A Testing Technique For Single Hydrocarbon Inclusions And Its Applications

A review, including in micro-fluorescence, micro-Raman spectroscopy, micro-Fourier transformation infrared spectroscopy, synchrotron radiation X-ray fluorescence microprobe, particle induced X-ray emissions and laser ablation inductively coupled plasma mass spectrometry, was presented about the testing techniques for single inclusions in recent years. Based on above techniques, an experimental setup lied on common inverted fluorescence microscope for measuring UV-VIS spectra of single hydrocarbon inclusions was brought up. This setup includes in an inverted fluorescence microscope(IFM), a reflective objective(RO), a micro-lens(ML), a fiber cable, a UV-VIS spectrometer and a computer. All the elements were integrated into a whole system by a fiber base plate and a RO-ML-fiber adaptor. It is easily to make the RO and the objective of the IFM con-focus by a 3D displacement stage with a 2μm space resolution. The minimum diameter of the focal point is 12um. By using this setup one can localize a single hydrocarbon inclusion in the middle of the vision field of the IFM and take photo for it, excite it using external light source or internal mercury lamp of the IFM, measure and analyze the UV-VIS spectrum or calculate the chromaticity coordinates.After the setup was successfully established, the sandstones from 5 oil wells localized middle-shallow layers in the south and west of Songliao Basin were under studied. The sandstone thin sections were observed under polarized light/fluorescence microscope. The GOI(grains containing oil inclusions), homogeneous temperature and salinity of the inclusions were measured. The above experiment results show that there were two times hydrocarbon accumulation for the strata of the 5 oil wells (Bai 95, Hua 5, Jian 22, Nong 29 and Fu 4). After above experiments, the UV-VIS spectra of 38 typical hydrocarbon inclusions of secondary charge(excited by the external light source or internal mercury lamp of the IFM) from 5 oil wells were measured. The results showed that the spectra excited by the internal mercury lamp were influenced by the fluorescence of the cement and the silicon grains. So the spectra cann't reflect the real information of the palio-oils in the inclusions. When the size of the focal point of the external light source is larger than that of the inclusion, one has to take into account the "background" fluorescence coming from the silicon grain. For the spectra excited by 250nm external light source, by comparison the spectra of the hydrocarbon inclusions with the standard aromatic hydrocarbons, one can quantitative determine the main aromatic hydrocarbons in the inclusions. The palio-oils in the inclusions are mainly middle weight aromatic hydrocarbon, for example, dicyclic, tricyclic, tetracyclic or dicyclic, tricyclic, tetracyclic and petracyclic aromatic hydrocarbons. They all contained some weight aromatic hydrocarbons and nonhydrocarbons. Further more, the maturities of the palio-oils and the source rocks can be quantitative obtained. And for the spectra excited by 365nm external light source, we defined an index S390-455/S455-680, which reflects the maturity of the oil. A relationship between S390-455/S455-680 and Rc calculated by GC-MS experiment was established.Except for the spectra of single hydrocarbon inclusions, we also measured the UV-VIS spectra of 29 crude oils from these 5 oil wells. For the spectra excited by 250nm light, by comparison the spectra of the crude oils with the standard aromatic hydrocarbons, one can quantitative determine the main aromatic hydrocarbons in the crude oils. The aromatic hydrocarbons in the crude oils are mainly dicyclic and tricyclic aromatics. There are some tetracyclic aromatics in the crude oils. The crude oils of the Nong 29 well are special. There are some weight aromatic hydrocarbons. The weight aromatics and nonhydrocarbons in the crude oils are far less than that in the palio-oils of the hydrocarbon inclusions. And by the peak positions and the HWFHs (half width of full height) of the spectra, one can quantitative determine the maturities of the crude oils. And by Qi index, the oil-water interface was obtained. But the Qi index was limited. For the samples contained more weight hydrocarbons or more single circle aromatic hydrocarbon, it will lose effect. And for the spectra excited by 365nm light, a relationship between S390-455/S455-680 and Rc calculated by GC-MS experiment was also established.By Colourometry principle, the chromaticity coordinates of the hydrocarbon inclusions, excited by 365nm of the external light source and the violet light of the internal mercury lamp of the IFM, and the crudes oils were calculated. The results showed that:(1) All the chromaticity coordinates of the crude oil are less than the ones of the single inclusions, this indicates that the maturities of the crude oils are higher than the palio-oils in the inclusions; (2) All the chromaticity coordinates of the single hydrocarbon inclusions excited by the external light source are less than that of the ones by internal mercury lamp, which shows the former wasn't influenced by the fluorescence from the cement and the silicon grains. The chromaticity coordinates of the single hydrocarbon inclusions excited by the external light source reflect the real colors of the inclusions; (3) The UV-VIS spectra show that the hydrocarbons contained in the solid-liquid or pure liquid inclusions are more weight than that in the gas-liquid inclusions; (4) The wider chromaticity coordinates ranges of the single hydrocarbon inclusions from same strata reflect the secondary oil charge may come from two maternal sources with different maturities.The prominent feature of this setup is not necessary make any rebuilt to the microscope. By combining the microscope and the RO, the setup can be used as an expensive UV microscope in measuring the UV-VIS spectra of single hydrocarbon inclusions. The total cost was greatly lowered. It is promising to measure the UV-VIS spectra of micro-size samples. Because the inverted microscope was assumed, it can also be used to measure UV-VIS spectra of bio-samples, such as cells or bio-inclusions.