TITLE:
Thermal History and Potential of Hydrocarbon Generated from Jurassic to Early Cretaceous Source Rocks in the Malita Graben, Northern Bonaparte Basin, Australia
AUTHORS:
Rakotondravoavy Jules, Ye Jia Ren, Cao Qiang
KEYWORDS:
Malita Graben, Northern Bonaparte Basin, Potential Generating Hydrocarbon, Thermal History
JOURNAL NAME:
International Journal of Geosciences,
Vol.6 No.8,
August
31,
2015
ABSTRACT: The Malita Graben is
located in the northern Bonaparte Basin, between the Sahul Platform to the northwest and the Petrel Sub-basin and
Darwin Shelf to the south. The wells Beluga 1, Heron 1, Evans Shoal 1, Evans Shoal 2 and
Seismic Line N11805 are selected to determine the thermal history and potential
of hydrocarbon generated from the Plover, Elang, Frigate Shale (Cleia and
Flamingo), and Echuca Shoals formations source rocks. The modeling was
performed by using Basin Mod 1-D
and 2-D techniques. The model results show that the geothermal gradients range
from 3.05 to 4.05°C/100 m with an
average of 3.75°C/100 m and present day heat flow values from 46.23 to 61.99 mW/m2 with an average of 56.29 mW/m2.
The highest geothermal gradient and present-day heat flow values occurred on a
terrace north of the Malita Graben. These most likely indicate that hot fluids
are currently variably migrating into this structure. The lower geothermal
gradient and heat flow values have been modeled in the southeast sites in the
well Beluga 1. The northern
Bonaparte Basin experienced several deformation phases including lithospheric
thinning; hence, heat flow is expected to vary over the geological history of
the basin. The higher paleo-heat flow values changing from 83.54 to 112.01 mW/m2 with an average of 101.71 mW/m2 during Jurassic rift event (syn-rift)
were sufficient for source rocks maturation and hydrocarbon generation during Cretaceous
post-breakup sequence (post-rift) in the study area. The Tuatara (Upper Frigate Shale) Formation source
rock with type II & III kerogen dominantly showing mixed oil- and
gas-prone, and Plover Formation with type III and gas prone have never reached
the peak mature oil window in the well Beluga 1. This area indicates that the
maturity of source rocks is low and considered to be from poor-to-good organic
richness with poor-to-fair potential for hydrocarbons generation. The post
mature Cleia (Lower Frigate Shale) and Echuca Shoals formations source rocks in
the well Evans Shoal 1 and an early mature oil window Echuca Shoals formation
source rock in the well Evans Shoal 2, characterized by type III kerogen dominantly
showing gasprone are a fair-to-very good source richness with poor potential
for hydrocarbons generation. The low to high maturity of Echuca Shoals and
Petrel (Frigate Shale) formations source rocks in the well Heron 1, Plover
Formation source rock in the Evans Shoal 1 well, and Cleia (Lower Frigate
Shale) and Plover formations in the well Evans Shoal 2, showing gas-prone with
type III and II & III kerogens
predominantly, have reached the late mature oil and wet gas generation stages
at present day. These last five formations source
rocks are seen from poor-to-very good organic richness with poor-to-very good potential for
hydrocarbons generation in the Malita Graben.