润湿性的改变对提高原油采收率的影响研究

注水开发几乎不能从低渗油湿性油藏中采出原油,如果油藏岩石的润湿性得到改变,通过自然的渗吸其采收率就能得到改进。因此,了解润湿性改变的影响因素及其机理对提高原油采收率意义重大。岩心流动试验表明:水驱时中性润湿岩心的采收率最高,强水湿岩心其次,强油湿岩心最低。润湿性由亲油向亲水方向的变化,油水相渗曲线右移,残余油饱和度下降了25%,油水共渗区范围明显增大,采出程度提高。目前认为加入表活剂改变油藏岩石的润湿性是提高原油采收率比较可行的方法。     

油藏岩石润湿性对气驱剩余油微观分布的影响机制

注气驱是目前油田进一步提高原油采收率的重要措施之一,油藏岩石润湿性对注气的效果有重要影响。基于三维孔隙级网络模型,运用孔隙级流动模拟方法,系统研究了6种不同润湿性油藏注气过程的油气水孔隙级分布和气驱效果。结果表明,水湿和MWS混合润湿(小孔隙为油湿)体系中的注气效果相对于另外4种润湿体系较差;这4种效果较好的润湿体系分别是油湿、中性润湿、MWL混合润湿(大孔隙为油湿)和部分润湿（其中30%孔隙水湿）体系。     

裂缝性碳酸盐储层中表面活性剂辅助重力泄油的模拟

注水开发几乎不能从碳酸盐岩油藏中采出原油,因为碳酸盐岩油藏通常是油湿性和裂缝性的.将稀释的表面活性剂溶液注入裂缝中能够降低油水界面张力(IFT),改变岩石与中间体/水湿性物质的润湿性从而提高原油产量.一个三维、两相、多组分、有限差分和全隐式数值模拟模型已开发出来,此模型综合了吸附作用、相态特性、润湿性、相关毛细管压力/相对渗透率变量.此模拟软件的可靠性已经通过对比岩心级模拟结果与实验室中得到的实验结果得以证实.从界面张力降低、润湿性改变和渗透率差异等方面来研究表面活性剂辅助重力泄油对这些过程参数的敏感性.在早期阶段通过改变润湿性来驱动原油生产,但在后期重力是主要驱动力.使润湿性向着水湿状态改变的表面活性剂能使高界面张力系统具有较高的采收率.对于低界面张力系统,不能改变润湿性的表面活性剂能使油田具有较高采收率.润湿性的大幅度改变可以提高原油采收率.对于低界面张力系统采收率随渗透率的降低而显著降低,而对于高界面张力系统影响很小.     

润湿性对采收率及相对渗透率的影响

通过实验研究了润湿性对采收率及相对渗透率的影响,还研究了利用原油老化控制岩石润湿性的方法。结果表明弱水湿岩石水驱采收率最高,亲水岩石油相相对渗透率高于亲油岩石,原油中极性物质的吸附会影响岩石表面润湿性,油湿性随老化时间增加而增强。     

润湿性对采收率及相对渗透率的影响

通过实验研究了润湿性对采收率及相对渗透率的影响 ,还研究了利用原油老化控制岩石润湿性的方法。结果表明弱水湿岩石水驱采收率最高 ,亲水岩石油相相对渗透率高于亲油岩石 ,原油中极性物质的吸附会影响岩石表面润湿性 ,油湿性随老化时间增加而增强。     

注水开发油藏润湿性变化及其对渗流的影响

为提高水驱开发油藏采收率预测精度,研究了油藏岩石润湿性与相对渗透率之间的变化规律及其对两相渗流的影响。采用室内润湿性实验测定方法,对水驱开发油藏润湿指数与含水饱和度的关系进行了定量表征,导出了适合润湿性变化型油藏的两相渗流方程,建立了变润湿性水驱开发油田的采收率预测方法。润湿实验结果表明:所测岩心的润湿指数的对数与取心油层的含水饱和度呈近似线性关系。相对渗透率实验所测的代表低含水期到高含水期岩心的油水两相等渗点对应的含水饱和度由41%增加到53%,亲水程度增强。一维模型计算结果表明,含水率达到98%时,油润湿和强水润湿性油藏的预测采收率分别为52.7%和73.3%。研究揭示的水驱油藏岩石润湿性变化规律和建立的数学模型,可为更加准确地预测水驱油采收率提供参考。      

