Acknowledgements
We sincerely appreciate the Petroleum Technology Development Fund of Nigeria (PTDF Grant ID: PTDF/E/OSS/PHDAOC/385/11), and the University of Liverpool, UK, and Missouri University of Science and Technology, USA for funding the first author’s doctoral studies and post-doctoral research fellowship, respectively. Professor Malcolm Hart (Plymouth University, UK) and Shell Petroleum Development Company are thanked for their help in terms of logical suggestions and the provision of the Gravity Cores samples, respectively.