Advanced Workflows for H₂S Evaluation Using Wireline Formation Testers

Accurate quantification of hydrogen sulfide (H₂S) and mercury (Hg) in formation fluids is essential for reservoir evaluation, asset viability, and safe facility design. However, measurement of low H₂S concentrations (<10 ppm) remains technically challenging due to its high reactivity, scavenging by metallic surfaces, contamination from drilling fluids, and uncertainty about its origin — whether native to the formation or caused by Drill Bit Metamorphism (DBM). This paper presents the first field-verified evidence of DBM and outlines an optimized workflow using advanced wireline formation testers (FT) to improve H₂S sampling reliability and data integrity.

The workflow addresses four technical challenges: contamination control (<1% OBM/WBM), equipment compatibility (coated sample bottles and inert flowlines), minimizing flow path distance, and DBM identification using downhole temperature-pressure analysis. Real-time monitoring with Downhole Fluid Analyzer (DFA) and integration with SLB’s WBI-DRE digital platform enables faster, data-driven decisions.

Field examples from Asia Pacific and the Gulf of Mexico validate the approach. Elevated H₂S zones aligned with aggressive bit weight confirmed DBM. Comparison of coated and uncoated sample bottle showed H₂S retention differences. Extended DFA-guided clean-up enabled recovery of <5 ppm H₂S.

This workflow enhances confidence in contaminant measurement and distinguishes formation-native from drilling-induced H2S.