(390i) Influence of Nanoadditives on the Thermal and Rheological Properties of Viscoelastic Surfactants Used in Matrix Acidizing

Viscoelastic surfactants (VES) have wide range of applications in the oil and gas industry including removing near well-bore damage. However, tolerance toward high concentration of di- and tri-valent ions and stability at high temperature are still challenging.

Product profiling was carried out based on unheralded sustainable rheology studies at upscale thermal measurements for subsequent selective test with counterions (Mⁿ⁺Cl_n, M=Na, Ca, Mg, Fe), COOH-functionalized carbon nanotubes (CNT) and quaternary amine-modified montmorillonite (MMT)-based organonanoclays in multi-component brine medium, hitherto undisclosed.

Incremental changes were observed in the viscoelastic properties of zero-shear viscosity (η_o) and elastic modulus (G’) by miniature additions of nanoparticles for all the counterions at elevated temperature of 95^oC.

Thermal resilience of composite VES samples within the context of in-situ temperature was studied by conventional thermogravimetric analysis (TGA).Free and bound solvent losses are indicative of declining rheological performance. The CNT-included samples showed the highest thermal endurance with regards to both solvent losses at 220^oC for the divalent ions which makes them most suitable for high-temperature formation applications.    

The (un)modified VES fractions were investigated by proton NMR spectroscopy. A marked chemical-shift band evolved from the NMR data distinguishing the compositions at different temperatures. The low-temperature samples showed strong alkylic character while the high-temperature equivalents depicted susceptible unsaturated bonds responsible for their otherwise improved rheological and thermal performance earlier observed. Routine integration of the proton NMR confirmed relative hydrogen abundance of the COOH-functionalized Carbon Nanotubes (CNT) samples over the quarternary amine-modified Nano Clays (NC) and pristine compositions.   

In the main acid stage of the single coreflooding experiment, the gelled acid and the gelled acid/NC mix indicated wormholes that travelled halfway and a high pressure response which underlines their good diversion potentials at 65^oC as against the regular acid and gelled acid/CNT mix which showed breakthrough response as confirmed by the picturesque CT scan implying they are less effective for diversion at this temperature.