The effect of nanoparticles on wettability alteration for enhanced oil recovery: micromodel experimental studies and CFD simulation

The applications of nanotechnology in oilfields have attracted the attention of researchers to nanofluid injection as a novel approach for enhanced oil recovery. To better understand the prevailing mechanisms in such new displacement scenarios,micromodel experiments provide powerful tools to visually observe the way that nanoparticles may mobilize the trapped oil.In this work, the e ect of silicon oxide nanoparticles on the alteration of wettability of glass micromodels was investigated in both experimental and numerical simulation approaches. The displacement experiments were performed on the original water-wet and imposed oil-wet(after aging in stearic acid/n-heptane solution) glass micromodels. The results of injection of nanofluids into the oil-saturated micromodels were then compared with those of the water injection scenarios. The flooding scenarios in the micromodels were also simulated numerically with the computational fluid dynamics(CFD) method. A good agreement between the experimental and simulation results was observed. An increase of 9% and 13% in the oil recovery was obtained by nanofluid flooding in experimental tests and CFD calculations, respectively.

Qualitative and Quantitative Evaluation of Permeability Changes during EOR Polymer Flooding Using Micromodels

Polymer solutions are used in chemical EOR processes to achieve incremental oil recoveries through obtaining favorable mobility ratios. In the process, the?in-situ?viscosity is a key parameter for the polymer flood design, as well as the changes in permeability due to the retention or adsorption (e.g.: plugging). Understanding the major causes of the plugging effects allows?predicting injectivity problems as well as optimizing project design. The objective of this work is to use glass-silicon-glass micromodels in combination with tracer particles—attached to the flooded fluids—to qualitatively and quantitatively describe the extent of permeability changes?after polymer injection. Laboratory work is performed in order to determine the physical properties of the polymer solutions when they flow through porous media, such as the presence of permeability reduction/plugging of the micromodel. A statistical analysis of the distribution and extent of plugged areas?is performed and a study of the pressure response during various injection stages will complement the study. A biopolymer (Scleroglucan) was tested and compared to a commonly used polymer, giving a direct insight into their pros and cons. Five different concentrations of polymers were tested and put into relation with their quantitative and qualitative amount of sort of called retention. The amount of adsorption was determined?experimentally in one case in order to draw the significance. By exploiting the potential of GSG-micromodels in combination with tracer particles, it was possible to visualize the reduction of flow paths and its increase during various injections for the first time. Expanding the working principle proposed in this work could provide further understanding of the behavior of any polymers.?The results obtained and workflow presented in this work allow for additional understanding of polymer solutions behavior in flooding applications. Furthermore, the definition of optimized workflows to?assess any kind of solutions in porous media and permeability changes is?supported.

Displacement mechanisms of enhanced heavy oil recovery by alkaline flooding in a micromodel

Enhanced oil recovery （EOR） by alkaline flooding for conventional oils has been extensively studied. For heavy oils, investigations are very limited due to the unfavorable mobility ratio between the water and oil phases. In this study, the displacement mechanisms of alkaline flooding for heavy oil EOR are investigated by conducting flood tests in a micromodel. Two different displacement mechanisms are observed for enhancing heavy oil recovery. One is in situ water-in-oil （W/O） emulsion formation and partial wettability alteration. The W/O emulsion formed during the injection of alkaline solution plugs high permeability water channels, and pore walls are altered to become partially oil-wetted, leading to an improvement in sweep efficiency and high tertiary oil recovery. The other mechanism is the formation of an oil-in-water （O/W） emulsion. Heavy oil is dispersed into the water phase by injecting an alkaline solution containing a very dilute surfactant. The oil is then entrained in the water phase and flows out of the model with the water phase.

The transport and retention of CQDs-doped TiO_(2) in packed columns and 3D printed micromodels

CQDs-doped TiO_(2)(C-TiO_(2))has drawn increased attention in recent because of its excellent catalytic performance.Understanding the transport of C-TiO_(2)in porous media is necessary for evaluating the environmental process of this new nanomaterial.Column experiments were used in this study to investigate ionic strength(IS),dissolved organic matter(DOM)and sand grain size on the transport of C-TiO_(2).The mobility of C-TiO_(2)was inhibited by the increased IS and decreased sand grain size,but was promoted by the increased DOM concentration.The promotion efficiency of DOM ranked as humic acid(HA)>alginate(Alg)>bovine serum albumin(BSA),which was in the same order as their ability to change surface charges.The micromodels of pore network were prepared via 3D printing to further reveal the deposition mechanisms and spatial/temporal distribution of C-TiO_(2)in porous space.C-TiO_(2)mainly attached to the upstream region of collectors because of interception.The collector ripening was observed after long-time deposition.The existence of DOM caused visible decrease of C-TiO_(2)deposition in the pore network.HA caused the most remarkable reduce of deposition in the three types of DOM,which was consistent with the column experiment results.This research is helpful to predict the transport of C-TiO_(2)in natural porous media.

