The Ichthys gas-condensate field is situated in the Browse Basin, North West Shelf of Australia, and the field production commenced in July 2018. The Brewster Member, one of the two reservoirs in the field, is a liquid-rich sandstone reservoir. One of the major uncertainties is the degree of well productivity impairment, caused by condensate banking since the dew point pressure is close to the initial reservoir pressure. The objectives of this study are to evaluate the condensate banking impact on well production performance, and to establish a modelling methodology to consider the condensate banking effect in a full-field simulation model, based on the field production data.
Permanent downhole gauges are deployed in the field, and thus, downhole pressure can be monitored continuously. We conducted high rate tests for selected wells to monitor well productivity impairment from the condensate banking. This production data was history-matched with a compositional sector model by applying Local Grid Refinement (LGR) and Velocity-Dependent Relative Permeability (VDRP) to account for more accurate physics in the near-well region. With the tuned VDRP model, skin trends were predicted to increase with various gas rates, and a skin correlation was established as a function of this gas rate. This correlation is applied to the full-field simulation where LGR and VDRP cannot be applied due to a simulation time constraint.
The skin correlation was validated through the history matching, using the full-field model and was used to predict the future field production performance. We need continuous monitoring of the condensate banking effect, to further validate the correlation, because the production data used in this study is less than one-year duration. The correlation is then flexible enough to tune the history matching when necessary.
We present the monitoring and modelling of the condensate banking effect with the actual production data. The implementation of the proposed well modelling will help reservoir engineers in considering the condensate banking effect in the field production forecast.