USE OF ACIDOBASIC INDICATORS TO DETECT INTERFACIAL REACTIVITY DURING ALKALINE FLOODING

A novel technique has been developed to detect the depletion of the al kaline reagent that occurs during the displacement of an acidified oil by an aqueous alkaline solution in a consolidated model porous medium . An acidobasic indicator (thymolphthalein) was added to the displacin g aqueous solution in order to monitor the progress of the chemical re action. The initially blue alkaline solution turned colorless after pr olonged contact with the acidified oil, indicating that the alkali in the vicinity of the interface became depleted as a direct result of in terfacial chemical reaction. Under such conditions, the displacement f ront changes to a nonreactive one, very similar to a pure water displa cement. The disappearance of color was particularly pronounced at low alkali concentrations and low flowrates.