Experimental study of the mechanism of nanofluid in enhancing the oil recovery in low permeability reservoirs using microfluidics

Due to the low porosity and low permeability in unconventional reservoirs,a large amount of crude oil is trapped in micro-to nano-sized pores and throats,which leads to low oil recovery.Nanofluids have great potential to enhance oil recovery(EOR)in low permeability reservoirs.In this work,the regulating ability of a nanofluid at the oil/water/solid three-phase interface was explored.The results indicated that the nanofluid reduced the oil/water interfacial tension by two orders of magnitude,and the expansion modulus of oil/water interface was increased by 77% at equilibrium.In addition,the solid surface roughness was reduced by 50%,and the three-phase contact angle dropped from 135(oil-wet)to 48(water-wet).Combining the displacement experiments using a 2.5D reservoir micromodel and a microchannel model,the remaining oil mobilization and migration processes in micro-to nano-scale pores and throats were visualized.It was found that the nanofluid dispersed the remaining oil into small oil droplets and displaced them via multiple mechanisms in porous media.Moreover,the high strength interface film formed by the nanofluid inhibited the coalescence of oil droplets and improved the flowing ability.These results help to understand the EOR mechanisms of nanofluids in low permeability reservoirs from a visual perspective.

激光微织构分布与形状对轮轨线接触下润滑性能的影响

针对轮缘润滑在改善轮缘磨耗和钢轨侧磨的同时容易造成轨道污染和润滑脂大量浪费的问题,拟在钢轨轨距角表面制备激光微造型,探究激光微造型技术应用于轮缘/钢轨轨距角润滑的可行性.用TY-FM-20S多工位带旋转光纤激光打标机在钢轨试样表面制备了不同分布率的矩形、圆形、菱形激光微织构,利用大滑差在MMS-2A摩擦磨损试验机上模拟地铁车辆通过小半径曲线路段,并开展不同喷涂油量的轮缘/轨距角润滑模拟试验,引入正交试验设计对试验和结果进行分析,结果表明:涂油量对轮缘润滑效率的影响最大,其次是微造型分布率,而微造型形貌影响最小.利用正交试验分析法中直观分析法与方差分析法进一步得出,当采用菱形形貌、分布率为5.25%(40个形貌)及0.2 mL喷涂油量时润滑效率最优,即,合适的激光微造型形貌与分布可以显著改善轮缘润滑效率.

安塞油田坪桥区、王窑区长6油层储层特征及驱油效率分析

分别在坪桥、王窑二区块取芯后制作了真实砂岩微观孔隙模型 ,并利用该模型在室内进行了油水两相渗流试验。结果表明王窑区长 6油层的驱油效率 (40 34 % )高于坪桥区 (30 48% )。分析认为二区块孔隙结构的差异 。

利用微观模型研究乳状液驱油机理

利用真实砂岩微观模型研究和分析乳状液在多孔介质中的驱油机理及其特性,结果表明,经过乳状液驱替后,水驱油形成的各类残余油均有减少。乳状液的驱油机理主要有两种:①利用乳状液堵塞大孔喉带产生的分流作用,减少绕流形成残余油的数量;②借助乳状液进入孔隙喉道中产生的挤压、拉、拽作用,有效驱赶分布在边缘及角隅部位的残余油。实验结果表明,经过乳状液驱替后,驱油效率可提高6%左右。

不同流动单元微观渗流特征研究--以华池油田长3油藏华152块为例

利用不同流动单元的真实砂岩微观孔隙模型,进行了不同流动单元微观渗流特征的试验研究,为提高油层开采效果提供科学依据。鄂尔多斯盆地华池油田华152块长3储层流动单元可分为A,B,C 3类,存储性能和渗透性能由好到差依次为A,B,C类。研究结果表明,不同流动单元的微观渗流特征有着明显的不同,体现在流体进入次序、流体驱替方式和剩余油类型上的不同。流体总是优先进入A类流动单元,其次进入B类流动单元,C类流动单元流体进入困难,在水驱油时,注入水无法进入C类流动单元;流体驱替方式不同,A类流动单元油驱水为非活塞式,而B类和C类流动单元油驱水均为活塞式;水驱油之后剩余油类型不同,A类流动单元主要为小绕流形成的小簇状油块和厚膜状残余油,而B类流动单元主要为大绕流形成的大簇状油块和珠状、滴状残余油。不同流动单元孔隙结构和润湿性的差别是造成各流动单元不同特征的主要原因。实验研究还表明,研究区C类和B类流动单元是剩余油的主要富集区,应加大挖潜力度。

