Determining the Timing and Impact of Break-Up Related Igneous Activity on Reservoir Development Within the Browse Basin

The Browse Basin contains ample evidence for igneous activity contemporaneous with the break up of the Argo micro-continent in the Late Jurassic. Emplacement of igneous rocks comprising widespread lava flows and shallow intrusives form part of a Large Igneous Province (LIP) in the outer Browse Basin. Deciphering the nature, spatial extent and timing of volcanic activity has a significant impact on how the palaeogeographic setting of reservoir rocks is reconstructed. A detailed re-evaluation of the distribution of igneous rocks has been completed utilising well, seismic and potential field data. These observations coupled with an extensive program of geochemical, petrographic and geochronological analysis of samples taken from recent and vintage wells has allowed the genesis of this system to be better described and the impact on the distribution of sedimentary rocks to be more fully understood. To better constrain the timing of emplacement a suite of radiogenic age dates have been obtained using 40Ar/39Ar dating of feldspars and (U-Th)/He dating of detrital zircons. These new data confirm the previous K-Ar radiogenic dates, with an age of about 153Ma, but deliver much higher precision and suggest emplacement over a short time period. Despite these improvements, however, pervasive alteration precluded age dating of key wells where seismic observations suggest multiple phases of emplacement have occurred. The evidence providing support for alternate models is critically examined as the accurate prediction of reservoir distribution represents a crucial aspect in risking exploration targets and determining the best development design for giant gas fields in the region.