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2018 AAPG International Conference and Exhibition

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Middle Cretaceous Depositional Environment and Reservoir Potential of Central Rovuma Basin, Offshore Mozambique

Abstract

Rovuma Basin has huge commercial hydrocarbon discoveries in Tertiary progradational low-stand track (LST) sequence of Rovuma Delta. Oil shows were also identified at Cretaceous, Albian, LST progradational sequences, at both onshore and offshore close to study area. Cachalote-1 well at study area, discovered gas in thicker, stacked sand section with good quality reservoir at structural closure of Albian age. Buzi-1 well although was dry at same stratigraphic level, almost 27 Km away, found stacked good quality sand reservoir. Both wells were drilled at high amplitudes seismic reflectors. The depositional environment of the study area was not understood and there are uncertainties about reservoir distribution and properties. The purposes of this study was to understand the depositional environment and predict the spatial distribution and properties of sand reservoir using seismic attributes and well log analysis. To achieve the goal, 3D seismic full stack data and well data, including logs data were used for analysis and interpretation and depositional models were generated. Seismic interpretation demonstrated the structural control of reservoir at southern part and stratigraphic control at northern. Seismic attributes such as similarity and RMS successfully mapped faults, channels and sand deposits. Attributes helped to better understand the depositional environment and sand reservoir distribution. Integration of seismic interpretation with seismic attribute and well log analysis demonstrated that the study area is dominated by progradational, LST sequence of deep water depositional environment. The sand reservoirs are mainly deposited as channel-levee systems at slope and basin floor fan with good reservoirs properties. For better understand the depositional environment, reservoir distribution and quality is recommended to map the stratigraphic horizons of interest and extract the seismic attributes in several windows along the interpreted horizon and integrate with rock properties intersected by wells at and/or near the zone of interest as well as doing seismic inversion for better prediction of reservoir distribution and quality.