Amangi field reservoir porosity and saturation estimation using seismic and well data

Abstract

The scientific knowledge of mapping reservoir geometries provide useful displays for understanding the sediment fairway orientation and transport direction, they are not detailed enough to define the best quality well connected reservoir areas needed for planning
development wells. Knowing that that long term development of this field will require excellent subsurface imaging to optimize the placement of future development and production wells, so to plan for this, we used strong reflected primaries (PP) and primary-shear (PS) waves imaging for the reservoir characterization. Porosity of two hydrocarbon reservoirs is investigated for the purpose of planning production operations in Amangi field of the Nigerian Delta. Well log derived porosities were measured at five appraisal wells in the field. Point information about the porosity of the reservoirs were determined from these well log data. However, lateral variations of porosity could not be delineated from measurements made only at the sparsely  located wells in the field. A 3D seismic data covering an area of about 20 km x 17.5 km were acquired to delineate the extent of the porous sand. After careful data processing, the lateral variations of seismic amplitudes were transformed to changes in rock impedances, which, in turn, are indirectly related to porosity. In contrast with the sparse well observations, the 3D seismic method provided a dense and regular areal sampling of the acoustic properties of the reservoir intervals. The results of the transformation of the 3D anisotropic seismic reflection data were integrated with petrophysical measurements at the wells to significantly improve the spatial description of porosity in this field.