西南石油大学学报(自然科学版)

• 地质勘探 • 上一篇    下一篇

时间域质心频移法估算品质因子Q

余连勇1,范廷恩1,胡光义1,曹思远2,王宗俊1   

  1. 1. 中海油研究总院,北京东城100027
    2. 中国石油大学(北京)CNPC 物探重点实验室,北京昌平102249
  • 出版日期:2014-08-01 发布日期:2014-08-01

Estimating Quality Factor Q with Time-domain Centroid Frequency Shift Method

Yu Lianyong1, Fan Ting´en1, Hu Guangyi1, Cao Siyuan2, Wang Zongjun1   

  1. 1. CNOOC Research Institute,Dongcheng,Beijing,100027,China
    2. CNPC Key Laboratory of Geophysical Exploration,China University of Petroleum(Beijing),Changping,Beijing 102249,China
  • Online:2014-08-01 Published:2014-08-01

摘要:

品质因子Q 是表征地下介质对地震波吸收衰减强弱的参量,是储层预测和油气检测的重要参量。质心法是估算Q 值的常用方法,精度和稳定性均较高,但该方法需要计算地震子波谱的质心和带宽,其精度依赖于波谱的提取质量。为避免地震子波谱的问题,提出时间域质心频移法,实现了在时间域估算品质因子Q,其核心是根据子波波形信息在时间域直接估算质心频率和带宽。对于常相位子波,其频谱的质心频率即包络峰值处的瞬时频率;对于Gauss 谱子波,其带宽可由包络宽度换算得到(两者乘积为一常量)。当地震子波近似为常相位及Gauss 谱时,可在时间域估算质心和带宽,按质心法公式估算Q 值,规避了地震子波谱的提取。VSP 下行波模型测试及实际资料应用表明,时间域质心频移法是可行可信的。

关键词: 时间域, 质心频移法, 品质因子, 瞬时频率, 带宽

Abstract:

The quality factor Q is the parameter that characterizes seismic wave energy attenuation caused by underground medium,and it is a key parameter in reservoir predication and hydrocarbon detection. Centroid frequency method is a common method to evaluate quality factor,which has high precision and stability. But this method needs calculation of the centroid frequency and bandwidth of spectrum,which mainly relies on the quality of seismic spectrum. To avoid extraction of wavelet spectrum,time-domain centroid frequency shift method(TCFS for short)is put forward. This method estimates the quality factor by calculating the centroid frequency and bandwidth of seismic wavelet in time domain. Centroid frequency of spectrum of constant-phase wavelet is the instantaneous frequency of its envelope at the peak,and Gauss window bandwidth can be calculated by converting the envelope width(the product of them is constant). When seismic wavelet approximates to constant phase and Gauss window,we can calculate the centroid frequency and bandwidth in the time domain,and evaluate the quality factor according to the centroid formula,which avoids the extraction of seismic wavelet spectrum. The test of VSP down-wave model shows that the time-domain centroid frequency shift method is feasible and credible.

Key words: time domain, centroid frequency shift, quality factor, instantaneous frequency, band width