Water flooding is one of the most commonly used methods for enhancing oil recovery.About 36 oil samples from 12 waterflooded wells in Quti-9 oil reservoir of Jiyang Depression were investigated for dynamic tracking and geochemical measurements

to characterize their quality alterations and component changing patterns during the water flooding production.The results show increasing saturates and decreasing aromatics in the samples through the progress of water flooding

the typical effect of water washing during water flooding.The Pr/n-C

17

and Ph/n-C

18

ratios change in two different ways:decrease first and increase later or increase first and decrease later

indicating an effect of a strata chromatography adsorption

along with the water washing effect or biodegradation.The increasing C

15

8β(H)-drimane/C

16

8β(H)-homodrimane ratio can equally suggest an alteration by biodegradation or water washing.The obvious increase of tricyclic terpanes/17α(H)-hopane

C

27

-diasterane/C

27

-sterane

sterane/17α(H)-hopane ratios

and subtle decrease of C

31

R/C

30

H ratios

all indicate biodegradation.The MPI

1

and DBT/P

C

28

TAS 20S/(20S+20R) and C

26

-/C

28

TAS(20S) ratios are constant

suggesting triaromatic steroid(TAS) is unaffected by water flooding.And the phenanthrene and dibenzothiophene show no clear signs of difference in solubility or biodegradation during the waterflooding.