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.
| Original language | English |
|---|---|
| Article number | 2795 |
| Number of pages | 15 |
| Journal | Energies |
| Volume | 11 |
| Issue number | 10 |
| DOIs | |
| Publication status | Published - 17 Oct 2018 |
Keywords
- Brine concentration
- Brittleness index
- Pore fluid
- Saturation degree
Cite this
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Effects of pore fluid chemistry and saturation degree on the fracability of Australian warwick siltstone. / Anne Perera, Mandadige Samintha; Suresh Madushan Sampath, Kadinappuli Hewage; Ranjith, Pathegama Gamage; Rathnaweera, Tharaka Dilanka.
In: Energies, Vol. 11, No. 10, 2795, 17.10.2018.Research output: Contribution to journal › Article › Research › peer-review
TY - JOUR
T1 - Effects of pore fluid chemistry and saturation degree on the fracability of Australian warwick siltstone
AU - Anne Perera, Mandadige Samintha
AU - Suresh Madushan Sampath, Kadinappuli Hewage
AU - Ranjith, Pathegama Gamage
AU - Rathnaweera, Tharaka Dilanka
PY - 2018/10/17
Y1 - 2018/10/17
N2 - 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.
AB - 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.
KW - Brine concentration
KW - Brittleness index
KW - Pore fluid
KW - Saturation degree
UR - http://www.scopus.com/inward/record.url?scp=85055976675&partnerID=8YFLogxK
U2 - 10.3390/en11102795
DO - 10.3390/en11102795
M3 - Article
AN - SCOPUS:85055976675
VL - 11
JO - Energies
JF - Energies
SN - 1996-1073
IS - 10
M1 - 2795
ER -