Quantitative Fourier Infrared Spectroscopy Model of a Single CO2 System Under High Temperature and Pressure and Its Application to Natural Inclusions
Fourier transform infrared spectroscopy is a commonly used in-situ non-destructive analysis technique for qualitatively identifying natural fluid inclusion components.The quantitative analysis of temperature-pressure components of natural inclusions is the focus,as well as the difficulty and development direction of laser spectroscopy geological applications.The quantitative method and Fourier transform infrared spectroscopy model for natural fluid inclusions have not been established.The infrared spectra of a single CO2 system with two stretching vibration peaks of 2v2+v3 and v1+v3 were collected and observed at 40～80 ℃ and 60～500 bar for the first time by high-pressure capillary silicon tube packaging technology combined with Fourier infrared spectrometer.The infrared spectral parameters at different temperature and pressure ranges were obtained.The peak area and peak displacement of the Fourier infrared spectrum under this system were obtained by fitting and calculation.The calibration model of the density and peak area,pressure,and peak area of the Fourier infrared spectrum fluid under the 2v2+v3 and v1+v3 stretching vibration bimodal system of CO2 was established.The variation characteristics of bimodal stretching vibration of 2v2+v3 and v1+v3 of CO2 with temperature and pressure are clarified,and the variation of peak displacement with temperature and pressure is discussed.Using Fourier transform infrared spectroscopy(FT-IR)of a single CO2 component,the densities of pure CO2 inclusions in quartz fractures of the Huangliu Formation reservoir in the Yinggehai Basin were calculated at 40 ℃ by collecting the double peak area of stretching vibration of the inclusions.At the same time,the Raman spectra of the inclusions were collected at room temperature,and the densities calculated by two different in-situ analysis methods were compared to verify the feasibility of FT-IR quantitative analysis.Compared with Raman quantitative analysis,Fourier transform infrared spectroscopy quantitative analysis is not limited by experimental instruments and environment.Its quantitative method can avoid errors caused by different laboratories where the instrument is located.
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