R. Bruce Ainsworth¹

(1) Woodside Energy Ltd, Perth, Australia

ABSTRACT: Deltaic Sandbody Connectivity: Sequence Stratigraphic-based Insights From 3-D Reservoir Modeling Studies, Sunrise-Troubadour Fields, Australia

The Sunrise-Troubadour Fields represent a 16.7 Tcf gas-condensate resource located in the Timor Sea, 450 km to the northwest of Darwin, Australia. The Middle Jurassic reservoir succession is relatively thin (80 m), but laterally extensive with a combined area of closure of over 1000 square kilometers. One of the major subsurface uncertainties in the evaluation of these fields is reservoir connectivity due to sandbody geometry and post-depositional faulting. This study addresses these connectivity uncertainties via a sequence stratigraphic-based 3-D reservoir modeling approach.

The deltaic/marginal marine reservoir is composed of fluvial-distributary channel, mouthbar, incised valley and wave/tide dominated shoreface depositional environments. The succession is divided into three Exxon-style sequences. Each systems tract is subdivided into parasequences which form the basic building blocks of the 3-D models. Sandbodies are modeled within this stratigraphic framework. For each sand/shale ratio 3-D depositional model scenario (low case, most likely case and high case), the connectivity of sandbodies within each parasequence, systems tract and sequence was calculated when the models were palinspastically restored to a depositional datum.

Once the top structure and fault architecture were incorporated into the 3-D models, sandbody connectivity was again calculated on the same basis for different fault sealing scenarios. The impact on sandbody connectivity of additional probabilistic sub-seismic faults was also analyzed.

As a scale dependency test the same connectivity analyses as described above were run only for the gas-bearing strata. The above results were then compared to a well connectivity analysis for the reference case field development scenario.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado