Fault Seal
, Migration and Accumulation: An Integrated Approach
Stephen Dee1, Dan Carruthers2, Brett
Freeman1, and Graham Yielding3
1 Badley Geoscience Ltd,
Lincolnshire, United Kingdom
2 The Permedia Research Group Inc, Ottawa, ON
3 Badley Geoscience Ltd, N/A, United Kingdom
Fault bounded traps in siciliclastic rocks depend on capillary seal
to
retain hydrocarbons. Estimates of fault zone properties such as SGR (shale gouge
ratio) or CSP (clay smear potential) can be used, in turn, to estimate threshold
capillary entry pressure. Modelling of fill spill and reservoir filling history
then depends on the effectiveness of that calibration. In this paper we use
capillary-based migration modelling to test the sensitivities in the
calibrations between fault-zone property and capillary entry pressure. Petroleum
migration occurs at geological timescales and solving petroleum flow
trajectories and emplacement patterns can be accomplished with modified invasion
percolation techniques. These algorithms honour the salient controls on
petroleum flow while having the advantage of low computation times. Speed of
processing encourages risk analysis by facilitating rapid evaluation of multiple
scenarios for the same geometric configuration, leading to an assessment of the
uncertainties involved in fault
seal
analysis. The migration model is defined as
a dense, regular, 2D or 3D grid of properties. Faults are introduced directly
into the model by their capillary properties at the appropriate grid cell.
Petroleum fluids are introduced at pre-specified locations and are free to move
according to the balance of the local water pressures, petroleum buoyancies and
resistive capillary pressures. We discuss a set of tightly constrained examples
that demonstrate the heterogeneity of fault-flow behaviour; for example a single
fault may be conductive or transmissive, horizontally or vertically at different
locations on its surface. We also examine the migration paths in terms of the
importance or stair-stepping versus vertical conductive flow.
AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005