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Highlights • We realized a quartz-enhanced photoacoustic (QEPAS) sensor for methane, ethane and propane detection using a single intercascade laser source. • We achieved for ethane a QEPAS record sensitivity of 7 ppb in 1-second integration time. • Detection of propane with QEPAS technique is reported for the first time. • We demonstrated methane, ethane and propane detection at atmospheric pressure avoiding the use of pump and pressure controller systems. Abstract Hydrocarbon detection in the gas phase represents a powerful tool to guide oil exploration and production operations for the oil & gas industry. This application requires highly sensitive, selective and robust spectroscopic techniques. In this work, a quartz-enhanced photoacoustic sensor system designed to detect methane (C1), ethane (C2) and propane (C3), employing a single interband cascade laser emitting in the spectral range 3.342–3.349 μm, is reported. Detection levels in the part-per billion concentration range for C1 and C2 and a few parts per million for C3 were achieved. Measurements at both low and atmospheric pressures were carried out for mixtures simulating typical downhole hydrocarbon concentrations. [ABSTRACT FROM AUTHOR]

• Quartz-Enhanced Photoacoustics for sensitive and selective hydrocarbon detection. • Shoe box sized (sizes 30 cm × 10 cm × 20 cm) QEPAS sensors deployable for real-time and in-situ gas analysis. • Methane, ethane minimum detection limit of 90 ppb and 7 ppb at 1 sec of integration time, respectively. • Propane detected down to 3 ppm at 1 sec of integration time. • 13CH4 and 12CH4 isotopes detected with a 13δ <10‰ at 0.1 sec of integration time. Quartz-enhanced photoacoustic spectroscopy represents a valuable candidate for natural gas analysis in the oil & gas field. The core element of this spectroscopy technique is a quartz tuning forks, employed as high quality-factor optoacoustic transducers, capable of operating in a wide range of temperatures and pressures. The robustness and compactness of these sensors, together with the possibility to avoid the use of optical detectors, open the way to the development of a new generation of small-sized gas spectrometers to be potentially employed downhole for source rock characterization and estimation of oil & gas properties. We report here on the realization of a shoe-box sized quartz-enhanced photoacoustic spectroscopy system capable of: i) selective detection of methane and ethane in the parts-per-billion range, and propane in the parts-per-million range, by employing a single interband cascade laser emitting at 3.345 µm; ii) selective detection of 12CH 4 and 13CH 4 isotopes at the parts-per-billion sensitivity level by employing a quantum cascade laser operating around 7.73 µm. [ABSTRACT FROM AUTHOR]