Research on the structure of oil content in-situ detection probe combining infrared absorption spectroscopy and fluorescence spectroscopy

To achieve in-site detection of petroleum produced fluids (oil water mixture), this study combines infrared absorption spectroscopy with fluorescence spectroscopy to select structural materials and optimize the optical path of the designed oil content in-situ detection probe based on the working conditions of Daqing petroleum production fluid. Particle size analysis of a sample with 20,091 mg/L oil content was performed using a Malvern 3000 laser analyzer to determine the proportional distribution of particle sizes for optical simulation. Optical simulations of the oil content in-site detection probe were performed to determine the aperture size and optimal positioning of the collimating apertures. The incorporation of collimating apertures enhanced the probe resistance to interference from scattered and refracted light, improving detection accuracy by approximately 10% compared to the pre-optimized design. At the same time, for surface fluorescence detection, excitation wavelength and emission spectrum were determined through three-dimensional fluorescence experiments, and fluorescence simulation was carried out in TracePro. The fluorescence focusing lens group was improved for the limited space inside the detection probe, so that the fluorescence was effectively focused on the receiver, retaining about 90% of the effective data of the incident fluorescence. The results of in-situ detection of oil content in produced fluid showed that the random forest model is better than the multiple linear regression model and the partial least squares model in terms of R² (0.72773) and RPD (close to 2.0), especially in the high concentration range of >8000 mg/L. The proposed design scheme provides a feasible approach for developing more accurate, reliable, and potentially cost-effective in-situ sensors for oil fields.