Abstract
Drastic loss of injectivity during waterflood using sea/produced water has been reported worldwide. It happens due to capture of solid and liquid particles from the injected water by the rock resulting in permeability decline, and also due to formation of low permeability cake on the wellbore. Both factors result in injectivity impairment.
Reliable prediction of injectivity decline should be based on mathematical modelling using coefficients that are well known for a specific well/field.
The mathematical model for injectivity damage contains four parameters: filtration and formation damage coefficients, critical porosity ratio and filter cake permeability. Nevertheless, just three constants can be extracted from two-piece-wise-linear injectivity decline curve.
In the current paper we propose the correlation between the formation damage coefficient and the critical porosity fraction to be used as a fourth equation allowing for characterization of injectivity damage system.
Eighteen well data have been treated, and values for four parameters of injectivity damage have been calculated. The obtained values have the same order of magnitude as those obtained from laboratory corefloods. It validates the proposal to use the correlation between the formation damage coefficient and the critical porosity fraction for characterisation of injectivity damage system from well history for the purpose of further prediction of well injectivity.
