A New, Data-Driven Methodology for the Integration of Seismic and Well Data Into Geological Model - Case Study Block 4, Offshore Angola, Lower Congo Basin

Abstract

Abstract The acquisition of high-resolution and high-fidelity seismic data opens the possibility of precision reservoir characterization, particularly for those formations that do display a very pronounced Amplitude Versus Offset (AVO) response. In a traditional approach, the integration of seismic and well data information is driven by the ideas and view of the geologist, whose ideas and views might introduce bias in reservoir representation. It is undeniable that the guidance of the model construction by the geologist is an absolute requirement where seismic data limitations (quality, fidelity or accuracy) does not allow extracting a high-resolution reservoir description as an input to the static model construction. This is evolving: Where AVO effects at reservoir level are significant, the grade of both seismic data and petrophysical measurements now available allow a very precise description of the reservoir, in terms of reservoir geometry and reservoir property distribution. In the study area, AVO response in the Upper Miocene turbiditic deposits, offshore Angola are suitable for detail reservoir characterization. In this paper, we shall demonstrate through a real case how the results of seismic inversion and attribute analysis have been used for the characterization of depositional elements and the modeling of reservoirs. We shall present first how seismic inversion results have been integrated with facies defined from logs, and how this was used to confirm and identify fluid type and contacts verified at wells, as well as for the delineation of structural and stratigraphic reservoir boundaries. A systematic approach to constructing the 3D static model was applied. The top reservoir was picked in detail, allowing for the channel geometries to be sculpted out using seismic inversion results. The integration of qualitatively and quantitatively delineated sand-body architecture, geometry and orientation from seismic data. Sequential Indicator Simulation method, using well data, allows the facies to be modeled hierarchically through a combination of deterministic and stochastic approaches. The advantages of this methodology are: (i) integrating fully facies characterization and geological concepts with seismic response, (ii) reducing uncertainty on reservoir distribution and extent and, (iii) constructing of a coherent reservoir description fit for dynamic model even with limited number of wells.