四川盆地及其周缘五峰组-龙马溪组有机质差异富集的主控因素探讨

The main factors of differential organic enrichment of the Ordovician Wufeng Formation and Silurian Lungmachi Formation in the Sichuan Basin and its adjacent areas

近些年来，四川盆地及其周缘五峰组-龙马溪组页岩气勘探开发实践表明页岩气具有差异富集特征。基于四川盆地及其周缘五峰组-龙马溪组页岩TOC、XRD及元素等分析数据，结合前人已发表的相关数据资料，对川南、川东及川东北地区开展了有机质差异富集特征初步分析，并从矿物组分（黏土矿物含量）、保存条件及古生产力3个方面探讨其控制因素。研究表明：1）有机质差异富集特征表现为：五峰组沉积时期，四川盆地及其周缘有机质富集程度差异相对较小，川东地区有机质富集程度略高于川南地区和川东北地区；而龙马溪组沉积早期，有机质富集程度差异相对较大，川东北地区有机质富集程度明显高于川东地区和川南地区；2）差异的保存（氧化还原）条件是造成四川盆地及其周缘不同地区五峰组-龙马溪组有机质差异富集的主控因素。

In recent years, the exploration and development practices of the Ordovician Wufeng Formation and Silurian Lungmachi Formation in the Sichuan Basin and its adjacent areas have showed that shale gas has the characteristic of differential enrichment. Based on the TOC, XRD and elemental analysis results of the Wufeng-Lungmachi shale in the Sichuan Basin and its adjacent areas, combining with the relevant data published by previous researchers, we preliminarily analyzed the differential enrichment characteristics of organic matters in South, East and Northeast Sichuan areas, and discussed its controlling factors from the aspects of mineral composition （clay mineral content） , preservation conditions and paleoproductivity. These conclusions can be reached from the study： 1） The differential enrichment of organic matters has the following characteristics ： In the depositional stage of the Wufeng Formation, the differential degree of organic matter enrichment is relatively low and the organic matter enrichment degree is slightly higher in East Sichuan than South and Northeast Sichuan; while in the early depositional stage of the Lungmachi Formation, the differential degree of organic matter enrichment is relatively high and the organic matter enrichment degree is significantly higher in Northeast Sichuan than South and East Sichuan. 2） Difference of preservation （redox） conditions is the main factor resulting in the differential enrichment of organic matters in different areas of the Wufeng Formation and Lungmachi Formation in the Sichuan Basin and its periphery.