Influences of bedding characteristics on the acoustic wave propagation characteristics of shales

Abstract

The acoustic response characteristics of shales were investigated by the acoustic transmission experiment, which is the basis of solving geological and engineering problems using the seismic or logging information during the process of the exploration and development of shale gas reservoirs. Based on the theory of acoustic wave and the background of acoustic transmission experiment, the initial condition, vibration source condition, boundary condition and stability condition were constructed, and the numerical simulation of acoustic transmission experiment of shales were completed through Matlab programming. The results show that under the same bedding angle, the acoustic time and attenuation coefficient of shales shown positive correlation with the bedding density; whereas under the same bedding density, the variation laws of the acoustic time and the attenuation coefficient of shales were more complex with the change of the bedding angle, that is, the acoustic time and attenuation coefficient of shales increased first, then decreased and then increased again with the increase of the bedding angle.

Keywords

Shale / Bedding characteristics / Acoustic wave / Numerical simulation

Declaration of competing interests

The authors declare that they have no conflict of interests.

Acknowledgements

This research is supported by the National Science and Technology Major Project (Grant No. 2019A-3307), the National Natural Science Foundation of China (Grant No. 41872167).

References

[1] U.S. Energy Information Administration (EIA), Technically recoverable shale oil and shale gas resources: an assessment of 137 shale formations in 41 countries outside the United States. http://www.eia.gov/analysis/studies/worldshalegas, 2013.

[2] Y. Wang, D. Dong, J. Li, et al., Features of shale gas reservoir in Longmaxi Formation of lower Silurian in south Sichuan, Acta Petrol. Sin. 33 (4) (2012) 551-561, https://doi.org/10.7623/syxb201204003.

[3] J. Tan, B. Horsfield, R. Fink, et al., Shale gas potential of the major marine shale formations in the Upper Yangtze Platform, south China, Part III: mineralogical, lithofacial, petrophysical, and rock mechanical properties, Energy Fuels 28 (4) (2014) 2322-2342, https://doi.org/10.1021/ef4022703.

[4] V.A. Mendhe, V. Kumar, V.K. Saxena, et al., Evaluation of gas resource potentiality, geochemical and mineralogical characteristics of Permian shale beds of Latehar-Auranga Coalfield, India, Int. J. Coal Geol. 196 (2018) 43-62, https://doi.org/10.1016/j.coal.2018.06.022.

[5] H. Deng, X. Xie, K. Chen, et al., Mineralogical characteristics of continental shale: a case study in Yan-Chang Formation, Ordos Basin, Aust. J. Earth Sci. 65 (6) (2018) 851-862, https://doi.org/10.1080/08120099.2018.1472665.

[6] J. Yan, S. Zhang, J. Wang, et al., Applying fractal theory to characterize the pore structure of lacustrine shale from the Zhanhua Depression in Bohai Bay Basin, Eastern China, Energy Fuels 32 (7) (2018) 7539-7556, https://doi.org/10.1021/acs.energyfuels.8b01501.

[7] J. Yan, J. Fan, M. Wang, et al., Rock fabric and pore structure of the Shahejie sandy conglomerates from the Dongying depression in the Bohai Bay basin, East China, Mar. Petrol. Geol. 97 (2018) 624-638, https://doi.org/10.1016/j.marpetgeo.2018.07.009.

[8] S. Jiang, X. Tang, S. Long, et al., Reservoir quality, gas accumulation and completion quality assessment of Silurian Longmaxi marine shale gas play in the Sichuan Basin, China, J. Nat. Gas Sci. Eng. 39 (2017) 203-215, https://doi.org/10.1016/j.jngse.2016.08.079.

[9] C. Yan, J. Deng, B. Wei, Q. Tan, et al., Study on collapse pressure of shale gas reservoir, Chin. J. Rock Mech. Eng. 32 (8) (2013) 1595-1602, 1000-6915(2013) 08-1595-08.

[10] L. Liang, J. Xiong, X. Liu, Experimental study on crack propagation in shale formations considering hydration and wettability, J. Nat. Gas Sci. Eng. 23 (2015) 492-499, https://doi.org/10.1016/j.jngse.2015.02.032.

