四川盆地东部下古生界页岩储集空间特征及其对含气性的影响

Shale Reservoir Space Characteristics and the Effect on Gas Content in Lower Palaeozoic Erathem of the Eastern Sichuan Basin

四川盆地东部下古生界海相页岩是一套有利的页岩气储层,通过野外泥页岩剖面及井下岩芯观察、电镜扫描、常规物性及微孔隙结构测试、等温吸附实验等技术方法,对页岩气储层空间特征进行了研究分析,发现下古生界页岩的孔隙可分为三大类六小类,裂缝可分为两大类五小类,具有颗粒细小、致密、大孔发育少、微孔发育多、具有一定孔隙度、渗透率小、喉道细、连通性差的特征。页岩总孔体积主体是由孔径小于200nm的微孔隙提供的,纳米级孔隙和微裂缝是页岩主要的储集空间,页岩有机质孔对于孔隙度具有一定贡献,是富有机质页岩的主要微孔隙类型。页岩的微孔隙结构决定了页岩气的赋存状态和流动方式,孔缝发育程度在一定程度上决定了页岩的含气性及其渗透性能,但大型或巨型裂缝的发育,将给页岩气的有效保存带来破坏。有机质(干酪根和沥青质)和黏土颗粒内的微孔隙表面是吸附态页岩气赋存的主要空间,但有机质孔提供了大部分具吸附性的孔比表面,是控制页岩吸附性能的主要因素,而黏土矿物的作用是次要的。

The marine facies shale of Lower Palaeozoic Erathem in the eastern Sichuan basin is set of favorable shale gas reservoir.By means of observing field shale section and drill core,scanning electron microscope,analysising convention petrophysical property and micro-pore structure of shale,isothermal adsorption experiment,etc,we studied shale gas reservoir space characteristics in Lower Palaeozoic Erathem.The study shows that Lower Palaeozoic Erathem shale has 3 big kinds and 6 small kinds of pores and 2 big kinds and 5 small kinds of fractures.The shale gas reservoir has the characteristics of tiny and dense particles,few macropores and macrofractures,more micropores and microfractures,moderate porosity,low permeability,fine throat and bad connectivity.The total pore volume of shale is provided mainly by the micropores which are less than 200 nm.Nanoporous and microfractures are main shale reservoir space.To some extent,micropores in organic matter amplify the porosity of shale,and is the main micropore type in organic rich shale.The storing status and flowing pattern of shale gas is very relevant with the micropores structure of shale.To some extent,the development degree of pores and fractures determines gas content and permeability of shale,but large or giant fractures would destroy effective preservation of shale gas.Micropores surfaces in organic matter（kerogen and asphaltene） and clay mineral are main spaces of storing absorbed shale gas,but organic matter supply most adsorptive specific surface,and is the main factor of determining shale adsorption property,and the effect of clay mineral is secondary.