基于米兰科维奇理论页岩岩相组合研究——以四川盆地南部龙马溪组一段为例
- 收稿日期:
2023-09-07
- 网络出版日期:
2023-12-22
摘要: 设计一套可靠、快速判断页岩岩相方法同时科学搭建页岩岩相组合框架，对研究页岩岩相组合纵、横向变化具有重要意义。通过X射线衍射分析、岩性测井、多矿物模型、Ipsom神经网络等方法准确计算出页岩矿物成分，利用Python软件进行“三端元”岩相快速划分；通过频谱分析、最优沉积速率估算、高斯滤波等时间序列分析方法提取地层高频旋回作为页岩岩相组合框架。结果表明：地层发育12类岩相，五级旋回划分出五级层序与纵向岩相变化具有较好对应性，四级旋回划定四级层序将地层分为8个405kyr沉积时长的岩相组合（E1-E8），以观音桥段地层为时间锚点推算各井岩相组合起止深度，搭建等时岩相组合框架；通过岩相组合对比研究发现，龙一段底部E1至E4岩相组合具有岩相种类多、纵、横向岩相变化快特点，E5至E8岩相组合的岩相类型相对简单，且横向变化小；从古构造低点至高点，E1岩相组合呈硅质页岩含量不断降低趋势，E2-E4岩相组合中混合质页岩含量明显下降，E5-E8岩相组合中富硅泥质页岩含量下降，富硅/泥混合质页岩含量明显上升。总体而言，基于时间序列分析方法搭建的页岩岩相组合框架配合新岩相判断方法，可以准确描述同期不同区域地层岩相组合差异，为量化分析页岩岩相非均质性及其变化趋势提供了新思路。
Research on Shale Facies Combination Based on Milankovitch Theory: Taking the First Member of Longmaxi Formation in the Southern Sichuan Basin as an Example
- Received Date:
2023-09-07
- Available Online:
2023-12-22
Abstract: Designing a reliable and rapid method for determining shale facies while scientifically constructing a framework for shale facies combination is of great significance for studying the vertical and horizontal changes of shale facies combinations. Accurately calculate the composition of shale minerals through methods such as X-ray diffraction analysis, lithology logging, multi mineral model, and Ipsom neural network, and use Python software to quickly divide the "three terminal element" lithofacies; Extracting high-frequency stratigraphic cycles as a framework for shale facies combination through time series analysis methods such as spectral analysis, optimal sedimentation rate estimation, and Gaussian filtering. The results show that there are 12 types of lithofacies developed in the strata, and the fifth order cycle is divided into five order sequences with good correspondence with vertical lithofacies changes. The fourth order cycle defines the fourth order sequence and divides the strata into eight 405kyr sedimentary lithofacies combinations (E1-E8). The Guanyinqiao Formation is used as a time anchor to calculate the starting and ending depths of each well lithofacies combination, and to build an isochronous ithofacies combination framework; Through comparative study of lithofacies combinations, it was found that the E1 to E4 lithofacies combinations at the bottom of the Longyi Formation have the characteristics of multiple types of lithofacies, rapid changes in vertical and horizontal lithofacies. The lithofacies types of the E5 to E8 lithofacies combinations are relatively simple, and the lateral changes are small; From the low point to the high point of the ancient structure, the E1 lithofacies combination shows a continuous decreasing trend of siliceous shale content, the E2-E4 lithofacies combination shows a significant decrease in mixed shale content, the E5-E8 lithofacies combination shows a decrease in siliceous shale content, and the siliceous/muddy mixed shale content significantly increases. Overall, the shale lithofacies combination framework built based on time series analysis methods, combined with new lithofacies judgment methods, can accurately describe the differences in stratigraphic lithofacies combinations in different regions during the same period, providing new ideas for quantitative analysis of shale lithofacies heterogeneity and its changing trends.
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