Comparative experimental study on porosity, mechanical and CO2 adsorption characteristics of coal and shale
Haitao LI, Guo YU, Xiaolei WANG, Dongming ZHANG
Comparative experimental study on porosity, mechanical and CO2 adsorption characteristics of coal and shale
To compare the pore structure, mechanical and CO2 adsorption properties of coal and shale, a series of experiments were carried out using nuclear magnetic resonance (NMR), uniaxial compression, Brazilian splitting, and high-pressure CO2 adsorption. The results show that the total porosity of coal is 7.51 times that of shale, and shale is dominated by adsorption pores, while adsorption pores and seepage pores in coal are equally important. Moreover, it is found that the micropores in shale are more advantageous, while meso-macropore in coal are more significant. The adsorption pore surface of coal is rougher than that of shale, and the seepage pore structure of shale is more complex. The uniaxial compressive strength, elastic modulus and absorption energy of shale are 2.01 times, 2.85 times, and 1.27 times that of coal, respectively, indicating that shale has higher compressive capacity and resistance to elastic deformation than coal. The average tensile strength, Brazilian splitting modulus, absorbed energy and brittleness index of shale are 7.92 times, 6.68 times, 10.78 times, and 4.37 times that of coal, respectively, indicating that shale has higher tensile strength and brittleness, but lower ductility, compared with coal. The performed analyses show that under the same conditions, the CO2 adsorption capacity of coal is greater than that of shale. The present article can provide a theoretical basis to implement CO2-enhanced coalbed methane (CBM)/shale gas extraction.
coal / shale / NMR / mechanical properties / adsorption characteristic
[1] |
Aybar U, Eshkalak M O, Sepehrnoori K, Patzek T W (2014). The effect of natural fracture’s closure on long-term gas production from unconventional resources.J Nat Gas Sci Eng, 21: 1205–1213
CrossRef
Google scholar
|
[2] |
Cao T T, Song Z G, Luo H Y, Liu G X (2015). The differences of microscopic pore structure characteristics of coal, oil shale and shales and their storage mechanisms.Nat Gas Geosci, 26(11): 2208–2218
CrossRef
Google scholar
|
[3] |
Chandra D, Vishal V, Bahadur J, Sen D (2020). A novel approach to identify accessible and inaccessible pores in gas shales using combined low-pressure sorption and SAXS/SANS analysis.Int J Coal Geol, 228: 103556
CrossRef
Google scholar
|
[4] |
Chen S, Zhu Y, Wang H, Liu H, Wei W, Luo Y, Li W, Fang J (2010). Research status and trends of shale gas in China.Acta Petrol Sin, 31(4): 689–694
CrossRef
Google scholar
|
[5] |
Chen S, Tang D, Tao S, Ji X, Xu H. (2019). Fractal analysis of the dynamic variation in pore-fracture systems under the action of stress using a low-field NMR relaxation method: an experimental study of coals from western Guizhou in China.J Petrol Sci Eng, 173: 617–629
CrossRef
Google scholar
|
[6] |
Feng G, Kang Y, Sun Z, Wang X, Hu Y (2019). Effects of supercritical CO2 adsorption on the mechanical characteristics and failure mechanisms of shale.Energy, 173: 870–882
CrossRef
Google scholar
|
[7] |
Gao S, Jia L, Zhou Q, Cheng H, Wang Y (2022). Microscopic pore structure changes in coal induced by a CO2–H2O reaction system.J Petrol Sci Eng, 208: 109361
CrossRef
Google scholar
|
[8] |
Geng W, Huang G, Guo S, Jiang C, Dong Z, Wang W (2022). Influence of long-term CH4 and CO2 treatment on the pore structure and mechanical strength characteristics of Baijiao Coal.Energy, 242: 122986
CrossRef
Google scholar
|
[9] |
