oa Drill-Bit Metamorphism Analysis using Hydrocarbon Gas Geochemistry, A Campos Basin Case Study

This study investigates the impact of drill-bit metamorphism (DBM) on hydrocarbon fluid characterization in well 6-DEV-18P-RJS, Campos Basin, Brazil. DBM, the thermal alteration of drilling fluids and rock cuttings at high temperatures during drilling, can generate artificial gases that confound reservoir fluid analysis. This research analyzes 140 samples from a depth interval of 5,001 m to 5,600 m, focusing on light hydrocarbon (C1-C5) molar composition, stable isotopic ratios (d13C and d2H), and FLEX/FLAIR gas data. Results reveal two significant anomalies at approximately 5,050 m and 5,300 m, marked by positive peaks in ethene, propene, methane, and ethane concentrations, along with d13C enrichment and a corresponding negative d2H peak for methane. FLEX/FLAIR data identifies a heavy fluid between 5,202–5,399 m, predominantly composed of methane (70–75%). This section was drilled using a turbine, amplifying the DBM effect. Correlation of gas parameters, using a plot adapted from Faber et al. (1988) , indicates a large zone of predominantly artificial gases. The study concludes that DBM significantly impacts reservoir fluid characterization, highlighting the importance of using mud gas and isotopic analyses to identify artificial geochemical anomalies and mitigate drilling risks. Identified anomalies are linked to drilling operations, such as turbine drilling.