1. Key Laboratory of Oil & Gas Exploration and Development Theory and Technology, China University of Geosciences (Wuhan), Wuhan 430074, Hubei, P. R. China
2. School of Earth Resources, China University of Geosciences (Wuhan), Wuhan 430074, P. R. China
3. Arusha Technical College, P.O. Box 296, Arusha 0255, Tanzania