油层润湿性对测井计算的含水饱和度的影响

根据对塔里木盆地某储层岩心样品洗油后及老化后的岩电实验及润湿性测量结果研究表明，老化前后储层岩样的润湿性有明显改变，且反映其电学性质的饱和度指数差别很大。根据Ｌ油田某油基泥浆取心井测井计算的含水饱和度和岩心分析的含水饱和度对比，表明油藏润湿性的变化对测井计算的含水饱和度有较大影响，所以，利用测井资料研究油藏饱和度一定要考虑油层润湿性的影响。     

淡水驱替过程中岩石电性实验研究

润湿性是影响储层岩石电阻率的重要因素.实验研究了不同润湿性的岩心淡水驱替过程中岩石电阻率随含水饱和度的变化规律,揭示了油层水淹后不同润湿性岩石的导电机理.实验结果显示水润湿岩心淡水驱替后.随含水饱和度变化电阻率变化曲线呈"U"型或"L"型,亲油岩心电阻率变化曲线呈单调下降趋势.岩石电阻率变化受储层原始润湿性影响.研究结果可为不同润湿性质的油藏水淹层识别和剩余油饱和度评价提供技术支持.     

混湿油藏的润湿性和相对渗透率研究

本文描述了Prudhoe湾油润湿性和相对渗透率的变化。我们的测量结果与有关含水饱和度、pH、润湿性和相对渗透率之间关系的新理论相一致。尤其要指出的是,油藏的润湿性从水油界面附近岩层的低水温状态逐渐变构造顶部的混湿状态。增加油湿通特征必然会降低含水饱和度。润湿性变化也伴随有注水采油率的变化,并且在Amott指数接近零时达到最佳状态。岩性也是影响石油采收率的一个因素,粘土含量丰富的岩石具有较高的残余油饱和度。     

润湿性,饱和度历史和上覆岩层压力对电阻率指数影响的实验研究

由电阻率测井计算含水饱和度，依据对有代表性岩样的实验室测量获得的电阻率指数Ｉ与含水饱和度Ｓｗ的关系。要精确评价油气远景，Ｉ￣Ｓｗ的实验室测量应在模拟储层压力、温度和储层岩石地下润湿性的储层条件下进行，并且减饱和过程也应模拟生产过程和饱和度历史。文章介绍了润湿性、饱和度历史和岩层上覆压力对Ｉ￣Ｓｗ曲线的影响。采用油／水多孔板减饱和方法，测量了１０块岩样的电阻率指数。沿岩心柱长度相邻间隔放置了六个电位     

含水饱和度指数n值计算方法探讨

研究了不同样品在不同实验条件下的含水饱和度指数n值的计算方法.根据岩电实验中含水饱和度Sw与电阻增大率I交会曲线的特征,分析了样品孔隙结构及含水饱和度对含水饱和度指数n值的影响,使用了I-Sw分段回归法、n-Sw相关分析法以更精确地计算样品的含水饱和度指数n值.实验分析了不同的油藏参数与含水饱和度指数n值的关系,认为储层性质和流体性质是影响含水饱和度指数n值的关键参数,对实际油藏应通过多因素拟合的方法求解含水饱和度指数n值.     

在不同润湿性条件下通过提高压差降低水驱残余油饱和度的系统研究

黏滞力和毛管力的比(一般表示为毛管数Nc)在确定残余油饱和度方面是至关重要的.在从接近中间润湿转变到强水湿的润湿性条件下,确定了通过系统增大Nc对均质白垩岩残余油饱和度的影响.在裂缝性白垩岩油藏中水驱残余油饱和度在很大程度上取决于润湿性.通过测量Nc不同时的可动油量,有助于确定三次采油的潜在目标.进行了一系列的注水驱油试验,以确定在不同润湿性条件下水驱中残余油量和增大毛管数之间的关系.通过Amott试验,用21个岩心柱样品建立并且量化了各种均匀分布混合润湿性条件.在水的Amott指数为0.3的润湿性条件下,Nc稳定时残余油最少.残余油饱和度随着毛管数增大而降低,在中等水湿到接近中间润湿条件下,水自吸后捕集的大量油开始流动.当增大毛管数时,在白垩岩油藏中得到的结果与在文献中报道的砂岩水驱残余油饱和度(随着润湿性和注入水PV变化)的结果相似.在采收率随着毛管数增加同时提高的情况下,采收率的穹隆形曲线(随着润湿性变化)反映了与较早水驱采收结果的相似性.     

