Geology and hydrocarbon prospectivity of the northern Houtman Sub-basin

Abstract

New 2D seismic data acquired by Geoscience Australia in the northern Houtman Sub-basin of the Perth Basin provides important information on the prospectivity of this frontier area. To date, lack of quality seismic data and limited geological understanding have led to the perception that the hydrocarbon potential of the area is very low. However, interpretation of newly collected data suggests that the northern Houtman depocentre contains up to 15 km of pre-breakup sediments comprised of Permian, Triassic and Jurassic successions, which potentially contain multiple source rock, reservoir and seal intervals. The Permian syn-rift succession is confined to a series of large half-graben that are controlled by basement-involved faults separating the Houtman depocentre from the Bernier Platform. This succession is up to 10 km thick and is mapped throughout the inboard part of the new seismic grid. A prominent unconformity at the top of the Permian syn-rift sequence is overlain by a thick (up to 1800 m) and regionally extensive seismic sequence interpreted as the Lower Triassic Kockatea Shale. The thickness of the overlying Triassic succession ranges from approximately 1 km in the inboard part of the basin to up to 5 km further outboard. The Jurassic succession is thickest (up to 4 km) in the outboard part of the basin and is interpreted to contain sequences corresponding to the Cattamarra, Cadda and Yarragadee formations. Our study integrates new results from regional mapping, geophysical modelling and petroleum systems analysis, which enables a more accurate prospectivity assessment of this frontier basin.

Unraveling Deep Structures Along A Rifted-Transform Margin: Insights From an Integrated Geophysical Study of The Northern Perth Basin

“…The GA349 regional seismic has clearly imaged pre-rift and major syn-rift sedimentary sections across the Houtman Sub-basin, and in many areas pre-Permian basement and the Moho interface are also imaged ( Figure 3A; Borissova et al, 2017;Southby et al, 2018). Extremely thin basement has been interpreted beneath the main depocentre bounded on the eastern side by a major southwest dipping fault that dies out at mid-crustal level (~18-20 km).…”

“…The first major stage of rifting was marked by Early-to Mid-Permian extension, which resulted in the formation of a series of northwest-oriented half graben filled with up to 10 km of synrift succession (Borissova et al, 2017;Southby et al, 2018). The second major rifting event began in the late Early Jurassic leading to Valanginian-Aptian transform margin development and associated regional uplift and erosion .…”

“…Regional correlation of the newly acquired 2D seismic stratigraphy across the northern Perth Basin suggests a much thicker sedimentary package including up to 16 km of Permian-Cretaceous succession (Borissova et al, 2017). Three petroleum wells have been drilled in the southern part of the sub-basin (Gun Island 1, Houtman 1 and Charon 1 - Figure 1), all of which reached TD within the Jurassic-Cretaceous succession .…”

“…The (GA349) regional 2D seismic project acquired by Geoscience Australia in 2014, part of the Geoscience Australia's regional petroleum program, was designed to better understand the rift structures and crustal architecture of the Houtman Sub-basin, a largely unexplored offshore frontier area covering 57 000 km 2 of the western Australian margin in the northern Perth Basin (Figure 1 - Borissova et al, 2017). The survey extends across the northern part of the Houtman Sub-basin at the transition between the nonvolcanic margin of the northern Perth Basin and the volcanic province of the Wallaby Plateau (Symonds et al, 1998).…”

Structural characteristics of northern Houtman sub-basin, Perth Basin

“…The model currently shows basement shallowing to less than 2 km on the Bernier Platform, however integrated interpretation of the seismic and potential field data suggests that a thicker (5 -6 km) pre-rift sedimentary succession may be present. This result, however is not taken into account in this study (Figures 3a and 3b) Sanchez et al, 2016;Borissova et al, 2017). New seismic data clearly images the Moho which is mapped between 30 and 35 km depth beneath the Bernier Platform and shallows to about 12 km on the western border of the Houtman Sub-basin (Figure 2c).…”