Impact of Dopants on SCAL Experiments, Phase I

It is a common practice in special core analysis (SCAL) to add sodium iodide (NaI) to the formation brine and injection brine during laboratory waterflooding experiments. It helps in improving the contrast between water and oil for in-situ saturation monitoring using an X-ray technique. Recent progress in our understanding of crude oil, brine, and rock interaction points towards a non-trivial role of NaI in wettability alteration. This alteration could introduce a significant bias in the SCAL experiments. This study addresses the impact of NaI in connate and injection brines on oil recovery during coreflooding experiments. In total, six Bentheimer samples have been tested. The samples were initially saturated with undoped or doped brines, brought to irreducible water saturation (Swi), and aged using crude oil at reservoir temperature. The samples were then loaded in Amott cells for spontaneous imbibition before being brought to residual oil saturation (Sor) during centrifuge-forced imbibition. The results show a significant NaI impact on oil recovery in clastic rocks, especially during the spontaneous displacement process. Additional work is needed to assess the NaI impact on carbonate rocks and the impact of iodide in oil (organic dopants such as iododecane).