【作者】 董晶颢；

【导师】 田禹；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2013， 博士

【摘要】 石油的需求量不断攀升而储量不断下降，使得特低渗透油田的开发已成为未来石油工业的主要发展方向。特低渗透油藏由于渗透率低，注水过程极易发生堵塞，对水质要求较高，而现有的采出水处理工艺难以满足这一回注水水质处理要求。本文针对大庆油田开发生产面临的技术问题，研发了高效稳定的特低渗透油田采出水回注处理工艺，并对其处理机理进行了深入研究。针对大庆外围特低渗透油田采出水的水质特性，研发了“破乳-分置式MBR（膜生物反应器）工艺”。对破乳除油处理的影响因素进行探讨，确定了无机盐对特低渗透油田采出水破乳的机理，在此基础上制备了新型破乳絮凝剂，并对运行条件进行了优化。优化了分置式MBR工艺的控制参数，并进行了动力学特性研究，考察了采出水中含有的表面活性剂及絮凝剂对系统运行及膜污染的影响及作用机理。最终对破乳-分置式MBR工艺进行了技术经济分析。具体研究成果如下：无机盐对特低渗透油田采出水乳状液破乳有重要影响。对无机盐破乳过程进行了模拟，确定了无机盐对特低渗透油田采出水乳状液破乳的主要机理为：无机盐电离后与油珠表面电荷以及采出水中的表面活性剂之间相互作用，导致Zeta电位发生变化，当电荷中和起主要作用时，Zeta电位下降，双电层被压缩，乳状液即被破坏。进一步推导出了特低渗透油田采出水乳状液的破乳絮凝动力学方程。制备了以聚硅酸硫酸铝、Ca2+以及微量的聚丙烯酰胺为主要成分的复合型破乳絮凝剂HXN。并对其操作条件进行优化：HXN投药量为4~6mg/L，搅拌强度控制在60~100r/min，搅拌时间为15~25min，沉淀时间35min。通过对大庆特低渗透油田采出水进行现场试验表明：破乳后出水平均含油量为7.8mg/L，SS平均为51.4mg/L，处理效果良好稳定。通过考察含油量、COD以及悬浮固体含量和粒径中值的变化，对系统运行条件进行优化：水力停留时间为6h，污泥停留时间25d，污泥浓度控制在3800~4300mg/L，曝气强度（以DO计）为3mg/L；膜组件的进水压力介于0.07~0.12MPa之间，浓缩液出口压力为0.06~0.08MPa。通过研究MBR工艺处理特低渗透油田采出水的有机物降解和微生物增殖规律，建立了相应的动力学模型。表面活性剂和絮凝剂对分置式MBR工艺处理采出水的效果以及对膜污染有一定的影响。由于特低渗透油田采出水中表面活性剂含量较低，在MBR工艺中对含油量和COD的去除影响不大，而对于膜污染的影响有利有弊，因此在分置式MBR工艺中可不单独对其进行处理。絮凝剂的投加则对于污染物的去除率均有所提高，其主要贡献是对于一些难生物降解的胶体物质和乳化油的去除，从而大大提高了去除效果的稳定性，降低了膜组件的负荷。投加絮凝剂后，污泥絮体粒径有所增大，同时活性污泥混合液中SMP降低，从而减轻膜孔的堵塞，改善膜污染。向生物反应器中投加絮凝剂PAC对污染物去除的改善效果较佳，投药量以20~30mg/L为宜。采用破乳-分置式MBR工艺处理大庆外围特低渗透油田采出水，并进行抗冲击负荷试验，结果表明出水满足特低渗透油田采出水回注指标要求：出水含油量为2.04~4.11mg/L，SS为0.36~0.97mg/L，粒径中值平均为0.7μm，且出水中未检测出硫酸盐还原菌，铁细菌和腐生菌均少于30个/mL。对运行成本进行核算，处理每特低渗透油田采出水成本为5.97元/m3。由此可见破乳-分置式MBR工艺对特低渗透油田采出水的处理是高效经济稳定的。从工艺运行、投资成本、运行成本和管理维护等方面，对大庆油田常规的物化处理工艺和破乳-分置式MBR工艺进行了技术经济比较。总的来说，破乳-分置式MBR在运行成本、出水水质以及抗冲击负荷能力方面要优于物化处理工艺。更多还原

