干酪根中类脂肪链含量的测定及石油地质意义

选取了红外光谱中2750～3000cm-1C-H振动峰面积作为反映干酪根中脂肪链含量的特征参数,并以完全饱和脂肪链的微晶石蜡为基准,建立了对干酪根中脂肪链含量进行测定的实验方法,同时讨论了实验条件、无机矿物、干酪根样品加入量等因素的影响。并通过对东营地区不同类型干酪根的低熟烃源岩样品进行的高压热模拟实验,研究了干酪根中脂肪链的百分含量与成熟度、沥青转化率及干酪根原素组成之间的关系。结果表明干酪根中脂肪链含量不仅与干酪根的类型有关,而且随成熟作用增加明显降低,其与热模拟生油量的关系和烃源岩的产烃率曲线相似,在脂肪链含量由15%降至5%时出现一个生油高峰。所以,脂肪链百分含量这一参数有可能成为烃源岩的判别及评价的一个新的重要指标。

The Method of Determination of Aliphatic Content in Kerogen by Quantitative FT-IR and Its Petroleum Geology Significance

A new method is developed to determine aliphatic content of kerogen using quantitative Fourier transform infrared spectra. The method uses micritic paraffin as reference standards, which consist of pure aliphatic chains. To discuss the experimental factors that may influence the result, different concentration of kerogen sample and fixed concentration of sample mixing with rock detriments or silicon mineral are analyzed respectively. The results indicate that the mixing minerals and rocks have little influence on the analytical results, in while high concentration of kerogens have much influence and should not exceed 3.5 mg when preparing the sample. So the quantitative method is reproducible, accurate and reliable. The simulating experiment is an important method in studying the evolution of organic matter, while studying natural evolving section is another. So kerogens in simulated samples and natural evolving samples in Dongying Depression are analyzed according to our quantitative method. After comparing the aliphatic contents of kerogens with different organic matter types, maturities and potentials of hydrocarbon, the author conclude that the aliphatic content obtained by FT IR can be a new index for evaluating hydrocarbon source rocks. The aliphatic content is determined by kerogen type under low maturity. The aliphatic contents often are higher than 20% in type Ⅰ kerogens, from 5% to 20% in type Ⅱ kerogens and below 5% in type Ⅲ kerogens, but with the same kerogen type the aliphatic content is determined by maturity. In low maturity the aliphatic content doesn't transform apparently, while in “oil window” the aliphatic content decrease faster and the aliphatic content will be near to naught over the "oil window". The relationship between aliphatic content and hydrocarbon/Toc indicated that the simulating and natural samples followed a slightly different evolving path if comparing the aliphatic content with the chroloform "A".