Pore Structure Analysis from CO2 Saturation using Gas Adsorption

摘要

Mechanical changes take place in the process of saturating shale rock with CO2,which influences the storage capacity of the shale pores.X-ray diffraction(XRD),and gas adsorption(N2)isotherm are some of the characterization approaches used on the shale rock to determine the pore changes due to CO2 saturation.Barret Joyner and Halenda(BJH)model was employed to determine the pore structure distribution(pore size,pore volume and surface area)before and after CO2 saturation.The results show that clay minerals and quartz increased whereas other minerals decreased after CO2 saturation.The average total organic carbon(TOC)is 13.85 %,surface area is larger in sample with higher TOC after 60 days saturation.The adsorption isotherms belong to the type IV.Hysteresis loop type H4 was observed in all the samples stages,showing the occurrence of mesopores falling between 7.6 to 19.96 nm and 13.8 to 18.3 nm for the Upper and Lower Bakken samples respectively before and after saturation.These findings will assist in the investigation of shale rock integrity for CO2 saturation in the Bakken and its potential for fault reactivation.Presence of quartz seem to be playing a role in the pore size structure of the shale samples.The higher the quartz the higher the pore size and the pore volume as seen in the lower Bakken.