致密砂岩自生伊利石的成因及其对相对优质储层发育的影响——以川西地区须四段储层为例  

The origin of authigenic illite in tight sandstones and its effect on the formation of relatively high-quality reservoirs: A case study on sandstones in the 4th member of Xujiahe Formation,western Sichuan Basin

作　　者：孟万斌[1,2] 吕正祥[3] 冯明石[1] 张世华[3] 李敏[1,2] 麦发海[1,2] 

机构地区：[1]成都理工大学油气藏地质及开发工程国家重点实验室,四川成都610059 [2]成都理工大学沉积地质研究院,四川成都610059 [3]中石化西南油气分公司勘探开发研究院,四川成都610081

出　　处：《石油学报》2011年第5期783-790,共8页Acta Petrolei Sinica

基　　金：国家科技重大专项(2008ZX05002-004-002);油气藏地质及开发工程国家重点实验室项目(国重科研G9)资助

摘　　要：川西地区须家河组四段为典型的致密砂岩储层,砂岩骨架颗粒中岩屑含量高而长石含量极低。自生黏土矿物主要为伊利石和高岭石,其中自生伊利石呈碎屑颗粒包膜、充填于次生粒内溶孔中的网状集合体和充填于粒间的非网状集合体3种方式产出。第一种为早期形成的蒙脱石经伊蒙混层转化而来;第二种由埋藏期钾长石的伊利石化作用形成;第三种由钾长石和早期形成的高岭石在深埋期间通过伊利石化作用形成。自生伊利石的形成对致密砂岩中相对优质储层的发育具有双重影响。它能降低储层的渗透率,影响储层质量,但颗粒包膜伊利石可以阻止石英次生加大的形成从而保护原生孔隙,埋藏成岩过程中蒙皂石-伊利石的转化反应以及钾长石和高岭石的伊利石化作用能促进钾长石的溶解形成次生孔隙。因此,自生伊利石的形成对于砂岩原生孔隙的保存和次生孔隙的发育具有积极作用,因而有利于相对优质储层的形成。The 4th member of Xujiahe Formation in the western Sichuan Basin is composed of typical tight sandstones that contain abundant debris but very scarce feldspar in skeleton grains.Authigenic clay minerals are dominated by illite and kaolinite,wherein authigenic illite can be divided into three principal types： grain-coatings,netted aggregates filled in secondary intragranular dissolved pores and non-netted aggregates filled in intergranular space.The first type transforms from the early-formed smectite through I/S mixed layer,the second type is derived from illitization by K-feldspar during burial metamorphism,and the third type is a product of illitization by K-feldspar and the early-formed kaolinite during deep burial.The formation of authigenic illite has a dual effect on the development of relatively high-quality reservoirs in tight sandstones.On the one hand,it can reduce sandstone permeability and lower the quality of reservoirs,and on the other hand,the grain-coaling illite can preserve the primary porosity by preventing quartz from cementation,while the transformation of smectite to illite and the illitization of K-feldspar and kaolinite during burial diagenesis can accelerate the dissolution of K-feldspar to form secondary pores.Therefore,the formation of authigenic illite generally plays a positive role in the primary porosity preservation and the development of secondary pores of sandstones,and consequently favors the formation of relatively high-quality reservoirs.

关 键 词：致密砂岩 自生伊利石 川西地区 须四段 相对优质储层 

分 类 号：TE112[石油与天然气工程—油气勘探]