基于倒双谱的套管井声学评价系统特性辨识

将发射探头(T)、接收探头(R)和TR之间介质视为套管井声学评价系统的组成部分，由套管井声波测井响应，采用倒双谱技术辨识该声学系统的冲激响应，计算得到了该声学系统的特性曲线(冲激响应曲线)。当T、R同时位于自由套管区域时，声学系统特性曲线幅度最高，并且曲线的两端和中心点附近都有比较大的起伏；当T、R同时位于水泥完全胶结区域时，特性曲线幅度最低且比较平坦；随着T、R间窜槽面积的增大，特性曲线幅度逐渐增加并且中心点附近幅度的增加比较明显。通过对该声学系统特性的辨识，从冲激响应曲线瀑布图中可直观反映出套管井水泥胶结的质量。该方法对丰富、完善声波水泥胶结测井资料解释工作具有重要参考价值。

Identification of the acoustic evalution system's characteristics for cased hole based on the Bicepstrum

The transmit transducer (T), receive transducer (R) and the medium between TR are the component parts of the acoustic evaluation system for a cased hole. The characteristic curve (impulse response curve) of the acoustic evaluation system can be calculated using the acoustic logging response based on the Bicepstrum. The amplitude of the characteristic curve is maximal and the central part of characteristic curve is fluctuant when the T and R transducer are all in the free region of the casing; the amplitude of the characteristic curve is minimal and the curve is flat when the T and R transducer are all in the bonded area; the amplitude of the characteristic curve increases, especially in the central part, with increasing area of the un-bonded region between the T-R transducers. The cement bond quality can thus be seen directly on the waterfall figure of the characteristic curve. This method has reference value for the explanation of cement bond logging.