长期水驱后润湿性变化对残余油饱和度影响的实验研究

当前普遍认为长期水驱后,储层孔隙度、渗透率、润湿性都会发生一定程度的改变,储层参数的变化对残余油饱和度会产生什么样的影响,对此研究甚少。针这一问题,选取两组平行天然岩心开展室内模拟实验。第一组岩心代表＂高渗＂;第二组岩心代表＂低渗＂。每组岩心包括两块样品,将每组岩心A号样品连续水驱,而B号样品当含水达90%以后,停止驱替,老化岩心90d后再继续驱替。实验结果表明,当长期水驱后,储层岩石残余油饱和度发生大幅度降低,最大降幅达50%以上。根据实验结果指出,开展油藏工程和数值模拟研究时,考虑储层岩石残余油饱和度变化,才能使模拟结果准确反映油藏实际特征。     

油气层润湿特性对电阻率的影响规律研究

为了进一步理解目前在储层润湿性对电阻率影响研究中的两种不同结果，根据润湿性对电性影响的微观机理以及储层特性的差异，首先提出了水湿储层中润湿水膜存在连续状和分散状这两种形式；接着利用逾渗理论研究了在具有不同连通性和均质性的储层中，润湿性对电阻率的影响规律；最后从阿尔奇公式出发，进一步分析了润湿性对电性影响的特征。根据阿尔奇公式的分析结果同逾渗理论结果一致。研究结果表明，在整个含水饱和度范围内，水湿储层的电阻率均比油湿储层低；在低含水饱和度下，润湿性对电性影响的差异可归因于储层连通性和均质性的不同。连通性好、非均质性不显著的水湿储层，其I-S_ｗ曲线呈现凸型；连通性差、非均质性显著的水湿储层，其I-S_ｗ曲线呈现凹型。在确定饱和度指数时，除考虑储层的润湿特性以外，还需要考虑储层孔隙的连通状况和均质性等因素。     

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。      

分子膜驱剂对束缚水饱和度和残余油饱和度的影响

阐述了分子膜驱剂NMD-300能够改变油藏岩石润湿性，使油湿性油藏和水湿性油藏都向弱水湿转变。通过驱替实验发现：与空白实验相比，用分子膜驱剂溶液浸泡过的石英砂，颗粒的润湿性向弱水湿方向转变，其束缚水饱和度明显升高，残余油饱和度有所降低，有利于提高采收率。     

Saturation exponent at various wetting condition: fractal modeling of thin-sections

Saturation exponents, along with resistivity log data, are usually needed for evaluating the initial saturation of a hydrocarbon reservoir. A number of experimental investigations have shown that reservoir wettability affects the exponent value. A remarkable divergence of conclusions, however, still appears in the literature. This paper presents the results of a study based on the application of fractal concepts. The concepts have been used to derive parameters such as clay content and electrical tortuosity of thin-sections at a given wetting condition and for various water saturations. A general equation of electrical resistivity was then developed, incorporating these parameters. The advantage of this approach is that, it is independent of rock–fluid equilibrium problems that commonly influence laboratory measurements. The present work employed 20 thin-sections of limestone and sandstone. It was found that the lowest exponent of 1.8 was obtained for strongly water-wet shaley sandstone and the highest value of 5.3 was for strongly oil-wet conditions. The exponent consistently increases as the wetting condition is shifted from strongly water-wet toward oil-wet. It is close to 2.0 for clean sandstone at strongly water-wet conditions; this supports Archie's empirical formula.     

Visualization of the Effect of Porous Media Wettability on Polymer Flooding Performance through Unconsolidated Porous Media using Magnetic Resonance Imaging

Abstract

Waterflooding effectiveness depends on the mobility ratio of the injected water to displaced fluids, and on the geologic heterogeneity of the reservoir rock. Rock wettability also affects the performance of water and polymer flooding. It is generally recognized that waterflooding in a water-wet reservoir is more efficient than waterflooding in an oil-wet reservoir. Polymer absorption/retention in porous media is also affected by rock wettability. The Centric Scan SPRITE Magnetic Resonance Imaging (MRI) technique is applied in this work to visualize the performance of polymerflooding and to quantify in situ fluid saturation distribution in rocks with wettability ranging from strongly water-wet to preferentially oil-wet.     

