--> Clinoform Architecture Variations and Their Effect on Reservoir Potential in an Eocene-Oligocene Carbonate Ramp, Browse Basin, Australia

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Clinoform Architecture Variations and Their Effect on Reservoir Potential in an Eocene-Oligocene Carbonate Ramp, Browse Basin, Australia

Abstract

The Browse Basin contains currently uneconomical hydrocarbon accumulations, however, a better understanding of lateral variability, internal geometries and seismic expressions of this carbonate ramp system is of significance for academia and the petroleum industry alike. This study sheds light upon the internal architecture and magnitude of thickness variation within clinoform packages and will enable a better prediction of reservoir qualities, geometries and drilling risks in analogue hydrocarbon-bearing carbonate systems. The objective is to better understand seismic expressions of carbonate clinoforms and the effect of sea level variation on clinoform growth architecture and thickness variability. This study focuses on the seismic geomorphology and sequence stratigraphy of an Eocene-Oligocene carbonate ramp in the Browse Basin of Australia using a 285km2 high-resolution 3-D seismic dataset and well logs (GR, RES, DT) from three wells. We utilize seismic attribute analysis (variance, curvature and amplitude) to facilitate the interpretation of the shelf edge, faults, slope channels and mass transport deposits (MTDs). Reflector geometry, amplitude, continuity and termination of the clinoforms and their internal elements was investigated to develop a sequence stratigraphic framework in accordance with eustatic sea level curves. Syndepositional and postdepositional events, such as slumping, sliding and faulting were identified in the same way. The relative timing between faults and channels was delineated by analyzing vertical fault terminations in relation to the channel-bearing reflector. Constraining this timing yields a better understanding of possible structural (fault related) controls of the MTDs. Subsequently, the seismic time volume was converted into a depth volume in order to quantify clinoform thickness variability and slope angles. Even though the system is classified as low angle carbonate ramp, significant channel complexes (on average 600 m wide, 30 ms deep) are identifiable along the slope. Quantifying slope angles helps to explain this observation. Working with the depth converted seismic volume, well log responses are linked to basic petrophysical properties (e.g. thickness, lithology, clay content, porosity) of the channels and MTDs to estimate their reservoir potential.