Rapid Analysis of Logging Wellhead Gases Based on Fourier Transform Infrared Spectroscopy

Gas logging provides essential compositional data on the gas within the mud (wellhead gas) during drilling operations, enabling the discovery and evaluation of hydrocarbon resources. However, the long analysis period for wellhead gas leads to lagging results and tends to miss thin oil and gas layers. Therefore, Fourier transform infrared (FT-IR) spectroscopy was used in this paper to rapidly analyze seven light alkanes (methane, ethane, propane, n-butane, i-butane, n-pentane, and i-pentane) in wellhead gases. Spectral analysis involves denoising, baseline correction, feature selection, and partial least squares (PLS) modeling to obtain the concentrations of the wellhead gas components. Finally, the efficiency of this method was validated on actual offshore rigs. It is shown that FT-IR has an analysis period of 15 s, is fast enough to recognize thin oil layers, can work at the wellhead, and is easy to operate and equip. This work improves the real-time performance of well logging and provides an application of FT-IR spectroscopy in actual oil and gas exploration sites.