摘要
富有机质页岩中的有机质孔是页岩储层中重要的孔隙类型,有机质孔的数量、孔径大小和分布特征对页岩油气的吸附和储集能力、储层渗透性、页岩油气赋存状态和含量均具有重要的影响。利用氩离子抛光和场发射扫描电镜分析等技术分析了鄂尔多斯盆地东南部延长组长7油层组页岩中的固体有机质和不同有机质中有机质孔的发育特征。结果表明,延长组长7油层组页岩的成熟度较低(Ro为0.62%~0.85%),固体有机质中的有机质孔比较发育,有机质孔的分布和发育程度具有明显的非均一性。运移固体有机质常充填于粒间孔、黄铁矿集合体粒内孔、溶蚀孔中,运移固体有机质中有机质孔较发育,孔径相对较大,孔隙数量多,而近似平行层理定向富集的干酪根中有机质孔数量相对较少或不发育。有机质孔的孔径主要介于6~60nm、占总数的84.9%,多数有机质孔的孔径小于30nm,孔径大于100nm的孔隙仅占总数的6.1%,最大孔径可达1μm以上,不同样品的有机质孔孔径分布特征存在一定的差异。固体有机质的类型及其与无机矿物间的关系对页岩中有机质孔的发育程度具有重要的影响,运移固体有机质含量越高,有机质孔越发育。
Organic pore in organic-rich shale is an important pore type in shale reservoir.The quantity,pore size and distribution characteristics of organic pore have important effects on the adsorption and reserving capacity,reservoir permeability,the occurrence and content of shale hydrocarbons.The solid organic matter in the shale of Chang 7 oil-bearing formation,Yanchang Formation,the southeastern Ordos Basin was analyzed by argon ion polishing and field emission scanning electron microscopy.The development characteristics of organic pore in different organic matters were discussed.The results show that despite the shale maturity of Chang 7 oil-bearing formation,Yanchang Formation is relatively low(Ro=0.62%-0.85%),the organic pores in solid organic matter are relatively developed.However,the distribution and development degree of organic pores have obvious heterogeneity.The migrated solid organic matters often fill the intergranular pores,iron pyrite aggregation intra-granular pores and dissolution pores,of which the organic pores are relatively developed in large quantity with relatively large size,while the organic pores of the kerogen directionally enriched in the approximately parallel bedding are less or undeveloped.The pore sizes of organic pore are mainly in the range of 6-60 nm,accounting for 84.9% of the total.The pore sizes of most organic pores are less than 30 nm,and the pores with the size larger than 100 nm is only 6.1% of the total.The pore size distribution characteristics of organic matter for different samples varies with the maximum pore size above 1μm.The relation between the types of solid organic matters and inorganic minerals has an important influence on the development degree of organic pores in shale.The higher the content of migrated solid organic matter is,the more developed the organic pores will be.
引文
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