Abstract Qudi oilfield had been producing for over twenty years and became waterflooded ten years ago. Samples from nine producing wells drilled recently in the Qudi oilfield were collected during the three recovery stages spanning an eight month interval of waterflooding and were analyzed for changes in their polycyclic aromatic compounds (PACs). The results indicate that most of waterflooded oils are characterized by increased tricyclic, tetracyclic, pentacyclic and triaromatic steroids concentrations. The irregular changes in parameters based on two or fewer alkyl-substituted naphthalenes (MNR, ENR, DBR, DNR-1) implies a different depletion order for the PACs because the abundances of the compounds are controlled by the predominance of water washing and biodegradation over a certain time. The increase in DBTs and DBFs with water washing reflects their strong resistance to biodegradation. Lower aqueous solubility and strong resistance to biodegradation are possibly responsible for the mainly unchanged values of the three or more alkylnaphthalene-related parameters (TNR-1, TDE-1, TDE-3, TBR and TeBR), tricyclic aromatics (MPI-1 and PP-1), tetracyclic aromatics (MCI, MCI2, 2-MC/1-MC, and BaA/(BaA + Chry)), triaromatic steroids parameters (C26-TAS/C28-TAS, C27-TAS/C28-TAS, C28-TAS 20S/(20R + 20S), and TA(I)/TA(I + II)), and heterocyclic aromatic parameters (4-MDBT/DBT, 4-MDBT/1-MDBT, and 4,6-DMDBT/(1,4 + 1,6)-DMDBT), confirming their validity for geochemical interpretation even after extensive water washing. However, pentacyclic aromatic parameters (BeP/Pe, (BeP + BaP)/Pe, BF/Pe, and BF/BeP), which are theoretically expected to be unaffected, change significantly with the advance of the waterflooding process, implying a complex alteration mechanism that needs further investigation.

中文翻译：

---

水驱油中多环芳烃的变化及其对地球化学解释的意义

摘要 曲堤油田已投产二十多年，十年前就已注水。最近在曲堤油田钻探的 9 口生产井的样品是在跨越 8 个月注水间隔的三个恢复阶段收集的，并分析了其多环芳烃化合物 (PAC) 的变化。结果表明，大多数水驱油的特征是三环、四环、五环和三环类固醇浓度增加。基于两个或更少的烷基取代萘（MNR、ENR、DBR、DNR-1）的参数不规则变化意味着 PAC 的不同消耗顺序，因为化合物的丰度受水洗涤和生物降解的优势控制某个时间。DBTs和DBFs随着水洗而增加，反映了它们对生物降解的强大抵抗力。较低的水溶性和较强的抗生物降解性可能是三个或更多烷基萘相关参数（TNR-1、TDE-1、TDE-3、TBR 和 TeBR）、三环芳烃（MPI-1 和PP-1)、四环芳烃（MCI、MCI2、2-MC/1-MC 和 BaA/(BaA + Chry)）、三芳族类固醇参数（C26-TAS/C28-TAS、C27-TAS/C28-TAS、 C28-TAS 20S/(20R + 20S) 和 TA(I)/TA(I + II)) 和杂环芳烃参数（4-MDBT/DBT、4-MDBT/1-MDBT 和 4,6-DMDBT /(1,4 + 1,6)-DMDBT)，即使经过大量水洗，也证实了它们对地球化学解释的有效性。然而，五环芳烃参数（BeP/Pe、(BeP + BaP)/Pe、BF/Pe 和 BF/BeP），