【作者】 郑雅梅；

【导师】 高从堦；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2009， 硕士

【摘要】 海上油田聚合物驱油最方便的用水来源应是海水;但直接采用海水配制聚合物溶液,由于海水矿化度很高,导致溶液粘度很低,不能满足聚驱要求。纳滤(NF)膜能够脱除水中的中、低分子量有机物及盐分,并且具有选择性分离二价及高价离子的特性,非常适于去除水中的钙、镁、硫酸根等离子,较石灰软化法、离子交换法等其他软化水工艺具有设备占地省、出水水质稳定等优点。在海上平台有限的空间内,采用纳滤软化海水进行注水配聚具有显著的实用价值。本文基于某海上油田聚合物驱油的粘度要求,对几种纳滤软化海水及驱油聚合物进行了筛选,并在此基础上开展了聚合物与软化海水配伍性、增粘性的研究,为实际软化海水用于聚驱采油的工程应用提供了一定的参考。针对两种编号为PAM-D和PAM-S油田聚驱用聚丙烯酰胺,本文研究了其溶液体系的粘度特性,探讨了聚合物溶液粘度的影响因素,其中包括溶解和使用温度、搅拌和剪切速率、溶液的pH值及矿化度等。结果表明聚丙烯酰胺溶液随着温度升高和剪切速率增大,粘度呈下降趋势。在强酸或强碱环境下,聚丙烯酰胺溶液的粘度衰减剧烈,甚至形成聚合物的橡胶状沉淀,适宜使用的pH范围为4-10。矿化度严重影响聚丙烯酰胺的粘度,矿化度每升高1000mg/L,粘度平均下降幅度达到16.9%;其中又以高价阳离子最为显著,如Al3+和Fe3+在很低浓度下(浓度50mg/L)就会明显地引起聚合物溶液的沉淀。同样,天然海水中浓度较高的Ca2+和Mg2+也会导致聚合物溶液粘度的显著下降,因此用于配聚的海水应予以软化处理,使两种离子的总含量控制在200mg/L以下。在掌握了聚丙烯酰胺粘度的影响因素后,本文开展了软化海水配制聚驱溶液的研究,包括聚合物在软化海水中的溶解实验、粘度实验以及驱替实验,筛选出了适于聚驱的编号为NFI的软化海水及编号为PAM-D的聚丙烯酰胺。实验结果表明经过纳滤处理后的NFI软化海水,钙镁离子显著降低,在油藏高温环境下增粘效果显著,90天内粘度保留率在70%以上。NFI软化海水和PAM-D聚丙烯酰胺进行配聚时,显示出了良好的水溶性和增粘性,岩心驱替实验也验证了该聚合物溶液与岩心的良好配伍性。更多还原

【Abstract】 The most convenient source of water for polymer flooding on offshore oil field is seawater, but it can’t be used directly because the high salinity can make the viscosity of polymer solution lower. Nanofiltration (NF) membrane has distinct advantages in removing divalent ions and multivalent ions such as Ca2+, Mg2+ and SO42-. Comparing with other softening processes, for example lime softening and ion exchange, NF has a bright future in application on the space-limited platform with the advantage of smaller land occupation and stable water quality.Based on the viscosity requirement of polymer solution for the offshore oil field, several kinds of water softened by NF membrane and polymers were studied and compatibility between polymer and softened seawater, viscosity property were studied. This work will provide experimental references for design of polymer flooding engineering on offshore platform using softened water.In this thesis, two types of polymer solutions prepared by polyacrylamide (PAM) numbered as PAM-D and PAM-S were studied. Influencing factors on the apparent viscosity of the PAM solution, including the dissolved and use temperature, stirring rate, shear rate, solution pH and salinity, were discussed. The results showed that the viscosity of PAM solution declined with the increasing temperature and stirring shear; and declined sharply in strong acid or alkali environment, which is suitable for use at the pH range of 4-10. The viscosity was seriously affected by salinity, especially by multivalent cation. For example, low concentration of Al3 + and Fe3 + (at 50mg/L) caused the precipitation of polymer from solution; Ca2 + and Mg2 + which are of high concentrations in seawater also caused the viscosity of polymer solution decreasing significantly, so these two ions in softened seawater for polymer flooding should be controlled below 200mg/L.After mastering the impact factors of polyacrylamide viscosity, the preparation of polymer solution using softened seawater, including dissolution experiments at different softened seawater, viscosity experiments and displacement experiments, were studied, then NFI membrane and PAM-D were chosen. The results showed that there was a significant reduction in Ca2+, Mg2+ and salinity of seawater after nanofiltration softening. The NFI softened water had an obvious viscosity enhancement at the reservoir environment, viscosity retention rate still maintained at 70% after 90 days. The core displacement experiments also showed that the solution of NFI softened water and PAM-D had good compatibility with the core.更多还原