基于多尺度分析的正交偶极子声波测井反演地层各向异性

INVERSION OF FORMATION ANISOTROPY BY CROSS-DIPOLE ARRAY ACOUSTIC LOGGING BASED ON MULTISCALE ANALYSIS

提出一种从四分量正交偶极子声波阵列波形数据中提取地层剪切波方位各向异性参数的有效方法。该方法利用了各向异性地层中快、慢主挠曲波的分裂特征 ,从四分量数据中计算出了主波列 ,构造了目标函数 ,并利用改进的模拟退火方法搜索目标函数的全局极小值 ,确定出各向异性参数和快横波方位角。对四分量数据进行了多尺度分析 ,在时间频率域内提取了挠曲波的动力学特征 ,解决了实际数据处理中遇到的波形畸变和干扰问题。与常规方法的对比表明 ,新方法不仅计算速度快 ,而且能够减少确定快横波方位角时的不确定性 ,提高了各向异性参数估计的精确度。

A new method for estimating formation S-wave anisotropy parameters from 4-component (4-C) data in cross-dipole array acoustic logging is proposed. The splitting of fast and slow flexural waves is adopted in this method. The principal waves are computed with 4-C data, and the object function is constructed and optimized to a global minimum to determine the anisotropy parameters and fast S-wave azimuth. The multi-scale analysis of 4-C data and extraction of dynamic features of different wave modes in time-frequency domain can solve many problems such as wave distortion and noise suppression. Comparison of this method with the conventional method shows that this method takes less computation and can decrease the ambiguity in determination of fast S-wave azimuth. The new method can give more precise estimation for anisotropy parameters as well.