盐源地区古生界页岩气地质条件分析

Analysis of shale gas geological conditions of Paleozoic in Yanyuan area

关键词:  页岩气  碳质泥岩  志留系龙马溪组  泥盆系坡脚组  盐源地区

Key words:  Shale gas  Carbonaceous mudstone  The Silurian Longmaxi Formation  The Devonian Pojiao Formation  Yanyuan area

摘要:

为了进一步探索我国西南地区的页岩气资源潜力，中国地质调查局成都中心对盐源地区开展公益性页岩气基础地质调查。在系统的地质调查和沉积学、石油地质学研究的基础上，对盐源地区进行页岩气地质条件分析。发现盐源地区早古生代发育志留系龙马溪组和泥盆系坡脚组两套富有机质页岩层系。志留系龙马溪组以碳质硅质泥页岩和碳质粉砂质泥页岩为主，以富有机质、硅质含量高、笔石发育为主要特征，发育于深水陆棚环境中。泥盆系坡脚组以含钙质碳质泥岩和钙质碳质粉砂质泥岩为主，以富有机质、黏土含量高、竹节石发育为主要特征，主要发育于潟湖环境中。两套富有机质页岩层系均具有有机质含量高，沉积厚度大，热演化程度高，脆性指数较高，低孔低渗的特征。盐源地区发育大量宽缓向斜，具备较好的页岩气保存条件。在志留系稗子田组和泥盆系坡脚组的勘探获得了油气显示，表明盐源地区页岩气具备良好的勘探潜力，研究成果为区域油气勘探评价提供借鉴与参考。

Abstract:

To further explore the potential of shale gas resources in southwest China, the Chengdu center of China geological survey (CGS) conducted a non-profit basic geological survey of shale gas in Yanyuan area. Based on the systematic geological survey and sedimentology study, the geological conditions of shale gas in the Yanyuan area are analyzed. It is found that two sets of organic-rich shale series,the Silurian Longmaxi Formation and the Devonian Pojiao formation, in Early Paleozoic in Yanyuan area. The Silurian Longmaxi Formation is dominated by carbonaceous siliceous shale and carbonaceous silty shale.It is characterized by rich organic matter, high silica content and development of graptolite, and it developed in the deep shelf environment. The Devonian Pojiao Formation is dominated by calcareous carbonaceous mudstones and calcareous carbonaceous silty mudstones.It is mainly characterized by rich organic matter, high clay content and development of tentaculites, and it developed in the lagoon environment. The two sets of organic-rich shales are with the characteristics of high organic matter contents, the huge deposition thickness, the high degree of thermal evolution, the high brittleness index, the low porosity and the low permeability. A large number of broad-gentle synclines occurred in Yanyuan area, which has good shale gas preservation conditions. Shale gas exploration has also achieved good results, with hydrocarbon shows obtained in the Silurian Baizitian Formation and the Devonian Pojiao Formation in the area. It indicates that shale gas in Yanyuan area has an excellent exploration potential. The research results provide a reference for regional hydrocarbon exploration and evaluation.