TY - JOUR
T1 - Geomechanical appraisal and prospectivity analysis of the Goldwyer shale accounting for stress variation and formation anisotropy
AU - Mandal, Partha Pratim
AU - Sarout, Joel
AU - Rezaee, Reza
N1 - Publisher Copyright:
© 2020 Elsevier Ltd
PY - 2020/11
Y1 - 2020/11
N2 - Profitable exploitation of unconventional shale gas reservoirs relies on the success of hydraulic fracturing stimulation. This is more likely in brittle rock formations because natural and hydraulic fractures remain open after stimulation, allowing for more hydrocarbon production. Identification of the most favourable depth intervals relies on the robust analysis of available well-logs, and on laboratory-derived mechanical and elastic data obtained under controlled stresses replicating the actual conditions at depth. Beyond their use for predictive geomechanical modelling such laboratory data can act as calibration points for existing well-logs. Well-logs can also be used to guide the selection of the rock samples to be characterised and tested in the laboratory, ensuring that they are representative of the rock formation. Here we apply the above principles and demonstrate how this improves the geomechanical appraisal of the Goldwyer formation and assesses its prospectivity. This workflow integrates Rock-eval geochemical analyses, elastic properties, anisotropy, in-situ stress state and pore pressure, mechanical brittleness and fracturing indices derived from petrophysical and sonic logs in the Theia-1 and Pictor East-1 wells. We estimated an average total organic carbon of 2 w. t.% (maximum 5 w. t.%), a moderate to high dynamic Young's modulus (14–52 GPa), a low Poisson's ratio (0.24–0.27), and an average elasticity-based brittleness index B1 of 41% in the deeper G-III unit. This unit also exhibits a low differential horizontal stress ratio and a high fracture index. Such attributes suggest a good prospectivity of the G-III unit, not only in terms of potential resources but as importantly in terms of fracability.
AB - Profitable exploitation of unconventional shale gas reservoirs relies on the success of hydraulic fracturing stimulation. This is more likely in brittle rock formations because natural and hydraulic fractures remain open after stimulation, allowing for more hydrocarbon production. Identification of the most favourable depth intervals relies on the robust analysis of available well-logs, and on laboratory-derived mechanical and elastic data obtained under controlled stresses replicating the actual conditions at depth. Beyond their use for predictive geomechanical modelling such laboratory data can act as calibration points for existing well-logs. Well-logs can also be used to guide the selection of the rock samples to be characterised and tested in the laboratory, ensuring that they are representative of the rock formation. Here we apply the above principles and demonstrate how this improves the geomechanical appraisal of the Goldwyer formation and assesses its prospectivity. This workflow integrates Rock-eval geochemical analyses, elastic properties, anisotropy, in-situ stress state and pore pressure, mechanical brittleness and fracturing indices derived from petrophysical and sonic logs in the Theia-1 and Pictor East-1 wells. We estimated an average total organic carbon of 2 w. t.% (maximum 5 w. t.%), a moderate to high dynamic Young's modulus (14–52 GPa), a low Poisson's ratio (0.24–0.27), and an average elasticity-based brittleness index B1 of 41% in the deeper G-III unit. This unit also exhibits a low differential horizontal stress ratio and a high fracture index. Such attributes suggest a good prospectivity of the G-III unit, not only in terms of potential resources but as importantly in terms of fracability.
KW - Anisotropy
KW - Brittleness
KW - Hydraulic fracturing
KW - In-situ stress
KW - Pore pressure
KW - Prospectivity
UR - http://www.scopus.com/inward/record.url?scp=85092524562&partnerID=8YFLogxK
U2 - 10.1016/j.ijrmms.2020.104513
DO - 10.1016/j.ijrmms.2020.104513
M3 - Article
AN - SCOPUS:85092524562
SN - 1365-1609
VL - 135
JO - International Journal of Rock Mechanics and Mining Sciences
JF - International Journal of Rock Mechanics and Mining Sciences
M1 - 104513
ER -