Effects of Pore Fluid Chemistry and Saturation Degree on the Fracability of Australian Warwick Siltstone

Mandadige Samintha Anne Perera, Kadinappuli Hewage Suresh Madushan Sampath, Pathegama Gamage Ranjith and Tharaka Dilanka Rathnaweera
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Mandadige Samintha Anne Perera: Department of Infrastructure Engineering, The University of Melbourne, Building 176, Melbourne 3010, Australia
Kadinappuli Hewage Suresh Madushan Sampath: Department of Infrastructure Engineering, The University of Melbourne, Building 176, Melbourne 3010, Australia
Pathegama Gamage Ranjith: Deep Earth Energy Laboratory, Department of Civil Engineering, Monash University, Building 60, Melbourne 3800, Australia
Tharaka Dilanka Rathnaweera: Deep Earth Energy Laboratory, Department of Civil Engineering, Monash University, Building 60, Melbourne 3800, Australia

Energies, 2018, vol. 11, issue 10, 1-15

Abstract: Fracability of unconventional gas reservoirs is an important parameter that governs the effectiveness of subsequent gas extraction. Since reservoirs are saturated with various pore fluids, it is essential to evaluate the alteration of fracability of varyingly saturated rocks. In this study, varyingly saturated (dry, water, and brine with 10%, 20% and 30% NaCl by weight) siltstone samples were subjected to uniaxial compressive loading to evaluate their fracability variation. Acoustic emission ( AE ) and ARAMIS photogrammetry analyses were incorporated to interpret the crack propagation. SEM analysis was carried out to visualize the micro-structural alterations. Results show that siltstone strength and brittleness index ( BI ) are reduced by 31.7% and 46.7% after water saturation, due to water-induced softening effect. High NaCl concentrations do not reduce the siltstone strength or brittleness significantly but may contribute to a slight re-gain of both values (about 3–4%). This may be due to NaCl crystallization in rock pore spaces, as confirmed by SEM analysis. AE analysis infers that dry siltstone exhibits a gradual fracture propagation, whereas water and brine saturated specimens exhibit a hindered fracturing ability. ARAMIS analysis illustrates that high NaCl concentrations causes rock mass failure to be converted to shear failure from splitting failure, which is in favour of fracability.

Keywords: brittleness index; pore fluid; saturation degree; brine concentration (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
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