High Resolution Reservoir Characterization in the Aquillus-Mollichuta Field

The oil-producing Birkhead Formation on the western flank of Cooper-Eromanga Basin in South Australia, is an intracratonic fluvial-lacustrine sequence deposited in a low accommodation environment during the middle to Late Jurassic age. Subtle class II to III type AVO is anticipated for the oil-bearing package. The three main challenges are (1) the substantial overlap infacies for the reservoir rock properties (2) lower signal-to-noise of the seismic data quality due to land acquisition; and (3) mapping of sand distribution across two different surveys. These challenges were addressed through the proven workflow comprising integrated and iterative seismic petrophysics and rock physics modelling (PP-RP), seismic conditioning followed by joint facies and elastic properties geostatistical inversion, with survey-varying wavelets. Uncertainties in facies overlaps, seismic-well ties, estimated wavelets are systematically reduced throughout the workflow before finally use in geostatistical modelling and geostatistical inversion. The geostatistical inversion results have provided much more insight for future well placement and field development. High resolution and more apparent geological features that are consistent with the interpreted depositional environment of the Birkhead interval can be observed. Notably, the prediction for the continuity of sand across the surveys now looks possible and geological.