Synthesis Of Standard Hydrocarbon Inclusion Samples And Its Characteristics Characterized By Micro-infrared Spectroscopy

In the sedimentary basins,petroleum-filled fluid inclusions trapped in minerals could provide direct evidence for the migration and accumulation of petroleum in the geologic past,based on the analysis of hydrocarbon inclusions,we can make a study of oil-source correlation,hydrocarbon migration and hydrocarbon accumulation period.Fluorescence analysis is a common method to quickly determine the generations of hydrocarbon inclusions at present,however,many studies have shown that even the same Fluid Inclusion Assemblage may include some hydrocarbon inclusions with different fluorescent colors.Fourier Transform Infrared Microspectrometry?FTIR?is a nondestructive analysis technique that can obtain the structural information of individual hydrocarbon inclusions,it's an effective method to identify and analyze hydrocarbon inclusions.This paper plans to analyze the standard hydrocarbon inclusion samples with known maturity,attempts to develop a method to analyze the thermal maturity of individual hydrocarbon inclusions by FTIR.This paper adopts the GC-MS spectrometer to analyze the composition and content of crude oils with different thermal maturity,based on the synthetic fluid inclusion technology,through the evaporation and crystallization of supersaturated sodium chloride solution under the condition of set temperature and pressure to trap petroleum with different thermal maturity to synthesize typical hydrocarbon inclusions.Using FTIR and Synchrotron Radiation Infrared Microspectrometry?SRIR?to analyze standard samples to obtain infrared spectrum characteristics of typical hydrocarbon inclusions,respectively.Synchrotron light source with high brightness,high strength and adjustable wavelength range,combined with microscopy could greatly improve the signal-to-noise ratio and spatial resolution of infrared microscopic spectrums and obtain infrared spectrums with better quality on the micrometer scale.Using Peakfit software to fit peaks for two kinds of infrared spectrums to calculate the infrared spectrum characteristic parameters such as peak height,peak area and so on.Comparison results show that SRIR is more effective in analyzing hydrocarbon inclusions.Calculating the thermal maturity parameters of petroleum such as C₂₉20S/?20S+20R?,C₂₉??/???+???,T_s/?T_s+T_m?,etc,and analyzing the relationship between FTIR CH_2a/CH_3a peak intensity ratio,?CH₂/?CH₃ peak area ratio and thermal maturity parameters.Experimental results show that C₂₉20S/?20S+20R?,C₂₉??/???+???and T_s/?T_s+T_m?decrease with the increase of FTIR CH_2a/CH_3a peak intensity ratio,?CH₂/?CH₃ peak area ratio,it means that as CH_2a/CH_3a peak intensity ratio,?CH₂/?CH₃ peak area ratio increase,the thermal maturity of hydrocarbon decrease.T_s/?T_s+T_m?decrease with the increase of SRIR CH_2a/CH_3a peak intensity ratio,?CH₂/?CH₃ peak area ratio.C₂₉20S/?20S+20R?,C₂₉??/???+???,T_s/?T_s+T_m?also decrease with the increase of X_inc,X_std and the average carbon numbers of crude oils,as the increase of carbon chain,the thermal maturity of hydrocarbon decrease.Based on the study results,through the relationship between characteristic parameters of infrared spectrum and thermal maturity parameters,we can achieve the quantitative analysis of thermal maturity of hydrocarbon inclusions by FTIR.