Enhanced Oil Recovery is firmly established in the hydrocarbon maturation plans of PDO and Shell with successful ongoing thermal and polymer field developments and many novel methods being piloted. The current developments and trials undergo in-depth study to leverage the learnings for portfolio-wide application. In optimizing a current or derisking a future EOR development, understanding of the reservoir is key and more crucial than during primary and secondary development because of the complexity of the processes and higher costs involved.
In this paper the use of an advanced history matching technique for improving reservoir understanding is discussed in the context of full field chemical flooding. A powerful feature of the Shell proprietary reservoir simulator is the availability of the so-called adjoint method which allows history matching of gridblock parameters such as permeability and porosity in an efficient and effective manner. The method is applied in a workflow coined model maturation (Joosten & Altintas (2011)), where the local permeability updates are used to highlight deficiencies in the geological model (e.g. missing faults, aquifer locations, pinch outs).
In this particular study the adjoint method improved the pattern match significantly but more importantly revealed the need for fine scale local geological features, confirmed by other data. The improved models describe the observed polymer behavior in line with our theoretical and analytical understanding of polymer flooding. The study showed that understanding EOR processes can only be done after a proper understanding of the reservoir.