以米氏旋回为标尺进行测井层序划分对比——以东海西湖凹陷古近-新近系地层为例

Comparison of well-log sequence stratigraphic classification and correlation using Milankovitch cycles:Paleogene-Neogene strata of Xihu sag in East China Sea

基于层序地层学和旋回地层学理论,以东海西湖凹陷钻井为例,运用小波分析技术对古近-新近系进行测井数据的地质学研究.选用小波变换模极值和米氏周期最佳匹配分析方法,对识别出来的优势周期进行剔除和选择,确定了本区地层中米氏旋回的小波尺度分别为14,28,71和290;通过分析不同准层序组的模拟测井信号,发现进积型的小波波谱图能量团表现为向浅部向大尺度迁移,与之相反的是退积型,在加积型的小波波谱图中为一套分布比较稳定的能量团,进而建立了识别层序单元类型及界面的模式.提出根据四级层序形成的驱动机制是长偏心率这一前提条件,将米氏旋回的识别和层序地层的划分对比相结合,以识别出来的米氏旋回为标尺,进行测井层序划分对比.研究结果表明,在实际钻井中米氏旋回曲线和波谱特征清晰,均划分出11个三级层序和3种体系域,建立了东海西湖凹陷古近-新近系层序地层对比格架.

Based on the sequence stratigraphic theory and cyclic stratigraphic theo carried out the geological study on logging data of Paleogene-Neogene strata in Xi China Sea by using wavelet transform technique. According to wavelet transform mum and Milankovitch cycle best matching method, dominant period has been the wavelet scales of Milankovitch cycles has been defined in the strata are 14, 28 ry, this study hu sag of East module extre- identified and , 71 and 290. Through analysis of simulated logging signals of subsequence sets to make the internal features of wavelet transform scalogram clear, it is shown that the energy group in progradation wavelet transform scalogram movesd from deed to shallow with an increasing large scale,but acted in reverse in retrogradation wavelet transform scalogram while dlstrlbutecl quite statue m aggraua- tion wavelet transform scalogram. The model was finally set up for identifying type and bound- ary of sequence stratigraphic units, This study proposed the precondition that long eccentricity was the driving mechanism for the formation of four level sequence, combining the Milanko- vitch cycles recognition with the sequence stratigraphy division and correlation using Milanko- vitch cycles as rulers to carry out the stratigraphy division and correlation of the wells. The re- sults show that it is because features of Milankovitch curves and wavelet scalogram are clear, this study classified the eleven third-order sequences and three system tracts and established the stratigraphic sequence framework of Paleogene-Neogene strata in Xihu sag.