Synergistic effect of nanoparticles and viscoelastic surfactants to improve properties of drilling fluids

The conservation of rheological and filtration properties of drilling fluids is essential during drilling operations. However, high-pressure and high-temperature conditions may affect drilling fluid additives, leading to their degradation and reduced performance during operation. Hence, the main objective of this study is to formulate and evaluate a viscoelastic surfactant (VES) to design water-based drilling nanofluids (DNF). Silica nanomaterials are also incorporated into fluids to improve their main functional characteristics under harsh conditions. The investigation included: ⅰ) synthesis and characterization of VES through zeta potential, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and rheological behavior; ⅱ) the effect of the presence of VES combined with silica nanoparticles on the rheological, filtration, thermal, and structural properties by steady and dynamic shear rheological, filter press, thermal aging assays, and SEM (SEM) assays, respectively; and ⅲ) evaluation of filtration properties at the pore scale through a microfluidic approach. The rheological results showed that water-based muds (WBMs) in the presence of VES exhibited shear-thinning and viscoelastic behavior slightly higher than that of WBMs with xanthan gum (XGD). Furthermore, the filtration and thermal properties of the drilling fluid improved in the presence of VES and silica nanoparticles at 0.1 wt%. Compared to the WBMs based on XGD, the 30-min filtrate volume for DNF was reduced by 75%. Moreover, the Herschel-Bulkley model was employed to represent the rheological behavior of fluids with an R² of approximately 0.99. According to SEM, laminar and spherical microstructures were observed for the WBMs based on VES and XGD, respectively. A uniform distribution of the nanoparticles was observed in the WBMs. The results obtained from microfluidic experiments indicated low dynamic filtration for fluids containing VES and silica nanoparticles. Specifically, the filtrate volume of fluids containing VES and VES with silica nanoparticles at 281 min was 0.35 and 0.04 mL, respectively. The differences in the rheological, filtration, thermal, and structural results were mainly associated with the morphological structure of VES or XGD and surface interactions with other WBMs additives.