四川盆地涪陵页岩气田五峰—龙马溪组岩矿纵向差异性研究——以JYA井为例

Vertical variation of rocks and minerals in Wufeng-Longmaxi formations in Fuling shale gas field,Sichuan Basin:A case study of well JYA

涪陵页岩气田是我国首个实现商业开发的大型页岩气田。通过对涪陵焦石坝区块JYA井五峰组—龙马溪组龙一段页岩开展岩石薄片和氩离子抛光扫描电镜观察,并结合全岩黏土X衍射、有机碳含量等分析测试,探究了该气田五峰组—龙马溪组龙一段页岩纵向上的矿物成分及含量的变化特征,明确了该套页岩主要成分为石英和黏土矿物,其次为长石和碳酸盐,以及少量的黄铁矿;其中石英和黏土矿物达70%以上,自下而上石英、长石及黄铁矿含量逐渐减少,黏土矿物含量逐渐增加。结合页岩矿物纵向上的差异性变化,探讨了其对页岩储集性、含气性和可压性的影响,明确了纵向上随着生物成因硅质含量增加,黏土矿物含量的减少,页岩自上而下呈现出有机质含量增加,有机质孔发育,页岩储集性能变好,页岩含气量增加的趋势;同时随着脆性矿物含量的增加,页岩的可压性也逐渐增强。

The Fuling shale gas field is the first to achieve commercial development in China.The well JYA in the Jiaoshiba area of Sichuan Basin was used as an example to study the vertical variation of rock and mineral composition based on thin section observation and scanning electron microscopy(SEM),and combined with X-ray diffraction of whole rock and organic carbon determination.The results showed that quartz and clay minerals are dominant in the Wufeng-Longmaxi shale,accounting for over 70%,followed by feldspar and carbonate,and a small amount of pyrite.From bottom to top,the contents of quartz,feldspar and pyrite gradually decrease,while that of clay minerals increases.The effects of shale mineral vertical variation on shale reservoir property,gas content and compressibility were discussed.With the increase of biogenic silicate and the reduction of clay mineral in vertical direction,the shale shows a tendency of increasing organic matter content,organic matter pore development,shale reservoir performance and shale gas content from top to bottom.At the same time,with the increase of brittle mineral content,the compressible property of shale is also gradually enhanced.