Aqueous drilling fluid comprising CuMgFe-layered triple hydroxide: Rheology, filtration loss, and H₂S scavenging performance

The presence of hydrogen sulfide (H₂S) in oil and gas reservoirs is very problematic during well development stages. The carryover of this extremely toxic gas with the drilling fluid and its subsequent release at the surface could expose working personnel to substantial health and safety risks. Further, H₂S is very corrosive, and its contact with metallic infrastructure could lead to severe corrosion issues and the subsequent failure of these units. To mitigate these safety and operational risks, it is very necessary to incorporate additives with high and effective H₂S scavenging performance into drilling fluid formulations. Herein, we synthesized CuMgFe-layered triple hydroxide (CuMgFe-LTH) and investigated the effects of incorporating this nanomaterial into aqueous drilling fluids on their rheology, filtration loss, and H₂S removal performance. The synthesized CuMgFe-LTH was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), nitrogen adsorption-desorption measurements, and thermogravimetric analysis (TGA). The obtained results indicate that the CuMgFe-LTH is compatible with the typical constituents of the formulated aqueous drilling fluid. More importantly, the addition of this nanomaterial provided an excellent H₂S scavenging performance, as it was able to scavenge about 216.3 and 268.0 mg H₂S/g LTH (corresponding to 2325.2 and 2881.0 mg H₂S/L mud) at breakthrough and saturation, respectively. Furthermore, the incorporation of these CuMgFe-LTH improved the apparent and plastic viscosities, yield point, carrying capacity, and gel strength of the drilling fluid. In addition, the base as well as the LTH-containing drilling fluids exhibited desirable pseudoplastic (i.e., shear thinning) behaviour, and curve-fitting analysis proved that the Herschel-Buckley model best fits the rheological behaviour of these muds. This further indicates that the addition of the LTH provides favourable rheological properties. To the best of our knowledge, none of the published studies on drilling fluids reported in the literature have investigated the utilization of any LTH or even any LDH (layered double hydroxide), highlighting the significance and novelty of the present work.