| Summary: | Bentonite suspension in water-based drilling fluid is susceptible to deterioration in high-temperature environments, hence requiring a deflocculant to stabilize the solid particles. Considering the use of highly toxic chrome-based deflocculant in the industry, Rhizophora spp. tannin-lignosulfonate (RTLS) was synthesized in this study as an alternative deflocculant. A viscometer was used to study the rheological properties, and the filtration performance was evaluated using low-pressure low-temperature and high-pressure high-temperature filter press in accordance with the American Petroleum Institute standard procedure. The addition of 0.5 wt% RTLS to water-based drilling fluid (WBDF) was effective in a significant reduction of the plastic viscosity (PV) and yield point (YP) of WBDF at elevated temperatures. As the amount of RTLS added to the suspension exceeds 0.5 wt%, the effect on PV and YP becomes negligible. A higher fluid loss of 13 mL was observed in the WBDF without RTLS aged at 177 °C. The addition of 2.0 wt% RTLS reduced the fluid loss to 10.7 mL. This suggests that RTLS is an effective deflocculant that can be used to improve the filtration properties of WBDF at high temperatures. The morphology of RTLS filter cakes was examined using field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy (FESEM-EDX). The interlayer between clay particles was identified as RTLS, a natural additive that plays a vital role in enhancing filtration while minimizing fluid loss. The outcomes of this research are promising, and this non-toxic deflocculant has the potential to replace chrome-based deflocculants that are still in use for borehole drilling. © The Author(s) 2024.
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