The Pore Structure and Difference between Wufeng and Longmaxi Shales in Pengshui Area, Southeastern Sichuan
Peng Nüjia
He Sheng
Hao Fang
He Xipeng
Zhang Peixian
Zhai Gangyi
Bao Shujing
He Chencheng
Yang Rui
Abstract：Pore structure and its difference is a basic issue in shale gas content and capacity evaluation.A number of studies have been made on the pore structure of the shale in the Wufeng Formation and Longmaxi Formation in Pengshui area, southeastern Sichuan.However, there is a lack of research on shale pore structure difference and organic pore quantitative characteristics.Using low-temperature and low-pressure N2 adsorption and Ar ion milling field emission scanning electron microscopy (FE-SEM), for Wufeng and Longmaxi marine shales in Pengshui area of southeastern Sichuan, this paper investigated the pore structure of shale samples with the pore size ranging from 3nm to hundreds nm, and its difference between Wufeng and Longmaxi formations was also analyzed by observing and counting nano-pores in two-dimension, and computing fractal dimension.Results indicate that organic pores from Wufeng and Longmaxi shales in Pengshui area are very developed.Results of N2 adsorption show the shale samples contain open cylindrical-like pores, layered slit-like pores and ink-bottle pores.And observation of scanning electron microscopy reveals organic pore morphology mainly is nearly circular, elliptic and polygon.The obvious difference of pore structure between Wufeng and Longmaxi shales is mainly reflected on the pore size, shape and quantity.N2 adsorption results show that Wufeng shales have higher specific surface area and total pore volume than that of Longmaxi shales, and micropore within Wufeng shales accounts for higher proportion of total pore;pore size of Wufeng shales is narrower than that of Longmaxi shales.Observation and statistics of FE-SEM two-dimensional images indicate organic pores in Wufeng Formation are mainly pores with diameter less than 35nm and have irregular shapes.While Longmaxi organic pores are mainly less than 50nm in diameter and pore shapes mainly are nearly circular or elliptic.Based on the pore fractal dimension calculation of N2 adsorption and FE-SEM, Wufeng Formation has higher pore fractal dimension values than Longmaxi Formation, which indicates that the pore structure of Wufeng shales is more complex than that of Longmaxi shales.
Keywords：pore structurefractal featuresWufeng FormationLongmaxi Formationmarine shalePengshui areapetroleum geology.
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：13( 1134-1146 )