Facies Analysis Application from Clastic Reservoir, Niger Delta

Taofeek Ademola Ogunyemi¹ and Peter Schlicht^2
1 Schlumberger, Port-Harcourt, Nigeria
² Schlumberger, Lagos, Nigeria

The importance of an accurate geological reservoir description cannot be overemphasized because it leads to improved reservoir management and increased recovery efficiency of oil and gas reservoirs. The geological and reservoir properties of sedimentary rocks depend on interplay of tectonics, sea level, sediments supply, physical and biological processes of sediment transport and deposition, and climate.

At basin scale, these processes interact to produce the stratigraphic architecture of the basin. At smaller scales, these processes control the external 'geometry' and internal 'anatomy' of clastic sediments bodies reservoir heterogeneity. Borehole images are important source of information for understanding reservoir anatomy and geometry, but they have seldom been used in the deep water reservoirs of Nigeria because most wells were drilled with oil-base mud. Only recently have high-resolution resistivity imaging tools been available for this environment.

This paper describes the use of geological evaluations, specifically facies discrimination, that compare 'image facies' and conventional 'electrofacies', and structural applications using dip data interpreted from image logs to further understand structures at sub seismic scales.

The examples demonstrate the value of borehole image logs in deep water reservoir evaluations, especially when fully integrated with core and seismic data, and their applications to reservoir modeling.