Optimize Drilling Decisions Based on Real-Time Detected Alkene and Hydrogen at Surface

The “bit burn” effect occurs when drilling efficiency decreases due to bit wearing, and therefore frictional effects increase. The increase of these frictional effects generates high temperatures, and unsaturated hydrocarbons and hydrogen start to be generated due to thermal cracking. Integrated analysis of alkenes (ethylene and propylene) and hydrogen artificially generated downhole with drilling parameters and saturated hydrocarbon data would refine the analysis for real-time monitoring of bit condition and, hence, drilling efficiency. Optimized extraction techniques are used to obtain a steady flow at constant volume and temperature of gas from the flowline. The concentration of these artificially generated gases is measured in real time, as well as naturally occurring saturated hydrocarbons, using three different chromatographs, two of them having optimized adapted columns that allow the separation of the different gasses. This is especially critical in the case of ethylene and propylene and their respective saturated counterparts. Finally, dedicated software allows integration with drilling parameters to determine any decrease in drilling efficiency. Real-time advanced gas detection (alkenes and hydrogen) was used while drilling. Integrated real-time advanced gas readings (alkenes and hydrogen) have been compared to the standard gas chromatography composition (methane through pentane) measured at the same time. The correlation between the trends from the two techniques was clearly identified. Data interpretation demonstrated evidence that hydrogen and unsaturated hydrocarbons presented across some drilling sections are not naturally occurring but a product of bit metamorphism in the presence of oil-based mud (OBM); in the case of water-based mud (WBM), another approach is under research and is not covered in this article. The origin of this cracked gas throughout the reservoir section has been confirmed by bit grading at surface, with high bit wear confirmed. This kind of analysis can provide an enhanced tool to estimate bit wear and optimize drilling costs in real time and avoid potentially substantial nonproductive time (NPT) that can arise from prolonged drilling with a worn bit. The method is low risk and cost effective, as it is not necessary to use any downhole tools, and all data can be provided by equipment already present in advanced mud-logging units.