Experimental study on the acoustic propagation and anisotropy of coal rocks

Abstract

In order to study the propagation laws of acoustic wave of coal samples from the Upper Permian Xuanwei Formation in the east of Yunnan Province, China, under saturated water and dry conditions, the basic physical parameters, acoustic parameters and anisotropic parameters were obtained through the experiments. Based on FFT and wavelet analysis theory, the spectral characteristics of coal samples under different conditions were studied. The results show that physical parameters of coal samples in different directions have different values, that is, the anisotropy of coal samples is obvious. When the coal samples are saturated with water, the acoustic velocities and the attenuation coefficient increase, whereas the dominant frequency decreases. The signal amplitude of the frequency domain significantly decreases, that is, the internal structure of coal samples is damaged. The P-wave velocity and S-wave velocity increase with the increase of the confining pressure, whereas the anisotropy parameters decrease with the increase of the confining pressure. Overall, this study provides the basis to understand basic acoustic information and anisotropy characteristics of coal samples.

Keywords

Upper permian xuanwei formation / Coal / Acoustic wave propagation / Frequency spectrum characteristics / Anisotropy

CRediT authorship contribution statements

Linlin Huang: Experiment, Data analysis, Writing-Reviewing. Xiangjun Liu: Investigation. Sen Yan: Experiment, Data analysis, Writing-Reviewing. Jian Xiong: Investigation, Data analysis. Haiming He: Experiment. Peng Xiao: Experiment.

Acknowledgements

This research is supported by the Young Scientific and Technological Innovation Team of Rock Physics in Unconventional Strata of Southwest Petroleum University(No. 2018CXTD13), the 19th issue college students’ Extracurricular opening experiment key projects, Southwest Petroleum University (No. KSZ19207), and Innovation and enterprise fund of School of Geoscience and Technology, Southwest Petroleum University(No. DCXP1930).

References

[1] R.G. Loucks, R.M. Reed, S.C. Ruppel, et al., Morphology, genesis, and distribution of nanometer-scale pores in siliceous mudstones of the Mississippian Barnett Shale[J], J. Sediment. Res. 79 (12) (2009) 848-861, https://doi.org/10.2110/jsr.2009.092.

[2] P. Zhang, S. Lu, J. Li, et al., Petrophysical characterization of oil-bearing shales by low-field nuclear magnetic resonance (NMR)[J], Mar. Petrol. Geol. 89 (2018) 775-785, https://doi.org/10.1016/j.marpetgeo.2017.11.015.

[3] G. Desbois, J.L. Urai, P.A. Kukla, et al., High-resolution 3D fabric and porosity model in a tight gas sandstone reservoir: a new approach to investigate microstructures from mm-to nm-scale combining argon beam cross-sectioning and SEM imaging[J], J. Petrol. Sci. Eng. 78 (2) (2011) 243-257, https://doi.org/10.1016/j.petrol.2011.06.004.

[4] R. Slatt, Important geological properties of unconventional resource shales[J], Open Geosci. 3 (4) (2011) 435-448.

[5] ˙I. G. S¸enel A.G. Gürüz H. Yücel, et al., Characterization of pore structure of Turkish coals[J], Energy & fuels 15 (2) (2001) 331-338, https://doi.org/10.1021/ef000081k.

[6] Q. Wei, X. Li, J. Zhang, et al., Full-size pore structure characterization of deepburied coals and its impact on methane adsorption capacity: a case study of the Shihezi Formation coals from the Panji Deep Area in Huainan Coalfield, Southern North China[J], J. Petrol. Sci. Eng. 173 (2019) 975-989, https://doi.org/10.1016/j.petrol.2018.10.100.

[7] M.A. Kassab, A. Weller, Study on P-wave and S-wave velocity in dry and wet sandstones of Tushka region, Egypt[J], Egyptian Journal of Petroleum 24 (1) (2015) 1-11, https://doi.org/10.1016/j.ejpe.2015.02.001.

[8] M. Nooraiepour, N.H. Mondol, H. Hellevang, et al., Experimental mechanical compaction of reconstituted shale and mudstone aggregates: Investigation of petrophysical and acoustic properties of SW Barents Sea cap rock sequences[J], Mar. Petrol. Geol. 80 (2017) 265-292, https://doi.org/10.1016/j.marpetgeo.2016.12.003.

[9] L. Jian-po, X. Shi-da, L. Yuan-hui, Analysis of rock mass stability according to power-law attenuation characteristics of acoustic emission and microseismic activities[J], Tunn. Undergr. Space Technol. 83 (2019) 303-312, https://doi.org/10.1016/j.tust.2018.09.023.

[10] H. Chen, B. Jiang, T. Chen, et al., Experimental study on ultrasonic velocity and anisotropy of tectonically deformed coal[J], Int. J. Coal Geol. 179 (2017) 242-252, https://doi.org/10.1016/j.coal.2017.06.003.

[11] Y. Wang, C.H. Li, Investigation of the P-and S-wave velocity anisotropy of a Longmaxi formation shale by real-time ultrasonic and mechanical experiments under uniaxial deformation[J], J. Petrol. Sci. Eng. 158 (2017) 253-267, https://doi.org/10.1016/j.petrol.2017.08.054.

[12] C. Matonti, Y. Guglielmi, S. Viseur, et al., P-wave velocity anisotropy related to sealed fractures reactivation tracing the structural diagenesis in carbonates[J], Tectonophysics 705 (2017) 80-92, https://doi.org/10.1016/j.tecto.2017.03.019.

