The polymer-pilot project performed in the 8 TH reservoir of the Matzen field showed encouraging incremental oil production. To improve further the understanding of recovery effects resulting from polymer injection, an extension of the pilot is planned by adding a second polymer injector.
Forecasting of the incremental oil production needs to take the uncertainty of the geological models and dynamic parameters into account. We propose a work flow that is composed of a geological sensitivity and clustering step followed by a dynamic-calibration step for decreasing the objective function (OF) to improve the reliability of a probabilistic forecast of the incremental oil recovery.
For the geological sensitivity, hundreds of geological realizations were generated by taking the uncertainty in the correlation of the sand and shale layers, logs, cores, and geological facies into account. The simulated tracer response was used as dissimilarity distance to classify the geological realizations. Clustering was then applied to select 70 representative realizations (centroids) from a total of 800 to use in the full-physics dynamic simulation.
In the dynamic simulation, an OF composed of liquid rate and tracer concentration of the produced fluids was introduced.
To improve the calibration further, the P50 value of incremental oil production as derived from simulation was compared with the incremental oil production determined from decline-curve analysis (DCA) from the wells surrounding the polymer-injection well. The mismatch between the P50 and the DCA was improved by adjusting polymer viscosity.
The calibrated models were then used for both a probabilistic forecast of incremental oil caused by an additional polymer injector and an estimate of the expected polymer concentration at the producing wells.