湘中南中奥陶统烟溪组页岩储层特征及勘探潜力

中奥陶统烟溪组作为湖南下古生界一个新的勘探层系广泛受到能源地质学家的重视。运用偏光显微镜、高分辨率扫描电镜、X射线全岩衍射、有机碳含量及低温液氮和二氧化碳吸附脱附等检测手段，对湘中南地区中奥陶统烟溪组页岩储层进行了综合研究。结果表明：湘中南地区中奥陶统烟溪组为斜坡—盆地相沉积，深水陆棚和深水盆地相页岩发育；矿物成分主要为石英和黏土，其次是黄铁矿和长石；脆性指数较高，有利于压裂开采；页岩储层主要发育有机质孔、生物结构孔、粒间孔、片间孔、晶间孔、溶蚀孔和黏土矿物层间微裂缝及矿物破裂缝；孔隙度中等，渗透率较好。研究区发育2种类型的孔隙结构，以介孔和微孔发育为主的孔隙结构，总孔容和微孔总孔容相对较大，比表面积也非常大，其储集性能和吸附能力相对较强，可作为烟溪组重点勘探的层段。中奥陶统烟溪组页岩孔隙发育主要受热演化程度的影响，其次受矿物组成和有机质丰度的控制。研究区中奥陶统烟溪组具有良好的生烃物质基础，有机质类型以Ⅰ型和Ⅱ2型为主，TOC含量介于0.05%～5.6%之间，RO值介于2.72%～3.82%之间，已达到高成熟或过成熟阶段，有利于页岩气的大量生成。湘中南地区中奥陶统烟溪组埋藏深度适中，...

Characteristics and exploration potential of shale reservoirs of Middle Ordovician Yanxi Formation in central-southern Hunan

The Yanxi Formation of Middle Ordovician， as a new exploration layer of Lower Paleozoic in Hunan， has been widely valued by energy geologists. The shale reservoirs of Middle Ordovician Yanxi Formation in central-southern Hunan was comprehensively studied by means of polarizing microscope， high resolution scanning electron microscope， X-ray whole rock diffraction， organic carbon content， low temperature liquid nitrogen and carbon dioxide adsorption desorption. The results show that the Middle Ordovician Yanxi Formation in central-southern Hunan is deposited in slope and basin facies， and shale is developed in deep-water shelf and deep-water basin. Its minerals are mainly quartz and clay minerals， followed by pyrite and feldspar. The brittleness index of the reservoir is high， which is conducive to fracturing and exploitation. There are mainly organic pores， biological structural pores， intergranular pores， interstratified pores， intercrystalline pores， dissolution pores， clay mineral interlayer microcracks and mineral fractures developed in the shale reservoirs in the study area. It has medium porosity and good permeability. There are two types of pore structures developed in the study area. Among the pore structures dominated by mesopores and micropores， the total pore volume and the total pore volume of micropores are relatively large， and the specific surface area is also very large. Its reservoir performance and adsorption capacity are relatively strong， which can be used as the key exploration interval of Yanxi Formation. The pore development of Yanxi Formation shale in Middle Ordovician is mainly affected by thermal evolution， and secondly controlled by mineral composition and organic matter abundance. The Middle Ordovician Yanxi Formation in the study area has a good material basis for hydrocarbon generation. The organic matter in the source rocks are mainly types Ⅰ and Ⅱ₂. The TOC content is 0.05%-5.6%. The R_O value is 2.72%-3.82%， which has reached the high mature or over mature stage， which is conducive to the massive generation of shale gas. The Middle Ordovician Yanxi Formation in central-southern Hunan has moderate burial depth， good reservoir physical properties and rich organic matter， which has great exploration potential. The favorable exploration area is mainly located in the Dongan-Yongzhou-Qiyang area of Lingling Depression.