Injectivity decline of oilfield injection wells is a widespread phenomenon during sea/produced water injection. The decline may result in significant cost increase of the waterflooding project. Reliable modelling-based prediction of injectivity index decrease is important for waterflood design as well as for the choice and preventive treatment of injected water. One of the reasons for well injectivity decline is permeability decrease due to rock matrix plugging by solid/liquid particles suspended in the injected water.
The mathematical model for deep bed filtration contains two empirical functions – the filtration coefficient and the formation damage coefficient. We consider the case where both coefficients are linear functions of retained particle concentration. In this case, the model is fully determined by four constants. These constants should be determined from laboratory coreflood tests by forcing water with particles to flow through core samples. A routine laboratory method determines the filtration coefficient from expensive and difficult particle concentration measurements of the core effluent; then the formation damage coefficient is determined from inexpensive and simple pressure drop measurements.
An alternative method uses pressure data at an intermediate point of the core, supplementing pressure measurements at the core inlet and outlet. The proposed method furnishes values for the four model parameters. The method is implemented in a simple and robust tool used in field conditions to characterise injectivity damage system and predict injection well behaviour.