Lignosulfonates as Efficient H2S Scavengers and Dispersants for Metal Sulfide Scale

Abstract Hydrogen sulfide (H2S) is a highly toxic and corrosive gas frequently encountered in oil and gas operations. The use of scavengers, especially based on triazines, is widespread at temperatures below 200°F (93°C). Triazines, however, have an optimum working range (pH, temperature), and a reduction in performance is observed at lower temperature and in acidic pH conditions. In addition, triazines pose environmental and operational challenges, including possible presence of free (residual) formaldehyde in the scavenger, formation of amorphous dithiazine as scavenging reaction product and increased risk of calcite scaling due to its tendency to increase pH. The present work therefore explores an alternate scavenger chemistry based on metal complexed lignosulfonate. Additionally, the scavengers were evaluated for their ability to contribute to calcite scaling, as well as the ability of lignosulfonates to disperse metal sulfide scale.