Abstract: The identification and determination of fractural zone plays an important role in achieving the research targets of the China Continental Scientific Drilling (CCSD) and providing the basic physical parameters in the drilling hole for geological study. The parameters of primary wave frequency spectrum derived from array acoustic logging provided the possibility to achieve this aim. Based on the analysis on primary wave frequency characteristics, some conclusions can be obtained: there were variations obviously for the characteristics of primary wave frequency spectrum in fracture zones, such as the dominant frequency shifted towards the low frequency, at this location the amplitude (energy) increased rapidly, and there were significant differences from the surrounding unbroken rocks. By using these characteristics, the structure fractured zones can be identified and determined properly. And also this paper suggested several parameters, such as main peak amplitude, the location drifting of the basic frequency, the width of main peak half-amplitude and the main peak energy of the basic frequency, and had acquired a good result by making use of these parameters to identify and determine the structural zones in CCSD.

Key words: frequency characteristics, acoustic logging, China Continental Scientific Drilling (CCSD)