Lei Qin

This study explores how liquid nitrogen (LN2) freezing affects the physical pore and fracture structure of coal. Under lab-controlled conditions, coal specimens were frozen with LN2 under different conditions and thawed, and then the uniaxial compressive strengths, acoustic emissions, and ultrasonic wave velocities of the different specimens were compared. After 60 min of freezing for one set of specimens and 30 freeze–thaw cycles for another set, the elastic moduli of the coal specimens decreas

Freeze-thaw induced fracturing coal by liquid nitrogen (LN₂) injection exerts a significant positive effect on the fracture permeability enhancement of the coal reservoir. To evaluate the different freeze-thaw variables which modify the mechanical properties of treated coals, the effects of freezing time, number of freeze-thaw cycles, and the moisture content of coal were studied using combined uniaxial compression and acoustic emission testing systems. Freezing the samples with LN<su

Liquid nitrogen (LN2) fracturing is an anhydrous fracturing technology that enhances coal permeability and supports unconventional oil and gas exploitation. In this Review, we provide a systematic review of five aspects of LN2 fracturing. They are the history of the technology’s development, research topics, factors influencing fracturing efficiency, fracturing mechanism, and engineering processes and systems. Liquid nitrogen fracturing transforms coal and rock pore structure through mechanisms

Studying the law of coal adsorption capacity under the action of liquid nitrogen is very important for the extraction of coalbed methane. For this study, the lignite’s ability to adsorb methane was studied after it had been frozen by a number of different freezing techniques. In addition, the changes in the organic functional groups on the coal after freezing were identified by using infrared spectroscopy. The results demonstrate that as the duration of liquid nitrogen freezing and the number of