润湿性及其演变对油藏采收率的影响

润湿性是油藏岩石、原油和水三者相互作用的综合表现形式.了解油藏润湿性及其演变过程对提高原油采收率有重要意义,文章综述了成藏前后润湿性的变化特征及其控制因素.原油运移进入储层后,原油中的表面活性组分可能引起油藏润湿性的改变,而水膜不稳定破裂是引起润湿性改变的关键环节.对水膜稳定的热力学条件分析表明,只有当水膜厚度及影响水膜稳定的变量的值在一定范围内,水膜才可能稳定,所以在实际油藏条件下,水膜的稳定性被破坏时,矿物与原油作用将使油藏最终润湿性偏离成藏之前的水润湿状态.水驱及化学驱对润湿性敏感程度的分析表明,可依据不同开采方式所对应的最有利润湿性类型,通过物理或化学方法改变油藏润湿性,提高原油采收率.     

碳酸盐岩油藏岩石润湿性评价实验研究

为了明确碳酸盐岩油藏岩石的润湿性及其影响因素,利用自吸驱替方法定量测定了碳酸盐岩岩心充分老化后的润湿性和渗吸采出程度以及蒸汽驱后岩心润湿性的变化,并通过相对渗透率法对碳酸盐岩储层岩石润湿性进行定性研究。结果表明:碳酸盐岩岩心呈亲油或者弱亲油的润湿特征,油藏渗流阻力较大,自吸采出程度低。岩石矿物组成及原油组分是润湿性的主要影响因素;而高温蒸汽驱后碳酸盐岩岩心润湿指数变小,润湿性由强亲油—亲油向弱亲油方向转变。热采条件下岩心润湿性得以改善,共渗区含油饱和度由20.5%提高到37.0%,较之冷采提高了1.8倍;热采通过降粘、润湿改善等作用机理,驱油效率由29.7%提高至59.0%。润湿性的改变有利于提高油藏的采出程度。     

储层润湿性改变对采收率的影响

改变储层润湿性是提高原油采收率的重要手段之一,传统的观点认为:注水开发时,岩石表层亲水更容易使油滴从岩石表面剥落下来。通过天然岩心润湿性测定和驱油剂驱油试验发现,驱油剂能提高驱油效率10%左右,驱油剂并不能将岩石的润湿性转变成水湿,而是向着中性润湿的方向发展。通过分析毛管力发现,在水驱油到残余油状态时,毛管力是阻力,将阻碍原油从微小的孔隙吼道中流出。由毛管力计算公式可知,当润湿角为90°时,毛管力最小。因此得出结论:中性润湿最有利于提高采收率;驱油剂不但能使储层岩石向中性润湿发展,同时能起到降压增注的作用。      

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。     

大庆油田三元复合驱驱油效果影响因素实验研究

通过岩心物理模拟实验及微观驱油实验,分析了界面张力、三元体系粘度、乳化油滴产生及岩石润湿性对三元复合驱驱油效果的影响规律和影响机理。研究结果表明,油水间平衡、动态界面张力大幅度降低可有效提高三元复合驱驱油效率,进行三元复合驱时,油水界面张力须降到10^-3mN/m数量级;增加体系粘度能够扩大三元复合驱的波及体积,水油粘度比大于2是三元复合驱提高采收率幅度达到20%的必要条件;乳化的油滴产生是三元复合驱提高驱油效率的主要形式,油水界面张力越低、驱替体系粘度越大,乳化油滴的产生能力越强,驱油效果越好;三元复合驱能够驱替亲油岩石表面的油膜,促进岩心润湿性由亲油向亲水转化。     

碳酸盐岩油藏低矿化度水驱作用机理实验

碳酸盐岩油藏低矿化度水驱应用潜力巨大,为了更好地推广其矿场应用而针对性开展作用机理的实验研究。首先,岩心驱替实验研究注入水矿化度和关键离子组成对采收率的影响;而后,润湿角测定实验分析注入水矿化度和关键离子组成对碳酸盐岩表面润湿性的影响;最终,根据实验结果建立碳酸盐岩油藏低矿化度水驱作用机理。研究发现：低矿化度水驱能有效改变碳酸盐岩表面润湿性进而提高油藏采收率,存在最优矿化度使得碳酸盐岩表面润湿性变化最大、采收率最高;Mg²⁺和SO₄^2-对碳酸盐岩表面润湿性和原油采收率的影响效果不同;随着溶液中Mg²⁺浓度升高,碳酸盐岩表面润湿性变化不断增强、原油采收率不断升高;随着溶液中SO₄^2-浓度增加,碳酸盐岩表面润湿性变化先增强后减弱、原油采收率先增加后稳定。碳酸盐岩油藏低矿化度水驱作用机理在于润湿性的改变：①SO₄^2-吸附在正电性的碳酸盐岩矿物表面,中和表面电荷,促进了Mg²⁺向矿物表面运动;②Mg²⁺与碳酸盐岩矿物表面的Ca²⁺发生取代反应,造成原油组分的解离。     

