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Energies 2018, 11(2), 385;

The Effects of NaCl Concentration and Confining Pressure on Mechanical and Acoustic Behaviors of Brine-Saturated Sandstone

State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou 221116, China
GeoEnergy Research Centre, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK
Author to whom correspondence should be addressed.
Received: 25 December 2017 / Revised: 16 January 2018 / Accepted: 23 January 2018 / Published: 7 February 2018
(This article belongs to the Special Issue Geothermal Energy: Utilization and Technology)
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To better understand the mechanical behavior of rock with brine saturation, conventional triaxial experiments were carried out on sandstone for a range of confining pressures (0–60 MPa) and NaCl concentrations (0–30%). As the confining pressure and NaCl concentration increased, the triaxial compressive strength, crack damage threshold, Young’s modulus, cohesion, and internal friction angle all increased. Real-time ultrasonic wave and acoustic emission (AE) techniques were used to obtain the relationship between acoustic behavior and stress level during the whole triaxial compression process. During the whole deformation process, the evolution of P-wave velocity and accumulated AE count could be divided into four phases. The microstructural characteristics of brine-saturated sandstone, before and after loading, indicated that the strength enhancement mechanism may be attributed to an increase in inter-particle friction resulting from salt crystallisation around the points of contact. The angle of friction increased by more than 86% at maximum NaCl concentration compared to that for distilled water. The NaCl deposition in the pore space resulted in nonlinear strength increases for the brine-saturated sandstone specimens with increasing salinity. The present study is expected to improve the knowledge of the strength and failure mechanisms of sedimentary rock in deep saline aquifers. View Full-Text
Keywords: sandstone; saline aquifers; strength; ultrasonic velocity; acoustic emission sandstone; saline aquifers; strength; ultrasonic velocity; acoustic emission

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Huang, Y.-H.; Yang, S.-Q.; Hall, M.R.; Zhang, Y.-C. The Effects of NaCl Concentration and Confining Pressure on Mechanical and Acoustic Behaviors of Brine-Saturated Sandstone. Energies 2018, 11, 385.

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