Gholami R, Rasouli V, Sarmadivaleh M, Minaeian V, Fakhari N (2016). Brittleness of gas shale reservoirs: a case study from the north Perth Basin, Australia.J Nat Gas Sci Eng, 33: 1244–1259
CrossRef
Google scholar
|
[10] |
Hou P, Xue Y, Gao F, Dou F, Su S, Cai C, Zhu C (2022). Effect of liquid nitrogen cooling on mechanical characteristics and fracture morphology of layer coal under Brazilian splitting test.Int J Rock Mech Min Sci, 151: 105026
CrossRef
Google scholar
|
[11] |
Jin K, Cheng Y, Liu Q, Zhao W, Wang L, Wang F, Wu D (2016). Experimental investigation of pore structure damage in pulverized coal: implications for methane adsorption and diffusion characteristics.Energy Fuels, 30(12): 10383–10395
CrossRef
Google scholar
|
[12] |
Joubert J I, Grein C T, Bienstock D (1973). Sorption of methane in moist coal.Fuel, 52(3): 181–185
CrossRef
Google scholar
|
[13] |
Langmuir I (1918). The adsorption of gases on plane surfaces of glass, mica and platinum.J Am Chem Soc, 40(9): 1361–1403
CrossRef
Google scholar
|
[14] |
Liu X, Zhang C, Nie B, Zhang C, Song D, Yang T, Ma Z (2022a). Mechanical response and mineral dissolution of anthracite induced by supercritical CO2 saturation: influence of saturation time.Fuel, 319: 123759
CrossRef
Google scholar
|
[15] |
Liu Z, Lin X, Cheng Y, Chen R, Zhao L, Wang L, Li W, Wang Z (2022b). Experimental investigation on the diffusion property of different form coal: implication for the selection of CO2 storage reservoir.Fuel, 318: 123691
CrossRef
Google scholar
|
[16] |
Liu Z, Lin X, Wang Z, Zhang Z, Chen R, Wang L, Li W (2022c). Modeling and experimental study on methane diffusivity in coal mass under in-situ high stress conditions: a better understanding of gas extraction.Fuel, 321: 124078
CrossRef
Google scholar
|
[17] |
Satya , Harpalani , Basanta , K. , Prusty , Pratik ,
CrossRef
Google scholar
|
[18] |
Shao X, Pang X, Li H, Zhang X (2017). Fractal analysis of pore network in tight gas sandstones using NMR Method: a case study from the Ordos Basin, China.Energy Fuels, 31(10): 10358–10368
CrossRef
Google scholar
|
[19] |
Sing K (1982). Reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity (Provisional).Pure Appl Chem, 54(11): 2201–2218
CrossRef
Google scholar
|
[20] |
Song Y, Zou Q, Su E, Zhang Y, Sun Y (2020). Changes in the microstructure of low-rank coal after supercritical CO2 and water treatment.Fuel, 279: 118493
CrossRef
Google scholar
|
[21] |
Su E, Liang Y, Chang X, Zou Q, Xu M, Sasmito AP (2020). Effects of cyclic saturation of supercritical CO2 on the pore structures and mechanical properties of bituminous coal: an experimental study.J CO2 Util, 40: 101208
CrossRef
Google scholar
|
[22] |
Wang G, Qin X, Shen J, Zhang Z, Han D, Jiang C (2019). Quantitative analysis of microscopic structure and gas seepage characteristics of low-rank coal based on CT three-dimensional reconstruction of CT images and fractal theory.Fuel, 256: 115900
CrossRef
Google scholar
|
[23] |
Wang H M, Zhu Y M, Li W, Zhang J S, Luo Y (2011). Two major geological control factors of occurrence characteristics of CBM. J China Coal Soc, 36(7): 1129–1134 (in Chinese)
|
[24] |
Wang X, Cheng Y, Zhang D, Liu Z, Wang Z, Jiang Z (2021a). Influence of tectonic evolution on pore structure and fractal characteristics of coal by low pressure gas adsorption.J Nat Gas Sci Eng, 87: 103788
CrossRef
Google scholar
|
[25] |
Wang X, Cheng Y, Zhang D, Yang H, Zhou X, Jiang Z (2021b). Experimental study on methane adsorption and time-dependent dynamic diffusion coefficient of intact and tectonic coals: implications for CO2-enhanced coalbed methane projects.Process Saf Environ Prot, 156: 568–580
CrossRef
Google scholar
|
[26] |
