H₂S scavenging performance and rheological properties of water-based drilling fluids comprising ZIF-67

Exposure to the toxic hydrogen sulfide (H₂S) gas during oilfield operations carries serious health and safety concerns, in addition to significant economic losses resulting from the corrosion and potential failures of the handling equipment. Although there are several H₂S scavengers reported in the literature or commercially available, they have their own limitations in terms of efficacy, toxicity, and/or environmental impact, among others. Thus, we report herein, for the first time, the H₂S scavenging performance of Zeolitic Imidazolate Framework-67 (ZIF-67) nanoparticles (NPs) and its effect on the rheological and fluid loss properties of water-based drilling mud. The synthesized ZIF-67 material was characterized using different characterization techniques. The incorporation of the ZIF-67 NPs into the drilling fluids was found to significantly enhance the H₂S scavenging performance, where the breakthrough and saturation capacities in the presence of 1 wt.% ZIF-67 NPs were more than 2300 and 495%, respectively, higher than those obtained using the base drilling mud. The remarkable H₂S scavenging performance of the ZIF-67 NPs in the drilling fluid can be attributed to their unique structural properties, abundant uncoordinated open metal (Co(II)) sites, high surface area, and the presence of active surface nitrogen functional groups. The fluid loss and rheological properties of the base drilling mud were not compromised by the addition of ZIF-67 NPs. Contrarily, the addition of ZIF-67 improved the plastic viscosity (PV), apparent viscosity (AV), yield point (YP), carrying capacity, and gel strength (GS) of the based mud. To the best of our knowledge, there are no published studies so far on H₂S scavenging using any ZIF material while submerged in a liquid phase or incorporated into a drilling fluid, highlighting the novelty and significance of this work.