Characterisation of formation damage during reactive flows in porous media

Abstract

Precipitation of solids due to chemical reactions or thermodynamic non-equilibrium is a common cause of formation damage in oil and gas wells. The traditional mathematical model for reactive flow in porous media contains two empirical parameters: the kinetics rate coefficient, which along with the reagent's concentrations determines the reaction rate; and the formation damage coefficient, which reflects the permeability reduction due to solid phase precipitation. These parameters are determined from laboratory coreflooding tests, which involve commingled injection of reacting fluids. A routine laboratory method determines the kinetics rate coefficient from expensive and cumbersome reagent concentration measurements at the core outlet, after which the formation damage coefficient can be calculated using inexpensive and robust pressure drop measurements. The current paper developed a laboratory method for determining both coefficients from pressure measurements only. The method utilised pressure measurements at the core inlet, outlet and some intermediate core port during commingled quasi-steady-state flow of incompatible fluids. The above data treatment was based on the analytical model for one-dimensional commingled flow of reacting fluids. The formulae for determining the model coefficients from pressure measurements have been derived. The intervals for inverse solution existence, uniqueness, and stability were established. The proposed method was validated by high agreement between the model constants determined by the customary method and the three-point-pressure method.