A method includes receiving images of a rock sample. The method also includes modifying a set of voxels related to one or more of the received images by applying a digital pore growing operation that changes non-pore voxels surrounding a pore space to pore voxels, wherein the digital pore growing operation is based at least in part on a predetermined dead oil estimate. The method also includes estimating a property of the rock sample based at least in part on the modified set of voxels.