The Pacific Journal of Science and Technology –261– http://www.akamaiuniversity.us/PJST.htm Volume 8. Number 2. November 2007 (Fall) Heat Flow Estimates in the Western Niger Delta Basin, Nigeria D.O. Ogagarue, Ph.D. Department of Integrated Science, College of Education, Agbor, Nigeria E-mail: dogagaru@yahoo.com ABSTRACT Present day heat flow values are calculated for twenty-one well-spaced petroleum wells in the western Niger Delta Basin, Nigeria using geophysical log data. Heat flow estimates vary between 27.6 mWm -2 and 68.3 mWm -2 , with a simple average of 43.92 mWm -2 . The north-central part of the study area is characterized by high heat flow which decreases towards the Niger Delta coast. The values obtained are comparable with those of other passive continental margins of the world. (Keywords: geophysical data, petroleum exploration, hydrodynamics, tectonics, hydrocarbon reserves ) INTRODUCTION The Niger Delta sedimentary basin is widely recognized as holding significant hydrocarbon reserves and continues to attract exploration interests. Successful exploration for these resources demand multi-disciplinary efforts to integrate all available data and utilize advanced technologies to mitigate the exploration and drilling risks. Heat flow data are important in investigating the geothermal resource potential in an area. Representations of heat flow data on contour maps offer suggestions for the interpretation of crustal tectonics and large-scale hydrodynamics, and formation of basins (Lachenbruch and Sass , 1977). For a sedimentary basin, the data provide an additional measure of investigating hydrocarbon maturation, migration and accumulation. Heat flow data have been estimated by Etim et al, 1996. They utilized the Thermal Resistance method of Bullard (1939) and Chapman et al., (1984) to estimate heat flow values for the northern Niger Delta sedimentary basin and obtained heat flow values varying between 38.70 mWm -2 and 64.28 mWm -2 with an average of 51.49 mWm -2 . In the present study, heat flow estimates are calculated for twenty-one petroleum wells in the western Niger Delta basin, following the Relative Heat Flow model of Houbolt and Wells (1980). The method calculates heat flow values in terms of subsurface temperature and one-way sound travel times. ± GEOLOGY OF THE NIGER DELTA BASIN Works by several authors (Hospers, 1965; Short and Stuable, 1967; Weber, 1971; Merki, 1972) show that the Niger delta is a sedimentary basin formed by the built out and up of sediments over a transitional crustal tract. This tract was developed by rift faulting during the Precambrian with outlines controlled by deep seated faults associated with the rifting (Weber,1971). The delta is situated on the Gulf of Guinea on the west coast of central Africa, and extends from longitude 3 0 E to 9 0 E and from latitude 4 0 30 ’ N to 5 0 20 ’ N. It started as separate depocenters in the Bende–Ameki area, east of the delta and in the Anambra shelf, west of the delta in the mid–late Eocene (Hospers, 1965). The two depocenters coalesced to form a single united Niger delta sedimentary basin in the late Miocene to date. The delta has a tripartite lithostrgraphic succession in which a regressive sequence is properly defined. The delta sequence is mainly a sequence of over pressurized marine clays (Akata Formation) overlain by a paralic sediment sequence (Agbada Formation), that is predominantly sandy and shaly at the top and bottom, respectively. These two formations were finally capped by continental gravels and sands (Benin Formation). Of these three formations, the Agbada Formation constitutes the main reservoir for hydrocarbon in the Niger delta (Short and Stauble, 1967). The maximum thickness of the sediments may be of the order of 40,000ft to the basement. The known thickness of the continental sands is variable but generally exceeds 6,000ft, while that of the paralic sequence is 10,000ft to 15,000ft at the center of the delta. The Akata Formation exceeds 4,000ft (Merki, 1972).