Unveiling Depleted Reservoirs Storage Potential for an Offshore CCS Project

This paper showcases an ongoing study for storage volume/efficiency calculation for a depleted gas reservoir. The objective of this study is to demonstrate how the model characteristics impact CO2 plume migration and storage efficiency.

Two sets of models were built:

1. a simple moving average (MA) model was built to represent a homogenous distribution of petrophysical properties using simple upscaling of the porosity well logs and using the moving average algorithm.
2. a full-field heterogeneous model was built using a hierarchical modeling approach

Similar to the nature of how the geomodels were built, the dynamic simulation results show that the CO2 gas appears to be distributed much more uniformly and continuously in the MA model, and in a much more patchy and discontinuous distribution in the heterogeneous model.

Highlight from the study is the assessment of the field storage efficiency lies in the range of 70%–90%.

Overall, the extensive modelling work and analysis in this study helps to build confidence on the total storage capacity of the field and may provide useful reference to other depleted oil and gas field CCS studies.