Well-data-based prediction of productivity decline due to sulphate scaling

Abstract

Sulphate scaling can have a disastrous impact on oil production in waterflood projects with incompatible injected and formation waters. This is due to precipitation of barium/strontium sulphate from the mixture of both waters and the consequent permeability reduction resulting in loss of well productivity. The system where sulphate scaling damage occurs is determined by two governing parameters: the kinetics coefficient characterising the velocity of chemical reaction and the formation damage coefficient reflecting permeability decrease due to salt precipitation. Previous work has derived an analytical model-based method for determination of two coefficients from laboratory corefloods during quasi-steady state commingled flow of injected and formation waters. The current study extends the method for determination of kinetics and formation damage coefficients from production well data consisting of barium concentrations in the produced water and of well productivity decline. We analyse production data for five wells from giant offshore field A, submitted to seawater flooding (Campos Basin, Brazil), and obtain values of the two sulphate scaling damage parameters. The two coefficient values were used for prediction of productivity decline for these wells. The values of kinetics and formation damage coefficients as obtained from either laboratory or field data vary in the same range intervals. These results validate the proposed mathematical model for sulphate scaling damage and the analytical model-based method "from lab and wells to wells". © 2009 Elsevier B.V. All rights reserved.