Injection of brine and nitrogen into a carbonate rock - steady-state: This published data collection contains 8 datasets obtained by X-ray tomographic microscopy of a carbonate rock sample 5 mm in diameter and 20 mm in length. We explore 3 total flow rates (brine flow rate + nitrogen flow rate): 0.1ml/min, 0.4ml/min, 0.7ml/min. With 3 fractional flows (brine flow rate / total flow rate) explored for each total flow rate: 0.85, 0.7 and 0.5. The 1st data set (0.1 ml/min, 0.85 fractional flow of brine can be found here: https://doi.psi.ch/detail/10.16907/46a4d882-4dec-4097-8289-8f6311a4aa36). The sample was not re-saturated between experiments. Data were collected and processed at the TOMCAT beamline X02DA of the Swiss Light Source. The initial state static data set of the carbonate rock saturated with KI-stained deinonized water can be found in a separate data collection: https://www.doi.org/10.16907/78bddca3-274f-42be-9826-ef729941e43e