元素、伽马能谱录井在川东地区下二叠统分层中的应用

The Application of Element and Gamma-Ray Spectrum Logging in Lower Permian Strata in the Eastern Sichuan Area

摘要: 川东地区下二叠统除梁山组外是以大套灰岩为主的地层，岩性单一，传统录井主要依靠岩屑颜色来划分地层，随着钻井工艺的发展与广泛应用，粉末状岩屑颜色普遍变浅，小层划分难度加大。川东地区下二叠统历经多个沉积小旋回，应用元素录井，通过元素含量、元素比值的细微差别可以直观地反映岩石成分的变化，从而划分出小层；同时鉴于川东地区茅口组、栖霞组各小层颜色差异的主要原因为富含有机质多少，应用岩屑伽马能谱录井更有助于小层划分。通过对川东地区下二叠统元素录井、岩屑伽马能谱录井特征分析，形成了特征参数趋势法、比值法、指数法等录井地层划分方法，并在现场应用取得了较好效果，为下步在该区推广奠定了基础。

Abstract: The Lower Permian in the eastern Sichuan Area was dominated by a large set of limestone except Liangshan Formation, it was simple lithology. Previously, traditional logging mainly relied on cuttings color for stratigraphic division. With the development and wide application of new drilling technology, powder-like cuttings were generally lighter in color; it was more difficult for division of sublayers. The Lower Permian in eastern Sichuan Area experienced several small cycles of deposition. Based on element logging, the subtle differences in element content and element ratio could visually reflect rock composition changes between sublayers, therefore identify the sublayers. Since the color difference of sublayers in Maokou Formation, Qixia Formation form eastern Sichuan Area was mainly due to organic matter content, the application of cuttings gamma spectrometer logging was more conducive to sublayer division. Based on the characteristics of element logging and gamma-ray spectrum logging in Lower Permian of the eastern Sichuan Area, characteristic parameter trend method, ratio method, and exponential method are established for strata division. Good results are achieved in the field application; they provide foundation for further promotion in the area.