Preparing for Analysis
Routine core analysis starts before geological section. This analysis includes core gamma logging, depth matching, CT-scanning, saturation determination, core cleaning, marking, plugging, and trimming the plugs. Natural gamma radiation is measured from the cores for depth matching. This is a very important stage for core–log data comparison and correlation. The depth should also be matched between the various runs of the wire line logs. In the next step, for virtual viewing of fractures before opening, CT-scan images are prepared from the cores. The CT-scan images can also be used for evaluation of some petrophysical parameters. Water saturation of some plugs is measured. Special attention should be given because water-based mud can change the water saturation of the samples. Cores are cleaned for the first stage of macroscopic description and the marking process. Routinely, three horizontal and one vertical plug are prepared from each meter of core. This could be changed according to the project purpose and the number of planned tests. Plugs are cleaned by the Soxhlet extraction method. Two sides of each plug are trimmed. The cleaning process is also applied to the trims in the case of heavy oil content. These trims are used for thin section preparation and starting the geological section of the study. In some cases, plugs are prepared using the sidewall coring method. After sidewall sampling, the other processes are the same. Sidewall coring is suitable in some exceptional cases.