Thermodynamic Pathways of CO2 Storage in Depleted Gas Reservoirs

The use of depleted hydrocarbon reservoirs for CO2 storage can be preferred as it offers financial and technical advantages in comparison to deep saline aquifers. Considering higher available space in unit pore volume depleted gas reservoirs (DGR) are particularly good candidates. However, the engineering of DGRs is not straight forward due to challenging thermodynamics in the injection and reservoir sides.

We investigate the topic to understand the engineering design questions using data from a Dutch offshore depleted gas field to be applied for CO2 storage. We use a commercial simulator and various realistic scenarios; our aim is to numerically emphasize and discuss various aspects of the challenge to widen the understanding and the use of related tools.

First, we speculate on the potential thermodynamic pathways of CO2 travelling from the emitter to the deep reservoir based on realistic injection scenarios. In a second step we study the cases modelling the gas reservoir using radial geometry to allow a more precise description of near wellbore region. Results of various thermodynamic pathways are presented in the paper and the results are discussed in terms of flow assurance during the lifetime of CO2 injection process.