Kraken 3D — Acquisition to Interpretation on the Edge of the Browse

Abstract

The broadband Kraken 3D Marine Seismic Survey was acquired during 2013 in the outer Browse Basin exploration permit WA-314-P with the specific goal of assessing risk and volumes at the Elvie prospect. The survey was acquired over a highly rugose sea floor, comprised of deep slump canyons that overlie a steeply prograding Miocene carbonate sequence.

Multiple attempts at processing the seismic data have already been made; including a post-stack time migration (a fast-track volume), pre-stack time and pre-stack depth migration. Conventional processing and pre-stack depth migration approaches were unable to fully resolve short-wavelength velocity anomalies below the sea floor that cause obvious residual imaging problems and impact upon depth conversion and seismic amplitude interpretation. A geomechanical pre-stack depth migration now underway to hopefully address the remaining imaging concerns.

Overall, the Kraken 3D is considered to be a significant improvement over the pre-existing 2D seismic. Interpretation was performed largely in the depth domain, although ties to nearby wells were made in the time domain using legacy 2D and 3D seismic. Mapping has further matured the Elvie prospect, which is a robust 4-way dip closure located on the divide between the Caswell and Seringapatam Sub-basins. The survey provides strong evidence for a thick top seal in the form of deep-marine muds of Miocene age, although there is evidence of minor seepage through a thin flank of the sealing unit. These shallow amplitude indicators, nearby surface seeps and pockmarks near the sea floor provide additional support for a working petroleum system. The Elvie structure appears to be draped by potentially high quality turbidite reservoirs of most-likely Paleocene age.