Ferrofluids are Fe3O4 based Magnetic Nano Particles (MNPs) and can be coated with a layer to form a super-hydrophobic material which selectively adsorbs oil. These colloidal ferromagnetic nano-particles show remarkable magnetic susceptibility. The ability of ferrorfluids was at display in the Gulf of Mexico and other oil spill clean-up. Excellent on-surface results suggest us to exploit its potential under sub-surface conditions too. The paper puts forward the potential on MNPs in EOR/IOR, proper production scenarios and techniques to inject this magnetically-controlled oil-adsorbing fluid through pad during hydraulic-fracturing operations.
Sodium oleate coated magnetite (Fe3O4) is found to be the best suited MNP constituent for pad fluid. Fe3O4 particles modified with sodium oleate have successfully been able to generate super-hydrophobic surfaces. Their average size ranges from ~5nm to 10nm, thus are capable of getting suspended in pad fluid during injection and passing through the oil bearing zone without plugging the pores during fracturing operation. MNP's motion can be forced and controlled by applying magnetic field which makes MNPs a great asset for improvisation of fracturing techniquesn (Experimentally tested over 100 different oil and heavy crude oil at FERMILAB, Batavia Illinois).
Injecting highly viscous Frackfluid ‘pad’ is amongst the primary part of fracturing job as it is used to initiate/propagate the fracture. Continuous loss of pad to formation will cause fracture propagation and at the final stage pad will be completely lost to the formation. Oleate coated MNP injected along with pad will selectively adsorb oil in the region where pad interacts with oil in formation. Initially applying outward magnetic field will cause solid MNPs to reach farther in formations, leaving behind the injected fluid in nearby formation, to sweep maximum reservoir volume. Second step is to apply an inward field towards the bore hole, which will force the MNPs to trace back into the wellbore along with adsorbed hydrocarbon on their surface. Magnetic field can easily drive these nanoparticles through tight/low permeable reserves and during heavy crude recovery. Their selective adsorption and hydrophobic nature can be of great significance in production through water bearing zones. Prepared MNP is both hydrophobic and lipophilic. Therefore Fe3O4 with sodium oleate could be soundly dispersed in the oil medium present in formations and recovered by applying magnetic field directed toward producing well.
This technique shows a new path for the industry in advanced fracturing operations involving fracturing through deep, heavy oil reserves, HPHT and highly water saturated reserves. Validity of the proposed process has been elucidated in the paper considering various technical and operational variables.