Evaluation of Reservoir Modeling Techniques to Assess the Impact of Stratigraphic Architecture on Production Performance

Carlos Pirmez, Frans van der Vlugt, Ciaran O'Byrne, Vaughan Cutten, Gareth Jenkins, Mark Barton, Ed Kruijs, Luiz Amado, Andrew Hoover, and Robert M. Stovall
Shell International Exploration & Production, Inc, Houston, TX

A detailed reservoir modeling study of a deepwater field offshore west Africa was conducted to assist with the evaluation of field development options. Our approach to evaluating the impact of various geologic and engineering parameters on reservoir performance required modeling a wide range of scenarios because of the limited amount of data available from the field. We compare the production performance forecast using two different reservoir modeling approaches: (1) Seismic-based reservoir models use information from the 3d seismic volume and wells to generate model scenarios. The range of scenarios generated by this approach is largely dependent on seismic amplitude calibration, and (2) Stratigraphic-based reservoir models combine seismic stratigraphic interpretation with geologic information derived from cores/logs, supplemented by an extensive proprietary database of reservoir element dimensions and heterogeneities. The range of scenarios is dependent on available data on key stratigraphic and structural heterogeneities present in the field. The available databases allow for initial estimation of likelihood of the various geologic scenarios. Both types of models were input to a dynamic reservoir simulator and the results compared to evaluate the impact of various parameters on production performance. Seismic-based models allow for very rapid assessment of in place volumes, production rates and ultimate volumes. However, production performance in such models cannot be evaluated independently of other parameters, such as in-place volumes. Our integrated stratigraphic modeling approach, provides a method to evaluate the impact of various geologic parameters independently of each other, as well as possible interactions among them