Combined with the outcrop and downhole geological data and using the methods of petrology and petrophysics, This paper discusses the shale-gas reservoirs characteristics in the Lower Cambrian Qiongzhusi Formation on the margin of Sichuan Basin. The thickness of the Lower Cambrian Qiongzhusi Formation ranges is 40～400 m on the margin of Sichuan Basin. The Qiongzhisi Formation shale is comprised of the black carbonaceous shale, gray silty mudstone, siltstone, fine sandstone, limestone and marlstone. The lower part of Qiongzhusi Formation shale is comprised of seven lithofacies, including the non-laminated rich-carbonaceous mudstone/shale, mudstone, calcareous mudstone, siltstone, laminated silty mudstone/pelitic siltstone, siliceous mudstone and calcareous siltstone/silty limestone. The brittle mineral is very rich in shale/mudstone and its content of 17. 2% is aphanitic quartz whose particle size is less than 0. 01 mm. The porosity measured in the core samples from Qiongzhusi Formation mudstone/shale reservoir in exploratory wells ranges is 0. 79 %～ 1. 25% on the average and the permeability range is 0. 004×10-3 ～0. 008×l0-3μm2. The micropores observed in the shale studied in thin sections is comprised of the intercrystalline pores in calcite and clay minerals, the dissolution pores of feldspar, and the intergranular pores of terrigenous fragments in mudstone. The size of the microfractures is about 2 μm× (50～120) μm. The ratio of shale/ mudstone is relatively higher in Weiyuan (south slope in paleo-uplift) and South Sichuan, but is relatively lower in the east of Chongqing and the Micangshan area. There is a better exploration prospect of shale gas in South Sichuan than in North Sichuan and East Chongqing, especially in South Sichuan. However, more attention should be paid to study the influence of the high maturity of the shale and the secondary hydrocarbon-generating process on the modification of the shale reservoir and the shale-gas accumulation mechanism.%通过地表地质和井下地质相结合,运用岩石学和岩石物理学方法,探讨了四川盆地周缘下寒武统筇竹寺组泥页岩储层特征.结果表明,四川盆地周缘下寒武统筇竹寺组厚40～400m,为一套黑色碳质泥页岩、灰色含粉砂泥岩、粉砂岩、细砂岩、灰岩及含泥灰岩建造.筇竹寺组下部岩性主要由富有机质(碳质)非纹层状泥页岩、泥岩、钙质泥岩、粉砂岩、纹层状粉砂质泥岩或泥质粉砂岩、(含)硅质泥岩、钙质粉砂岩或粉砂质灰岩7种岩性构成.泥页岩中脆性矿物含量高,其中隐晶质石英平均质量分数为17.2％,粒径＜0.01 mm.筇竹寺组泥页岩储层平均孔隙度为0.79％～1.25％,渗透率为0.004×10-3～0.008×10-3μm2.微孔隙主要有:自生方解石晶间孔、黏土矿物晶间孔、长石溶蚀孔、泥岩内部陆源碎屑粒间孔.微裂缝规模一般在2 μm× (50～120 μm)±.筇竹寺组泥页岩厚度在古隆起南斜坡的威远地区和川南地区较大,而在渝东地区和米仓山地区则相对较小.下部黑色碳质泥页岩在川东南地区的厚度为60～200m,在川北和渝东地区不发育.川南地区较渝东和川北地区具有更好的页岩气勘探前景,但需重点加强页岩高成熟作用及二次生烃过程对页岩储层改造、页岩气成藏机理等方面影响效应的研究.
展开▼
