This investigation pretend to obtain improve on seal and reservoir rocks composition studies in oil fields, more certain in the formations characterization, and to prove the necessity of analytical nuclear techniques’ incorporation to petrophysical methods’ complex used in the Cuban oil prospection. This investigation used computer axial tomography method in consolidated cores’ rock and free software Image J as tomography interpretation support, resulting in novel improvement to the petrophysical laboratory. The following results were obtained: the computer axial tomography on cores’ rock were carried out; the resulted images were analyzed in quantitative and qualitative way, using Image J software, obtaining a good correlation with expert’s description of those cores’ rock. A methodology which permit to find average porosity and density values per pixel using tomography images were obtained, with the necessary corrections per lithology. This methodology is now in the initial phase of its development.