四川盆地不同成熟度下志留统龙马溪组页岩有机孔特征  

Characteristics of organic matter-hosted pores in Lower Silurian Longmaxi shale with different maturities,Sichuan Basin

作　　者：仰云峰[1] 鲍芳[1] 腾格尔 潘安阳[1] 申宝剑[1] YANG Yunfeng;BAO Fang;BORJIGIN Tenger;Pan Anyang;SHEN Baojian(Wuxi Research Institute of Petroleum Geology,SINOPEC,Wuxi,Jiangsu 214126,China;Oil and Gas Survey,China Geological Survey,Beijing 100083,China)

机构地区：[1]中国石化石油勘探开发研究院无锡石油地质研究所,江苏无锡214126 [2]中国地质调查局油气资源调查中心,北京100083

出　　处：《石油实验地质》2020年第3期387-397,共11页Petroleum Geology & Experiment

基　　金：国家科技重大专项(2017ZX05036-002);国家自然科学基金(U1663202,41690133)联合资助。

摘　　要：有机质孔隙是页岩气的主要储集空间,也是页岩天然渗流通道的重要组成部分。选取四川盆地不同热成熟度的下志留统龙马溪组页岩,采用场发射扫描电镜开展页岩不同显微组分有机质孔隙形成演化研究。笔石是龙马溪组页岩主要的结构有机质,含量较少,自身不发育有机质孔隙。成岩过程中由脂类原位聚合或外部地质聚合物交代使得笔石化石具有一定的生烃潜力,导致局部存在有机质孔隙。固体沥青是龙马溪组页岩最主要的显微组分,也是有机质孔隙发育的主要载体。考虑细粒沉积物成岩和有机质生烃演化,结合固体沥青赋存形态,可将固体沥青区分为前油沥青和后油沥青,且后油沥青含量占绝对优势。固体沥青有机质孔隙演化与热成熟度密切相关。总体上,随着热成熟度增加,固体沥青有机质孔隙越来越发育。成熟-高成熟早期(GR_o<2.3%),固体沥青孔隙不太发育,可能受到有机质生成的烃类物质掩盖。高成熟晚期-过成熟早期(2.3%4.5%),有机质炭化对页岩孔隙产生强烈破坏作用,导致页岩气勘探风险加剧。Organic matter-hosted pores provide reservoir space and migration pathways for shale gas.The evolution of organic matter-hosted pores(OM pores)of different macerals from Longmaxi shale with a wide variety of thermal maturities has been investigated using field emission scanning electron microscopy(FE-SEM).The Longmaxi shale contains rare graptolites which are the main component of structured organic matter.No OM pores occur in graptolite fragments,irrespective of thermal maturity.OM pores locally developed in graptolite fragments are formed from hydrocarbon generation of organic matter which was replaced by macromolecular material from surrounding sediment or in situ polymerized by lipids from the organism itself.Solid bitumen is not only the major organic component in the Longmaxi shale,but also the main host of OM pore development.The diagenesis of fine-grained sediments and thermal evolution of organic matter have been combined with the morphology of solid bitumen to distinguish pre-oil solid bitumen and post-oil solid bitumen.The post-oil solid bitumen is dominant.The evolution of OM pores within solid bitumen is closely related to thermal maturity.Generally,OM pores within solid bitumen become greater as thermal maturity increases.During the mature to early postmature(GR_o<2.3%)stages,OM pores within solid bitumen are not well developed probably due to the masking by oil and bitumen generated from organic matter.OM pores within solid bitumen are well developed during the late postmature to early overmature(2.3%4.5%)stage,organic matter carbonization will cause intense damage to shale pores so that the exploration risk of shale gas increases.

关 键 词：有机质孔隙 热成熟度 显微组分 固体沥青 页岩 龙马溪组 下志留统 四川盆地 

分 类 号：TE122.2[石油与天然气工程—油气勘探]