四川盆地五峰组—龙马溪组页岩气形成与聚集机理  

Mechanisms of shale gas generation and accumulation in the Ordovician Wufeng-Longmaxi Formation,Sichuan Basin,SW China

作　　者：腾格尔[1,2] 申宝剑[1,2] 俞凌杰[1,2] 仰云峰[1,2] 张文涛[1,2] 陶成[1,2] 席斌斌[1,2] 张庆珍[1,2] 鲍芳[1,2] 秦建中[1,2] 

机构地区：[1]页岩油气富集机理与有效开发国家重点实验室,江苏无锡214126 [2]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

出　　处：《石油勘探与开发》2017年第1期69-78,共10页Petroleum Exploration and Development

基　　金：国家自然科学基金"古生界页岩含气性原生有机质控制作用研究"(U1663202)

摘　　要：综合运用有机超显微组分识别、聚焦离子束扫描电镜、高温高压等温吸附和页岩气稀有气体同位素年龄测定等技术,深入研究四川盆地涪陵地区页岩气主力产层上奥陶统五峰组—下志留统龙马溪组的烃源品质、有机质孔隙发育特征、页岩气赋存形式和封存机制。结果表明:1五峰组—龙马溪组富有机质页岩主要形成于表层水生产力高、底层水缺氧的沉积环境,TOC值呈两段式分布,下段TOC≥3%,主要由浮游藻类、疑源类、细菌和笔石等成烃生物及残留沥青组成,其中笔石是TOC值的主要贡献者之一,但页岩气主要来自浮游藻类、疑源类等富氢富脂质有机质及由其生成的液态烃裂解。2有机质孔隙主要发育在固体沥青和富氢有机质中,是页岩气的主要储集空间。笔石等大量有机质呈纹层状、堆积式分布,为页岩气提供了更多的储存空间和各类孔隙连通、流体流动的优势通道。3涪陵页岩气处于超临界状态,以游离气为主。页岩气封闭体系的形成时间与生气高峰期之间的有效匹配,以及后期构造活动对页岩气封存条件的改造程度低是复杂构造区高热演化页岩气滞留富集的关键,页岩的吸附作用、毛管封闭以及低速扩散形成了页岩气微观滞留富集机制。可见,复杂构造区高热演化海相页岩气的形成与富集受缺氧的沉积环境、优质的烃源品质、优越的储集空间和良好的封存条件综合控制。The source rock quality, organic pore structure, occurrence state and sealing mechanisms of shale gas in the Ordovician Wufeng-Longmaxi Formation （O3w-S1l）, Fuling region, Sichuan Basin were studied using ultra-microscopic organic maceral identification, FIB-SEM, high temperature/pressure isothermal adsorption and isotopic age dating of noble gas. The results show that： （1） O3w-S1l organic-rich shale was mainly formed in a sedimentary environment with high productivity in surface water and hypoxia in bottom water, it can be divided into two sections according to TOC, of which the lower section （TOC≥3%） is mainly composed of graptolite, phytoplankton, acritarch, bacteria and solid bitumen, among them, graptolite is the main contributor to TOC, but the shale gas is mainly derived from phytoplankton, acritarch and other hydrogen-rich organic matter, as well as the pyrolysis of liquid hydrocarbons produced by this kind of organic matter. （2） Organic pores, as principal reservoir space for shale gas, exist in hydrogen-rich organic matter and solid bitumen. The graptolites and plenty of other organic matter stacking distribution in lamina provide more reservoir space for shale gas, and effective pathways of connected pores for fluid flow. （3） Shale gas in Fuling region is in supercritical state and dominated by free gas; the match of formation time of closed shale gas system and gas-generation peak, as well as slight alteration degree of sealing conditions in the later stage, are key factors controlling the retention and accumulation of shale gas in the regions with high thermal maturity and complex structural areas; adsorption, capillary sealing and slow diffusion of shale are the main microscopic mechanisms for the retention and accumulation of shale gas. It thus can be seen that the generation and accumulation of marine shale gas with high thermal maturity in complex structure areas is controlled jointly by anoxic depositional environment, excellent hydrocarbon rock quality, superior reservoi

关 键 词：四川盆地 涪陵气田 页岩气 成烃生物 储集空间 赋存形式 封存机制 

分 类 号：TE122.1[石油与天然气工程—油气勘探]