Wang X, Geng J, Zhang D, Xiao W, Chen Y, Zhang H (2022a). Influence of sub-supercritical CO2 on pore structure and fractal characteristics of anthracite: an experimental study.Energy, 261: 125115
CrossRef
Google scholar
|
[27] |
Wang X, Liu H, Zhang D, Yuan X, Zeng P, Zhang H (2022b). Effects of CO2 adsorption on molecular structure characteristics of coal: implications for CO2 geological sequestration.Fuel, 321: 124155
CrossRef
Google scholar
|
[28] |
Wang X, Zhang D, Liu H, Jin Z, Yue T, Zhang H (2022c). Investigation on the influences of CO2 adsorption on the mechanical properties of anthracite by Brazilian splitting test.Energy, 259: 125053
CrossRef
Google scholar
|
[29] |
Wang X, Zhang D, Su E, Jiang Z, Wang C, Chu Y, Ye C (2020). Pore structure and diffusion characteristics of intact and tectonic coals: implications for selection of CO2 geological sequestration site.J Nat Gas Sci Eng, 81: 103388
CrossRef
Google scholar
|
[30] |
Wang Z, Fu X, Hao M, Li G, Pan J, Niu Q, Zhou H (2021c). Experimental insights into the adsorption-desorption of CH4/N2 and induced strain for medium-rank coals.J Petrol Sci Eng, 204: 108705
CrossRef
Google scholar
|
[31] |
Wang Z, Pan J, Hou Q, Yu B, Li M, Niu Q (2018a). Anisotropic characteristics of low-rank coal fractures in the Fukang mining area, China.Fuel, 211: 182–193
CrossRef
Google scholar
|
[32] |
Wang Z, Pan J, Hou Q, Niu Q, Tian J, Wang H, Fu X (2018b). Changes in the anisotropic permeability of low-rank coal under varying effective stress in Fukang mining area, China.Fuel, 234: 1481–1497
CrossRef
Google scholar
|
[33] |
Wu T, Du X, Li Q (2020). Comparative analysis of pore structure and adsorption characteristics of coal and shale.Safe Coal Mines, 51(11): 6
CrossRef
Google scholar
|
[34] |
Yang K, Zhou J, Xian X, Jiang Y, Zhang C, Lu Z, Yin H (2022a). Gas adsorption characteristics changes in shale after supercritical CO2-water exposure at different pressures and temperatures.Fuel, 310: 122260
CrossRef
Google scholar
|
[35] |
Yang K, Zhou J, Xian X, Zhou L, Zhang C, Tian S, Lu Z, Zhang F (2022b). Chemical-mechanical coupling effects on the permeability of shale subjected to supercritical CO2-water exposure.Energy, 248: 123591
CrossRef
Google scholar
|
[36] |
Yang Q, Li W, Jin K (2020). Supercritical CO2 interaction induced pore morphology alterations of various ranked coals: a comparative analysis using corrected mercury intrusion porosimetry and low-pressure N2 gas adsorption.ACS Omega, 5(16): 9276–9290
CrossRef
Google scholar
|
[37] |
Yu Y, Wang T (2004). Study on relationship between splitting behaviour and elastic modulus of Three Gorges granite.Chinese J Rock Mechan Eng, 23(19): 3258–3261
CrossRef
Google scholar
|
[38] |
Zhang K, Hou CH, Zhao DF, Guo YH, Hui XU (2017). Comparison of pore structure characteristics fractal characteristics between coal and shale through nitrogen adsorption experiment with the example of Shanxi Formation 15# Coal and shale in Yangquan Area.Sci Techn Eng, 29: 68–75
CrossRef
Google scholar
|
[39] |
Zhang X G, Ranjith P G, Ranathunga A S, Li D Y (2019). Variation of mechanical properties of bituminous coal under CO2 and H2O saturation.J Nat Gas Sci Eng, 61: 158–168
CrossRef
Google scholar
|
[40] |
Zheng J, Huang G, Cheng Q, Zhen L, Cai Y, Wang W (2022). Degradation of mechanical and microporous properties of coal subjected to long-term sorption.Fuel, 315: 123245
CrossRef
Google scholar
|
[41] |
Zhou J, Xie S, Jiang Y, Xian X, Liu Q, Lu Z, Lyu Q (2018). Influence of supercritical CO2 exposure on CH4 and CO2 adsorption behaviors of shale: implications for CO2 sequestration.Energy Fuels, 32(5): 6073–6089
CrossRef
Google scholar
|
/
〈 | 〉 |