Intermittent injection of supercritical CO₂ in oil-brine-saturated rocks: Experimental data and numerical modelling

We present both experimental and numerical modelling results for an unsteady-state core flooding experiment, designed to mitigate risks associated with CO2 injection in a depleted oil field offshore Denmark. The change in the samples’ permeability before and after the experiment is shown to be minimal, suggesting that a potential reduction in injectivity is unlikely. The experimental data include differential pressure measurements across the sample and brine saturation measurements in the sample as a function of time. We demonstrate that the experimental data can be history-matched with a range of parameters defining the relative permeability and capillary pressure functions for the three-phase oil-brine-CO2 system. Two numerical models are developed for solving the forward problem: a computationally expensive, comprehensive equation-of-state based model and a faster incompressible immiscible proxy model. The inverse problem solutions are estimated using the proxy model, and the best-obtained saturation functions are utilized to solve the forward problem with the comprehensive model. The obtained indicative uncertainty ranges can be useful in the absence of more complex and costly experimental data, such as in-situ X-ray saturation measurements.