京西青白口系下马岭组沉积相及页岩气地质条件分析

沉积相作为反映沉积环境及其演化特征等地质信息的重要载体，通过对有机地化特征进行评价，可为该组页岩气的地质条件评价提供基础数据。以野外实测剖面和室内实验为研究方法，对北京西山（简称京西）下苇甸地区青白口系下马岭组所采的15件细粒沉积岩样品进行岩石学、地球化学特征及沉积相研究，并对下马岭组的页岩气地质条件进行了评价。结果表明，研究区下马岭组中上部以灰黑色-黑色泥岩为主，其有机质含量较高，沉积厚度大，热演化程度为高-过成熟阶段，脆性指数较高，另一方面，结合区内的岩相以及沉积相特征，得出下马岭组的沉积模式为:陆源碎屑浅海沉积模式。其中，浅海陆棚亚相是有机质聚集的良好场所，表明下马岭组具有良好的生烃潜力。研究成果为今后燕山地区该组的沉积环境演化及对比提供基础资料。 

Sedimentary facies and shale gas geological conditions of Xiamaling Formation of Qingbaikouan System in western Beijing

Sedimentary facies, as an important carrier for reflecting the sedimentary environment and its evolution characteristics and other geological information, is of great significance for its research. In addition, the evaluation of the characteristics of organic geochemistry can provide basic data for the evaluation of the geological conditions of the formation of shale gas. Based on the field survey profile and indoor geochemical experiments, 15 petrified sedimentary rock samples collected from Xiamaling Formation of Qingbaikouan System in Xiaweidian area of Western Beijing were studied for petrology, geochemistry, and sedimentary facies. Shale gas geological conditions were evaluated. The results show that the upper part of the Xiamaling Formation in the study area is dominated by gray black-black mudstone, with high organic matter content, large sedimentary thickness, high degree of thermal evolution in the over-mature stage, and a high brittleness index. On the other hand, from the perspective of lithology and sedimentary characteristics, we summarized the lithofacies and sedimentary facies characteristics of the study area, and concluded that the sedimentary model of the Xiamaling Formation is a shallow-marine sedimentary system. Among them, the shallow sea shelf subfacies was a good place for the accumulation of organic matter. It provides research data for the evolution and comparison of the sedimentary environment of Yanshan area in the future. And this group has ideal geological conditions for shale gas.