四川盆地周缘筇竹寺组泥页岩储层特征

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...

Mud shale reservoirs characteristics of Qiongzhusi Formation on the margin of Sichuan Basin, China

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 0.004×10-3~0.008×10-3 μm2.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.