四川盆地平桥地区五峰—龙马溪组页岩微观孔隙特征研究

基于氩离子抛光扫描电镜、吸附脱附实验等方法，对四川盆地平桥地区五峰组-龙马溪组下部页岩微观孔隙进行了研究。结果表明，富有机质的硅质页岩和碳质页岩微观孔隙以有机孔和微裂缝为主；孔隙结构相对复杂，孔隙形态丰富，孔径范围较大。吸附脱附实验显示，该页岩既有狭窄的平行板片状孔、少量的锥形平板孔和楔形孔，孔隙连通性相对差，又有规则开放圆孔与一端开口的墨水瓶状孔，孔隙开放性、连通性相对好。氩离子抛光扫描电镜法测量有机孔以细介孔为主且偏向微孔；吸附法测量比表面积为9～32.6 m²/g，平均18.0 m²/g，值偏低，BET法孔径为3.23～4.35 nm，BJH法孔容平均0.016 5 cm³/g，以细介孔为主，且偏向微孔界线。综合分析认为，研究区页岩储层微观孔隙以细介孔为主，且介孔和微孔贡献了绝大部分的比表面积。

Micro-pore characteristics of shale from Wufeng-Longmaxi formations in Pingqiao area,Sichuan Basin

The microscopic pore characteristics of shale from the lower Wufeng-Longmaxi formations in the Pingqiao area of the Sichuan Basin were studied using argon ion polished sample scanning electron microscopy and nitrogen adsorption-desorption experiments. Organic-rich siliceous shale and carbonaceous shale micro-pores are dominated by organic pores and micro-cracks. The pore structure is relatively complex, with rich pore morphology and a wide range of pore sizes. Argon ion polishing scanning electron microscopy showed that the organic pores are mainly thin and partly belong to micro-pores. Nitrogen adsorption-desorption experiments showed that the shale has narrow parallel plate-like holes, a small number of conical plate holes and wedge-shaped holes with a poor connectivity, and regular open round holes and ink bottle-shaped holes with open ends. The specific surface area measured by nitrogen adsorption-desorption experiments was 9-32.6 m2/g, with an average of 18.0 m2/g, which was low. The pore diameters measured by the BET method were 3.23 to 4.35 nm, and the average pore volume by the BJH method was 0.016 5 cm3/g. The fine meso-pores were dominant, and they were biased toward the micro-pore boundary. According to the comprehensive analysis, the microscopic pores of shale reservoirs in the study area are mainly mesoporous, and meso-pores and micro-pores contribute most of the specific surface area.