Constraining Fault Seal Risk Using Seismic Velocities and Well Data

Abstract

Fault seal capacity is an important component in the conventional petroleum system. Assessing the capacity for a fault to seal or leak can be difficult to determine, particularly where well constraint is lacking. In the frontier basin, in a marine setting, seismic velocities may be the only data available. However, useful constraints on a faults sealing capacity can be extracted from this data alone. This study investigates the robustness of a number of empirical relations that can assist in extracting useful constraints from seismic velocities and amplitudes. Information on maximum and minimum stress magnitudes and pore pressures can be calculated and combined with basic fault architecture analysis, to place practical constraints on fault risk. A study area on the Rankin Trend, North West Shelf of Australia, found good correlation between well-based and seismic velocity-based pore pressures and stress magnitudes allowing a Coulomb Failure Function to be calculated. Faults separating the Rankin 1 well block from the Dockrell/Keast Field, were shown to be within a stable stress regime. Well data for this area confirms a SHmax orientation of approximately 110° N +/− 10° indicating that steeply dipping faults striking within 20° of this direction may be at high risk of failure within the neotectonic setting, where stress magnitudes, pore pressures, and fault geometry predicate fault slip.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015