Kerogen type classification method based on FTIR analysis

Abstract

The invention relates to a kerogen type classification method based on FTIR analysis. According to the method, the difference of functional groups reflected by absorption peaks corresponding to different wave numbers of Fourier transform infrared (FTIR) is used; the characteristics of infrared spectrum absorption peaks of functional groups such as aliphatic hydrocarbon, aromatic hydrocarbon and oxygen in kerogen are established; the relative content of the functional groups is determined; the relative content of the functional groups can reflect the relative content of C, H and O in kerogen; therefore, the correlation between the relative content of O / C and H / C and the characteristic spectrum in kerogen infrared spectroscopy (FTIR) is constructed; and the organic matter type of kerogen isanalyzed through a normal form diagram, so as to judge the type of kerogen. The method has characteristics of simpleness, rapidness and low cost, has characteristics of no damage on a sample, less use amount and substantially improved accuracy, and has a significant application value.

Description

technical field [0001] The invention relates to a method for classifying kerogen types based on FTIR analysis, which belongs to the application of FTIR technology in the field of petroleum geology. Background technique [0002] There are generally three-point, four-point and five-point methods for the classification of kerogen types. Among them, Tissot BP et al. (1978) proposed to divide kerogen into three types: I, II, and III, among which type I is called sapropel type, type II is sapropel humic type, and type III is humic type. The four-point method and the five-point method are subdivisions based on the three-point method (Yang Wanli, 1981; Huang Difan et al., 1984). [0003] At present, the commonly used methods to determine the type of kerogen include kerogen microcomponent analysis, organic element analysis, organic carbon and pyrolysis chromatography analysis. The corresponding parameters or graphs are determined by methods such as TI index, paradigm graph (H / C, O / ...

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Problems solved by technology

[0007] In general, the use of pyrolysis experiments to determine the type of organic matter still has the following defects: (1) some relatively high-energy C-O bonds are broken due to uneven heating at the low temperature stage; (2) there are a large number of aromatic hydrocarbons / The C=C bond energy of olefins is greater than the C-O bond, so that the high temperature corresponding to S in the pyrolysis process 3 There is a large difference between the response and the oxygen content of kerogen; (3) Since the C=C bond energy is almost the same as the C-O bond energy, a large area of ​​mixing zone is easy to form during the rapid heating process; (4) The kerogen is The structure and composition are relatively complex. In addition to C, H, and O elements, there are also a certain amount of S, N and other elements, which will affect the analysis results of pyrolysis data

In this method, the wave numbers 2930cm-1 and 2860cm-1 mainly reflect the relative content of the C-H bond of CH2 and CH3, and the wave number is 1630cm -1 Correspondingly is the composition of C=O and C=C bond; Therefore directly by these three Fourier transform infrared (FTIR) bands can't effectively extract C=O relative content from C=O and C=C bond, so finally There is also a large error in getting the VanKrevelen diagram

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