Modeling Crustal Structures of Southern Nigeria Basins from Aeromagnetic Data: Implication on Hydrocarbon Prospectivity | Chapter 06 | Advances in Applied Science and Technology Vol. 1
Southern Nigeria has major and minor
sedimentary basins. This study covers parts of 5 sedimentary basins in southern
Nigeria, this includes the Niger Delta, Benue Trough, Calabar Flank, Mamfebasin
and Lower Benue
Trough. Aeromagnetic data
has been used
by many authors
worldwide in evaluation of
subsurface basin configuration. This
study covers parts
of five basins
(Niger Delta, Calabar Flank,
Anambra Basin, Mamfe Basin, and Lower Benue Trough) in Nigeria. The study
utilized twenty aeromagnetic maps on a scale of 1:100,000. The maps were
digitized manually along flight lines and a total of 16,689 data points
obtained. The data was processed using computer techniques including map
merging, reduction to pole, polynomial and power spectrum filtering for
residual and regional anomaly separation,
and forward and inverse
2.5D Saki modeling.
Results obtained from power spectrum depth analysis indicate
depth to magnetic sources vis –a –vis sediment thickness from the Niger Delta area (2.75 km -3.75 km),
Anambra basin (1.5 km –2.6 km), Calabar Flank (1.3 km –2.3 km), Mamfe basin
(2.0 km –3.4 km), and Lower Benue Trough (1.5 km –3.2 km). Also, depth to
basement results from forward and inverse modeling indicate the Niger Delta has
thickness of sediments ranging between 1.0 km-8.0 km, Anambra basin (1.4 km
–2.7 km), Calabar Flank (0.8 km-2.5 km), Mamfe Basin (1.0 km –2.7 km), and
Lower Benue Trough (1.4 km –2.7 km). Also, results from modeled number of
intrusives indicate that the Calabar Flank has five intrusives, Niger
Delta has four intrusives,
Mamfe basin has
six intrusives, Anambra
basin has five
intrusives, and Lower Benue
Trough has four intrusives. The implications of the increased number of
intrusives are that generated hydrocarbons might be converted to gas, this is
more likely in areas around Calabar Flank, Mamfe basin and Anambra basins,
given the high number of occurrence of intrusives within these areas.
Whereas areas around
the NigerDelta and
Lower Benue Trough
with significantly increased
depth and lower number of intrusive are less prone to excessive heat from the
intrusive and may produce more
oil. The study
support further exploration
activities within the
Niger Delta and Lower Benue Trough areas. The
significance of this study is the wide range appraisal of the basin
architecture and configuration of the offshore and inland basins in Southern
Nigeria. The Niger Delta basin areas of Portharcourt, Bonny with sediment
thickness of about 8.0km and less occurrence of intrusives has the highest
hydrocarbons exploration potentials. The Bansara area within the Mamfe basin
has (2.6 km) sediment thickness that
could generate hydrocarbons given that another condition is favourable, but the
presence of numerous intrusives may make the area prone to excessive heat
and may
produce more gas
than oil. The
Anambra basin and
the Lower Benue
Trough have a moderate
depth of sediments
thickness(2.5km) and less
number of intrusives,
these areas came second to the Niger Delta among the
studied basins for good prospects in hydrocarbon exploration investigations. It
is concluded that
this study reveals
the order of
preference of the
choice of investigating the
hydrocarbon prospective potentials of
Southern Nigerian basins using the potential field magnetic method, it is recommended that
other geophysical methods such as gravity, and seismic be used to identify
possible hydrocarbon habitats within the
Southern Nigeria Basins.
Biography of author(s)
Dr. Dominic Akam Obi
Department of Geology,
University of Calabar, Nigeria
Anthony Michael George
Department of Physics,
University of Calabar, Nigeria.
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