薄油层时移地震差异波形特征探讨

Discussion on characteristics of time-lapse seismic differential waveform of thin oil layer

开发导致的时移地震差异代表了油藏的岩石物理性质变化,本文从差异波形角度出发,明确了声波阻抗界面的反射系数与油层声波阻抗变化之间的函数关系,进而分析薄油层时移地震差异波形特征.通过分析得出,开发前后油层阻抗变化越大,时移地震的差异振幅幅度越大;薄油层的差异波形特征仅与油层的声波阻抗变化有关,油层声波阻抗增大导致与地震子波微分形式相同的差异波形,油层声波阻抗减小产生的差异波形与180°相位的地震子波微分形式相同;油层声波阻抗变化方向导致差异波形振幅幅度变化的快慢.

Time-lapse seismic differences reflect rock physical property change of oil reservoirs caused by oil field exploitation.In this papas the function is deduced between reflection coefficient change of acoustic impedance interface and oil layer impedance change,and diiferential waveform features of thin oil layer is analyzed.The larger change of oil field acoustic impedance is,the bigger difference amplitude is.The waveform features of thin oil layers are related only with oil layer acoustic impedance change.If only oil layer acoustic impedance increases,the waveform of the thin oil layer is the same as differential of seismic wavelet.The waveform is the same as 180°differential of seismic wavelet so long as oil layer acoustic impedance decreases.And the extent of difference amplitude caused by impedance decrease is more than equivalent impedance increase.