Abstract: The sedimentary process of Wutonggou formation is controlled by coastal underwater alluvial fan and alluvial fan in the Tainan depression of Tuha basin. For the complicated sedimentary setting, it's difficult to identificate the microfacises with lacking of systematic studies on log facies. The representative sedimentation microfacies with obvious facies marker were selected to make contrast and summarize up the features of well loggs. The model was established for different microfacies. The first 11 lowfrequence wavelet coefficients can perform well in reconstructing variation trend of GR log. There are significant differences in the wavelet coefficients and reconstructed lowfrequence curves and highfrequence curves among different sedimentation microfacies. The variation law of lowfrequence wavelet coefficients in every microfacies was analysized from the hydrodynamic force and other sedimentology aspects. By doing these, the abstract information of sedimentation microfacies belonging to geological space was converted into specific low dimensional feature vector of digital space. Based on this point and combing the characteristic of lowfrequence curves and highfrequence curves, a set of sedimentation microfacies identification templates was established. Sedimentation microfacies were identified by calculating the minimum Euclidean distance of logging curves between small layer and identification templates, with the combination of comparing the characteristic of lowfrequence curves and highfrequence curves between them.

Key words: Tainan depression, Log facies, Quantitative analysis, Sedimentary microfacies, Wavelet coefficients

摘要： 吐哈盆地台南凹陷梧桐沟组为一套从近岸水下扇到冲积扇的沉积,受其复杂沉积特征的制约,对测井相缺乏系统的研究,制约着沉积微相的划分。针对该问题,对取心层段长、相标志明显的典型沉积微相段的电性特征进行综合分析,建立不同微相对应的测井相模式。自然伽马曲线的变化趋势可被前11个低频小波系数较好地重构出来,且这些小波系数以及重构出的低频小波曲线在不同微相之间存在着明显的差异性。分析各小波系数所代表的沉积学意义,将沉积水体的能量、稳定性以及沉积期次等复杂的空间问题转换为简单的线性几何分析,从而建立沉积微相的定量识别图版,通过计算未知相段测井曲线的小波系数与图版的最小欧氏距离,就能准确快速地判别沉积微相。

关键词: 台南凹陷, 测井相, 定量分析, 沉积微相, 小波系数