Achieving Decision Support the Modern Way: Ensemble-based Modelling of a Pre-salt Reservoir with Large Uncertainties

Development of pre-salt reservoirs is technically and economically challenging. In a co-operative study, the authors made use of ensemble-based modelling and created a holistic workflow spanning from Geosciences to Reservoir Engineering. The workflows ensured a consistent approach, where the different disciplines worked together on the model, increasing the understanding of the complexities involved in the different disciplines, and reducing complications when transferring the model between the disciplines.

An ensemble of data conditioned equi-probable models is achieved encompassing realistic uncertainties in the static and dynamic domains. Analysis of the models helped the team gain better understanding of the properties and locations that needed to be optimized to achieve the history match. These insights are vital for management and further development of the field and allows for the understanding of associated risks.

The ensemble-based modeling approach provided not only multiple history-matched models for the field, but also achieved that in a comparable amount of time to a more traditional 20th century type deterministic approach. In addition, risks and uncertainties were quantified in forecast response of the ensemble to provide actionable intelligence about the reservoir, enabling a more proactive, rather than reactive, reservoir management strategy.