Quantifying Uplift using Decompaction: A case study from the Exmouth Plateau, North West Shelf

Uplift events have caused the failure of hydrocarbon seals resulting from subsequent deformation and fault development or reactivation. On the other hand, escaping hydrocarbons from the breached seals may accumulate in new traps, and fracturing of brittle reservoir rocks during uplift enhances reservoir productivity. These and other factors justify the importance of quantifying and constraining the distribution of uplift within sedimentary basins for hydrocarbon exploration purposes. Multiple studies have discovered evidence of uplift in the Exmouth Plateau of the Northern Carnarvon Basin; however, the temporal and spatial distribution of this uplift has not been fully quantified. Common methods use sediments' thermal properties to estimate maximum burial depth and subsequently quantify and constrain sediment uplift. However, these thermal-based methods lack accuracy where sediments have been heated by magmatic intrusions, for example, the Triassic Mungaroo formation sediments in the Northern Carnarvon Basin. In this work, we use compaction-derived methods to quantify and constrain the distribution of uplift and its impact on the hydrocarbon systems in the Exmouth Plateau, Northern Carnarvon Basin. We used porosity data (corrected for digenesis) from 68 wells of the Australian National Offshore Petroleum Information Management System (NOPIMS) to accurately estimate maximum burial depths and subsequently estimate uplift. Results indicate larger uplift (up to 1.4km) in the central and southwestern part of the Exmouth Plateau from midTriassic to the present. The spatial distribution of uplift correlates with the distribution of magmatic intrusions in the region. We suggest that, in addition to compression, the multiple Late Triassic to Early Cretaceous rifting events in the Northern Carnarvon Basin triggered magmatic intrusions that produced permanent uplift. Uplift results from Vitrinite Reflectance are slightly higher than those from compaction-based methods, suggesting extra heat input from these intrusions. This uplift majorly controlled the distribution of Jurassic source rocks in the Northern Carnarvon Basin. Keywords: Uplift, Exmouth Plateau, Porosity, magmatic intrusions, Hydrocarbon systems