This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 144196, ’Reduction of Fines Migration by Nanofluids Injection - An Experimental Study,’ by A. Habibi, SPE, M. Ahmadi, and P. Pourafshary, SPE, University of Tehran, and Sh. Ayatollahi, SPE, Shiraz University, prepared for the 2011 SPE European Formation Damage Conference, Noordwijk, The Netherlands, 7-10 June. The paper has not been peer reviewed.
Formation damage because of fines migration is a major reason for productivity decline. Many studies have characterized fines and their migration effect on permeability reduction. Nanofluids that contain nanoparticles (NPs) show specific properties including a high tendency for adsorption and being a good candidate for injection into the near-wellbore region because of the very small NP sizes. The study indicates that fines could adhere to the matrix grains, hindering their migration, when the porous materials are soaked with nanofluids.
Fines are loose unconsolidated particles (smaller than 37 µm) that move with fluid flow and cause formation damage because of the filtering action of the porous media. The biggest drawbacks of this process are pore plugging and productivity-index reduction. Various surface forces have been found to be responsible for fines detachment and release from the pore surfaces. London/van der Waals attraction, double-layer and Born repulsion, and hydrodynamic forces are the dominant forces in the detachment of fines from porous media. When the total interaction energy between fines and pore surface becomes positive, the repulsive forces are bigger than attractive forces and fines detachment occurs.
NP size ranges from 1 to 100 nm, and NPs have high specific surface area and unique properties, such as very high adsorption potential and heat conductivity. NPs have been used for formation-damage control, enhancing oil recovery, and wettability alteration. In the proppant packs, NPs strengthened the attractive forces and fixed the suspended fines in the porous media. In this experimental study, porous media were soaked with nanofluid for 24 hours and then the suspended fines were passed through porous media to determine the most efficient component. In the next step, a glass-bead-packed column containing uniformly distributed fines in the bed was flooded with distilled water. To investigate the main parameters in this process, the NP concentration and fluid-injection rate were investigated. The zeta potential of the treated models was measured, and the total interaction energy was calculated to verify the results. Finally, scanning-electron-microscope (SEM) images of the surface were obtained for qualitative observation of fines attachment to the pore surfaces.