Abstract
Effective coating of nanoparticles on the proppant pack has been regarded as a promising technique for enhancing proppant functions to achieve multiple objectives. In this work, a dynamic soaking technique which we refer as “pseudo-continuous fixed bed (PCFB)” adsorption has been employed for the first time for coating of four bare NPs (Al2O3, SiO2, MgO, ZrO2) with divergent physical and chemical properties, onto a fixed adsorbent glass bead proppant pack. A systematic study of the formulated nanofluid (brine+NPs) adsorption onto the proppant pack was conducted vis-à-vis salinity (0 to 10.5 wt% NaCl), temperature (298.15 to 348.15 K), NPs loading (0.01 to 0.2 wt%), and injection rates (1 to 50 mL.min−1). Nanofluid stability was measured via zeta-potential measurements, where NP adsorption was verified through optical microscopy and atomic force microscopy. Results show that PCFB adsorption of NPs with higher specific surface area resulted in faster adsorption (adsorbed in ~25 mins) with >99% immobilisation of NPs on the proppant pack. Adsorption kinetics showed reasonable conformity with the pseudo-first-order model, where isothermal adsorption followed a Sips model. The adsorption capacity of MgO NPs (specific surface area 50–80 m2.g−1, 7.0 wt% NaCl) at 298.15 K was found to be the highest when compared with silica NPs. Accordingly, this method can be used for onsite treatment of proppants with nanoparticles, which can then be injected into a fractured formation to achieve multiple objectives.
The three stages of proppant pack
(left side – captioned Untreated Glass bead Proppant pack) Glass beads proppant pack 30 g, with similar proppant packing were prepared for the adsorption experiments.
(middle one – captioned nano-treatment adsorption on glass bead proppant pack) explains the experimental set-up, whereby a nano-formulation based in brine is pumped into the proppant pack via a peristaltic pump, which when reach the bottom is again treated until all the nanoparticles have been adsorbed on the proppant pack.
(right side – captioned Nano treated Glass Bead Proppant Pack) The final stage when all the proppant surface has adsorbed nanoparticles via. Mono-layer adsorption mechanism.
Note Optical microscopy results are attached next to the nano-treated and non-treated proppant pack confirming the physisorption of nanoparticles on the proppant pack. [Display omitted]
•A practical, robust adsorption PCFB method is introduced.•Four metal oxide nanoparticles are adsorbed onto glass bead proppant.•Investigated nanoparticle dosage, NFs salinity and injection flow rate.•Validation through AFM, optical microscopy, and zeta-potential measurements.