| Summary: | >Magister Scientiae - MSc === The thesis aims to determine the depositional environments, rock types and petrophysical
characteristics of the reservoirs in Wells E-S3, E-S5 and F-AH4 of Area X in the Bredasdorp Basin,
offshore South Africa.
The three wells were studied using methods including core description, petrophysical analysis,
seismic facies and multivariate statistics in order to evaluate their reservoir potential. The thesis
includes digital wireline log signatures, 2D seismic data, well data and core analysis from
selected depths.
Based on core description, five lithofacies were identified as claystone (HM1), fine to coarse
grained sandstone (HM2), very fine to medium grained sandstone (HM3), fine to medium
grained sandstone (HM4) and conglomerate (HM5). Deltaic and shallow marine depositional
environments were also interpreted from the core description based on the sedimentary
structures and ichnofossils.
The results obtained from the petrophysical analysis indicate that the sandstone reservoirs
show a relatively fair to good porosity (range 13-20 %), water saturation (range 17-45 %) and a
predicted permeability (range 4- 108 mD) for Wells E-S3, E-S5 andF-AH4.
The seismic facies model of the study area shows five seismic facies described as parallel,
variable amplitude variable continuity, semi-continuous high amplitude, divergent variable
amplitude and chaotic seismic facies as well as a probable shallow marine, deltaic and
submarine fan depositional system. Linking lithofacies to seismic facies maps helped to
understand and predict the distribution and quality of reservoir packages in the studied wells.
Multivariate statistical methods of factor, discriminant and cluster analysis were used. For Wells
E-S3, E-S5 and F-AH4, two factors were derived from the wireline log data reflecting oil and
non- oil bearing depths. Cluster analysis delineated oil and non-oil bearing groups with similar
wireline properties. This thesis demonstrates that the approach taken is useful because petrophysical analysis,
seismic facies and multivariate statistics has provided useful information on reservoir quality
such as net to gross, depths of hydrocarbon saturation and depositional environment.
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