【Abstract】 Petroleum is facing with declining reserves as a result of increasing demand.Extra-low permeability oilfield exploitation has been a primary developingdirection. Because of low porosity and permeability, extra-low permeability oilfieldis prone to form rock stratum locking damage during water flooding. Therefore,higher quality injection water is demanded. The existing produced water disposalprocesses are difficult to meet the standard of extra-low permeability oilfieldreinjection water quality. Based on Daqing Oilfield exploitation correlated technicalproblems, the article aims to develop a highly efficient and stable produced waterdisposal process for extra-low permeability oilfield and investigate thecorresponding mechanism.The demulsification–recirculated MBR (Membrane Bioreactor) process isdeveloped by analyzing the produced water quality of extra-low permeabilityoilfield. The influencing factors of demulsification have been investigated and themain mechanism of demulsification is confirmed. According to the results, newflocculant is developed and its operating conditions are optimized. Operatingcondition parameters of recirculated MBR are obtained and relevant kineticsresearch is carried out. The impacts of surfactant and flocculant on quality ofproduced water and membrane fouling mechanism are investigated. Finally, thispaper conducts the technical and economical analysis on the demulsification–recirculated MBR. The main results are as follows:Inorganic salts are believed to be the principal influence factor ondemulsification. Inorganic salts demulsification process is simulated based onexperimental results and the main mechanism of demulsification is confirmed:inorganic salts interact with oil bead surface charges as well as surfactants inproduced water after ionization, thus Zeta electric potential changes. When chargeneutralization plays a leading role, Zeta electric potential decreases and electricdouble layer is compressed, thus emulsion is destroyed. Moreover, demulsification-flocculation kinetics equation of produced water in extra-low permeability oilfieldis deduced.Flocculant HXN, with the main components of poly-silicate aluminum sulphate (PSAS), Ca2+and a trace of polyacrylamide, has been developed and itsoperating condition has been optimized without regulating temperature or pH value:reagent concentration is4~6mg/L, stirring intensity is60~100r/min, stirring timeis12~25min, settling time is35min. Field test shows good treatment efficiencies:the average oil content is7.8mg/L, average SS is51.4mg/L.Through investigating the variations of oil content, COD and suspended solidcontent and average diameter, the system optimum operating condition is obtained:the hydraulic retention time is6h, sludge retention time is25d, sludgeconcentration is3800~4300mg/L, aeration strength (measured by DO) is3mg/L;feed water pressure of membrane module is about0.07~0.12MPa, outlet pressure ofconcentrated liquid is about0.06~0.08MPa. Furthermore, relevant kinetics equationhas been established by studying the organic matter degradation and biomassaccumulation in recirculated MBR.Surfactant and flocculant have impacts on treatment efficiency of producedwater and membrane fouling in recirculated MBR. With regard to the low surfactantcontent, the removal of oil and COD is influenced slightly while it has both positiveand negative impacts on membrane fouling, thus surfactant can be neglected duringrecirculated MBR process. Flocculant contributes to the removal of COD, oil andsuspended solid. Its principal contribution may be the removal of colloidalsubstance and emulsified oil which are non-biodegradable. This improves thestability of process removal efficiencies greatly and reduces the load of membranemodule simultaneously. After the addition of flocculant, the sludge floc sizeincreases and SMP (soluble microbial products) decreases, which reduce themembrane pore blocking and membrane fouling to some extent. The pollutantsremoval efficiency is increased after the addition of PAC with20~30mg/L in thebioreactor.The extra-low permeability oilfield produced water has been treated bydemulsification–recirculated MBR process and the shock load test has been carriedout. The result shows that effluent water quality meets the produced waterreinjection index of extra-low permeability oilfield: oil content is2.04~4.11mg/L,SS is0.36~0.97mg/L, average particle size is0.7μm, no sulfate-reducing bacteriaare detected, iron bacteria and saprophytic bacteria contents are below30cfu/mL.Operation cost evaluation illuminates that treating produced water will cost 5.97RMB/m3. Thus it can be seen that demulsification–recirculated MBR process isan efficient and economical treatment method for extra-low permeability oilfieldproduced water.Finally, this paper compares the traditional physicochemical process in DaqingOilfield to demulsification–recirculated MBR process on the basis of processoperation, investment cost, operating cost and maintenance both technically andeconomically. In general, demulsification–recirculated MBR process is superior tophysicochemical process on operating cost, removal efficiency and shock loadcapacity.更多还原