Sedimentary characteristics and paleoenvironment of shale in the Wufeng-Longmaxi Formation, North Guizhou Province, and its shale gas potential
Sedimentary characteristics and paleoenvironment of shale in the Wufeng-Longmaxi Formation, North Guizhou Province, and its shale gas potential
复制标题
黔北五峰组—龙马溪组页岩沉积特征、古环境及页岩气潜力
DOI：
10.1007/s12583-016-0932-x
复制
发表时间：
2017-12-01
影响因子：
3.3
通讯作者：
Guo, Ling
中科院分区：
文献类型：
--
作者：
Liang, Chao;Jiang, Zaixing;Guo, Ling
五峰-龙马溪古生界页岩是四川盆地页岩气勘探的主要层位之一。利用露头、岩心和薄片观察、X射线衍射分析、微量元素地球化学等方法，对贵州北部五峰-龙马溪页岩的沉积特征进行了认识，并在适宜的沉积古环境中识别了烃源岩。五峰-龙马溪组厚度20~200m，主要沉积在深水陆架上。TOC含量高，高达5.75%。无机矿物主要为碎屑石英和粘土矿物，并有少量斜长石、钾长石、方解石、白云石和黄铁矿。也有生物成因的微晶石英。已识别出六种岩相：硅质页岩、粘土页岩、钙质页岩、粉质页岩、碳质页岩和泥质粉砂岩。利用生物Ba、V/(V+Ni)、TOC、V/Cr、B、Sr/BA等指标，估算了原始生产力、氧化还原条件和古盐度，结果表明，五峰-龙马溪沉积早期处于强缺氧、高古盐度条件下，TOC含量高，具有良好的页岩气源潜力。五峰-龙马溪沉积晚期，缺氧环境遭到破坏，有机碳含量降低，有可能成为优质烃源岩。有机孔隙是页岩的主要储集空间，孔隙主要为中孔，孔径大多小于20 nm。硅质页岩具有较高的总有机碳含量和脆性矿物(石英)含量，是页岩油气勘探的重要目标。
The Paleozoic Wufeng-Longmaxi shale is one of the main horizons for shale gas exploration in Sichuan Basin. Outcrop, core and thin section observations, X-ray diffraction analysis, trace element geochemistry and other methods have been used to understand the sedimentary characteristics and identify hydrocarbon source rocks in suitable sedimentary paleoenvironments in the Wufeng-Longmaxi shale in northern Guizhou Province. The thickness of the Wufeng-Longmaxi Formation ranges from 20 to 200 m and it was mainly deposited on a deep-water shelf. The TOC content is high, up to 5.75%. The main non-organic minerals are detrital quartz and clay minerals, with a little plagioclase feldspar, potassium feldspar, calcite, dolomite and pyrite. There is also biogenic microcrystalline quartz. Six lithofacies have been identified: siliceous shale, clay shale, calcareous shale, silty shale, carbonaceous shale, and muddy siltstone. Using biological Ba, V/(V+Ni), TOC, V/Cr, B, Sr/Ba and other indicators, we estimate primary productivity, redox conditions and paleosalinity and show that the early stage of Wufeng-Longmaxi deposition occurred under strong anoxic conditions, high paleosalinity and yielded a high TOC content and an excellent potential shale gas source. The anoxic environment was destroyed at the late stages of Wufeng-Longmaxi deposition, the TOC content decreased, so that it is likely to be a high quality source rock. Organic pores acted as the key reservoir space in the shales, and the pores are mainly mesopose, with most pore diameters less than 20 nm. The siliceous shale has high TOC content and brittle mineral (quartz) content making it an important exploration target for shale oil and gas exploration.