ABSTRACT: Modern and ancient analogues for Permian cool-temperate peat forming fluvial lacustrine reservoir successions

Lang, Simon C.¹, Jochen Kassan², L. Claire Avenell³, and Nick Hall⁴
(1) University of Adelaide, Adelaide, Australia 
(2) Whistler Research, Brisbane, Australia 
(3) Stanmore Power, Brisbane, Australia 
(4) Santos Ltd, Brisbane, Australia

Permian coal-bearing successions in the Cooper and Bowen Basins, Australia, are host to numerous producing oil and gas fields. These successions formed in a vast region of low-lying, peat forming environments in a cool-temperate palaeoclimate in eastern Gondwana, in both intracratonic and foreland basin settings. They contain a variety of reservoir elements (fluvial and distributary channel fills including several styles of bar-forms, lateral accretion, levees, crevasse splays, distributary mouth bars) and seals (channel abandonment mud/clay plugs, floodplain/basin fines, coals, and enveloping fine-grained lacustrine facies). Construction of 3D reservoir models for these settings with relatively sparse well control can benefit from comparison with modern and ancient analogues. Data required include facies, scale (width/thickness ratios), channel belt width, planform geometries (individual and composite), bifurcation frequency, and interconnectedness. These parameters are becoming increasingly important to provide "reality-checks" for interpretation of amplitude maps from high resolution 3D seismic, and to predict lateral and down-dip extent of reservoirs.

Modern analogues include the Cumberland Marshes in Saskatchewan and the Ob River in western Siberia. Both represent cool-temperate, peat-forming, fluvial environments dominated by flood generated crevasse-splay and anastomosing fluvial systems. They illustrate how the Permian reservoirs in similar settings may be narrow and elongate, with significant heterogeneity. Ancient analogues from the intensely drilled Permian Bowen Basin coal mines, show a similar picture based on subsurface and highwall mapping (aided by computer visualisation) of reservoir elements.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia