Reservoir quality controls for the Sandpiper Sandstones (Upper Jurassic), Bonaparte Basin, Offshore Australia: Pre-drill predictions and post-mortem

Abstract

Two vertical exploration wells were recently drilled near the junction of the Malita Graben and the Sahul Syncline in the Bonaparte Basin, offshore Australia as part of an exploration program targeting Jurassic marginal marine sandstones at high burial depth. Present-day temperatures are high (>170°C) and the quartz arenites are expected to be completely cemented by quartz overgrowths. Core samples from the first well and cuttings from both wells are used to characterize the controls on reservoir quality. The target sandstone reservoirs are medium grained, moderately well sorted quartz arenites. Compaction is normal for quartz-rich sandstone and quartz cement is the main mineral cement present. Reservoir quality is moderate and porosity is dominated by primary intergranular pores. The core was taken in an aquifer which may have been HC charged in the past. Cuttings investigated from the dry well suggest lower porosities than the core. Fluid inclusions in quartz cements and healed grain fractures from core and cuttings yield homogenization temperatures and salinities of paleo-fluids. These data provide important constraints on the quartz diagenesis at this location. TouchstoneTM models were created for the pre-drill predictions. The models were updated to reflect well results and suggest that the cored well exhibits anomalous porosity preservation which is not well understood. Touchstone models were used to test possible scenarios for the inhibition of quartz cement.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015