富有机质页岩生烃阶段孔隙演化——来自鄂尔多斯延长组地质条件约束下的热模拟实验证据  

Porous Evolution of the Organic-Rich Shale from Simulated Experiment with Geological Constrains,Samples from Yanchang Formation in Ordos Basin

作　　者：薛莲花[1] 杨巍[1,2] 仲佳爱[1,2] 徐勇[1,2] 陈国俊[1] 

机构地区：[1]甘肃省油气资源研究重点实验室/中国科学院油气资源研究重点实验室,兰州730000 [2]中国科学院大学,北京100049

出　　处：《地质学报》2015年第5期970-978,共9页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41272144);国家自然科学基金青年基金(编号41402130);中国科学院战略性先导科技专项(B类)(编号XDB10010300);中科院"西部之光"项目"甘肃陇东地区三叠系湖相页岩气的赋存条件研究";甘肃省重点实验室专项(编号1309RTSA041)联合资助成果

摘　　要：通过加水的高温高压热模拟实验对鄂尔多斯盆地延长组长7段陆相低熟油页岩进行地质条件约束下的模拟,获得不同热演化程度的页岩样品,并对其孔隙特征及纳米级孔隙的分布进行研究。结果表明,原始样品微孔隙类型主要有原生残留孔隙、次生溶蚀孔隙、黏土矿物粒间孔和黄铁矿晶间孔,及一些表生作用形成的收缩孔,其中一些孔隙被残留烃所充填。随着温、压的升高,有机质孔开始发育,样品孔隙度呈现出先增加后减小的演化规律,从原始样品的3.8%升高至350℃、32.5 MPa的17.53%后又逐渐降低,370℃、42.9 MPa时为8.15%,孔径峰值从20～100nm变为2～10nm,尔后又升至20～200nm,页岩孔隙度的增加主要是有机孔的贡献。低熟阶段样品中有机质纳米级孔隙发育有限,而是多在有机质与骨架颗粒接触边缘发育长条形、狭缝状的孔隙。随着成熟度的升高,在有机质内部开始出现孔隙,黏土颗粒间的有机质也开始分解,出现纳米级层间孔。随温度、压力的继续增大,压实作用、矿物相变及有机孔形成速度减缓的共同作用而减孔显著,岩样孔隙度减小幅度达5.68%,因此对于富有机质页岩来说,深埋阶段压实作用不容小视。Immature continental shale samples collected from the outcrops of the Chang 7member in Ordos Basin were analyzed by hydrous pyrolysis experiment.Seven samples with different simulated buried depth were obtained in the laboratory.The characteristics and pore size distribution were observed using field emission scanning electron microscope and low pressure nitrogen adsorption experiments.The results indicated there were mainly five types of pores in primary oil shale,including：primary pores,secondary dissolved pores,intergranular pores between clay minerals,intracrystal pores and shrinkage pores.Some of them were filled with residual hydrocarbon.Organic pores began to form with increasing temperature and pressure,they contributed to the whole porosity.The porosity began to decrease after drastically increasing-from original3.8%to 17.53%,and then reduce to 8.15%.Peak pore sizes appeared between 50～200nm.It had not yet reached gas window as a low thermal evolution for the primary sample,immature source rocks with high organic matter abundance had not begun to generate a great deal of hydrocarbons.The linear,slit pores developed a lot at the contact edge of organic material and skeletal grains.When the temperature reached 350℃and above with a depth deeper than 2500 m,pores began to form in the organic matter,and especially,interlayer pores generated with the decomposition of organic material within the clay.With the increasing simulated depth,compaction,phase transformation of minerals and less organic pores made a remarkable porosity reduction by 5.68%,compaction is the key issue of the organic-rich shale reservoir.

关 键 词：热模拟实验 油页岩 孔隙类型 有机质纳米孔 孔径分布 

分 类 号：P618.13[天文地球—矿床学]