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对多深度和多井源距VSP试验所观察到的地震旅行时进行τ-p反演来估算速度各向异性的方法现已开发成功。这种方法是把从井中固定深度观测到的一套地震记录道转换到τ-p城。与入射角有关的层速度是在考虑上覆地层的影响后根据相于测量而产生的曲线中提取的。为了试验这种方法,我们从钻穿平坦沉积层的一口浅井中获得了地震记录。由均匀生物扰动页岩组成的一个深度段近乎各向同性。1m左右砂泥岩交互的第二个层段速度显示出15%的速度各向异性,其速度是随入射角的增加而增加的(从近乎垂向(θ<30°)入射到斜向(3°<0<55°)入射)。斜向入射的速度总是大些。砂页岩五层深度段显示的最大各向异性也是声波测井的最不均匀性,实验结果表明薄层产生各向异性。该层理论上的垂向—横向速度各向异性是14.2%,它是在假设各向同性地层的基础上计算的。这一理论数值与更小入射角度范围内获得垂向—倾斜值的比较表明,理论值太小。这种偏差可能是由于页岩层本身的内部各向异性未被考虑在理论计算中的缘故。
Methods to estimate velocity anisotropy for multi-depth and multi-well sources from τ-p inversion of seismic travel observed in the VSP test have been developed. This method transforms a set of seismograms observed at a fixed depth into the τ-p-city. The layer velocity associated with the incident angle is extracted from the curve resulting from the relative measurements, taking into account the effect of the overburden. To test this method, we obtained seismograms from a shallow well drilled through a flat sedimentary layer. A depth segment composed of uniform bioturbation shales is nearly isotropic. The velocity of the second interval of sandstone-mudstone interaction at 1 m shows a velocity anisotropy of 15%, the velocity of which increases with increasing incident angle (from near vertical (θ <30 °) ° <0 <55 °). Oblique incidence is always larger. The maximum anisotropy of sandstone shale is also the most inhomogeneity of sonic logging, and the experimental results show that the anisotropy of thin layer is produced. The theoretical vertical-lateral velocity anisotropy of this layer is 14.2%, which is calculated on the assumption of isotropic strata. A comparison of this theoretical value with the vertical-tilt value obtained for a smaller angle of incidence shows that the theoretical value is too small. This deviation may be due to the fact that the internal anisotropy of the shale layer itself is not accounted for in theoretical calculations.