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.