Petrophysical characteristics of igneous rocks in the Outboard Browse Basin, North West Shelf of Australia: implications for predicting igneous sequences prior to exploration drilling

Abstract

Abstract The Browse Basin is one of Australia's major hydrocarbon provinces, where significant discoveries have been made in recent decades including the Ichthys and Prelude fields, which accounted for ∼15% of the cumulative Australian liquified natural gas (LNG) production in 2019–20. This rift basin hosts extensive Mesozoic intrusive and extrusive igneous rocks, having been identified from both well and seismic data, and which are recognized as one of the key challenges for exploration and production activities in this region. Their impact on petroleum exploration is demonstrated by the number of wells which encountered unpredicted or thicker than expected igneous rock units both within and adjacent to target sections. This study therefore aims to document the reasons of such unexpectedness, and to develop capability to predict the occurrence of igneous rock units prior to drilling in the Browse Basin and other rift settings that contain igneous rocks. Multiple case studies of uncommercial exploration wells are developed by integrating petrophysical and seismic reflection data, focusing in particular along the outboard part of the basin where igneous rocks are most prevalent. Our study highlights the importance of understanding petrophysical, spatial and chemical heterogeneities of igneous rocks in basins to explain their emplacement and distribution, and thereby predict their occurrence prior to exploration and development activities.