Systematic Laboratory and Modelling Study of Kaolinite in Rocks on Formation-Damage-Fines-Migration Non-Equilibrium Effects, Analytical Model

Abstract

Abstract The main objective of this work is to characterize the formation damage induced by fines migration in reservoir rocks with different kaolinite contents. The problem is particularly important for water production during oil and gas well operations, and for injectivity and sweep during low-salinity waterflooding. We perform laboratory corefloods using aqueous solutions with different salinities in engineered rocks with different kaolinite content, yielding fines migration and permeability alteration. A novel methodology of preparing artificial sand-packs with a given kaolinite fraction has been established. Sequential injections of aqueous solutions in order of decreasing salinity were performed in five sand-packs with different kaolinite fractions varying from 1 to 10 weight percentage. Severe permeability decline was observed when deionized water was injected into the cores. A new analytical model that captures the effects of fines release with delay and their re-entrapment by the rock has been developed. The new model allows for explicit expressions for the attached, suspended, and strained particle concentrations, as well as the pressure drop across the core. The analytical model shows good agreement with the laboratory-observed phenomena across a wide range of kaolinite concentrations. The model constants are presented for each of the five cores and lie within typically reported values. The laboratory protocol and mathematical model allows for reliable prediction of fines-migration related formation-damage during waterflood, EOR, and commingled production of low-salinity water with oil or gas.