辽河西部凹陷欢喜岭地区沙河街组层序界面的识别

Identification of sequence boundary in Shahejie Formation of Huanxiling area in western Liaohe depression

对辽河西部凹陷欢喜岭地区层序地层的研究,总结出4种层序界面的识别方法:①钻井、测井资料;②泥砂比曲线;③小波变换;④地震时频分析。方法①表现为在沙河街组各三级层序界面处,岩性、相序、曲线形态和幅值有不同程度的突变;方法②表现为在一个完整的三级层序中,泥砂比曲线由小变大再变小,其中泥砂比值最大处为最大湖泛面(MFS)位置;方法③表现为在一个完整的三级层序中,谱系图从低频到高频再到低频的变化,在系数曲线上表现为一个或近似一个完整的振荡旋回,其中谱系图中高频部分对应着最大湖泛面位置;方法④在剖面上层序界面处为低频部分,高频部分是最大湖泛面位置。通过测井与地震信息相结合,综合运用4种方法识别出7个层序界面和6个最大湖泛面,由此建立了研究区的高精度层序地层格架。

By research on the sequence strata in Huanxiling area in western Liaohe depression,the authors introduced four methods for identifying sequence boundary,including ①data of well drilling and logging,②mudstone/sand ratio curve,③wavelet transformation,and ④seismic time-frequency analysis. The first method appears varying abrupt change of lithology,facies sequence,curve type and amplitude in every third-order sequence interface of Shahejie Formation. The second method appears that mudstone/sand ratio curve changes from narrow to wide,then to narrow,and the position of maximum amplitude is MFS in one complete third-order sequence. The third method appears that the frequency spectrum changes from low frequency to high frequency,then to low frequency and shows one or approximate one vibration cycle in coefficient curve,and the position of high frequency is MFS in one complete third-order sequence. The fourth method appears that the position of low frequency is sequence boundary and the position of high frequency is MFS. Combining with logging and seismic information,the authors applied the four methods to identify seven sequence boundaries and six MFS,then built the high precision sequence stratigraphy framework.