泥饼对声波全波波形确定渗透率的影响

The influence of mud cake on permeability determination using full acoustic waveform.

根据Biot提出的孔隙地层的波动理论,采用Johnson动渗透率模式,针对测井中泥饼问题,计算出声波全波列的合成波形。由合成波形可以看出,井壁上的边界条件对声波波形影响很大,由此产生的斯通利波的幅度变化并不完全代表地层渗透率的变化。当泥饼层薄时,可用斯通利波的幅度衰减量来估算地层的渗透率,但要作一些必要的校正;当泥饼层较厚时,用斯通利波幅度衰减量来估算地层渗透率及提取的横波时差是错误的。高频伪瑞利波爱瑞相(低速)也是地层渗透率很好的指示标志,但要考虑环境条件的影响;低频伪瑞利波(高速)能很好的估算原状地层的横波衰减量,进而估算地层的渗透率。

In order to cope with mud cake problem in acoustic logging,we produced the synthetic waveform of full acoustic wave train by using Biot's wave theory in porous formation and Johnson's dynamic permeability pattern. It can be seen from synthetic waveform that the influence of well-wall boundary condition on acoustic waveform is so serious that the amplitude variation of Stoneley wave fails to reflect true variation of formation permeability. In the case of thin mud cake,the amplitude attenuation of Stoneley wave may be applied to estimation of formation permeability,with necessary correction being done. It is wrong for us to derive both formation permeability and shear wave time difference from Stoneley wave amplitude attenuation when mud cake is thick. Airy phase of high-frequency pseudo Rayleigh wave (low velocity) is good permeability indicator when environmental condition is taken into account. Low-frequency pseudo Rayleigh wave (high velocity)can be used to estimate shear wave attenuation, then permeability in original state formation.