井间地震层析成像分辨率研究

通过大量数值模型试验,并根据射线密度、射线正交性和点扩散函数,对井间地震层析成像的分辨率问题进行了研究。结果表明,井间地震层析成像的分辨率在空间上是可能性变的,垂直方向的分辨率好于水平方向,而且高速异常体和低速异常体的图像形态和分辨率是非一致的。高速异常体波形CT的图像水平方向最小分辨率距离为1/2波长,垂直分辨率最小分辨率距离为3/10波长;而低速异常体的波形CT图像的水平方向的最小分辨率约为2/5波长,垂向最小分辨率约1/5个波长;走时CT的图像水平方向最小分辨率为3个像元,垂直方向的最小分辨率距离为2个像元;当井深与井间距之比为2时,图像分辨率最高。

RESOLUTION IN CROSSHOLE SEISMIC TOMOGRAPHY

Resolution in crosshole seismic tomography has been studied in this paper by means of ray density, ray orthogonality and point-spread function. Numerical experiments indicate that the resolution is better in the vertical direction than in the horizontal, and the high velocity anomalous body is different from the low velocity anomalous body in resolution and shapes of tomography. For the high velocity anomalous body, the spatial resolution of the waveform velocity tomogram in horizontal is about 1/2 of the wavelength, and that in vertical about 3/10 of the wavelength. For the low velocity anomalous body, the spatial resolution of the waveform velocity tomogram in horizontal is about 2/5 of the wavelength, and that in vertical about 1/5 of the wavelength. The spatial resolution of the traveltime velocity tomogram in horizontal is about three tomographic elements width, and that in horizontal about two tomographic elements width. When the ratio between the borehole depth and well offset is equal to 2.0, the spatial resolution of the velocity tomogram is the best.