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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Structure and Facies Development in the Niger Delta
Resulting from Hydrocarbon Maturation
By
Conoco Inc., Houston, Texas
A new depositional model relates
the formation of Niger Delta toe
thrusts
and growth faults to source rock maturation.
Specifically it is proposed that an
oil prone source rock at early maturity
generates enough fluid and pressure to
initiate major fault movement by gravity
sliding.
Recently acquired, high quality
deepwater seismic data show a well-defined
decollement surface that links
toe
thrusts, growth faults, and counter-regional
faults in the progradational
wedge. It is believed the decollement
occurs in an Aptian source rock known
to be present in West Africa and Brazil.
Regional cross-sections were constructed
through the delta, using the
published positions of shorelines
through time and assuming a maximum
post-Aptian sediment wedge of eight
kilometers. Maturation modeling was
performed and the results at various
times from Late Cretaceous to Recent
were plotted and compared to
paleopositions of the shelf edge and toe
of slope. The modeling illustrates how
the maturation of an Aptian source rock
may have significantly influenced structural
development and facies distribution
in the delta.
The present-day time slice shows a
strong correlation between the location
of the early mature window of the proposed
source rock and the position of
the leading toe
thrust in the delta. A
similar correlation is found between the
location of the post gas-mature window
and the position of significant fluvial
facies accumulation. The fluvial facies
occurs as the result of shoreline advance
caused by the loss of source-related lubrication
of the decollement surface.
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