Pore Characteristics of Marine Shale in Lower Cambrian Hetang Formation in Xiuwu Basin

doi:10.7657/XJPG20200506

Abstract

Abstract:

Based on porosity and low temperature N₂ and CO₂ adsorption experiments, the pore characteristics of the shale in the Lower Cambrian Hetang formation were quantitatively characterized. And combined with TOC, whole rock X-ray diffraction and previous research on the thermal evolution of organic matter, the controlling factors on the pore characteristics were discussed and analyzed. The results show that most pores are wedge-shaped, and less are like bottle-neck and slits. The porosity of the shale ranges from 1.24% to 2.91%, of which mesopores, micropore and macropore account for 44.53%, 35.45% and 20.01%, respectively. The total pore volume of the shale ranges from 5.33× 10^-3 cm³/g to 20.10×10^-3 cm³/g, of which the average pore volumes of BJH and DFT are 7.40×10^-3 cm³/g and 2.24×10^-3 cm³/g, respectively. The total specific surface area is 7.62 to 17.84 m²/g, of which the average specific surface areas of low-temperature N₂ adsorption and CO₂ adsorption are 5.23 m²/g and 7.41 m²/g, respectively. The peak pore size is less than 10.00 nm, and the micropore structures are complex. The pores of 0.30-0.70 nm are relatively developed, but the larger specific surface area provides more room adsorbing shale gas. TOC is the controlling factor on micropore development, and it is helpful to the development of mesopores, but influences less on macropores. Clay minerals reduce the shale porosity, while quartz is a favorable factor on the total pore volume and total specific surface area. With the similar characteristics to the Lower Jurassic Ziliujing formation shale in the western Hubei province, the marine shale of the Lower Cambrian Hetang formation in Xiuwu basin has a good reservoir capability.

Key words: Xiuwu basin, Lower Cambrian, Hetang formation, pore, CO₂ adsorption, low-temperature N₂ adsorption, pore size, marine shale

CLC Number:

TE122.2

GUO Chunli, YANG Shuang, WANG Andong, ZHANG Shuanglong, QI Xing. Pore Characteristics of Marine Shale in Lower Cambrian Hetang Formation in Xiuwu Basin[J]. Xinjiang Petroleum Geology, 2020, 41(5): 550-556.

Figures/Tables 8

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