Injectivity decline under suspension injection with Langmuir's fines capture: analytical model

Injectivity decline due to injection of colloidal suspensions and emulsions occur in numerous areas of geo-energy production, geo- and environmental engineering. This phenomenon is attributed to colloidal capture by porous media resulting in permeability decrease. The shortcoming of the traditional analytical model predicting injectivity decline is the assumption of constant filtration coefficient (probability of the capture) leading to infinite retained particle concentration . This restricts the model application to short injection periods only. This paper derives explicit formulae for particle concentrations and well injectivity for Langmuirian filtration coefficient that decreases during injection and yields a limited retained concentration . The permeability damage occurs in well vicinity, which is significantly smaller than the drainage radius, so we use an asymptotic method for analytical modelling. It was shown that second-order asymptotic approximation provides sufficient accuracy for the prediction of the skin factor, its stabilization period, and damage radius. The explicit analytical formulae allow for multivariant sensitivity study for well impedance with respect to filtration and formation damage parameters. This study reveals that the most influential parameters are the permeability decline exponent and formation damage coefficient, while the initial filtration coefficient almost does not affect the impedance growth. Besides impedance, the analytical model provides formula for skin stabilization period and damage radius. Matching the field case data on well injectivity history by the lab-based asymptotic model exhibits high accuracy, which validates the asymptotic model for injectivity decline prediction.