A new method to characterize scaling damage from pressure measurements

Abstract

Sulphate scaling with consequent deposit formation and wellbore damage is a well-known phenomenon that occurs during waterflooding, when mixing of incompatible injection and formation waters may result in sulphate salt precipitation and flow restriction. The reliable productivity decline prediction is based on mathematical modelling with well-known model coefficients. The sulphate scaling system contains two governing parameters: the kinetics coefficient characterising the velocity of chemical reaction and the formation damage coefficient showing how the permeability decreases due to salt precipitation. Previous works have derived analytical-model-based method for determination of both coefficients from breakthrough concentration and pressure drop during laboratory coreflood on quasi steady state commingled flow of injected and formation waters, and also from just pressure drop measurements during two corefloods with two different ratios “formation water : seawater”. This paper extends the previous works, by sequence of two commingled injections of incompatible waters into the same core with two different ratios “formation water : seawater”. Two different slopes of skin factor increase during two injections allow calculating the kinetics and formation damage coefficients in order to predict scaled-up well behaviour.