地层物性与声波全波列波形的关系

Relationship Between Formation Physical Parameters and Acoustic Full Waveform Logs in Fluid-saturated Porous Formations

从孔隙地层的应力与应变关系(Biot,1962年)出发,导出了井中压力波的具体表达式,针对流体饱和的粒间孔隙地层,采用具有一般意义的Johnson动渗透率公式,计算出声波全波列测井合成波形,并分析了地层物性诸参数与全波波形的关系。结果表明,在源中心频率低(≤5kHz)时,用斯通利波求渗透率较适合;在源中心频率较高时,用伪瑞利波艾雷相求渗透率较适合,但要考虑其他因素的影响;用纵波和横波时差比可确定泥质含量,也可用来识别含气层;用横波时差求孔隙度比纵波时差准确,在源中心频率不太高时,用纵波后续波有可能确定地层泊松比;在提取斯通利波信息时要注意高频水波和艾雷相的影响。文中还提及了横波的波至问题,认为横波初至主要受纵波后续波的影响,横波的后续波主要受伪瑞利波的影响,而这些影响与源中心频率、源距等有很大关系。

An expression of pressure wave is derived from stress-strain relation in porous formations. For fluid-saturated grain-to-grainporous formations, acoustic full waveform synthetic microseismograms are calculated with Johnson's dynamic permeability equation of general sense. A relationship between formation physical parameters and acoustic synthetic full waveform is established. The results show that in low frequency source Stoneley wave data is fit for computing the permeability, while in high frequency source Airy phase of pseudo-Rayleigh wave may do better, but other effects must be considered. The velocity ratio between p-wave and s-wave may be used to determine shaliness, and to investigate gas layer. Porosity from s-wave slowness is better than p-wave slowness. The p-wave leaky mode is considerably related to Poisson's ratio of formation. The effect of high frequency water wave, Airy phase of pseudo-Rayleigh wave and environment factors on Stoneley wave should be considered. The effect of p-wave leaky mode on the first arrival of s-wave is prominent, whereas pseudo-Rayleigh wave only affects the continuing arrivals of s-wave. This is considerably related to acoustic source frequency, source-receive separation, and so on.