注水开发过程中原油的生物降解与水洗作用

Biodegradation and water washing effects on oil during water flooding

注水开发是提高原油采收率的常用方法。为了探索注水开发过程中原油遭受的次生蚀变作用和组分变化规律,对典型注水开发的济阳坳陷曲堤油田曲9油藏进行了动态跟踪和地球化学对比分析。研究结果表明,随着注水开发过程的推进,原油族组成中饱和烃相对含量呈升高趋势,而芳烃相对含量呈降低趋势,体现出典型的水洗作用效应。Pr/nC_(17)和Ph/nC_(18)比值呈现出先降低后升高,或先升高后降低的复杂变化,推测不仅受到水洗作用或生物降解的影响,还有类似地质色层效应的加入。C158β(H)-补身烷/C168β(H)-升补身烷逐渐升高,指向生物降解抑或水洗作用的蚀变,尚无法区分。三环萜烷/17α(H)-藿烷、C_(27)重排/C_(27)规则甾烷和甾烷/17α(H)-藿烷均呈现明显增高趋势,C_(31)藿烷22R/C_(30)藿烷(C_(31)R/C_(30)H)则呈现幅度较小的降低趋势,均指示生物降解作用的结果。甲基菲指数(MPI1)、二苯并噻吩/菲(DBT/P)、C_(26)三芳甾烷20S/(20S+20R)与C_(26)/C_(28)三芳甾烷(20S)基本保持不变,表明水驱过程中三芳甾烷并不受影响,菲系列和二苯并噻吩系列未表现出显著的水溶性或抗生物降解能力差异。

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,C27-diasterane/C_（27）-sterane,sterane/17α（H）-hopane ratios,and subtle decrease of C_（31）R/C_（30） H ratios,all indicate biodegradation. The MPI1,and DBT/P,C_（28） TAS 20S/（20 S ＋ 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.