小波尺度域含气储层地震波衰减特征

CHARACTERISTICS OF SEISMIC ATTENUATION OF GAS RESERVOIRS IN WAVELET DOMAIN

黏弹性衰减因子Q的可靠估计可通过Q反褶积来提高地震资料的分辨率并有助于振幅分析 .本文从小波理论出发 ,结合地震波在黏弹性介质中的传播方程 ,推导出小波尺度域地震波能量衰减公式 .能量衰减公式具有下列性质 :(1)Q值越大 ,能量衰减得越慢 ;Q值越小 ,能量衰减越严重 ;(2 )尺度越小 ,信号中保留的能量越少 ;(3)对于脉冲源来说在理想的无衰减介质 (即Q趋近于∞ )中传播时 ,信号在不同尺度内的能量相同 .利用尺度能量公式 ,可从反射地震资料中直接估计品质因子Q(即衰减因子 ) ,也可以提取不同尺度的能量衰减剖面作为储层描述的属性参数 ,用来进行岩性识别和指示气藏 ,与经典的谱比法相比 ,避免了谱比法所面临的双时窗问题以及进行谱估计的窗选择问题 .理论模型试验表明了本文方法的正确性和有效性 .

Reliable estimates of the anelastic attenuation factor, Q, are desirable for improvement of resolution through inverse Q filter and to facilitate amplitude analysis. This paper derives an energy attenuation formula of seismic waves in the wavelet-scale domain from the wavelet theory and seismic wave propagation equation in anelastic medium. The energy attenuation formula has the following features: (1) The larger Q is, the more slowly the energy attenuates; and the smaller Q is, the faster the energy attenuates. (2) The smaller scale, the less the energy involving in signal. (3) The energy of a signal on different scales is equal while the impulse source propagates in an ideal elastic medium (i.e. Q∞). The energy attenuation formula can be used to estimate the quality factor Q from surface seismic data and to extract energy attenuation section of varied scales as an attribute parameter for discriminating fluid contents and lithology. It avoids window problems that the classic spectral ratio method encounter. Theoretical model experiments show the correctness and effectivity of this method.