裂缝性油藏中的渗吸作用及其影响因素研究

对裂缝性油藏建立了以毛管自吸为主要采油机理的数学模型,并对影响裂缝性油藏采出程度的敏感参数进行研究,结果表明：对于等温渗流过程,裂缝密度是影响采出程度的主要因素,裂缝密度越大,采出程度越高;当裂缝系统充填有高温流体时,岩块表面温度对采出程度的影响大于裂缝密度,温度的升高通过降低原油粘度、增加弹性能量和改善岩石表面的润湿性增加最终采收率;采出程度随裂缝密度呈指数变化规律,衰变指数与基质表面温度有关     

无机正电胶双聚钻井完井液技术研究

表面润湿性和电性是油藏岩石的两个重要表面特性。润湿性通过控制油藏岩石孔隙中流体的分布和非混相流体的流动、决定岩石孔道中毛细管力的大小和方向、控制油气层微粒的运移三个方面，影响油气采收率。地层微粒保持中性润湿可以避免地层微粒运移导致的油气层损害；地层表面保持中性润湿，有利于提高水驱的波及系数，有利于提高原油采收率。油藏岩石表面带电性影响原油在岩石孔隙中的渗流，电中性的岩石表面不仅使原油易于通过岩石多孔介质，而且使原油不产生电性润湿现象，因而有利于提高采收率。在综合分析钻井完井液性能与井壁稳定、油气层保护和提高油气采收率关系的基础上，提出了钻井完井液不仅应该满足钻井正常作业和保护油气层的要求、还应该有利于提高油气井产能的观点，并以无机正电胶、聚合醇和聚合物为主剂，开发了无机正电胶双聚钻井液体系。试验表明，该体系兼有正电胶钻井液和聚合醇钻井液的优点，具有独特的流变性、优良的润滑性、稳定井壁作用，以及显著的保护储层和提高油气采收率的功能。     

Surfactant induced reservoir wettability alteration: Recent theoretical and experimental advances in enhanced oil recovery

Reservoir wettability plays an important role in various oil recovery processes.The origin and evolution of reservoir wettability were critically reviewed to better understand the complexity of wettability due to interactions in crude oil-brine-rock system,with introduction of different wetting states and their influence on fluid distribution in pore spaces.The effect of wettability on oil recovery of waterflooding was then summarized from past and recent research to emphasize the importance of wettability in oil displacement by brine.The mechanism of wettability alteration by different surfactants in both carbonate and sandstone reservoirs was analyzed,concerning their distinct surface chemistry,and different interaction patterns of surfactants with components on rock surface.Other concerns such as the combined effect of wettability alteration and interfacial tension (IFT) reduction on the imbibition process was also taken into account.Generally,surfactant induced wettability alteration for enhanced oil recovery is still in the stage of laboratory investigation.The successful application of this technique relies on a comprehensive survey of target reservoir conditions,and could be expected especially in low permeability fractured reservoirs and forced imbibition process.     

生物酶改变岩石表面润湿性实验研究

根据岩石润湿性的衡量标准,用光学投影法测定岩石接触角,对生物酶改变岩石表面润湿性进行了实验研究,包括生物酶与岩石作用后岩石润湿性的变化、毛管力的变化以及粘附功的变化。实验结果表明,生物酶与岩石作用后,可以明显改变水驱油毛营力的大小,可以加速剩余油的流动,从而提高油藏的采收率。     

低渗透油藏渗流物理特征的几点新认识

对于低渗透油藏,油水界面张力、岩石润湿性和孔喉比是影响产量和采收率的重要因素,而润湿指数和润湿角通过毛管数与驱油效率有直接的定量关系。该文提出了一个关联着界面张力、润湿性和孔喉比的修正毛管数概念,建立了基于Amott润湿指数与USBM指数的润湿角表征方法,继而推导出低渗透储层毛管数表达式,并通过岩心实验确定出其与残余油饱和度的关系。以此为基础给出不同界面张力与润湿情况下的相对渗透率曲线、驱油效率和注入能力的计算公式,揭示了各种油藏物理参数之间的关联性,为优化低渗透油层化学驱改变界面张力、润湿性控制参数,进而为提高驱油效率和采收率提供了理论依据。     

