Carbonate rock with deionised water in the pore space. This is the initial state sample measurement before the injection of brine and nitrogen into a carbonate rock (https://www.doi.org/10.16907/c72b4062-b9b1-4706-8c22-a9d213b97810). This published data collection contains 1 dataset obtained by X-ray tomographic microscopy of a carbonate rock sample 5 mm in diameter and 20 mm in length. Data were collected and processed at the TOMCAT beamline X02DA of the Swiss Light Source.