聚合物驱后油藏内源微生物驱油研究与试验

Laboratory evaluation and field trial of activation indigenous microbial displacements in the reservoirs after polymer flooding

我国大多数陆上主力油田已进入"双高"(高含水、高采出程度)开采阶段。为进一步提高聚合物驱后油藏的石油采收率,本研究发现了一种促进油藏内源微生物生长代谢的高效激活剂,且该激活剂已通过室内产气和物理模拟驱油实验及岩心电镜观察和454(Pyrosequencing)焦磷酸测序方法的评价。结果表明激活剂在高压容器中静置培养60 d后产气增压达到2 MPa,用量0.35 PV,浓度为1.8%(W/W)的激活剂溶液在聚合物驱后的天然岩心上石油采收率可再提高3%,并在电镜观察到岩心内部激活的内源微生物菌体及其代谢产物。现场于2011年12月在萨南南二区东块的1注4采井组开展了试验,监测到4口有效生产井的甲烷和二氧化碳气体δ13C(PDB)含量产生明显变化,与萨南南二区东块对照试验区产油量增幅35.9%,含水稳定在94%,在3年半期间阶段累计增油5 957 t,为同类油藏进一步提高石油采收率提供了一条有效途径。

Most main oilfields in China have already entered a ＂double high＂ development stage（high water cut, high recovery degree）. To further enhance oil recovery in reservoirs after polymer flooding（RAPFs）, an efficient activator formulation for promoting metabolism of endogenous microorganism was studied by aerogenic experiments, physical simulation experiments, electron microscopy scanning and pyrophosphate sequencing. Results show that the activator could activate the endogenous microorganisms in the injected water and make the pressurized gas reach 2 MPa after 60 d static culture of the activator in a high pressure vessel. The oil recovery efficiency of natural core physical simulation flooding can be improved by more than 3.0%（OOIP） in RAPFs when injected 0.35 PV activator with 1.8% mass concentration, and a lot of growth and reproduction of activated endogenous microorganism in the core was observed by electron microscopy scanning. Field trial with 1 injector and 4 producers was carried out in the east of south Ⅱblock of Sa Nan in December 2011. By monitoring four effective production wells, changes of carbon isotope δ^13C（PDB） content of methane and carbon dioxide were –45‰ to –54‰ and 7‰ to 12‰. Compared with east Ⅱof Sa Nan block, the oil amount increased by 35.9%, water cut stabled at 94%. The incremental oil was 5 957 t during the three and a half years, which provides an alternative approach for further improving oil recovery in similar reservoirs.