Shear Rheology Using De Noüy Ring To Evaluate Formation and Inhibition of Calcium Naphthenate at the Water/Oil Interface

The extraction of crude oils rich in tetraprotic naphthenic acids along with formation water under pH conditions above 6.5 favors the formation of naphthenic acid salts that can generate deposits with high consistency and very low solubility in the oil and water phases. There is still much uncertainty regarding the behavior of naphthenates, and only a small number of tests exist to evaluate it. The aim of this study was to obtain the parameters necessary to assess the formation of calcium naphthenate film through shear rheology (Du Nouy ring method) and to assess the rheological behavior of this film at the water/oil interface as a function of the ARN acid concentration, calcium concentration, presence of magnesium ions, and addition of commercial chemical inhibitors. We observed an increase in the elastic modulus (G′) and a reduction of the viscous modulus (G″) with the formation of the calcium naphthenate film and that the viscous deformation is restricted, which is coincident with the formation of a cr...