Specific Surface Area and Characteristics of Nanopores Structures in Jiaoshiba Area, China

Abstract

The marine shales of the Ordovician Wufeng Formation to the Silurian Longmaxi Formation in Jiaoshiba area of China are shale gas exploration intervals. Accurate evaluation of shale reservoir pore volume is meaningful for the prediction of favorable gas bearing zones. This study is focused on the specific surface area and nanopores structures characteristics analyses using N2 adsorption methods and scanning electron microscope to measure the pore structures. The results are summarized to four points: (1) The porosities of the marine shales range from 1.17% to 7.98%, mainly distributed in 3.5%–6.0%, Aperture range from < 2 nm to 332 nm, and the average pore size of 5.05 nm – 6.65 nm. (2) The specific surface area of the nanopores ranges from 15.14 m²/g to 35.86 m²/g in Longmaxi Formation and 36.48 m²/g – 41.02 m²/g in Wufeng Formation. Pore volumes varying 0.0128 cm³/g to 0.0365 cm³/g in Longmaxi Formation and 0.029 cm³/g – 0.036 cm³/g in Wufeng Formation. (3) Surface area of micropore, mesopore and macropore accounted for the total surface area of 65.72%, 34.11% and 0.17%, and their pore volume accounted for the total pore volume of 35.92%, 56.85% and 7.23%. Micropores(<2nm) and mesopores(2–50nm) are the main places for shale gas storage that they mostly contribute to the specific surface area and pore volume. (4) According to the graph of adsorption and desorption, the pore structure of the shale gas reservoir of Wufeng and Longmaxi Formation is relatively complex, which is composed of nanopores and possesses a certain random structure(the amorphous pore), pores are open in style and mainly consist of the slit-shaped pores, and contain many other pores.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015