Visualization of physical processes occurring on liquid nitrogen injection into water

2015 ◽  
Vol 24 (4) ◽  
pp. 322-329 ◽  
Author(s):  
V. E. Nakoryakov ◽  
I. V. Mezentsev ◽  
A. V. Meleshkin ◽  
D. S. Elistratov
Keyword(s):  
Liquid Nitrogen ◽  
Physical Processes ◽  
Nitrogen Injection

scholarly journals The effect of liquid nitrogen cooling on coal cracking and mechanical properties

2018 ◽  
Vol 36 (6) ◽  
pp. 1609-1628 ◽  
Author(s):  
Chengzheng Cai ◽  
Feng Gao ◽  
Yugui Yang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Acoustic Emission ◽  
Liquid Nitrogen ◽  
Wave Velocity ◽  
Count Rate ◽  
Initial State ◽  
Nitrogen Injection ◽  
Strength Tests ◽  
Liquid Nitrogen Cooling

Liquid nitrogen is a type of super-cryogenic fluid, which can cause the reservoir temperature to decrease significantly and thereby induce formation rock damage and cracking when it is injected into the wellbore as fracturing fluid. An experimental set-up was designed to monitor the acoustic emission signals of coal during its contact with cryogenic liquid nitrogen. Ultrasonic and tensile strength tests were then performed to investigate the effect of liquid nitrogen cooling on coal cracking and the changes in mechanical properties thereof. The results showed that acoustic emission phenomena occurred immediately as the coal sample came into contact with liquid nitrogen. This indicated that evident damage and cracking were induced by liquid nitrogen cooling. During liquid nitrogen injection, the ring-down count rate was high, and the cumulative ring-down counts also increased rapidly. Both the ring-down count rate and the cumulative ring-down counts during liquid nitrogen injection were much greater than those in the post-injection period. Liquid nitrogen cooling caused the micro-fissures inside the coal to expand, leading to a decrease in wave velocity and the deterioration in mechanical strength. The wave velocity, which was measured as soon as the sample was removed from the liquid nitrogen (i.e. the wave velocity was recorded in the cooling state), decreased by 14.46% on average. As the cryogenic samples recovered to room temperature, this value increased to 18.69%. In tensile strength tests, the tensile strengths of samples in cooling and cool-treated states were (on average) 17.39 and 31.43% less than those in initial state. These indicated that both during the cooling and heating processes, damage and cracking were generated within these coal samples, resulting in the acoustic emission phenomenon as well as the decrease in wave velocity and tensile strength.

Numerical simulation of liquid nitrogen injection in a container with controlled atmosphere

2019 ◽  
Vol 187 ◽  
pp. 53-68
Author(s):  
Jiaming Guo ◽  
Xinyu Wei ◽  
Xiannan Du ◽  
Junjie Ren ◽  
Enli Lü
Keyword(s):  
Numerical Simulation ◽  
Liquid Nitrogen ◽  
Controlled Atmosphere ◽  
Nitrogen Injection

scholarly journals Freezing Method for Rock Cross-Cut Coal Uncovering: Aging Characteristic of Effective Freezing Distance on Injecting Liquid Nitrogen into Coal Seam

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Heyi Ma ◽  
Chuanqu Zhu ◽  
Pengtao Zhao ◽  
Binbin Wang
Keyword(s):  
Thermal Conductivity ◽  
Coal Seam ◽  
Liquid Nitrogen ◽  
Water Injection ◽  
Engineering Practice ◽  
Power Exponent ◽  
Nitrogen Injection ◽  
Artificial Freezing ◽  
Freezing Test ◽  
Aging Characteristic

Based on artificial freezing engineering practice, the comprehensive technology is suggested to realize safe and fast rock cross-cut coal uncovering, which mainly includes four steps of drilling, water injection wetting coal, gas drainage, and injection liquid nitrogen into coal seam. Freezing test of liquid nitrogen injection into coal is carried out to obtain the cooling curves, and comparing the test results, the numerical inverse method is applied to determine the thermal conductivity of coal seam. Then, the model of injecting liquid nitrogen into coal seam is established to simulate and analyze the aging characteristic of effective freezing radius. The results show that the thermal conductivity of wetting coal increases linearly with temperature decreasing. The periodic method with 8h intervals can be adopted to inject liquid nitrogen into coal seam, and the freezing wall is formed around the injection hole. With the increase of freezing time, the effective freezing radius (below 273.15 K) increases by power exponent, and the freezing speed in coal seam decreases gradually. This result will provide a theoretical basis for layout optimization of injection holes in rock cross-cut coal uncovering.

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