Abstract
Three samples of shale recovered from late Campanian to Danian sediments around Ugwueme area, Anambra Basin were studied for their particulate organic matter distribution and hydrocarbon potentials. Two major palynofacies were identified and designated palynofacies A and palynofacies B. Palynofacies A occupies the basal unit (Nkwe mudstone unit of Nkporo Shale) and the topmost unit; Umuaku shale unit of Nsukka Formation).Palynofacies A is dominated by abundant amorphous organic matter (AOM) and some phytoclastmaterials majorly of macerol marine exinite and some terrestrial influenced materials. Palynofacies B represents the middle unit bed (AcharaUgwueme shale unit of Mamu Formation) constitutes abundant phytoclasts with opaque debris of well-preserved terrestrial influenced plant fragments. The kerogen investigation result shows Nkwe mudstone unit of Nkporo Shale Formation and Umuaku shale unit of Nsukka Formation to be type II/III kerogens known to be oil-gas prone material. The study reveals that AcharaUgwueme shale unit of Mamu Formation is of type III kerogen known to be gas-prone. Estimation of the maturation stage of the samples using the exinecolours of pale-yellow to yellow, the sporomorphs shows (1+ to 2+)thermal alteration index(TAI) and reflectance values of 0.3% for both Nkwe mudstone and AcharaUgwume shale unit, thus are thermally immature to generate hydrocarbons while Umuaku shale unit with exinesporomorphscolour of yellow –light brown, (2to2+), thermal alteration index (TAI) and reflectance value of 0.5% to be thermally immature to early mature (early oil phase of hydrocarbon generation).
Highlights
The study area lies within the Anambra Basin, Southeastern Nigeria, West Africa, latitudes 06000’ and 06007N and longitudes 007021’and 007028E.Anambra Basin is a north-east-southwest heading syncline having a roughly triangular shape with a total sediment thickness of about 9km
Sedimentation in Benue Trough was controlled by three major tectonic phases and the first tectonic phase
Materials and Method: Three samples belonging to Nkporo Formation, Mamu Formation and Nsukka Formation of upper Cretaceous sediments exposed at Nkwe, AcharaUgwueme and Umuaku villages within Ugwueme and environs were obtained for the analysis
Summary
The study area lies within the Anambra Basin, Southeastern Nigeria, West Africa, latitudes 06000’ and 06007N and longitudes 007021’and 007028E (fig. 1).Anambra Basin is a north-east-southwest heading syncline having a roughly triangular shape with a total sediment thickness of about 9km. Adeigbe and Salufu(2010) established that Enugu Shale, Mamu Formation and Nsukka Formation ; all in Anambra Basin are all potential source rocks but only that of Mamu Formation has reached oil generating window. Unomah and Ekweozor(1993) reported that the organic facies of the Nkporo Shale are provincial with the Calabar Flank having the highest oil potential while those in the Anambra Basin and Afikpo Synclines are gas prone. They established a predominant gas prone basin for Anambra Basin.
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