All-solid-state sensors used in drilling muds to prevent H2S gas evolution on oil wells

During oil or water drilling, the evolution of gaseous hydrogen sulfide (H2S) may occur. A better solution would be to prevent the evolution of the gas by simultaneously measuring the presence of sulfide ions (S2-) in the drilling mud and the pH, sulfide ions being predominantly under gaseous H2S form when pH is smaller than 7. We proposed then to perform in situ measurements, using a potentiometric technique, to simultaneously record the presence of sulfide and the pH of the mud. In case of a rapid decrease of pH, human action could be done to rapidly increase the pH and to prevent H2S evolution. A new type of all-solid-state reference electrode based on thick films of lithium lanthanum titanium oxide (LLTO) has therefore been developed. This reference electrode is associated with a solid state pH electrode and an ionic selective electrode for the detection of sulfide ions. •New sensors have been proposed for detection of sulfide ions.•Preventing hydrogen sulfide exhaust is possible.•The all solid state sensors can be used in oil drilling rigs.