[13] S. Ji, Q. Wang, M.H. Salisbury, et al., P-wave velocities and anisotropy of typical rocks from the Yunkai Mts.(Guangdong and Guangxi, China) and constraints on the composition of the crust beneath the South China Sea[J], J. Asian Earth Sci. 131 (2016) 40-61, https://doi.org/10.1016/j.jseaes.2016.09.006.

[14] H. Tak, J. Choi, S. Jo, et al., Stress anisotropy analysis and its effect on unconventional resource development in Montney play, Kakwa, Canada[J], J. Appl. Geophys. 139 (2017) 177-187, https://doi.org/10.1016/j.jappgeo.2017.02.018.

[15] K. Liu, J.J. Sheng, Experimental study of the effect of stress anisotropy on fracture propagation in Eagle Ford shale under water imbibition[J], Eng. Geol. 249 (2019) 13-22, https://doi.org/10.1016/j.enggeo.2018.12.023.

[16] C.M. Sayers, L.D. den Boer, Shale Anisotropy and the Elastic Anisotropy of Clay minerals[C]// 2014 SEG Annual Meeting, Society of Exploration Geophysicists, 2014, https://doi.org/10.1190/segam2014-0114.1.

[17] T.I. Ivankina, I.Y. Zel, T. Lokajicek, et al., Elastic anisotropy of layered rocks: ultrasonic measurements of plagioclase-biotite-muscovite (sillimanite) gneiss versus texture-based theoretical predictions (effective media modeling)[J], Tectonophysics 712 (2017) 82-94, https://doi.org/10.1016/j.tecto.2017.05.005.

[18] Y. Zhao, H. Song, S. Liu, et al., Mechanical anisotropy of coal with considerations of realistic microstructures and external loading directions[J], Int. J. Rock Mech. Min. Sci. 116 (2019) 111-121, https://doi.org/10.1016/j.ijrmms.2019.03.005.

[19] B. Chen, J. Liu, M.K. Kaban, et al., Elastic thickness, mechanical anisotropy and deformation of the southeastern Tibetan Plateau[J], Tectonophysics 637 (2014) 45-56, https://doi.org/10.1016/j.tecto.2014.09.007.

[20] G. Wang, D. Yang, Z. Kang, et al., Numerical investigation of the in situ oil shale pyrolysis process by superheated steam considering the anisotropy of the thermal, hydraulic, and mechanical characteristics of oil shale[J], Energy Fuels 33 (12) (2019) 12236-12250, https://doi.org/10.1021/acs.energyfuels.9b02883.

[21] J. Xiong, K. Liu, X. Liu, et al., Influences of Bedding Characteristics on the Acoustic Wave Propagation Characteristics of shales[J]. Petroleum, 2020, https://doi.org/10.1016/j.petlm.2020.03.005.

[22] R. Shen, L. Qiu, E. Zhao, et al., Experimental study on frequency and amplitude characteristics of acoustic emission during the fracturing process of coal under the action of water[J], Saf. Sci. 117 (2019) 320-329, https://doi.org/10.1016/j.ssci.2019.04.031.

[23] F. Du, K. Wang, G. Wang, et al., Investigation of the acoustic emission characteristics during deformation and failure of gas-bearing coal-rock combined bodies[J], J. Loss Prev. Process. Ind. 55 (2018) 253-266, https://doi.org/10.1016/j.jlp.2018.06.013.

[24] Z Sun, X Liu, L Liang, et al., Analysis of factors influencing the Stability of coal Seam gas well Cutting shaft wall, Coal Sci. Technol. 46 (04) (2018) 117-122, https://doi.org/10.13199/j.cnki.cst.2018.04.020.

[25] J. Havens, M. Batzle, Thomsen parameter relationships and estimation from laboratory ultrasonic data[C]// SEG Technical Program Expanded Abstracts 2014, Society of Exploration Geophysicists, 2014, pp. 2772-2777, https://doi.org/10.1190/segam2014-0809.1.

[26] J.G. Berryman, Exact seismic velocities for transversely isotropic media and extended Thomsen formulas for stronger anisotropies[J], Geophysics 73 (1) (2008) D1-D10, https://doi.org/10.1190/1.2813433.

[27] J. Liu, D. Liu, Y. Cai, et al., Effects of water saturation on P-wave propagation in fractured coals: an experimental perspective[J], J. Appl. Geophys. 144 (2017) 94-103, https://doi.org/10.1016/j.jappgeo.2017.07.001.

[28] T.I. Ivankina, H.M. Kern, A.N. Nikitin, Directional dependence of P-and S-wave propagation and polarization in foliated rocks from the Kola superdeep well: evidence from laboratory measurements and calculations based on TOF neutron diffraction[J], Tectonophysics 407 (1-2) (2005) 25-42, https://doi.org/10.1016/j.tecto.2005.05.029.

[29] W. Si, B. Di, J. Wei, et al., Experimental study of water saturation effect on acoustic velocity of sandstones[J], J. Nat. Gas Sci. Eng. 33 (2016) 37-43, https://doi.org/10.1016/j.jngse.2016.05.002.

[30] T. Lokajíˇcek, T. Svitek, Laboratory measurement of elastic anisotropy on spherical rock samples by longitudinal and transverse sounding under confining pressure[J], Ultrasonics 56 (2015) 294-302, https://doi.org/10.1016/j.ultras.2014.08.015.

[31] P. Ding, D. Wang, F. Gong, et al., Laboratory observation of velocity anisotropy affected by clays and microcracks in artificial clay-rich shale samples[J], J. Petrol. Sci. Eng. (2020) 107156, https://doi.org/10.1016/j.petrol.2020.107156.