Dude, where’s my AVO? A case study from the Browse Basin, North West Shelf, Australia

Summary

The Braveheart-1/ST1 well (2009) was drilled on a pronounced Class III AVO anomaly identified on the Braveheart 2D and Braveheart infill 2D seismic data in the Browse Basin, Australia. The well was dry with no indication of hydrocarbons. During a post-drilling analysis of the well, the seismic synthetics generated displayed no Class III AVO anomaly at the well location. The failure of seismic to predict a correct AVO response at the well raised major questions around the legitimacy of AVO and Quantitative Interpretation (QI) approach for prospect generation and maturation in the Browse Basin.

In 2011, Searcher Seismic acquired the long offset (8km) Vampire 2D seismic survey in the Browse Basin that tied 60 wells (including Braveheart-1/ST1). The assessment of the Vampire PSDM (2018) data at Braveheart-1/ST1 reveals that the Class III AVO anomaly is absent. Looking back at the well result it is likely that the generated Class III AVO in the vintage 2D data was caused by insufficient acquisition parameters and an inappropriate processing workflow.

This paper demonstrates how the acquisition of long streamer seismic, with appropriate processing could help to avoid misidentification of false AVO anomalies and also help identify true AVO anomalies, which have been masked by unsuitable acquisition and processing workflows. This paper could help support a more successful drilling program.

The Vampire long streamer 2D PSDM seismic data with preserved amplitude, provides great opportunities for the geoscientist to reassess the exploration potential in the Browse Basin. Using this dataset with 60 well ties also offers profound opportunities to run a 3-term AVO Inversion for reservoir characterisation and field development planning of the main fields in the Browse Basin.

• M. australis sand
• Vampire 2D
• PSDM processing
• AVO inversion
• prospect generation