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