Encapsulated Fluorescent Tags to Label Drill Cuttings for Improved Depth Correlation: A Field Application

Drill cuttings logging (mud logging) is a technology with great potential to deliver formation evaluation and completion efficiency. However, the conventional mud logging technology determines the cutting sample depth using the lag time of the cutting’s return trip, which results in depth uncertainties of ±20 ft or more. We previously proposed to tag cuttings at the bit face with penetrating, impregnating polymeric NanoTags and to determine the cuttings’ depth using the NanoTag’s downward trip time, which could reduce the depth uncertainties to ±1–2 ft. The first field test to test the first generation of NanoTags was completed in December 2019. In that test, the signals of the NanoTags in the cuttings were detected using pyrolysis gas chromatography mass spectrometry (Py-GC/MS) analysis. The second field test for the development of this technology was performed in 2022 using a new generation of optical NanoTags that encapsulated a rhodamine dye. A detection method was also developed to analyze the optical tag on cuttings semiquantitatively using a fluorescent microscope and ImageJ software. Our results suggest that the depth determined by our tagging technology is accurate and correlates well with the mud logging data; the results also indicated that the optimal gap time between each tag injection should be greater than 10 minutes.