Regional Pressure Studies in the Niger Delta – their Role in Safe, Cost Effective Well Planning and the Generation of New Exploration Opportunities

In this paper, we review some of the results from regional pressure analysis of the Deep Water/Ultra-Deep Water and Shelf areas, Niger Delta. Direct pressure data have been analysed to produce a set of maps of reservoir overpressure. Wireline logs from hundreds of wells were analysed for shale pressures, and compared to direct measurement of reservoir pressures where available. Shale pressure algorithms were qualified by careful analysis of overpressure mechanisms, with particular reference to the deep Shelf where temperatures reach 140oC in the Agbada shales. The comparison between sand and shale pressures leads to conclusions about regional reservoir connectivity, vertical pressure communication and seal effectiveness. Both regional and local relationships to describe fracture pressure and overburden have also been developed as part of this study, all of which lead to more confidence for safe and cost-effective well planning, as well as estimates of seal breach for highly pressured traps. In addition, the nature of regional reservoir connectivity predicts trapping geometries and relationships between hydrocarbons and fluid flow phenonema which would otherwise be ignored. Careful analysis of pressure data in producing fields confirms many of these relationships.