The Barremian Deep Marine Confined Channel System:
Singh, Varsha1, Jeff Aldrich1
(1) PetroSA,
A number of gas and gas-condensate
discoveries are present in the
Five of the discoveries are Barremain-Aptian deep marine channel deposits. The
geological model envisages sandstone deposition in a confined channel within an
anastomosing system.
During the early Hauterivian,
deep marine turbidite deposition was controlled by an
already well-established half-graben system. A palaeovalley developed on the hanging-wall side of the
northwest-southeast striking fault. The Barremian to Aptian progradational deposition
of sediment accompanied the progressive widening of the
A second half graben
resulted from an increased rate of fault movement during the Barremian, creating a major erosional
valley parallel to the fault system. At this stage the valley experienced
predominantly erosion, pushing the depocentre further
down-dip. An early Barremian compressional
period created structural closures in a predominantly extensional regime.
During the Aptian,
stacked and amalgamated channels and lobes were formed in a retrogradational
setting. These sandstones are poorly imaged on the seismic data because of the
low acoustic impedance contrast between the sandstones and encasing shales. In addition, the reservoirs are difficult to map
due to thin sandstone beds.
This paper reviews the geological model
of a single 3rd order channel system, spread over a depositional corridor of
~25km. Sixteen wells have penetrated the channel
system with approximately 160 m of cores.
Channel widths and heterogeneity are
documented as well as the effect of the above on the hydrocarbon trapping
mechanism.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California