[11] X. Liu, J. Xiong, L. Liang, Y. Ding, Investigation of the physico-chemical and mechanical properties of hard brittle shales from the Shahejie Formation in the Nanpu Sag, northern China, J. Geophys. Eng. 14 (3) (2017) 445, https://doi.org/10.1016/10.1088/1742-2140/aa5f83.

[12] M.J. Wilson, L. Wilson, M.V. Shaldybin,Clay mineralogy and unconventional hydrocarbon shale reservoirs in the USA. II. Implications of predominantly illitic clays on the physico-chemical properties of shales, Earth Sci. Rev. 158 (2016) 1-8.

[13] E. Rybacki, T. Meier, G. Dresen, What controls the mechanical properties of shale rocks?ePart II: Brittleness, J. Petrol. Sci. Eng. 144 (2016) 39-58, https://doi.org/10.1016/j.petrol.2016.02.022.

[14] X. Chen, P. Eichhubl, J.E. Olson, et al., Effect of water on fracture mechanical properties of shales, J. Geophys. Res.: Solid Earth 124 (3) (2019) 2428-2444, https://doi.org/10.1029/2018JB016479.

[15] C. Ping, H.A.N. Qiang, M.A. Tianshou, et al., The mechanical properties of shale based on micro-indentation test, Petrol. Explor. Dev. 42 (5) (2015) 723-732, https://doi.org/10.1016/S1876-3804(15)30069-0.

[16] P. Domnesteanu, C. McCann, J. Sothcott, Velocity anisotropy and attenuation of shale in under-and overpressured conditions, Geophys. Prospect. 50 (5) (2002) 487-503, https://doi.org/10.1046/j.1365-2478.2002.00329.x.

[17] Q. Chen, X. Liu, H. Liu, et al., Ultrasonic transmission test of stratigraphic shale formation, Nat. Gas. Ind. 33 (8) (2013) 140-144, https://doi.org/10.3787/j.issn.1000-0976.2013.08.025.

[18] F. Xu, Q. Chen, H. Zhu, et al., Response analysis of shale bedding structure to ultrasonic characteristics and its application, Petrol. Explor. Dev. 46 (1) (2019) 82-92, https://doi.org/10.1016/S1876-3804(19)30007-2.

[19] G.T. Baechle, A. Colpaert, G.P. Eberli, et al., Effects of microporosity on sonic velocity in carbonate rocks, Lead. Edge 27 (8) (2008) 1012-1018, https://doi.org/10.1190/1.2967554.

[20] R.J. Weger, Eberli, Baechle, Massaferro, et al., Quantification of pore structure and its effect on sonic velocity and permeability in carbonates, AAPG (Am. Assoc. Pet. Geol.) Bull. 10 (93) (2009) 1297-1317, https://doi.org/10.1306/05270909001.

[21] Q. Chen, X. Liu, L. Liang, et al., Numerical simulation of acoustic attenuation coefficient in fracture model, Chin. J. Geophys. 55 (6) (2012) 2044-2052, https://doi.org/10.6038/j.issn.0001-5733.2012.06.026.

[22] Q. Chen, F. Xu, L. Cheng, et al., Shale ultrasonic numerical simulation based on the viscoelastic medium wave theory, Nat. Gas. Ind. 39 (6) (2019) 63-70, https://doi.org/10.3787/j.issn.1000-0976.2019.06.007.

[23] S. Wang, X. Liu, Q. Chen, et al., Numerical simulation of ultrasonic evaluation of porosity in carbonate reservoir, Prog. Geophys. 30 (1) (2015) 267-273, https://doi.org/10.6038/pg20150138.

[24] L. Liang, L. Zhou, X. Liu, et al., Study on the effect of cavity structure on ultrasonic attenuation characteristics, Chin. J. Rock Mech. Eng. 34 (s1) (2015), https://doi.org/10.13722/j.cnki.jrme.2014.0279.

[25] A.C. Reynolds, Boundary conditions for the numerical solution of wave propagation problems, Geophysics 43 (6) (1978) 1099-1110, https://doi.org/10.1190/1.1440881.

[26] A.R. Mitchell, D.F. Griffiths, The Finite Difference Method in Partial Differential Equations, John Wiley and Sons Ltd, New York, 1980.