基于地震波振幅分辨塔河油田溶洞最小高度的理论探讨

Theoretical discussion on resolution of maximum height of cavity in the Tahe oilfield based on seismic amplitude

塔河油田奥陶系灰岩溶洞反射特征表现为"串珠状"强振幅短同相轴反射结构,但该串珠状反射的地震属性在空间展布的视体积与其对应的实际体积差异很大,因此,需要确定地震波振幅分辨塔河油田溶洞最小高度.本文在分析塔河油田钻遇储层段储层厚度特征的基础上,分别导出洞穴内一次反射波和含一次多次波的时域反射脉冲响应的振幅谱关于洞穴高度的解析表达式,进而对不同洞穴高度、不同类型的充填物时洞穴反射振幅谱特征以及相位关于频率的变化率的变化特征进行分析,结果表明,谱出现极大值相应的洞穴高度在相位关于频率变化率曲线上对应的洞穴高度处也出现极大,可以利用相位关于频率的变化率来检测溶洞内是否有充填物.

The reflection features of cavities in Ordovician carbonate in the Tahe oilfield is of reflected structure with strength amplitude and short events of ＂a string of beads＂. However, the difference between the apparent volume in space of seismic attributes with respect to the reflection in cavities and actual volume of the cavities is very large. Hence, it is necessary to determine the resolution of maximum height of cavity based on seismic amplitude. We analyze the features of the statistics of reservoir thickness from drilling in the Tahe oil field and present respectively analytic expressions of amplitude spectra of primary and multiple reflected pulse responses in time domain via height of cavity. We also analyze the features of amplitude spectra of reflection with multiple in cavity via various heights of cavity with various types of filling and the features of derivative of phase of reflection with multiple in cavity with respect to frequency via various heights of cavity. The results show that the maximum on the amplitude spectra via vari ous heights of cavity occurs at some heights at which the maximum on derivative of phase with respect to frequency via various heights of cavity also occurs. Hence, there are any fillings that can be determined by the derivative of phase with respect to frequency.