Pore structure analysis by mercury intrusion and nitrogen adsorption after LN2 treatment: An experimental study for granite rocks in ‘O’ field, Kazakhstan

This research investigates for first time granite from almost (4000 m) from an active oil field in west Kazakhstan (‘O’ field), the effects of LN₂ treatment on the pore structures of granite aiming at an environmentally friendly hydraulic fracturing process. Mercury Intrusion Porosimetry (MIP) and Low-Pressure Nitrogen Gas Adsorption (LN2GA) isotherms were used to assess how varying freezing durations and freeze-thaw cycles affect the pore characteristics. Total pore volume, assessed through nitrogen adsorption and mercury intrusion methods, grew with more prolonged exposure durations, reaching maximum levels in samples subjected to 20 freezing-thawing cycles. The widening of the hysteresis loop suggested an increase in average pore size. The surface area of pores expands during freezing, indicating the formation of more small pores. Freezing-thawing cycles form macropores and pore networks better as temperatures increase than the freezing time method.