1.Oil and Gas Survey, China Geological Survey, Beijing;2.Oil and Gas Survey, China Geological Survey
National Science and Technology Major Project
摘要： 【研究目的】研究黔东南地区牛蹄塘组页岩孔隙结构特征及其对页岩气富集的影响，甩开不利因素，为黔东南地区页岩气勘探提供建议。 【研究方法】通过聚焦离子束扫描电镜(FIB-SEM)、场发射扫描电镜（FE-SEM）和氮气吸附等手段，对页岩微纳米孔隙结构进行多尺度表征，并结合研究区牛蹄塘组页岩的生烃及埋藏史，研究构造运动与孔隙结构关系，进而分析对页岩气富集的影响 【研究结果】牛蹄塘组页岩主要发育毫米级微裂缝、微米级黄铁矿晶间孔以及纳米级有机质孔隙，以墨水瓶状孔隙和平板结构的狭缝孔为主，孔隙结构复杂；结合FIB-SEM三维重构结果，有机质在页岩中占比较高，其孔隙度在0.04-2.48%，对总孔隙的贡献率介于14%-96%，与有机质共生的黄铁矿晶间孔是沟通裂缝的主要孔隙类型；该地区页岩气赋存状态以欠饱和的吸附气为主，游离气含量偏低。 【结论】牛蹄塘组页岩大量构造裂缝，沟通了有机质孔及黄铁矿晶间孔，改变了原有孔隙结构，致使原位聚集的页岩气沿裂缝逸散，是牛蹄塘组页岩含气量低的关键因素。热演化程度适中、构造保存好的区域是古隆起周缘下一步页岩气勘探的有利方向。
【Abstract】： 【Objective】To study the pore structure characteristics of Niutitang Formation shale in Southeast Guizhou and its influence on shale gas enrichment, avoid unfavorable factors, and provide suggestions for shale gas exploration in Southeast Guizhou. 【Methods】Multi-scale characterization of the shale micro-nano pore structure is carried out by means of focused ion beam scanning electron microscopy (FIB-SEM), FE-SEM, and nitrogen adsorption. Combined with the hydrocarbon generation and burial history of the Niutitang Formation shale in the study area, the relationship between tectonic movement and pore structure is studied, and its control effect on shale gas enrichment is analyzed. 【Results】The Niutitang Formation shale mainly develops millimeter-scale micro-cracks, micron-scale pyrite intercrystalline pores and nano-scale organic pores, mainly ink bottle-shaped pores and slit pores with a flat plate structure, and the pore structure is complex. Combined with the results of FIB-SEM three-dimensional reconstruction, organic matter accounts for a relatively high proportion of shale, with a porosity of 0.04-2.48% and a contribution rate of 14%-96% to the total porosity. The pyrite crystals co-existing with organic matter Pores are the main type of pores that communicate fractures , the shale gas in this area is dominated by undersaturated adsorbed gas, and the free gas content is low. 【Conclusions】A large number of structural fractures in the Niutitang Formation shale have connected organic matter pores and pyrite intercrystalline pores, and changed the original pore structure, causing the in-situ accumulated shale gas to escape along the fractures ，which is a key factor in the low gas content of the shale of the Niutitang Formation. Finding areas with moderate thermal evolution and well-preserved structures is a favorable direction for shale gas exploration on the periphery of paleo-uplifts.