TPE offers a high effective oxide scavenger that is effective at the pH levels found in most drilling fluids.
Zinc oxide readily reacts with the H2S ion (HS-) and sulphide ions (S2-) to form insoluble zinc bisulphide and zinc sulphide. Consequently, zinc oxide provides a very effective means of combating H2S intrusion and protecting ferrous hardware from hydrogen embrittlement and rig personnel from poisoning.
The reaction is rapid as a consequence of the very high speciﬁc surface area of the product and proceeds over a wide pH range, though the common primary method for mitigating the hazards of H2S is a high drilling ﬂuid pH. (However, high pH simply ensures that H2S remains in its dissociated, soluble forms; that is, HS- and S2-. The hazard presented by H2S is only permanently removed by precipitation as an insoluble salt; in this case, zinc sulphide.)