Toward sustainable drilling: application of Algerian Malva sylvestris and Plantago ovata in biopolymer-based fluids

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This study investigates the valorization of two locally available Algerian plant biomasses, Malva sylvestris and Plantago ovata, as sustainable and eco-friendly biopolymer additives for water-based drilling fluids. Their effects on key rheological and filtration properties, including apparent viscosity, yield point, gel strength, and fluid loss control were comparatively evaluated at concentrations of 2, 4 and 6.6 g per 330 mL of base fluid. Fourier Transform infrared spectroscopy analysis confirmed the presence of polysaccharide-related functional groups, while Scanning Electron Microscopy observations revealed distinct microstructures, with M. sylvestris exhibiting fibrous cellulose-like morphologies and P. ovata showing porous textures favorable for water retention and gel formation. Rheological measurements indicated that all formulations displayed pseudo-plastic shear-thinning behavior, with apparent viscosity decreasing from above 2000 mPa.s. at low shear rates to below 200 mPa.s. at high shear rates. At the highest concentration, M. sylvestris achieved higher shear stress (85 Pa) and gel strength (9.6 Pa), while P. ovata reached 70 Pa. Both additives reduced API fluid loss to 9.5 mL, with M. sylvestris providing improved pH stability (11.5) and more consistent pressure control. Overall, the results highlight the potential of these renewable, locally sourced biomaterials as sustainable alternatives to synthetic drilling fluid additives contributing to cost effective and environmentally friendly drilling operations.