南堡凹陷原油高分辨质谱特征及其地球化学意义

Characterization of Crude Oils from Nanpu Depression by High Resolution Mass Spectrometry and Its Geochemical Significance

南堡凹陷深部油气资源丰富,油气成因研究薄弱.首次采用高分辨质谱(负离子电喷雾离子源(electrospray ionization,简称ESI)傅里叶变换离子回旋共振质谱(Fourier transform ion cyclotron resonance mass spectrometry,简称FT-ICR MS)技术对南堡凹陷原油中杂原子化合物的组成与分布特征及其地球化学意义进行了研究.应用负离子ESI FT-ICR MS检测出9种主要杂原子组合类型,分别为N1、N1O1、N1O2、N1O3、N2、O1、O2、O3和O4类,其中N1、O1和O2类在所有样品中普遍存在且相对丰度较高.经研究发现成熟度对原油中N1、O1类化合物碳数分布、缩合度有明显的控制作用.实验观察到N1类DBE(等效双键数)=12,15的高低分子量同系物相对丰度参数C16-20/C21-50-DBE12-N1和C20-24/C25-50-DBE15-N1、N1类缩合度参数DBE12/DBE9-N1及O1类缩合度参数DBE8-9/DBE4-O1与成熟度指标Ts/Tm、TMNr具有良好的相关性,认为它们可作为该区原油成熟度评价指标,反映烃类演化的热动力学原理.南堡凹陷不同层系原油高分辨质谱特征有明显差异,指示其可应用于母源岩性质识别.综合研究认为,FT-ICR MS在成熟度评价、油气成因与油源识别等方面地球化学意义显著,其在油气地球化学理论研究和油气勘探中具有潜在的应用价值.

Nanpu depression is abundant in deep oil and gas resources,but the origin of the hydrocarbon is still unclear.High resolution mass spectrometry（negative-ion electrospray ionization（ESI）Fourier transform ion cyclotron resonance mass spectrometry（FT-ICR MS））is utilized to carry out the composition and distribution of heteroatom compounds of crude oils from the Nanpu depression and its geochemical significance for the first time.The heteroatoms,N1,N1O1,N1O2,N1O3,N2,O1,O2,O3 and O4class species,were identified by negative-ion ESI FT-ICR MS.And N1,O1,O2 class species are universal in all samples with higher relative abundance.It is found that thermal maturity obviously controls the distribution of carbon numbers and the degree of condensation of N1 and O1class species.It is observed that parameters like C16—20/C21—50-DBE12-N1,C20—24/C25—50-DBE15-N1,DBE12/DBE9-N1 and DBE8—9/DBE4-O1 have a good correlation with Ts/Tm and TMNr.They could be used as indicators of thermal maturity of crude oils in the depression,reflecting the kinetics of thermal evolution of hydrocarbons.Significant difference was found among different layers of oils detected by negative-ion ESI FT-ICR MS,indicating that it can be applied to characterize source rocks.After a comprehensive investigation,we believe that FT-ICR MS technique is applicable in multiple geochemical aspects,such as maturity level estimation and source rock and relevant hydrocarbons determination.FT-ICR MS is significant in both the compositional characterization of the NSO compounds and the application in petroleum exploration.