The effect of waterflooding on the occurrence of alkyl naphthalenes and phenanthrenes in crude oil

Using GC and GC-MS, the occurrence of alkyl naphthalenes and alkyl phenanthrenes in 36 waterflooded oils in the Qu9 reservoir was investigated. Compared with the early waterflooded oils, the later ones feature a loss of aromatics but a gain of saturates. Possibly due to their much lower solubility and stronger resistance to biodegradation, the alkyl naphthalenes with three or more alkyl substituent-related parameters are substantially unaltered in values, the same as the alkyl phenanthrene-related parameters with the advance of waterflooding. The random changes of alkyl naphthalenes with two or less alkyl substituent-related parameters during waterflooding are possibly the mixed results of water washing and biodegradation.