Seismic, petrophysical and petrological constraints on the alteration of igneous rocks in the Northern Carnarvon Basin, Western Australia: implications for petroleum exploration and drilling operations

The Northern Carnarvon Basin (NCB) hosts an extensive record of Jurassic–Cretaceous rift-related igneous activity, manifested by a >45 000 km2 intrusive complex and series volcanic centres constrained seismic mapping. However, there are relatively few well penetrations these rocks (<1% ~1500 exploration wells) in comparison to other basins that witness magmatism, thus, their lithological petrophysical characteristics poorly understood. Here, we describe the properties encountered nine petroleum wells scientific boreholes NCB evaluate impacts on development issues. Igneous characterised pervasive alteration, with ramifications for imaging drilling. For example, low acoustic velocities mafic lavas altered clays Toro-1 were mistaken overpressure, whilst Palta-1 initially unrecorded only recognised due subsequent post-drilling thermal history analysis. alteration reduces impedance contrasts relative sedimentary host rocks, making identification prior drilling more challenging. Whilst preferential emplacement Triassic strata deeper than reservoir targets is primarily responsible paucity penetrations, our findings suggests additional may intersect as yet unrecognised or extrusive sequences.