受原油黏度影响的鄂尔多斯盆地油湿和水湿砂岩导电响应规律

为了明确原油黏度对油湿和水湿砂岩储层的电性影响规律和机理,选用鄂尔多斯盆地长庆油田原油(黏度约为90 mPa·s)和煤油配置原油(黏度约为1 mPa·s),针对油湿和水湿的中—低渗透延长组砂岩开展了岩电、核磁共振、扫描电镜等对比实验,从岩石物理角度探索了不同黏度原油对油湿和水湿砂岩导电响应规律的影响机理。研究结果表明：(1)不论原油黏度高低,相同饱和度下油湿岩心电阻率都明显高于水湿岩心;(2)原油黏度对水湿岩心的岩电响应特征影响较小,但对油湿岩心影响很大,即油湿岩心的电性曲线呈明显的分段特征,且原油黏度越大,分段性越明显;(3)造成油湿岩心电性差异的主要原因在于高黏度原油对孔隙结构的叠加影响。研究成果对于油湿储层的油层识别和饱和度模型建立具有一定指导意义。在实际的岩石物理实验中,要注意原油黏度对油湿岩心岩电响应规律的影响,选取与地下原油黏度相近的油品进行实验才能得到具有代表性的结果。     

东濮凹陷油层岩石润湿性的分析

本文认为原油中“非烃+沥青质”是影响油层岩石表面润湿性的关键因素,当其含量达到一定数值时,则油层内的含油孔道岩石表面润湿性可以改变成亲油。当含油孔道岩石表面亲油时,其润湿性受含水饱和度的影响,即含水饱和度低于30%时是亲油、高于40%时是亲水。指出油田随注水开发时间的延长,油层的润湿性将由亲油逐渐改变成亲水。     

油湿灰岩储层中季胺类物质对周期注水开发效果的影响

周期注水是开发灰岩储层低渗透基质中原油的一种有效方法,但对于亲油储层效果较差。对基质含水饱和度变化特征进行了分析,建立了基质含水饱和度变化特征方程,提出了周期注水与润湿反转技术相结合的开采方式。利用油湿灰岩裂缝模型,在注入水中加入低浓度具有润湿反转能力的季胺类物质——十六烷基三甲基溴化铵(CTAB)进行了周期注水室内模拟研究。结果表明,CTAB可使油湿灰岩储层的表面性质发生明显变化,基质毛管的自吸及滞水排油能力增强,周期注水开发效果明显改善。     

川南地区龙马溪组页岩润湿性分析及影响讨论

国内外大部分学者研究认为泥页岩表面润湿性为水湿,而页岩气藏中页岩岩石存在有机质影响,页岩表面润湿性表现比较复杂,因此选择四川盆地龙马溪组野外露头及井下岩心进行分析,通过开展一系列实验,研究分析了龙马溪组页岩润湿性,并从3个方面初步探索讨论了润湿性对页岩气藏的影响。研究结果表明龙马溪组页岩表面既亲油又亲水,且页岩表面更倾向于油湿,页岩岩石孔隙表面处润湿性存在差异,出现非均匀润湿性即斑状润湿|页岩自吸吸水率、吸油率随时间增加而先上升后趋于稳定,页岩自吸吸水率大于自吸吸油率|页岩浸泡在水中水化应力随着时间增加而先呈上升后趋于稳定,而先浸泡白油后浸泡水中水化应力上升速度减慢|页岩硬度随浸泡时间增加、浸泡温度升高以及浸泡压力增大而呈下降趋势,其中浸泡白油中硬度下降幅度较小,而浸泡水中硬度下降幅度较大|页岩表面吸附特性与表面自由能有关,表面自由能随水接触角减小而增大,同时页岩表面亲油对气态烃有较强吸附能力|页岩表面亲水性易造成水锁,而表面亲油性可减轻水锁伤害,页岩气藏水锁伤害评价应考虑页岩表面既亲油又亲水特性影响|油基钻井液对页岩强度影响较小,而水基钻井液对页岩强度影响较大,易造成井壁失稳,水基钻井液体系优化需考虑抑制其水化作用。     

