Identifying Gas-Washing and Water-Washing of Oil Reservoirs by Fluorescence and Infrared Spectra of Single Oil Inclusion

Samples in the two oil fields with reported gas-washing and water-washing were collected for fluid inclusion analysis.Micro-fluorescence and Fourier infrared spectra of single oil inclusions were measured to study the different effects of gas-washing and water-washing on oil compositions.The results show that spectral parameter QF_(535)values of the oils altered by gas-washing were expanded toward decreasing and increasing,respectively.The CH_(2)/CH_(3)distribution range ratio does not expand significantly,but the peak values are averaged.And the distribution of H_(2)O/Alkanes has no change.The QF_(535)values of the oils affected by water-washing increased towards the increase direction,and the distribution ranges of both CH_(2)/CH_(3)and H_(2)O/Alkanes increase significantly.The changes of QF_(535)in light oil reservoirs altered by gas-washing and CH_(2)/CH_(3)in heavy oil reservoirs by water-washing are not obvious.Therefore,two spectral parameter distribution trend charts of light and heavy oil reservoirs are summarized to discriminate the gas-washing and water-washing processes.This study is of great practical significance to utilize fluid inclusion analysis to restructure stages and processes of petroleum accumulation.

Study of genetic evolution of oil inclusion and density of surface oil by measurement of fluorescence lifetime of crude oil and oil inclusion

By using fluorescence lifetime image microscope （FLIM） and time-correlated single photon counting （TCSPC） technique, we measured fluorescence lifetime of crude oils with density of 0.9521-0.7606 g/cm3 and multiple petroleum inclusions from Tazhong uplift of Tarim Basin. As indicated by the test results, crude oil density is closely correlated with average fluorescence lifetime following the regression equation Y=-0.0319X＋0.9411, which can thus be used to calculate density of oil inclusions in relation to fluorescence lifetime and density of corresponding surface crude. For type A oil inclusions showing brown-yellow fluorescence from Tazhong 1 well in Tarim Basin, their average fluorescence lifetime was found to be 2.144-2.765 ns, so the density of surface crude corresponding to crude trapping these oil inclusions is 0.852-0.873 g/cm3, indicating that they are matured oil inclusions trapped at earlier stage ofoil formation. For type B oil inclusions with light yellow-white fluorescence, their average fluorescence lifetime was found to be 4.0294.919 ns, so the density of surface crude corresponding to crude trapping these oil inclusions is 0.784-0.812 g/cm3, indicating that they are higher matured oil inclusions trapped at the second stage of oil formation. For type C oil inclusions showing light blue-green fluorescence, their average fluorescence lifetime was found to be 5.0634.168 ns, so the density of surface crude corresponding to crude trapping these oil inclusions is 0.743-0.779 g/cm3, indicating that they are highly-matured light oil inclusions trapped at the third stage of oil formation.