湖南雪峰山前陆盆地沉积特征及页岩气勘探潜力

Sedimentological Characteristics and Shale Gas Exploitation Potentials of the Foreland Basins of Xuefeng Mountain

刘辰生 王辉 史乐 冯宁

LIUChensheng WANGHui SHILe FENGNing

有色金属成矿预测与地质环境监测教育部重点实验室(中南大学), 湖南 长沙 410083 有色资源与地质灾害探查湖南省重点实验室, 湖南 长沙 410083 中南大学地球科学与信息物理学院, 湖南 长沙 410083 中国石油新疆油田分公司采油二厂, 新疆 克拉玛依 834000

MOE Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring(Central South University), Changsha, Hunan 410083, China Provincial Key Laboratory of Nonferrous Resources and Geological Hazard Detection, Changsha, Hunan 410083, China School of Geosciences and Info-physics, Central South University, Changsha, Hunan 410083, China The Second Oil Recovery Plant of Xinjiang Oilfield Company, CNPC, Karamay, Xinjiang 834000, China

雪峰山志留系前陆盆地分布在湘中-湘西北-四川盆地，是上扬子板块主要的盆地类型，但目前针对该前陆盆地沉积特征和页岩气勘探潜力的研究少见。根据野外资料、测井资料和分析测试资料分析了湘西北和湘中地区前陆盆地沉积建造过程和页岩气勘探潜力。结果表明，湘中前陆盆地前渊带以浊积扇和浅海陆棚相沉积为主，而湘西北隆后盆地沉积相类型丰富，包括潮坪相、浅海陆棚相、滨岸相、三角洲相和碳酸盐岩台地相等。虽然前渊带和隆后盆地沉积相类型和沉积厚度差异较大，但沉积旋回的划分却一致，因此，前渊带和隆后盆地相互连通，雪峰山对其两侧盆地的遮挡作用有限。大量的地球化学测试分析表明，研究区隆后盆地页岩的有机碳含量、有机质类型均较四川盆地的焦石坝差。湖南地区志留系页岩各项地化指标较差的主要原因是其缺少龙马溪组第一旋回的黑色碳质页岩。

The Silurian foreland basins of Xuefeng Mountain are distributed in the central and northwestern parts of Hunan and the Sichuan Basin and are the dominant basin type on the upper Yangtze Plate. However, at present, there are few studies the sedimentological characteristics and shale gas exploitation potentials of these foreland basins. Based on field survey and well logging data and test results, the sedimentological history and shale gas exploitation potentials of the foreland basins in the central and northwestern parts of Hunan were determined. The results show that the foredeep zones of the foreland basins in the central part of Hunan are dominated by turbidite fans and shallow marine continental shelf deposits. Meanwhile, there are various sedimentological facies in the post-uplift basins in the northwestern part of Hunan. These include tidal, shallow marine continental shelf, littoral, delta, and carbonate platform facies. Although the foredeep zones and the post-uplift basins significantly differ in their sedimentological facies and sedimentation thickness, the division of their sedimentation cycles is consistent. Hence, it is concluded that the foredeep zones and the post-uplift basins are interconnected and Xuefeng Mountain caused limited shielding effects on the basins along its two sides. Numerous geochemical analyses demonstrate that the organic carbon content and the organic matter type of the shales in the post-uplift basins of the study area are less than those of Jiaoshiba in the Sichuan Basin. The Silurian shales in the southern part of Hunan have relatively low values for various geochemical indexes mainly because the area has no black carbonaceous shales of the first sedimentation cycle found in the Longmaxi Formation.

10.11885/j.issn.1674-5086.2018.10.10.01