【作者】 马宝东；

【导师】 高宝玉；

【作者基本信息】 山东大学 ， 环境工程， 2014， 博士

【摘要】 油田注水开发中后期大量污水产生,目前胜利油田油井产液量为86.7×104m3/d,综合含水92%,产水量为79.8×104m3/d。从地下采出的油田污水均需再次回注地下油藏用于驱替原油,从而实现污水的循环再利用。从地下采出的污水中含有原油、固体悬浮物、细菌以及大量的无机盐,在油田污水回注过程中主要存在两个方面的问题：一方面由于中低渗透油藏储层物性差、渗透率低、微孔隙发育、渗流阻力大等原因,在油田污水回注过程中普遍存在水井注水压力高、注水量小和水驱采收率低等问题。采用表面活性剂提高油田污水回注率是补充地层能量,提高油井产能的新方法。表面活性剂通过改善油/水界面和岩石/水界面活性,提高油水两相在地层中的渗流能力,降低污水回注压力,增加污水回注量。该研究在减少污水外排,实现污水注采良性循环以及中低渗油藏高效开发等方面具有重要意义。另一方面污水是导致化学驱油体系中聚合物溶液粘度损失的主要原因。在化学驱油过程中,通过投加大量的聚合物增加注入水粘度是提高原油采收率的主要手段。然而,污水中各种复杂的化学组分对聚丙烯酰胺分子的降解作用导致聚合物溶液在配制和注入过程中溶液粘度下降,驱替相的流度控制能力变差,驱油效率降低,进而限制了该项技术在油田的推广应用。本文在大量文献调研和文献分析基础上,从界面力学研究入手,分析油水两相在地层微孔隙中的渗流阻力和渗流特征；通过扫描电镜技术分析聚丙烯酰胺分子链的空间构象,研究聚丙烯酰胺分子降解机理。探索表面活性剂提高污水回注量及其驱油效率的内在机制,为实现油田污水循环再利用和中低渗油藏高效开发提供理论指导。主要研究内容及结果如下：1.采用物理模拟实验技术和核磁共振技术,分析了水驱油过程中的毛管阻力、贾敏效应、岩水界面摩阻和水驱毛管数与表面活性剂物化特性的相关性。研究结果表明,在水驱油过程中,用于提高低渗油藏注水能力的表面活性剂并非界面活性越高越好。在史深100油藏条件下,当活性剂体系将油水界面张力降至4×10-2～2×10-2mmN/m时,注水压力降幅最大达到75%。2.合成并提纯了不同种类阴离子表面活性剂,并分别测定了其主要物化性能,包括表面活性剂的表面张力(γcmc)、临界胶束浓度(cmc)、界面饱和吸附量、pC20、表面压、Gibbs吸附能。研究结果表明：(1)对于单一体的阴离子磺酸盐类表面活性剂,仅石油磺酸盐(SHL-PS、KAQ-PS)、C2024AOS、 C18AESO-3可以在较短时间内使动态界面张力瞬时达到10-3mN·m-1数量级,甚至10-4mN·m-1数量级,平衡界面张力维持在10-2mN·m-1数量级。其它表面活性剂因亲水性较强,因此油水界面张力较高,一般分布在10-1mN/m或更高数量级。(2)在以C2024AOS为主的二元体系中,按协同增效作用从小到大的排列顺序为：C2024AOS/C416AOS<C2024AOS/C16AESO-3<C2024AOS/Dow8390,由此可初步认为：亲水基体积小的阴离子表面活性剂与亲水基体积大的阴离子表面活性剂的协同增效效果相对较好,而两种亲水基体积小的阴离子表面活性剂之间协同增效效果不明显。(3)在以石油磺酸盐为主的二元体系中,在C1416AOS/SHL-PS复配比例为1：19时,产生了较强的协同效应,其动态界面张力始终维持在10-3mN/m；不同EO数C18AESO均可以与SHL-PS发生协同增效效应,将界面张力降低到10-3数量级,三者瞬时最小动态界面张力的大小顺序为C18AESO-3<C18AESO-5<C18AESO-7。鉴于C18AESO与C1416AOS的亲水性大小和分子结构具有显著的不同,推断两个复配体系在降低界面张力的机理上是有所差别的。3.考察了几组阴离子表面活性剂及复配体系的物化性能(γcmc、cmc)与应用性能(界面张力、乳化性能、油膜粘附功、岩石润湿性、洗油率)之间的相关性。研究结果表明：(1)对于不同种类的磺酸盐表面活性剂,总体来看,临界胶束浓度越低,界面张力亦较低,二者大体上呈正相关性。(2)不同表面活性剂水溶液的表面张力与其界面张力间无明显的关联。(3)降低临界胶束浓度,有利于提高乳化性能,但不同系列表面活性剂的临界胶束浓度与乳化指数之间无明确的对应关系。适度增加疏水链长度,有利于提高乳化力；EO数增加,不利于乳化。(4)表面活性剂的表面张力与乳化性能无相关性。(5)不同系列表面活性剂水溶液的表面张力与接触角、粘附功基本上呈正相关性,即在同一亲油固体表面上的接触角随表面张力降低而减小,但分子结构不同,润湿反转的能力不同。(6)表面活性剂的临界胶束浓度与油膜粘附功及润湿性之间无相关性。(7)对于亲油表面而言,界面张力和乳化对洗油率的影响程度不及润湿性。换言之,当润湿性处于中性润湿状态时,驱油效率最高。(8)较低的界面张力、较高的乳化能力和中等润湿状态均有利于提高驱油效率,且三者的贡献具有加合性。(9)不同分子结构的表面活性剂对原油和石蜡的洗脱能力明显不同。脂肪醇聚氧乙烯醚磺酸盐表面活性剂能有效洗出原油中的芳烃类组成,而对石蜡类物质的洗脱能力较低,Dow8390对石蜡的洗脱能力较高。4.采用单因素分析法系统研究了油田污水中的各水质参数对聚合物溶液粘度的影响。采用正交实验分析法研究了各水质参数在降低聚合物溶液粘度过程中的协同作用以及影响聚合物溶液粘度的主要水质参数。研究结果表明：(1)油田污水中含有大量的金属离子,这些金属离子对聚合物溶液粘度具有不同程度的影响,阳离子对聚合物溶液粘度的影响程度由大到小的为Fe2+>Fe3+>Ca2+、Mg2+> Na+、K+。(2)油田污水中的Fe2+、S2等离子具有还原性,这种离子对聚合物溶液粘度的影响远大于其它离子,它们对聚合物溶液的粘度的影响与溶解氧的存在有密切的关系。在密闭条件下,Fe2+、S2对聚合物溶液粘度的影响较大;当的溶解氧一定浓度时,污水中的Fe2+、S2大幅度减少或消失。5.采用红外光谱和扫描电镜分析方法,探讨了污水降低聚合物溶液粘度的机理。研究结果表明：(1)Na+、K+、Ca2+、Mg2+引起聚合物溶液粘度下降的原因是Na+、K+、Ca2+、Mg2+所带的正电荷,具有屏蔽聚丙烯酰胺分子羧酸基上负电荷的能力,从而使聚丙烯酰胺分子发生去水化作用,分子链收缩,导致聚合物溶液粘度降低,其中Ca2+、Mg2+因为具有较多的电荷而且Mg2+、Ca2+易与羧酸基相结合且不易电离,导致聚合物溶液粘度降低程度更大。(2)Fe2+对聚合物溶液粘度的影响由Fe2+的氧化还原反应引起。它在水中与氧发生反应生成氧自由基,同时在水的存在下生成过氧化物,诱发一系列的自由基链反应,从而使聚丙烯酰胺分子链断裂,聚合物溶液的粘度降低。S2-的影响机理与Fe2+相类似。要想保持聚合物水溶液粘度的稳定性,必须改善聚丙烯酰胺分子的空间效应,增加聚丙烯酰胺分子的电荷密度,增强聚丙烯酰胺分子链节的静电斥力,增加聚丙烯酰胺分子的溶剂化作用。以增强聚合物溶液粘度稳定性为主要功能的表面活性剂配方设计可以从这三方面攻关研究。6.针对油田污水对聚合物溶液粘度的影响,研制了三种表面活性剂配方进行水质改性,将污水配制的聚合物溶液粘度从12.5mPa·s提高至30mPa·s以上,实现了油田污水在化学驱油单元的资源化利用。更多还原

