化学元素测井资料在地层界面处的响应特征研究

On the Data of Response Characters of Elemental Capture Spectroscopy (ECS) Logging at Stratum Boundary

化学元素测井直接测量地层中的Si、Fe、Ca和Ti等重要元素的含量,这使得准确识别岩性以及岩性界面处的响应特征成为可能。简要讨论了化学元素测井的基本原理,给出了几个化学元素测井资料划分岩性和识别风化壳实例。研究表明,碳酸盐岩风化壳中Ca元素含量降低;Fe元素含量增高;Gd元素含量异常增高。如果风化壳被剥蚀搬运,或在水下被削截引起地层缺失,则在下伏地层顶部不能见到典型的风化壳界面特征,仅能见到岩性的突变。

The purpose of elemental capture spectroscopy (ECS) logging is to directly measure the contents of Si, Fe, Ca and Ti. It is possible that the lithology and the response characters at the lithologic boundary are recognized accurately. The basic principle of ECS logging is discussed in brief. Examples for lithologic and weathering crust identification using the data of ECS are provided. The study shows that Ca content in weathering crust is reduced, Fe content is raised, while Gd Content is raised abnormally. If the weathering crust is eroded and migrated or eroded under water, formation failure is caused, thus the boundary characters of typical weathering crust could not be seen on the top of underlying formation, only the lithologic discontinuity could be seen.