Model calibration and optimization of a post-combustion CO2 WAG pilot in a mature oil field

Abstract

A carbon dioxide (CO₂) water-alternating-gas (WAG) pilot was conducted to gain insights into tertiary oil recovery potential via CO₂ flood in the West Ranch Field as part of the Petra Nova project, the world's largest post-combustion CO₂ capture and utilization initiative. With a fluvial formation geology, this is a challenging and novel application of CO₂ enhanced oil recovery. The aim of this study is two-fold. First, to build a predictive dynamic model that incorporates the data acquired during the pilot operation. Second, to utilize this model to provide guidance for optimal design for a field-wide CO₂ EOR operation.

This study began with an initialization of the pilot sector model extracted from a calibrated full-field model. The pilot model calibration follows a two-step hierarchical workflow. First, we performed a large-scale update of the permeability distribution by integrating available bottomhole pressure and multiphase production data. Next, local permeability field is fine-tuned using a streamline-based method to match CO₂ breakthrough times at the producers. The predictive capability of the calibrated model was verified through two blind validation tests: (1) the model showed good agreement with saturation logs acquired at two observation wells; and (2) the model reproduced the CO₂ recovery as a fraction of the injected CO₂.

Sensitivity studies were conducted using the calibrated pilot model to evaluate the effects of various operational parameters. Finally, we performed a Design of Experiment based multi-objective optimization of the CO₂ WAG processes using the influential operational parameters identified from the sensitivity analysis.