Analyzing the wettability changes of rocks in various states of core plugs

Current core plugs preparation standards for laboratory studies are developed for water-wet reservoirs and do not consider other types of wettability. Researching how different core preparation methods affect laboratory studies and wettability changes is relevant and important for petrophysical reserve estimation. Preconditions of doing this work was the question how core plugs impacts wettability changes in carbonate formations from several Eastern Siberian fields. The article describes the SCAL results of measuring the USBM wettability on core plugs at various states: a core plug with preserved saturation (before extraction), a core plug after extraction, and a core plug after wettability restoration. The authors showed how each of the stages of core plugs preparation affects wettability changes in rocks, the study of which is complicated by strong diagenetic changes: uneven salinization, bituminization, and anhydritization. The most accurate results were obtained from core plugs with preserved saturation. Overall, wettability of core plugs shifted towards a more hydrophilic state after extraction, but extraction did not fully change wettability from hydrophobic to hydrophilic.