【Abstract】 Large amount of wastewater has been produced in middle and later stage of water-flooding oilfield. At present, Shengli oilfield is characterized by fluid production rate86.7×104m3/d, composite water cut92%, and daily water production7.6×104m3. All of oilfield sewage will be reinjected underground reservoir for displacing oil and realizing the resource recycling.There are two main problems in the sewage reinjection process for oilfield sewage containing oil, suspended solids, bacteria and a large amount of inorganic salts. At first, the main characteristics of medium-low permeable reservoir are bad reservoir physical property, low permeability, narrow channel which oil and water pass by, very strong percolation flow resistance force, the notable interaction force between liquid-solid interface and liquid-liquid interface. That results in high water injection pressure, low water injection rate and Enhanced Oil Recovery. Enhancing sewage reinjection rate by surfactant is the new method of supplement the formation energy and improving well productivity. Surfactant can reduce sewage reinjection pressure and increase sewage injection rate by improving the oil-water and rock-water interface activity to improve oil-water percolation capacity in stratum. The study plays an important role in reducing sewage discharge, increasing sewage injection production cycle and oil displacement efficiency of mid-low permeability reservoir.On the other hand, sewage is the major cause of the polymer solution viscosity loss. In chemical flooding processes, increasing the viscosity of injected water is the main means of enhancing oil recovery by adding a lot of polymer. As a result of polyacrylamide molecular degradation for a variety of complex chemical composition in oilfield sewage, the polymer solution viscosity decreased in the preparation and injection process, the mobility control ability weaken, the oil displacement efficiency reduced. That has been hindering application of the chemical flooding technique in oilfield. On the basis of the analysis of a large number of literatures and documents, the seepage resistance and percolation characteristics of oil-water two-phase flow was analyzed starting with the interface mechanics research. The polymer molecular chain conformation was described by the scanning electron microscopy for analysis of degradation mechanism. The internal mechanism was explored to increase injection production and oil displacement efficiency by the surfactant. All these possess the theoretical guidance for oil field sewage reuse and efficient development of the mid-low permeability reservoir. The main research contents and results are as follows:1. Analysis of surfatant’s correlation with the capillary resistance, Jiamin effection, Interfacial friction and water flooding capillary number in the process of water flooding by physical simulation experimental technique and NMR techniques.The research result shows that the better interfacial activity of surfactant is not corresponding to the better water injection capacity in low permeability reservoir. Under Shishen100reservoir conditions, the injection pressure drop maximum up to75%as oil-water interfacial tension4x10-2～2×10"2mN/m.2. Synthesis and purification of different kinds of anionic surfactant, which physicochemical properties including surface tension (ycmc), the critical micelle concentration (cmc), interface adsorption quantity of PC20, surface pressure, Gibbs adsorption energy. We obtained the following relation:(1) As the single sulfonate surfactant, petroleum sulfonate (SHL-PS, KAQ-PS), C2024AOS, C1gAESO-3can rapidly reduce the dynamic interfacial tension to10-3mN/m or10-4mN/m, and equilibrium interfacial tension is maintained at10-2mN/m finally. While the oil-water interfacial tension of other surfactant is at10-1mN/m or higher due to their stronger hydrophilicity.(2) In the binary system mainly of C2024AOS, according to synergistic effect the sequence from small to large were C2024AOS/C1416AOS<C2024AOS/Ci6AESO-3<C2024AOS/Dow8390, which can be considered that anionic surfactants has better synergistic effect between the small hydrophilic group and the big hydrophilic group, but not between the small hydrophilic groups.(3) The binary system mainly of petroleum sulfonate has a strong synergistic effect at C1416AOS/SHL-PS mixed ratio1:19, which dynamic interfacial tension is stably maintained at10-3mN/m. all of different EO number C18AESO has synergistic effect with SHL-PS, which can reduce oil-water interfacial tension to10-3mN/m. The sequence of dynamic interfacial tension from small to large were C18AESO-3<C18AESO-5<C18AESO-7. In view of the significantly different between C18AESO and C1416AOS in hydrophilic group size and molecular structure, it is suggested that two complex systems are different in the mechanism of reducing the oil-water interfacial tension.3. The correlation was investigated between properties (ycmc, cmc) and performance (interfacial tension, emulsion performance, oil film adhesion work, wettability, oil cleaning efficiency) of a few groups of anionic surfactants and compound system. We obtained the following relation:(1) Overall, it is substantially positive correlation between the critical micelle concentration and the oil-water interfacial tension for different types of sulfonate surfactants.(2) There is no apparent association between the surface tension and the oil-water interfacial tension for the different sulfonate surfactants solution.(3) To reduce the critical micelle concentration is beneficial to improving the emulsifying properties, but there is no apparent relationship between CMC and emulsified index for different series of surfactants. To moderately increase alkyl chain length is beneficial to improving the emulsifying capacity. To increase the number of EO is not conducive to the emulsion.(4) There is no correlation between the surface tension and emulsion performance.(5) It is a basically positively correlated among the surface tension, the contact angle and the adhesion work for series of different surfactants solution, i.e. the contact angle decreases as the surface tension reduces on the same hydrophobicity solid surface, but the wettability reversal ability is changing with the molecular structure.(6) There is no correlation among critical micelle concentration, oil membrane adhesion work and wettability.(7) Wettability has greater influence than interfacial tension and emulsification on oil displacement efficiency for lipophilic surface. In other words, with the rock wettability transfered to middle wetting state, the oil displacement efficiency could get up to the highest value.(8) Lower interfacial tension, stronger emulsifying ability and medium wetting surface are beneficial to enhance oil displacement efficiency, which contributions have good additity.(9) With different molecular structure, surfactants have significantly different elution capacities for crude oil and paraffin. Aliphatic alcohol ether sulfonate can wash out the aromatic in the oil, but not waxy substance. Dow8390has high eluting capacity on paraffin. 4. Influence of quality parameters on polymer solution viscosity was investigated by the method of single factor analysis. The method of orthogonal testing was used to study the synergistic effect of water quality parameters on reducing the polymer solution viscosity, and to determine main water parameters for the viscosity of polymer solution. We obtained the following relation:(1) Large amounts of metal ions in oil field sewage have different effects on the polymer solution viscosity. The sequence of cationic from big to small effcting polymer solution viscosity were Fe2+> Fe3+> Ca2+/Mg2+> Na+/K+.(2) Fe2+/S2-possesses reducing property in oilfield sewage and more impact on the polymer solution viscosity than the other ions, that is closely related to dissolved oxygen in oilfield sewage. Under oxygen free conditions, Fe2+/S2-would rapidly reduce the polymer solution viscosity of. As the oxygen reach the best concentration, Fe2+/S2-would significantly decrease or disappear.5. By the method of infrared spectroscopy and scanning electron microscope analysis, the degradation mechanism of the polymer was discussed. We obtained the following relation:(1) Influence of Na+, K+, Ca2+, Mg2+on the polymer solution viscosity should mainly owe to their positive charge, which shield polyacrylamide molecule carboxyl negative charge, then make the polyacrylamide molecule to hydration, molecular chain to contraction, and polymer solution viscosity to reduction, in which Ca2+/Mg2+decreased more polymer solution viscosity because of more charge, firmly bonded to carboxylic acid moiety.(2) Fe2+affects on polymer solution viscosity by redox reaction between Fe2+and oxygen. Fe2+reacts with oxygen and generates oxygen free radicals, at the same time generates of peroxides in water, then induces a series of free radical chain reaction, thus makes the polyacrylamide molecular chain fractured and polymer solution viscosity reduced. The degradation mechanism of S2-is similar to Fe2+.For the stability of the polymer solution viscosity, it is need to improve the spatial effect, the charge density and salvation of polyacrylamide molecular. Surfactant design for viscosity stability can be considered from these three aspects.6. In view of influence of sewage on the polymer solution viscosity, three kinds of surfactants were designed for quality modification, that increased the polymer solution viscosity from12.5mPa·s to above30mPa·s, implemented resource utilization of oilfield sewage in chemical flooding.更多还原