A novel approach for the enhancement of H₂S removal and rheological properties of water-based drilling fluids through the inclusion of layered triple hydroxides

The release of hydrogen sulfide (H₂S) gas during well drilling operations presents considerable health and safety risks. The discharge of this toxic and corrosive gas to the surface not only endangers the well-being of the drilling crew, but also diminishes the mechanical properties of the drilling infrastructure due to corrosion, sulfide stress cracking, and loss of ductility of steel resulting from hydrogen embrittlement, causing substantial economic losses and a reduction in the overall reliability of the drilling operations. This necessitates the implementation of stringent measures to abate these effects by removing H₂S in-situ while drilling using nano-additives with high affinity for H₂S. Interestingly, the high basicity, high anion exchange capacity, low cost, suitable chemical and thermal stability, and high surface area of layered triple hydroxides (LTHs) make them excellent nano-additives for addressing this issue. However, LTHs application in drilling formulation and other oilfield operations is still lacking, to the best of our knowledge. Thus, we report herein, for the first time, the synthesis of MnCoFe-LTH, MnZnFe-LTH, and MnCuFe-LTH and their incorporation into water-based drilling fluids with the aim of enhancing the H₂S-removal performance of the drilling fluids. In addition, the rheological properties and fluid loss volume were investigated for the examined mud samples. The synthesized LTHs proved to be compelling additives that significantly improved the H₂S removal capacity. At saturation, the scavenged H₂S capacities of the base mud increased by 109.2 %, 127.5 %, and 211.8 % for MnCoFe-LTH, MnZnFe-LTH, and MnCuFe-LTH, respectively. Additionally, the incorporation of LTHs succeeded in upholding rheological parameters within the prescribed thresholds. Notably, the LTH-based muds exhibited pseudoplastic behavior akin to that of the base mud. This observation indicates that the introduction of these LTHs into the base mud had no detrimental influence on the fluid flow characteristics. Furthermore, among the various rheological models examined, the Herschel-Bulkley model exhibited the highest degree of congruence with the measured shear rate-shear stress data of the formulations. Despite a marginal increase in filtration loss, it is imperative to emphasize that the incremental filtration loss resulting from the inclusion of LTHs remains well within the recommended range. In essence, the utilization of LTHs in drilling applications confers several advantages, notably in terms of their enhanced capacity for H₂S scavenging, thus highlighting their promising commercial potential for oilfield applications.