
TY  - JOUR
A1  - Lyon, P.J. 
A1  - Boult, P.J. 
A1  - Watson, M. 
A1  - Hillis, R.R. 
T1  - A SYSTEMATIC FAULT SEAL EVALUATION OF THE LADBROKE GROVE AND PYRUS TRAPS OF THE PENOLA TROUGH, OTWAY BASIN
JF  - The APPEA Journal
JO  - The APPEA Journal
Y1  - 2005
VL  - 45
IS  - 1
SP  - 459
EP  - 476
KW  - 
UR  - https://doi.org/10.1071/AJ04036 
N2  - Juxtaposition mapping of lithology onto the Ladbroke Grove Fault plane shows that the Pretty Hill Sandstone reservoir, which hosts a 90 m gas column, juxtaposes massive shale units in the hangingwall. Retention of the column at Ladbroke Grove can thus be attributed to favourable across-fault, reservoir-seal juxtaposition. The free water level (FWL) of the Ladbroke Grove column coincides with an abrupt change in strike of the fault from east&#x2013;west to northwest&#x2013;southeast. Fault re-activation risking using the FAST (Fault Analysis Seals Technology) technique indicates that the northwest&#x2013;southeast striking segment of the fault is critically oriented within the in-situ stress field for reactivation, whereas the more east&#x2013;west trending segment is associated with a relatively lower risk of fault re-activation. Hence recent slip along the northwest&#x2013;southeast segment may have created permeable fracture networks along this part of the fault plane and thus limited the extent of the column to that bounded by the east&#x2013;west trending fault segment. This hypothesis is supported by data on soil gases acquired across the fault which suggest that the fault is leaking CO2 across its northwest&#x2013;southeast striking segment, but not across its east&#x2013;west striking segment.The Pyrus Fault is not presently sealing by across-fault, reservoir-seal juxtaposition. The throw on the fault plane is sufficient to juxtapose the Katnook Sandstone in the hangingwall against the Pretty Hill Sandstone reservoir in the footwall, providing a sand-on-sand juxtaposition leak point at the structural apex of the trap. Fault re-activation along this fault is likely to have caused fracturing of any shale gouge veneer that may have been present along this sand-on-sand contact resulting in across-fault leakage of hydrocarbons into the Katnook Sandstone and leakage up the fault along permeable fracture networks. FAST predictions of fault re-activation show that the fault is critically oriented within the in-situ stress field for re-activation and soil gas measurements at the surface suggest the fault is leaking CO2. 
ER  -

