Automatic calculating grain size of gravels based on micro-resistivity image of well

Since the micro-resistivity imaging logging tool cannot achieve 360° full coverage imaging around the well, there will be interval blank zone, resulting in the missing information of geology. In order to measure the size of gravels from the images, this paper adopts the ordinary kriging interpolation method to interpolate the missing images to restore the blank zone and then uses the automatic characterization method to measure the size of gravels on the restored images. The results show that the method can not only restore the outline and characteristics of the gravels in the blank zone and fill in the missing parts of the image effectively, but also measure the gravel grain size from the restored logging image directly, which greatly reduces the manual measurement workload. As well, there is slight difference between the measured size and the actual size of the gravels. This method can be applied to the automatic quantification of gravel grain size in uncored well sections, which will provide fine information for basic geological research in whole well.