Nanoparticles Adsorption, Straining and Detachment Behavior and its Effects on Permeability of Berea Cores: Analytical Model and Lab Experiments

摘要

The aim of this paper is to present both experimental and theoretical investigations on nanofluid flow with dynamic adsorption, detachment and straining behavior, and its associated formation damage. In this paper, we conduct core-flooding experiments on oil-wet Berea sandstone. Hydrophilic Nano-structure particles (NSP) is dispersed in the injected brine stream at 0.05, 0.2 and 0.5wt% concentrations. During the core-flooding of nanoparticles injection and post-flush of brine, the corresponding pressure drops across the cores and the effluent nanoparticles concentration are recorded. In order to quantify nanoparticles adsorption/ detachment and straining behavior and associated effects on fluid flow, an analytical model is derived using method of characteristics. The interplay between nanoparticles and rocks is described by the coupled the classical particles filtration theory and maximum adsorption concentration model. All the necessary parameters, i.e., the maximum adsorption concentration, reversible or detachment adsorption concentration, nanoparticles adsorption and straining rates, and the corresponding formation damage coefficients, are characterized by matching analytical solutions with the effluent nanoparticles concentration history and real-time pressure drop. The experimental results indicated that both adsorption and straining occur during the injection. The extent of adsorption and straining for Nano-structure particles (NSP), i.e., maximum adsorption concentration, particles adsorption rate and straining rates, increases along with the increase of nanoparticles injection concentration. As the results, the breakthrough time of nanoparticles injection is delayed, the steady-state effluent concentration decreases, and the pressure drop increases more rapidly. The adsorption amount of nanoparticles includes the reversible and irreversible adsorption. During the post-flush of brine, the reversible adsorbed nanoparticles detach from the already adsorption layers. With the increase of nanoparticle injection concentration, the reversible or detachment of adsorbed nanoparticles also increase. In practice, this paper will contribute for the following applications 1) apply lab experiments to highlight the importance of nanoparticles adsorption, straining and detachment behaviors oh the formation damage.