Publication Name: Eromanga Basin Symposium, Summary Papers
Authors: A J KANTSLER, A C COOK, M ZWIGULIS
Publication Volume: Adelaide, 9 - 11 November 1982
Date Published: December 1982
Number of Pages: 25
Reference Type: Conference Proceedings
Abstract:
Vitrinite reflectance data from 90 wells which penetrate the JurassicCretaceousEromanga Basin sequence above the Permian-Triassic of the
Cooper and Pedirka Basins vary from less than 0.3% in parts of the
Cretaceous Winton Formation to more than 1.7% in some intersections of
the Jurassic Hutton Sandstone. Isoreflectance surfaces show varying
relationships to regional structure and present-day temperature gradient
variation. Vitrinite reflectance modelling studies indicate a highly .
variable thermal history. Basin-wide high heat flow is related primarily
to high levels of crustal heat production. The Jurassic-Cretaceous
was characterised by a phase of lower heat flow. Subsidence was accompanied
by the local development of temperature 'highs' on prominent
structural trends in response to lateral dewatering of the sub-basins.
Late Tertiary-Recent artesian flow has created temperature anomalies
within the Eromanga section. Model results suggest that ir. many areas
the high present-day temperature gradients (up to 60?C/km) are a rela tively
recent phenomenom.
Coal beds and land plant related organic detritus are present throughout
the section which includes at least three potential source rock horizons.
The onset of significant hydrocarbon generation followed the rapid
deposition of the Cenomanian Winton Formation. However, host rocks for
most Eromanga Basin oil and gas discoveries are associated with relatively
low levels of organic maturity, implying a source either from
underlying,_ mature, Permian coal-bearing sequences or from more mature
Jurassic section downdip. Maturation maps at the top of several potential
Jurassic-Cretaceous source intervals indicate that most commercial
Eromanga Basin oil discoveries will be found flanking mature Jurassic
sequences such as those in the Nappamerri Trough.