A Nanocomposite of Halloysite/Surfactant/Wax to Inhibit Surfactant Adsorption onto Reservoir Rock Surfaces for Improved Oil Recovery

Abstract

Surfactant adsorption onto reservoir rock surfaces is a major issue in enhanced oil recovery (EOR) applications, decreasing the economic success of an EOR project. A method to minimize loss of surfactant is to encapsulate the surfactant and deliver it directly to the oil–water interface. This can be done through the use of naturally occurring clay nanotubes known as halloysites, where surfactants can be encapsulated in the lumen of the nanotubes. Halloysite nanotubes are about 1 μm in length with an outer diameter of about 70 nm and a lumen diameter of about 50 nm. These natural clay nanotubes are thermally stable, inexpensive, abundantly available, and environmentally friendly. An interesting aspect of the halloysite is that it has a predominantly negatively charged outer silica surface and a positively charged inner alumina surface. The surfactants are loaded into the halloysite nanotubes (HNTs) and coated with a thin layer of paraffin wax through a vacuum suction and solvent evaporation method. A thin paraffin wax coating/skin over the surfactant-loaded halloysites prevents the premature release of surfactants until they are in contact with oil, which promotes dissolution of the wax, releasing the surfactant. Imbibition experiments are carried out by measuring oil recovered after pushing injection fluids containing the HNTs through a capillary packed tightly with fresh and crude oil-saturated crushed shale cores. At 70 °C, the wax-coated surfactant-loaded halloysites system exhibited 40% oil recovery, compared to just 16% for surfactant alone and 3% for wax-coated halloysite (no surfactant). A much lower oil recovery for the surfactant alone (16%) can be attributed to excessive surfactant adsorption to the fresh core (85% adsorption), making these adsorbed surfactants unavailable to be in contact with the oil for enhancing the recovery. The method of surfactant encapsulation in wax-coated halloysites therefore leads to a targeted, stimulus-responsive delivery system to the oil–water interface in shale reservoirs with the potential to enhance oil recovery.

Nanomaterials in EOR: A Review and Future Perspectives in Unconventional Reservoirs

“…Consequently, these materials are ideal for selective permeability enhancement and emulsion stabilization. Ojo et al used Kaolinite/surfactant/wax nanocomposites to suppress surfactant adsorption on reservoir rocks, achieving a 40% recovery rate at 70 °C . Similarly, Chen et al used carbon nanotubes as surfactant carriers to increase oil recovery, achieving an accumulated tertiary oil recovery rate of 42.7% and 38.1%, respectively.…”

Tubular Clay Nano-Straws in Ordered Mesoporous Particles Create Hierarchical Porosities Leading to Improved CO2 Uptake

“…The length of HNTs is 0.5 to 2 μm, external diameter is 50–80 nm, and lumen diameter ranges from 15 to 30 nm (Figure S2). The lumen of HNTs provides ample volume for the loading and release of guest molecules, enabling applications in drug delivery, corrosion inhibition, surfactant delivery for oil spill remediation, , and oil recovery . Halloysite nanoclays have also been studied as a solid adsorbent for amine modification and CO 2 capture. , In the work by Cai and co-workers, HNTs loaded with PEI was shown to be a stable adsorbent for CO 2 capture with an optimum capacity of about 54.8 mg/g adsorbent at 35 wt % PEI loading, but the CO 2 capture capacity declined above 35 wt % PEI loading, which was attributed to the saturation of the halloysite lumen by PEI, causing restrictions to CO 2 diffusion.…”

Integrating Halloysite Nanostraws in Porous Catalyst Supports to Enhance Molecular Transport

“… 14 , 15 The lumen can be used to load a variety of compounds including drugs and surfactants. 16 − 18 Of key importance is the lumen diameter of 15–30 nm, which is significantly higher than the 2–4 nm pore size of MCM-41. Thus, HNTs when inserted into particles of MCM-41 would allow easier access of molecules that approach the size of the pores of MCM-41.…”

“…Halloysite is a naturally occurring two-layered aluminosilicate similar to kaolinite, but with a hollow tubular structure caused by the lattice mismatch between the two different layers of clay sheets that leads to the curling of sheets into scrolls. The anionic external surface of a HNT is made up of Si–O–Si tetrahedra, while the internal surface of the lumen consists of Al–OH octahedra with a net cationic charge. , The hollow tubular structures of HNTs have a length of 0.5–3 μm, an external diameter of 50–100 nm, lumen diameters varying from 15 to 30 nm, and relatively low surface areas of 22–81 m 2 /g. − The silanol external surface of HNTs allows modification with polymers , and organosilanes and can be used as a support for metal nanoparticles. , The lumen can be used to load a variety of compounds including drugs and surfactants. − Of key importance is the lumen diameter of 15–30 nm, which is significantly higher than the 2–4 nm pore size of MCM-41. Thus, HNTs when inserted into particles of MCM-41 would allow easier access of molecules that approach the size of the pores of MCM-41.…”