基于变分模态分解的营四段厚层砂砾岩地层细分层序

Subdivision Sequence of Thick Glutenite Strata in the Fourth Member of Yingcheng Formation Based on Variational Mode Decomposition

利用常规测井曲线对厚层砂砾岩储层进行层序细分,存在界面不清难以确定划分标准的问题。变分模态分解(variational mode decomposition, VMD)方法分解精度高并且抗噪性能优越,受模态混叠影响小,可以将测井数据内的各级基准面旋回信息分解出来。本文对松辽盆地徐家围子断陷徐西凹陷营城组四段(简称营四段)厚层砂砾岩地层测井曲线应用VMD方法分解得到各频率域固有模态函数(intrinsic mode function, IMF),优选出相关性高的IMF1和IMF10,根据瞬时频率范围和采样率推算出高频IMF1对应短周期旋回,低频IMF10对应长周期旋回。选取对应周期的IMF可以指导对应级别层序的划分,划分出两个三级层序和五个四级层序。VMD方法在营四段的应用表明,该方法适用于厚层砂砾岩地层的高频层序划分。

Utilizing conventional well-logging curves for sequence division of glutenite reservoirs faces the problem of unclear interfaces and difficulty in determining division criteria.The variational mode decomposition(VMD)method has high decomposition precision and superior noise resistance,and is less affected by mode mixing,which can decompose the datum cycle information of each level in logging data.In this paper,VMD method is applied to obtain the intrinsic mode function(IMF)of each frequency domain from logging curves of thick glutenite strata in the Fourth Member of Yingcheng Formation of Xujiaweizi fault depression in Songliao basin,and the highly correlated IMF 1 and IMF 10 are selected.According to instantaneous frequency range and sampling rate,the high-frequency IMF 1 corresponds to the short cycle,and the low-frequency IMF 10 corresponds to the long cycle.The selection of the IMF corresponding to the cycle can guide the division of the corresponding level sequence,which can be divided into two three-level sequences and five four-level sequences.The application of VMD in the Fourth Member of Yingcheng Formation shows that this method is suitable for high-frequency sequence division of thick glutenite strata.