复杂地层声波测井时差处理方法研究

A study on the processing method for acoustic slowness logging in complex formations

在复杂地层(如砂-泥岩薄互层)的声波测井中,由于地层声速变化及界面反射波叠加干扰,导致不同接收器的地层纵波波形幅度差异明显,且相关性很差,使得提取的时差误差较大。这一声场特征可从薄互层声波测井的有限差分数值模拟中看到。针对这一现象,本文利用频率-波数域相关滤波处理技术来消除薄互层声波测井的界面反射干扰,以改善地层纵波波形的相关性。本文给出了砂-泥岩薄互层数字声波测井的现场资料处理实例,处理结果证明了该方法有效地消除了界面反射波的干扰,明显改善了地层纵波的相关性,提高了地层纵波时差曲线的分辨率,清晰地刻画出了薄互层特征。

During acoustic logging in complex formations, the logging waveforms are often distorted by formation velocity changes and by the interference of acoustic reflections from formation bed boundaries. The waveform distortion causes different receivers in the receiver array to have significantly different amplitudes, and the resulting slowness estimation from the array data suffers from large errors due to poor signal coherence. This wave phenomenon, can be seen from a finite difference simulation of acoustic logging for the thin-bed sand-shale sequence model. To improve the slowness estimation accuracy for this situation, we use a Frequency-Wavenumber Coherence Filtering method to suppress the bed-boundary reflection interference in acoustic data and enhance the coherence of formation compressional （P） waves in array. We have applied the technique to both synthetic modeling and field logging data. The results show that this method effectively suppresses the interference of bed-boundary reflections and significantly improves the coherence of formation P-waves, allowing for increasing the resolution of the P-wave slowness log curve and detecting the thin-bed characteristics of sand-shale sequences in formation.