Petroleum Geochemistry of the Central and Eastern Onshore Niger Delta Basin: Oil-Oil Correlation Using Biomarkers and Multi-Variate Statistics
Inyang O. Oyo-Ita *
Department of Pure and Applied Chemistry, Organic Geochemistry Research Group, University of Calabar, Calabar, Nigeria.
Victoria Ogbonna
Department of Pure and Applied Chemistry, Organic Geochemistry Research Group, University of Calabar, Calabar, Nigeria.
Akin Akinlua
Department of Pure and Applied Chemistry, Organic Geochemistry Unit, Obafemi Awolowo University, Ile Ife, Nigeria.
Orok Esu Oyo-Ita
Department of Pure and Applied Chemistry, Organic Geochemistry Research Group, University of Calabar, Calabar, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Petroleum geochemistry of oils in several depobelts of the world has been well documented based on biomarkers. However, there is paucity of data regarding the use of multi-variate statistics in oil-oil correlation study, particularly in the Sub-Saharan African region. The purpose of the study was to gain an insight into the geochemical differences and identify their cause(s) through the application of bulk properties, biomarker indices and multi-variate statistics. Correlation of oils from eight wellheads of three stratigraphic units within the Central and Eastern onshore Niger Delta Basin fields (AG and AS) were undertaken by gas chromatography-flame ionization detector. Utilization of bulk properties, biomarker indices and cross plot parameters somewhat separated the mature AG1-4, AS3 and AS4 oils deposited in oxic/suboxicshaly environment from AS2 oil deposited in anoxic fluvio deltaic environment. In-reservoir alteration and migration differences were the major factors responsible for the observed slight geochemical variability in the studied oils. Nevertheless, multi-variate principal component analysis indicated that the Central and Eastern onshore Niger Delta Basin oils were principally generated from similar organic matter sources. The implication here was that the geochemical variations in the studied oils were not significant, a conclusion corroborated by Pearson correlation model data.
Keywords: Depositional environment, lithology, Niger Delta Basin, correlation, biomarker