An outcrop analogue for deepwater salt withdrawal mini-basins: lateral and vertical variations in basin-fill

Abstract

Mini-basins are well known targets for petroleum exploration as they can contain significant hydrocarbon reserves, such as in the Gulf of Mexico. Though mini-basins have been studied before, their reservoir rock distributions remain poorly predictable. This is especially the case where mini-basins are near salt-diapirs. The Donkey Bore Syncline in the Flinders Ranges, South Australia, presents an excellently exposed deepwater mini-basin reservoir analogue. Detailed outcrop study, including vertical and lateral logged sections presented here, shed considerable light on the depositional system, especially with regards to depositional style and stages of basin-fill. Based on the observed facies and deposit geometries, the authors have been able to detect the change from a carbonate to a siliciclastic deposition system and interpret mini-basin-fill initiation and progradation processes. Sandy gravity-flow deposit lobe areas are identified, enclosed within shales. Along with paleocurrent data, these enable the description and interpretation of basin-fill stages and the lateral character of reservoir-analogue depositional tracts. This will be useful for better interpretation of mini-basin turbidite sequences and will help reduce uncertainties in subsurface exploration. This may also improve prediction of basin-fill where well spacing is inadequate.