不同润湿性条件下适合于不同渗透率油层的超低界面张力驱油体系

研制了无碱无聚合物且界面张力达到10^-3mN/m超低值的表面活性剂驱油体系,对于岩石表面润湿性条件为强亲油、中亲油、弱亲油以及强亲水情况,随着渗透率的增加,该体系的采收率逐渐增加.当渗透率增加到某个值时,随着渗透率的增大采收率迅速提高;然后随着渗透率的进一步增大,采收率增加幅度明显降低,将采收率不再增加时的渗透率值称为临界渗透率值.岩石表面亲水性越强,临界渗透率越低,适合于超低界面张力驱油体系的渗透率越小.实验表明,随着岩石表面亲水性的增加,可以使残余油滴活化的最小孔喉半径或渗透率明显降低,在低渗透率、特低渗透率以及超低渗透率的条件下,可将残余油驱替出来.因此,超低界面张力驱油体系不仅适合于中、高渗透率的油层,在一定条件下还可用于低、特低和超低渗透率的油层.     

The Role of Wettability in Petroleum Recovery

Various findings on core handling effects and crude oil/brine/rock (COBR) interactions have indicated how the wettability of a core sample is altered when retrieved from a reservoir. Moreover, it is revealed that wettability of a core will affect almost all types of physical parameters necessary for reservoir management, such as capillary pressure. However, the most accurate results are obtained when native or restored-state cores are used with native crude oil and brine at reservoir temperature and pressure. Such conditions provide core that have the same wettability as the reservoir. Equally, the wettability of originally water-wet rock can be altered by the adsorption of polar compounds and/or the deposition of organic material that was originally in the crude oil. The degree of alteration is determined by the interaction of the oil constituents, the mineral surface, and the brine chemistry. Factors that influence wettability alteration are considered, and how this in turn affects the capillary pressure, is determined. Due to the capillary pressure dependence on water saturation, the effect of wettability alteration on reserve estimation through the initial water saturation is shown. The implications for oil recovery prediction and reservoir management are discussed. The main objective is to do a critical analysis on how wettability alteration dictates the success or failure of reservoir management irrespective of the technical or operational input, early in the life of a reservoir. It is believed that reserve estimation at the early stage is either optimistic or pessimistic with the consequent effect on oil recovery prediction and reservoir planning. The overall effect would be poor reservoir management at the early life of the reservoir, which effects on the later life of the reservoir is inestimable. This explains why the petroleum business is the riskiest business in the world. This would continue to be so unless a method is devised to measure reservoir parameters in situ, devoid of wettability alteration to any extent.     

Adsorption of surfactants on minerals for wettability control in improved oil recovery processes

Chemical-flooding schemes for recovering residual oil have been in general less than satisfactory due to loss of chemicals by adsorption on reservoir rocks, precipitation, and resultant changes in rock wettability. Adsorption and wettability changes are determined mainly by the chemical structure and mix of the surfactants, surface properties of the rock, composition of the oil and reservoir fluids, nature of the polymers added and solution conditions such as salinity, pH and temperature. The mineralogical composition of reservoir rocks plays an important role in determining interactions between reservoir minerals and externally added reagents (surfactants/polymers) and their effects on solid–liquid interfacial properties such as surface charge and wettability. Some of the reservoir minerals can be sparingly soluble causing precipitation and changes in wettabilty as well as drastic depletion of surfactants/polymers.Most importantly, the effect of surfactants on wettability depends not only how much is adsorbed but also on how they adsorb. A water wetted rock surface that is beneficial for displacement of oil can be obtained by manipulating the orientation of the adsorbed layers. New surfactants capable of tolerating harsh conditions created by extremes of pH, temperature or inorganics and capable of interacting favorably with inorganics and polymers are promising for enhanced oil recovery. In this regard, such surfactants as sugar based ones and pyrrolidones are attracting attention, as they are also biodegradable. In many cases, mixed surfactants perform much better than single surfactants due to synergetic effects and ability to alleviate precipitation. Also, addition of inorganics such as silicates, phosphates and carbonates and polymers such as lignins can be used to control the adsorption and the wettability. In this paper, use of specialty surfactants and their mixtures is discussed along with the mechanisms involved.