic wave propagates through oil & gas bearing sandstone,high frequency energy is dramatically attenuated,studying the attenuation could provide useful information for hydrocarbon detection.In this paper for two medium models which are isotropic medium model and the model with caprock being elastic medium and reservoir being attenuated medium respectively,by utilizing three types of gas-bearing sandstone model and based on wave theory reflectivity method,the pre-stack seismic records are modeled respectively,generalized S-transform was used to conduct frequency division processing for modeling records,and the AVO characteristics for different frequencies were analyzed.The studies show that for elastic media AVO response curse is not affected by frequency,but when caprock is elastic medium and reservoir is attenuated medium,AVO response curves for different frequencies are different,and the seismic wave attenuation increases with frequency increase.According to the conclusion the field data in S oilfield were analyzed,the study results show that based on the abnormally high attenuation characteristics of the gas-bearing layer,the spectral decomposition technique can be used to effectively predict the gas layer's distribution.