Abstract
Nanofluids are prepared by dispersing silica nanoparticles in aqueous media (brines). The purpose of this work is to address brine/rock interactions in presence of nanoparticles. Our previous studies have shown that silica nanofluids are effective in reducing formation damage in sandstone reservoirs. This study addresses effect of individual ions on dispersed silica nanoparticles’ interaction with Berea Sandstone minerals. The selected ions are Mg2+, SO42− and Na+, in MgCl2, Na2SO4 and NaCl, which are the major constituents of seawater. Three flooding stages for Berea Sandstone cores were followed. The first flooding stage was without nanoparticles, the second one was a slug of the nanoparticles with tracer and the third stage was a post-flushing of the core with the respective ion. The effluent tracer concentration, nanoparticle content, ion concentrations and pH reflect the effect of individual ions on nanoparticle/mineral interaction which were used for suggesting possible interaction mechanisms. Presence of Mg2+ and SO42− ions improved the adsorption of nanoparticles on minerals, however the effect of Na+ was lesser. In general, in all the cases nanoparticles reduced the mineral dissolution and associated fine migration/possible formation damage.
Highlights
The fall in oil prices over the last few years has led to increased focus on developing efficient enhanced oil recovery (EOR) techniques that can make oil production from maturing oil fields economically attractive [1,2,3]
Silica nanoparticles (NPs) dispersed in various fluids have emerged as an attractive option since they have the potential to effective at very low volume concentrations [4] thereby reducing the cost of applying this technology
This study investigated the effect of single salt brines, MgCl2, Na2SO4 and NaCl, as stabilizing fluids which are the major ion constituents of Synthetic seawater (SSW) on silica NP performance
Summary
The fall in oil prices over the last few years has led to increased focus on developing efficient enhanced oil recovery (EOR) techniques that can make oil production from maturing oil fields economically attractive [1,2,3]. Most offshore oil reservoirs are flooded with seawater due to easy availability and low cost. It is well established in the literature that ionic composition of injection brine affects the crude oil brine system [20,21,22]. Khilar and Fogler [25] proposed a limit on brine salinity for injection in sandstones known as critical salt concentration (CSC). They proposed that if the injected salinity below was below CSC, there may be a release of clay particles and this may cause formation damage. Formation damage by lowering injection brine salinity has been reported by other research groups [26,27,28]
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