H₂S Scavenging Capacity and Rheological Properties of Water-Based Drilling Muds

Abstract

Drilling hydrocarbon formations where hydrogen sulfide (H 2 S) is present could lead to the carryover of H 2 S with the drilling mud (i.e., drilling fluid) to the surface, exposing working personnel to this lethal gas. Additionally, H 2 S is very corrosive, causing severe corrosion of metal parts of the drilling equipment, which in turn results in serious operational problems. The addition of an effective H 2 S scavenger(s) in the drilling mud formulations will overcome these health, safety, and operational issues. In this work, zinc oxide (ZnO), which is a common H 2 S scavenger, has been incorporated into waterbased drilling mud. The H 2 S scavenging performance of this ZnOcontaining drilling mud has been assessed. Additionally, drilling mud formulations containing either copper nitrate (Cu(NO 3 ) 2 •3H 2 O) or potassium permanganate (KMnO 4 ) have been prepared, and their H 2 S scavenging performances have been studied and compared to that of the ZnO-containing drilling mud. It has been observed that the scavenging performance (in terms of the H 2 S amounts scavenged up to the breakthrough time and at the saturation condition) of the ZnO-containing drilling mud is very poor compared to those of the copper nitrate-containing and KMnO 4 -containing drilling muds. For instance, the amounts of H 2 S scavenged up to the breakthrough time by ZnO-containing, copper nitrate-containing, and KMnO 4 -containing drilling muds were 5.5, 15.8, and 125.3 mg/g, respectively. Furthermore, the amounts of H 2 S scavenged at the saturation condition by these drilling muds were, respectively, 35.1, 146.8, and 307.5 mg/g, demonstrating the superiority of the KMnO 4 -containing drilling mud. Besides its attractive H 2 S scavenging performance, the KMnO 4 -containing drilling mud possessed more favorable rheological properties [i.e., plastic viscosity (PV), yield point (YP), carrying capacity of the drill cuttings, and gelling characteristics] relative to the base and the ZnO-containing and copper nitrate-containing drilling muds. The addition of KMnO 4 to the base drilling mud increased its apparent viscosity, PV, and YP by 20, 33, and 10%, respectively. Additionally, all tested drilling muds possessed acceptable fluid loss characteristics. To the best of our knowledge, there are so far no published studies concurrently tackling the H 2 S scavenging (i.e., breakthrough time, breakthrough capacity, saturation time, saturation capacity, and scavenger utilization) and the rheological properties of water-based drilling muds, as demonstrated in the current study, highlighting the novelty of this work.

Optimum Selection of H2S Scavenger in Light-Weight and Heavy-Weight Water-Based Drilling Fluids

“…A similar response was observed in potassium permanganate-containing drilling muds. Onaizi et al observed a similar response that the addition of copper nitrate and potassium permanganate increased the fluid loss as noticed in this study with the light-weight drilling muds, LWM/Cu and LWM/K. For LWM/Cu + K and HWM/Cu + K, no change in the fluid loss volume was observed compared to base drilling muds.…”

“…Therefore, copper-based scavengers are not commonly used in the industry and have been largely replaced with scavengers based on iron or zinc compounds. The detailed scavenging capacity of copper nitrate was discussed in our previous study by Onaizi et al 45 Furthermore, to address the corrosion issue, during the drilling of an H 2 S-containing formation, the drilling fluids are combined with a corrosion inhibitor to protect the metals from the severe effects of H 2 S. These corrosion inhibitors can be useful in mitigating the adverse effects of other acidic compounds produced during the scavenging process.…”

“…This increase in PV is observed in the literature as well. For instance, Onaizi et al 45 investigated that potassium permanganate increased the PV of WBDFs. The addition of copper nitrate and potassium permanganate as a synergist slightly increased the PV of LWM, as shown in LWM/Cu + K. The PV of HWM stayed the same.…”

Investigation of Using Various Quantities of Steelmaking Waste for Scavenging Hydrogen Sulfide in Drilling Fluids

“…In terms of the 5 Geofluids YP/PV ratio that measures solids' carrying capacity and hole cleaning performance [83], the BASE had a value of 1.64, which was improved to 1.72 by SWM1 and 1.66 by SWM2, but lowered by SWM3 to 1.64. All values, however, satisfy the requirement of being higher than 0.75 [12,33,61].…”

“…Hydrogen peroxide is a nonselective reactant that causes an uncontrollable scavenging process, making it inappropriate for use in drilling fluid [3,19,28,29]. Potassium permanganate has a better mud rheological effect, but it is ineffective with heavy mud weight [30][31][32][33][34].…”