Prediction of wettability variation and its impact on flow using pore- to reservoir-scale simulations

We describe a pore- to reservoir-scale investigation of wettability variation and its impact on waterflooding. We use a three-dimensional pore-scale network model of a Berea sandstone to predict relative permeability and capillary pressure hysteresis. We successfully predict experimentally measured relative permeability data for the water-wet case, and demonstrate that the model captures experimentally observed trends in waterflood recovery for mixed-wet media. We then focus upon the effect of variations in initial water saturation associated with capillary rise above the oil–water contact (OWC). This may lead to wettability variations with height because the number of pore-walls which may be rendered oil-wet during primary drainage, increases as the oil saturation increases. We investigate empirical hysteresis models in which scanning curves are used to connect bounding drainage and waterflood curves for a given initial water saturation, and find that if wettability varies with initial water saturation, then the scanning water relative permeability curves predicted by the empirical model are significantly higher than those predicted by the network model. We then use a conventional simulator, in conjunction with the relative permeability curves obtained from the network and empirical models, to investigate the reservoir-scale impact of wettability variations on waterflooding. If the wettability varies with height above the OWC, we find that using the network model to generate scanning relative permeability curves yields a significantly higher recovery than using empirical models or assuming that the reservoir is uniformly oil-wet or water-wet. This is because the scanning water curves are generally low (characteristic of water-wet media), yet the residual oil saturation is also low (characteristic of oil-wet media). Our aim is to demonstrate that network models of real rocks may be used as a tool to predict wettability variations and their impact on field-scale flow.     

阿尔奇公式数值分析及其意义

根据欧姆定律及微积分原理,推导出几种理想情况下的Archie(阿尔奇)公式,模拟分析了胶结指数以及饱和度指数的影响因素.模拟结果表明,亲油储层饱和度指数高于亲水储层,亲油储层饱和度指数相对稳定,而亲水储层饱和度指数受饱和度变化的影响较大,建立了两者的数学关系式.储层水淹程度对Archie公式的影响很大,在水淹层测井解释时须给予重视.     

Impacts of Wettability on Immiscible Fluid Flow Pattern-Microfluidic Chip Experiment

Immiscible fluid flow is frequently found in resource recovery or soil remediation. The flow pattern in the porous media is affected by the wettability of pore surface. In this study, quartz substrates and microfluidic chips are treated by silica nanoparticles(SNP) and triethoxy(octyl)silane(TES) to fabricate the water-wet and oil-wet surfaces. The wettability of the treated-surface is measured in term of contact angle for several combinations of surrounding fluid and a liquid droplet. The effect of the wettability on the fluid flow pattern is explored by injecting oil and water alternately into the surface-treated microfluidic chips. The results reveal that the SNP-coated quartz substrate shows strong water-wet property and the TES coating makes water-repellent/oil-wet surfaces. In addition, it is found that the maximum and minimum oil and water saturation during alternate injection of oil and water depends on the surface wettability of the microfluidic chips. The characteristics of the pore-scale fluid flow pattern are also described.     

Effect of wettability on oil recovery and breakthrough time for immiscible gas flooding

The effect of wettability on oil recovery at higher water saturation is still not fully understood, especially in the case of mixed wettability. This study was conducted to examine the effects of wettability on oil recovery and breakthrough time through experiments for two wettability conditions (water-wet and mixed-wet) and three water saturations (20%, 40%, and 60%). Clashach sandstone core with a porosity of 12.8% and a permeability of 75 md was utilized as the porous media. Immiscible gas flooding was performed by injecting nitrogen gas into the core at room temperature and pressure. The results showed 54.3% and 48.8% of the initial oil in place (IOIP) as the ultimate oil recovery at 40% water saturation from mixed-wet core and water-wet core respectively. In contrast, the water-wet core displayed better results (32.6% of the IOIP) in terms of breakthrough time compared to the results of water-wet core (10.6% of the IOIP) at the same water saturation. In conclusion, oil recovery was found highly dependent on water saturation while breakthrough time was mainly affected by the wettability of the cores.