To confirm oil charge stages in the Bonan Subsag

Bohai Bay Basin

Twenty six samples collected from twenty four wells in Shahejie member 4(Es

4

) were used for fluid inclusion analysis.Based on microscopic identification

micro-beam fluorescence spectra and homogenization temperature testing in combination with sedimentary burial and thermal evolution histories

oil charge stages and their timings were obtained.There mainly developed three types of inclusions in the Es

4

reservoirs including aqueous inclusions

oil inclusions and hydrocarbon brine inclusions.In addition

asphalt inclusion and filling asphalt in cracks and pores were also observed in some samples.Fluorescence colors of oil inclusions mainly are yellow-yellowgreen and blue-white

with a little of orange color.Main peak wavelength (λ

max

) distribution of orange

yellow-yellowgreen and blue-white oil inclusions are 555.76-576.88

513.25-555.76

and 491.13-497.93 nanometers respectively.Red-green entropy Q

650/500

and Q

t 535

of the three colors oil inclusions are 0.21-0.39 and 2.25-2.71

0.43-0.96 and 0.99-2.45

and 0.95-1.17 and 0.60-1.13 respectively.Homogenization temperatures of coeval aqueous inclusions of the three colors oil inclusion are 92.6-112.2

106.4-143.7(mainly 120-140) and 143.2-162.7 degree centigrade.Conclusion could be drawn that reservoirs in the Es

4

had experienced at least three oil charging stages(early

middle and later stages)with different maturity of the oils.By positioning the aqueous inclusions homogenization temperature values on sedimentary burial and thermal evolution history chart

the geological times of the three oil charging stages are obtained which are 30.7-27.7

18-5 and 3.8-0 million years respectively.Current oil and gas found in the Es

4

were mainly accumulated during the second and the third charging stages.