Automatic Injection of NanoTags for Improved Cutting Depth Correlation
Authors:   Aramco Services Company, Thomas Gawain , Antoniv Marta ,   Aramco Services Company, Zhu S. Sherry ,   Aramco Services Company, Poitzsch Martin ,   Aramco Services Company, Kwak Hyung T. ,   Saudi Aramco
Published: November 2024

Real-time evaluation of drill cuttings in the field is highly desired because direct petrophysical characterization of the formation, when integrated into mud-logging workflows, can effectively support logging and measuring while drilling (LWD and MWD) and geosteering. In unconventional reservoirs and for extended-reach horizontal drilling circumstances, an economically affordable method for formation evaluation can optimize well placement, improve the efficiency and safety of drilling and completion, and ultimately maximize recovery cost effectively. Conventional mud-logging technology determines the cuttings’ depth based on the lag time of the return trip up the annulus. The return trip may be underestimated, however, from overgauge drilling, hole caving, gravitational debris accumulation, etc. Thus, the depth assignment may result in uncertainties of 10 to 20 ft or more, assuming a lag time of 30 minutes. We have demonstrated that injecting polymer nanoparticles (NanoTags) into drilling mud can label cuttings for accurate determination of the cuttings’ depth of origin. The NanoTagging technology uses the downward lag time, estimated via the internal volume of the drillpipes and mud hydraulics, and thus reduces the uncertainties of the cuttings’ depth of origin due to variation in annular volume. We demonstrated the NanoTagging technology in 2019 via a field test when drilling a gas well in a carbonate formation, where the cuttings’ depth variation was reduced to ± 1 ft at a drilling speed of about 1 ft/min. Here we report our design and demonstration of the automatic injection of barcoded NanoTags during the drilling of a gas well located in a carbonate formation in 2022. The automatic processing of the recovered cuttings to extract tags from the cuttings after the field test is also discussed. Our newly designed and in-house constructed air-powered rapid-multiplexing tag injection apparatus consists of high-pressure fluid tanks for tag colloids, air lines for pressuring the tank, needle valves for flow rate control, one-way check valves, and a LabView-based automation software to operate the apparatus. During the drilling of a gas well located in a carbonate formation, we programmed the injection time and flow rate for each tag based on the flow rate of the water-based mud (WBM). We then injected three NanoTags into the mud pumps’ intake line through a small valve on a flange. The apparatus delivered sharp pulses of each tag, which mixed into the mud without any adverse impact on the drilling operations. We have also customized a robotic platform to prepare the field cuttings for analysis. The robotic platform weighed cuttings, added solvent, filtered the cuttings, and vacuum-dried 48 batches of cuttings within 24 hours. This workflow recovered the tags from the field cuttings, and the nanograms of tags recovered from the limestone samples were detected by pyrolysis-GCMS. The customized automation platform significantly reduced the time and manpower that were required to prepare the cuttings for characterization. The automation of the NanoTagging technology has improved the efficiency and accuracy of mud logging cost effectively. The technology will also create new opportunities for logging in conditions where traditional mud logging is not available.