Triassic petroleum systems on the central North West Shelf – Learnings from the greater Phoenix area seismic mapping and geochemical studies

Abstract

Triassic petroleum systems on the central North West Shelf Rollet et al.

Palaeogeographic evolution of the Triassic succession, central North West Shelf

“…Marine mudstone GDF prevailed during Interval 1 and was replaced by extensive fluvio-deltaic GDF during Interval 2. In the Bedout Sub-Basin, a new petroleum system (Thompson et al, 2018;Rollet et al, this volume) is linked to these intervals. Back-stepping of the fluvio-deltaic complexes, and their replacement by carbonate-rich GDF, commenced at the start of Interval 3 on the CNWS, compared to Interval 4 (Adamson et al, 2013) in the greater Northern Carnarvon Basin.…”

Geochemical evidence for a new Triassic petroleum system on the western margin of Australia

“…The oils, natural gas and rock samples analysed in this study for bulk isotopic and biomarker compositions are listed in Table 1. The Phoenix South 1 oils were recovered from the Middle Triassic Barret Member between TR15.0_SB and TR16.0_SB, whereas the Roc 1-2 gases and condensates were taken from the Lower to Middle Triassic Caley Member between TR10.0_SB and TR15.0_SB (Thompson et al 2018;Rollet et al 2019) (Fig. 1b).…”

“…1b), Lower to Middle Triassic rocks were investigated for their hydrocarbon source potential using publicly available Rock-Eval pyrolysis data to identify the most suitable candidates for oil to source correlations. Sediments between TR10.0_SB and TR15.0_SB were deposited in a fluvial-deltaic environment with occasional minor marine influences (Abbott et al 2019;Rollet et al 2019). In the Bedout Sub-basin, sedimentary rocks that have available geochemical data have a mean total organic carbon (TOC) content of 3.1 wt.% and a mean genetic potential S1 þ S2 of 9.4 mg hydrocarbons (HC)/g rock, exhibiting good to excellent hydrocarbon-generating potential.…”

“…4 wt.% (up to 23.2 wt.%) and HI . 300 mg HC/g TOC (Rollet et al 2019;Grosjean et al 2019a). Caley Member shales are enriched in the maceral liptinite, an oil-prone source rock organic component.…”

“…With a mean TOC content of 1.4 wt.% and HI in the range 33-331 mg HC/g TOC in wells of the Bedout Sub-basin, fluviodeltaic sedimentary rocks between TR15.0_SB and TR16.0_SB are not as organic-rich as the sequence below but the organic matter consists of mixed type II/III kerogen adequately capable of generating oil and gas (Rollet et al 2019).…”