The modern oil and gas industry, driven by a surging global energy demand, faces the challenge of exploring deeper geological formations. Ensuring the robust performance of drilling fluids under harsh wellbore conditions is paramount, with elevated temperatures and salt contamination recognized as detrimental factors affecting the rheological and filtration loss properties of drilling fluids. We successfully synthesized a polyethyleneimine-grafted graphene oxide nanocomposite (PEI-GO), and its functional groups formation and thermal stability were verified through Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). Our findings demonstrated a significant improvement in the plastic viscosity and yield point of the base drilling fluid with the addition of PEI-GO. The inclusion of 0.3 wt% PEI-GO outperformed the base drilling fluid at 160 °C, improving the yield point/plastic viscosity (YP/PV) value and reducing filtration loss volume by 42% and 67%, respectively. The Herschel-Bulkley model emerged as the superior choice for characterizing rheological behavior. PEI-GO exhibited compatibility with high-salt formations, maintaining satisfactory filtration volumes even when subjected to sodium chloride (NaCl) and calcium chloride (CaCl2) contamination concentrations of up to 20 and 10 wt%, respectively. The remarkable rheological and filtration properties of PEI-GO are attributed to its electrostatic interactions with clay particles through hydrogen and ionic bonding. These interactions lead to pore plugging in the filter cake, effectively preventing water infiltration and reducing filtration loss volume. This study emphasizes the potential of PEI-GO in water-based drilling fluids, particularly in high-temperature and salt-contaminated environments.
Membrane-based technology is an attractive option for the treatment of oily wastewater because of its high oil removal efficiency, small footprint and operational simplicity. However, filtration performance is highly restricted by membrane fouling, especially when treating oil/water emulsion as a result of strong interaction between oil droplets and the hydrophobic property of the membrane. This study explores the fabrication of polyvinylidene fluoride (PVDF)-based membrane via the vapour induced phase separation (VIPS) method while incorporating polyvinyl pyrrolidone (PVP) as a hydrophilic additive to encounter membrane fouling issues and improve membrane filterability. The resulting membranes were characterized and tested for oil/water emulsion filtration to evaluate their hydraulic, rejection and anti-fouling properties. Results show that the changes in membrane morphology and structure from typical macrovoids with finger-like substructure to cellular structure and larger membrane pore size were observed by the prolonged exposure time from 0 to 30 min through the VIPS method. The enhanced clean water permeability is attributed to the addition of PVP-LiCl in the dope solution that enlarges the mean flow pore size from 0.210 ± 0.1 to 7.709 ± 3.5 µm. The best performing membrane was the VIPS membrane with an exposure time of 5 min (M-5), showing oil/water emulsion permeability of 187 Lm-2 h-1 bar-1 and oil rejection of 91.3% as well as an elevation of 84% of clean water permeability compared to pristine PVDF developed using a typical non-solvent induced phase separation (NIPS) method. Despite the relatively high total fouling, M-5 was able to maintain its high permeability by water flushing as a simple operation for membrane fouling control. The performance was achieved thanks to combination of the large mean flow pore size and hydrophilic property from residual PVP in the membarne matrix. Overall, the results demonstrate the potential of the optimum VIPS method in the presence of PVP and LiCl additives for oil/water emulsion treatment.