ABSTRACT: Fault
geometry and seal attribute mapping in the Bass and Otway Basins,
Australia
Boult, Peter1, and Richard M Jones2
(1) BORAL Energy
Resources Ltd, Adelaide, Australia
(2) Thebarton Campus, Adelaide, Australia
Gridding of geometrical fault
attributes dip, strike and horizon displacement aids in
constraining interpretation of deep horizon based data and structural history. In
tectonically complex regions such as the Otway Basin the seismic image is often poor at
depth and
fault
traces are easier to interpret than horizons. By modelling
fault
geometrical attributes, faults can be regarded as extra data loci linking interpretation
across seismic dip lines in areas of 2D seismic. In the Bass Basin
fault
geometry
attributes aid in the timing interpretation of cross-cutting faults.
For fault
seal analysis both the tendency for
fault
reactivated structural permeability
and across
fault
leakage (AFL) are assessed. The former is more important in the Otway
Basin and the latter in the Bass Basin. Relative probability of seal failure through
effective structural permeability is mapped directly along centreline
fault
locations for
individual horizons. This technique provides a rapid assessment tool for risking
fault
bound prospects. For AFL and juxtaposition analysis, stratigraphy between mapped horizons
is assigned to hangingwall and footwall locations using sedimentology principles. In the
Bass Basin volcanic sills and dykes are incorporated into 3D
fault
models. For
fault
rock
analysis, the tendency for
fault
rock / shale gouge to be entrained is calculated directly
from wireline log data and attributes such as shale gouge ratio (SGR) are plotted directly
onto the
fault
surface. For
fault
seal risk analysis SGR values are then cross-plotted
with across
fault
pressure data and compared with known accumulations within the basin and
world-wide analogues.
AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia