致密油藏纳米微乳液性能评价与驱油机理分析

自发渗吸为致密油藏提高采收率的主要方式,但常规驱油所用的表面活性剂易被岩石吸附,吸附损失较大,在苛刻油藏中不能满足强化采油的使用要求,提高自发渗吸采收率效果不明显。以环辛烷、脂肪醇聚氧乙烯醚类乳化剂、乙二醇、三乙醇胺为原料,制得以有机相为内相、表面活性剂为壳膜的纳米微乳液。通过界面张力及润湿反转实验揭示了其驱油机理,通过自发渗吸实验验证了提高采收率效果。结果表明,0.3%的纳米微乳液体系粒径尺寸约为10 nm,油水界面张力为3.56 m N/m,可将油湿石英片表面的润湿性（130.6°）反转为水湿表面（11.7°）,具有良好的润湿反转能力。岩心在该乳液中的最终自发渗吸采收率为43.2%,约为水的2.4倍,自发渗吸提高采收率效果显著。     

阳离子型Gemini润湿反转剂提高砂岩岩心原油采收率

本文研究了阳离子Gemini型表面活性剂(GS12-2-12)对砂岩岩心原油采收率的影响。结果表明:GS12-2-12在岩石表面能够产生动态吸附,动态吸附量为0.3 0.7 mg/g。在润湿反转剂驱替后,亲水/亲油岩心表面都呈现向中间润湿状态转变的规律,接触角最大变化有50°。在此过程中,原油与岩心表面的黏附功有下降趋势,此趋势有助于减弱"贾敏"效应,降低油水运动阻力,驱油效率提高5%。在用可视化光刻蚀微观驱油模型研究润湿反转剂驱油过程中观察到了明显的油膜剥离现象,发现这种剥离式驱替方式启动了水驱难以启动的残余油。     

声波振动与岩石表面润湿性

通过水与岩石表面接触角的测定、声被驱油实验和理论分析,研究考察了声波振动对原油─岩石、水─岩石界面特性的影响,从界面化学角度对岩石表面的润湿性和声波驱油机理进行了探索。结果表明:经原油浸泡后,由于原油中极性化合物(胶质、沥青质等)在岩石表面的吸附,岩石表面由水相润湿为主转变为油相润湿为主;无论岩石表面以水相润湿为主还是油相润湿为主,在水浸泡过程中,声波振动可促进其表面亲油性减弱和亲水性增强,毛细管阻力降低;伴随着岩石表面润湿性的改变,原油对岩石表面的粘附功明显降低;减弱了原油与岩石表面间的粘滞力,使原油更易于从岩石表面上剥离,提高原油采收率;岩石的渗透率越低,声波振动作用越显着。     

自发乳化驱油方法Ⅱ:自发乳化驱油试验研究

研究了模拟油在岩心中的自发乳化驱油效果及提高采收率机理。不同渗透率岩心中,自发乳化驱油效果好于表面活性剂驱及聚合物驱。碱聚合物自发乳化驱替后采收率在水驱基础上还可提高23.7%,远远高于单独碱自发乳化驱、聚合物驱和表面活性剂驱,说明这一自发乳化驱油体系具有良好的驱替能力,能够大幅度提高采收率。模拟油在岩心中的自发乳化驱采收率和总采收率分别为24.5%和71.8%,与超低界面张力聚合物表面活性剂驱相近。高于三元复合驱、高浓聚合物驱。微观驱油试验证实光刻模型中发生了自发乳化现象。残余油自发乳化成小油滴,很容易穿过孔喉,以水包油型乳化状态开采出来。     

液固表面的润湿热和吸附热

为了深入了解润湿热和吸附热的意义,从概念和相互关系方面进行了探讨,分析了它们在采油中的作用和应用,并进行了渗吸驱油试验。理论分析和试验结果表明:润湿与吸附关系密切,在采油中起着举足轻重的作用;油在岩石表面的润湿热越大,越不容易被驱走;驱油剂溶液在岩石表面的润湿热越大,越有利于自发渗吸,有利于提高洗油效率;驱油剂在岩石表面的吸附热越大,吸附能力越强,越有利于改变岩石表面的性质。     

聚氧乙烯脂肪胺乳状液性能——不同pH值清洗条件下对硅酸盐岩储集层润湿性、渗透性的影响

通过室内岩心驱替实验、接触角测量、红外光谱分析研究了不同p H值清洗条件下聚氧乙烯脂肪胺乳状液对硅酸盐岩润湿性、渗透性的影响规律及聚氧乙烯脂肪胺在硅酸盐岩表面的吸附行为,提出了关于可逆逆乳化钻井液储集层损害特性和机理的新认识,以及可改进完井、固井效果的井眼清洗方法。研究表明:p H值为4~8的清洗条件下,聚氧乙烯脂肪胺在硅酸盐岩表面发生吸附,使岩石表面由水润湿状态转变为油润湿状态,严重损害储集层渗透性;p H值为10的清洗条件下,聚氧乙烯脂肪胺发生脱附,使储集层岩石表面恢复为水润湿状态,有利于减轻钻井液对储集层渗透性的损害。建议采用"先酸后碱"的井眼清洗方法,或者在酸清洗液中加入润湿反转剂。图2表2参21     

2清洁压裂液返排液驱油体系性能评价及矿场应用

为实现清洁压裂液返排液体系的重复利用,针对一类新型纳米复合清洁压裂液体系展开室内研究,评价了返排液作为驱油体系的界面活性、润湿性、乳化性能以及吸附性能.在此基础上,对驱油体系提高低渗透油藏岩心水驱后的采收率进行了研究.结果表明:在驱油体系质量分数为0.08％,温度为60℃的条件下,与脱气原油之间的界面张力即可达到10-3mN/m数量级,可以使稠油黏度降低率达到95％以上,并具有良好的乳化性能;驱油体系能够使亲水岩石表面转变为中性润湿;驱油体系中的表面活性剂在岩心中的最终滞留量为2.8 mg/g,而纳米颗粒的滞留量为8.8mg/g.岩心模拟驱油实验结果说明,驱油体系可以使饱和脱气原油低渗岩心水驱后的采收率平均提高17.26％,取得了良好的驱油效果.矿场试验结果表明,增油效果显著.     

化学驱实用数学模型及其应用

为了使数值模拟能更加准确地描述化学驱油的复杂机理,根据近年来化学驱油理论研究的新认识,建立了描述化学驱油过程的数学模型。模型是一个三维多组分化学驱模拟器,具有单一相对分子质量聚合物驱、多种相对分子质量聚合物驱和表面活性剂一聚合物-碱复合驱模拟功能。该模型除具备商业化模型已有的流度控制和毛管驱替机理描述功能外,还新增了如下模拟功能:提高微观驱油效率的聚合物弹性描述、多种相对分子质量聚合物的混合驱油过程描述、低表面活性剂浓度化学复合驱过程的化学剂复合协同效应的表征,聚合物弹性和毛管数对相对渗透率的影响以及化学驱油过程所发生的对流、弥散、扩散和吸附等一系列物理化学现象的描述。该模型已在大庆油田化学驱油科研和生产实践中成功应用。     

清洁压裂液返排液驱油体系性能评价及矿场应用

为实现清洁压裂液返排液体系的重复利用,针对一类新型纳米复合清洁压裂液体系展开室内研究,评价了返排液作为驱油体系的界面活性、润湿性、乳化性能以及吸附性能。在此基础上,对驱油体系提高低渗透油藏岩心水驱后的采收率进行了研究。结果表明:在驱油体系质量分数为0.08%,温度为60℃的条件下,与脱气原油之间的界面张力即可达到10-3m N/m数量级,可以使稠油黏度降低率达到95%以上,并具有良好的乳化性能;驱油体系能够使亲水岩石表面转变为中性润湿;驱油体系中的表面活性剂在岩心中的最终滞留量为2.8 mg/g,而纳米颗粒的滞留量为8.8mg/g。岩心模拟驱油实验结果说明,驱油体系可以使饱和脱气原油低渗岩心水驱后的采收率平均提高17.26%,取得了良好的驱油效果。矿场试验结果表明,增油效果显著。     

提高乳化酸稳定性纳米颗粒材料的室内研究

乳化酸的稳定性对其运用效果具很重要作用,将纳米颗粒材料引入到乳化酸中从而提高其乳化稳定
性。室内合成了疏水性较强的纳米颗粒材料,其平均粒度为１０６．４ｎｍ,表面水润湿接触角可达１２０°以上。表面疏
水性的纳米颗粒材料可以与乳化酸的表面活性剂形成协同效应,对乳化酸稳定性大幅度提高;乳化酸中添加１．０％
纳米颗粒材料后,缓蚀效果比常规乳化酸提高了２３．７％。并联模拟岩心驱替实验表明,含有纳米颗粒材料的乳化
酸选择性酸化过程中绝大多数进入油润湿的模拟岩心中,对油润湿模拟岩心改造的渗透率增加幅度为１．７７倍,对
水润湿的模拟岩心增加幅度为０．６２倍。     

聚合物驱与多元驱替微观实验对比与机理研究

利用非均质微观刻蚀可视化玻璃模型,模拟油层不同驱替剂(聚合物P体系、表面活性剂-聚合物SP体系,以及碱-表面活性剂-聚合物ASP体系)的驱油效果,观察不同注入体系引起的油层油滴的变化及运移、再分布动态,研究不同注入体系对剩余油分布的影响,进一步根据剩余油分布及微观模型基本参数得到地层油采出程度和采收率,P驱、SP二元驱及ASP三元驱微观驱替的采收率分别为43%、59%和92%。聚合物的调剖作用、表面活性剂的乳化降黏作用、碱引起的超低界面张力、润湿反转及形成油膜等现象均在实验过程中得到验证并详细解释和分析。综合对比分析实验结果认为,碱/表面活性剂/聚合物ASP三元驱替仍将是化学驱提高采收率的重要措施。     

大庆油田三元复合驱中岩石润湿性的变化

通过室内模拟实验,研究了在三元复合驱中大庆油田岩石润湿性的变化规律,分析了润湿性的变化机理。结果表明,三元复合驱后,岩石润湿性发生变化,总的趋势是岩石润湿性向亲水方向转化,其转化幅度与三元复合体系中化学剂浓度有关。三元复合驱中岩石润 性的变化主要是因为化学剂与地层中二价阳离子、岩石矿物相互作用,改变岩石的表面性 及碱对吸附在岩石表面的刚性油膜的溶解,使各相之间的界面张力发生变化。     

Numerical Simulation of Surfactant Flooding in Darcy Scale Flow

One of the methods that is used nowadays in enhanced oil recovery is surfactant flooding. The main mechanisms of surfactant flooding in reservoir consist of reduction of interfacial tension between water and oil and modification of rock wettability. In this study, the authors simulate the surfactant injection process in Darcy scale and in one-dimensional, multicomponent, multiphase state, and effects of physical phenomena such as adsorption, dispersion, convection, and exchange between fluids and solids are considered. Wettability alteration of reservoir rock due to presence of surfactant in injected fluid is detected in relative permeability and capillary pressure curves. First, the authors express the governing flow equations in the system and then discretize them. The variables consist of water and oil saturations, surfactant concentration in water phase, water and oil pressures, and velocities in each block. Second, the discretized equations are solved by IMPES method and pressure and saturation variables are calculated and after that, the concentration of surfactant in water phase is calculated. Finally, results of simulation are shown.     

A New Type of Surfactant for Enhanced Oil Recovery

abstract

Most naturally fractured reservoir rocks are mixed to oil wet and do not imbibe the injected water, which translates into low-efficiency waterflood recovery. To enhance the spontaneous imbibition process, a low concentration of surfactants is dissolved into the injected water to induce wettability alteration of the reservoir rock by changing the wettability of the rock toward a more water-wet state. Zizyphus spina-christi leaves, which are grown in the Middle East, produce a special surfactant called saponin. This surfactant can be used for chemical flooding in Iranian oil fields due to its low cost and availability. Saponin was extracted from leaves using a spray-drying method and the interfacial tension (IFT) between saponin–water–oil was determined. For interfacial tension measurements the pendant drop method was used. A typical pendant drop apparatus is presented in this article. The algorithms used to infer interfacial tension from the geometrical profile of the pendant drop are described in detail; in particular, a new method for evaluation of the value of the radius at the apex of the drop, necessary for calculation of interfacial tension, is presented. Saponin caused a reduction in interfacial tension from 48 to 9 dyn/cm, which can be decreased to ultralow IFT by the addition of salt and alcohol. According to the results, saponin can be used as a surface-active agent for enhanced oil recovery.     

改变低渗透油藏润湿性提高采收率技术研究进展

油藏岩石润湿性是储层物性的一个基本特征参数,是影响油田特别是混合润湿或油湿性低渗透油田开发的重要因素.文中针对目前通过改变油藏岩石润湿性以提高原油采收率方面的相关技术及研究进行了详细调研,系统总结了改变油湿性油藏岩石润湿性以提高原油采收率的方法.经过归纳总结,认为目前这些方法主要分为物理法、化学法和微生物法3大类.润湿...     

Experimental and modeling study of wettability alteration through seawater injection in limestone: a case study

Water flooding is widely applied for pressure maintenance or increasing the oil recovery of reservoirs. The heterogeneity and wettability of formation rocks strongly affect the oil recovery efficiency in carbonate reservoirs. During seawater injection in carbonate formations, the interactions between potential seawater ions and the carbonate rock at a high temperature can alter the wettability to a more water-wet condition. This paper studies the wettability of one of the Iranian carbonate reservoirs which has been under Persian Gulf seawater injection for more than 10 years. The wettability of the rock is determined by indirect contact angle measurement using Rise in Core technique. Further, the characterization of the rock surface is evaluated by molecular kinetic theory(MKT) modeling. The data obtained from experiments show that rocks are undergoing neutral wetting after the aging process. While the wettability of low permeable samples changes to be slightly water-wet,the wettability of the samples with higher permeability remains unchanged after soaking in seawater. Experimental data and MKT analysis indicate that wettability alteration of these carbonate rocks through prolonged seawater injection might be insignificant.     

Recent advances in application of nanotechnology in chemical enhanced oil recovery: Effects of nanoparticles on wettability alteration,interfacial tension reduction,and flooding

Chemical methods of enhanced oil recovery (CEOR) are applied for improving oil recovery from different kinds of oil reservoirs due to their ability for modifying some crucial parameters in porous media, such as mobility ratio (M), wettability, spreading behavior of chemical solutions on rock surface and the interfacial tension (IFT) between water and oil. Few decades ago, the surfactant and polymer flooding were the most common CEOR methods have been applied for producing the remained hydrocarbon after primary and secondary recovery techniques. Recently, more attention has been focused on the potential applications of the nanotechnology in enhanced oil recovery (EOR). For this purpose, many studies reported that nanoparticles (NPs) have promising roles in CEOR processes due to their ability in changing oil recovery mechanisms and unlocking the trapped oil in the reservoir pore system. This paper presents a comprehensive and up-to-date review of the latest studies about various applications of nanoparticles (NPs) within the surfactant (S), polymer (P), surfactant-polymer (SP), alkaline-surfactant-polymer (ASP) and low salinity waterflooding processes, which exhibits the way for researchers who are interested in investigating this technology. The review covers the effects of nanoparticles on wettability alteration, interfacial tension reduction and oil recovery improvement, and discusses the factors affecting the rock/fluid interaction behavior in porous media through the nanofluid flooding.     

特低渗砂岩油藏CO2-低界面张力黏弹流体协同驱油机理研究

目的 特低渗油藏储层物性差、层间非均质性强,造成CO₂驱易发生气窜,提高采收率效果欠佳,其中,CO₂水气交替驱作为结合CO₂驱和水驱优势的方法,具有较高的适用性。为进一步改善CO₂-水交替驱的开发效果,开展了CO₂-低界面张力黏弹流体协同驱油研究。方法 通过界面张力和润湿性能测试评价低界面张力黏弹流体基本性能,并利用微观可视化驱油实验及岩心驱油实验等,探究了不同驱替方式的驱油效果和CO₂-低界面张力黏弹流体协同驱油过程中二者之间的“协同作用”机理。结果 低界面张力黏弹流体具备良好的界面活性和改变岩石表面润湿性能力,水驱后开展CO₂驱、低界面张力黏弹流体驱、CO₂-低界面张力黏弹流体交替协同驱,采收率可在水驱基础上分别提高0.91%、10.66%、16.25%,其提高采收率机理包括降低界面张力、改善流度比、改变岩石表面润湿性及乳化作用的协同效应等。结论 CO₂-低界面张力黏弹流体协同驱既可有效...     

原油沥青质沉积和吸附引起储层损害的机理及损害程度评价

原油沥青质沉积对储层孔喉的堵塞和沥青质吸附引起的油藏岩石润湿性改变是造成储层损害、导致油井产能下降的重要机理之一。首先,从热力学平衡和溶解度两个方面论述了原油沥青质发生絮凝和沉积的机理,并采用粘度法测定了沥青质絮凝初始点;然后利用岩心流动实验方法,定量评价了沥青质沉积对储层岩石渗透率的影响;并采用经改进的自吸速率法,研究了原油沥青质吸附所引起的润湿性改变及其对产能的影响。实验结果表明,储层岩心油相渗透率下降的程度与沥青质沉积量、储层岩心的原始渗透率、沉积颗粒粒径以及原油流速等因素有关。原油沥青质在油藏岩石上的吸附所引起的润湿性改变是导致储层油相渗透率降低,从而造成储层损害的一个重要原因。