苏北盆地草舍油田泰州组储层水敏伤害及其对注水开发的影响

运用真实砂岩微观模型实验技术,对苏北盆地草舍油田泰州组储集砂岩进行了浸泡型水敏性实验。结果显示,该砂岩具中等水敏。为充分了解水敏伤害对注水开发的影响,开展了真实砂岩微观模型水驱油实验,包括单模型及组合模型两种实验类型,分别模拟微观及宏观水驱油,并比较了水敏伤害前、后水驱油特征的变化。结果表明,水敏伤害没有改变水驱油方式及残余油形态,但单模型的绕流现象整体增强,驱油效率降低,主要受注水压力、注水位置及微观非均质性等因素影响;而组合模型的采收率整体呈下降趋势,受微观非均质性及宏观非均质性共同控制。为避免水敏伤害对注水开发的影响,建议注入水矿化度为11.99 g/L左右。

应用微观透明模型研究微生物驱油机理

在模拟大港油田官 69断块油藏条件下 ,在微观透明仿真蚀刻模型上进行了该断块候选嗜热驱油菌种的驱油实验 ,在孔隙级别考察了微生物驱油机理。模型孔隙最大直径为 80 0 μm ,最小直径为 8μm ,渗透率 0 .3— 0 .6μm2 。由实验观测得到该菌液的驱油机理如下 :①乳化、携带并启动剩余油 ;②剥离油膜 ;③不动生物气的Jamin效应导致液流转向 ,可动生物气泡与粘附的细小油滴一起流动。在非均质透明薄板夹砂模型上进行菌液驱油 ,观察到显著的重力作用 (菌液下移 ,气体上移 )。

真实砂岩微观模型在鄂尔多斯盆地泾川地区长8砂岩微观非均质性研究中的应用

砂岩储层的微观非均质性特征是储层地质学研究的重要内容之一。通过真实砂岩微观模型实验,客观并且真实的分析了鄂尔多斯盆地泾川地区长8砂岩的微观非均质性特征,发现该区长8储层为致密型砂岩,真实砂岩微观模型实验直观地显示出长8砂岩具有很强的微观非均质性,砂岩的成岩作用和孔隙结构是影响本区长8砂岩微观非均质性的主要原因。在低渗透砂岩中,溶蚀作用引起砂岩产生强烈的非均质性,而这些砂岩则形成长8砂岩的高渗带。

砾岩油藏聚合物驱微观机理研究

应用微观透明仿真刻蚀模型和平面填砂模型研究了砾岩油藏聚合物微观驱油机理。微观模型驱油实验结果表明,聚合物可驱替砾岩油藏喉道和孔道中的剩余油,不能驱出盲端剩余油;油的流动机理,在亲水模型中以剪切夹带为主,而在亲油模型中以拉丝、桥接为主。平面填砂模型聚合物驱实验中明显看到形成油墙,波及体积增加,水驱剩余油明显减少。6种平面填砂模型聚合物驱提高采收率程度不同,最终采收率有较大差别。砾岩模型的最终采收率低于砂岩模型,这是由于砾岩油藏中不流通孔道和盲端较多,残留在其中的油较多。砾岩模型的非均质性越严重,聚合物驱的效果越好。砾岩储层岩心颗粒均匀充填模型的聚驱采收率增值为10.56%,主流线两侧充填密度不同的、主流线充填密度较高的及均匀充填的3个以陶瓷颗粒模拟砾岩颗粒的填砂模型,聚驱采收率分别为9.95%,9.06%及8.87%。聚合物驱仍能用于水驱后的砾岩油藏。图14表1参12。

用微观模型组合实验研究最低吸水层渗透率

利用不同微观模型之间的物性差异及其直观性的特点，设计了微观模型组合实验，模拟油层注水，以研究储层非均质对油水运动的影响。通过模型组合实验，可以确定一个合注层段内不吸水小层的渗透率下限，即最低吸水层渗透率Ｋｗｍｉｎ，研究Ｋｗｍｉｎ与合注层段中最大渗透率值Ｋｍａｘ及注水压力梯度之关系，从而可以进一步根据油层的实际注水压力梯度及用该井取心、测井资料确定的渗透率剖面，求取一个合注层段、一口井、一个油藏的最低吸水层渗透率。最低吸水层渗透率值可以用来进行油藏注水开发效果分析，研究油层剩余油分布。应用Ｋｗｍｉｎ对鄯善油田三间房组油层部分注水井合注层段的吸水状况做了初步分析，获得了比较满意的结果。可以预料对最低吸水层渗透率的深入研究，将获得该参数更广泛的用途。

注水开发油田油层结垢机理及油层伤害

通过砂岩微观孔隙模型模拟实验 ,分别对 Ba SO4和 Ca CO3结垢机理及结垢油层伤害规律进行了研究。研究结果表明 :1油层结垢是在多次的异相成核—晶体生长过程形成的 ,晶体生长在孔隙中和喉道处均可发生 ;2不同类型结垢 ,其结垢特点不同。Ba SO4结垢呈现出水混合—结垢交替间断进行及垢晶体晶形发育差、晶粒细小之特点 ,而 Ba SO3结垢呈现出连续进行及垢晶体晶形发育好、晶粒粗大之特点 ;3结垢油层伤害是一复杂问题 ,即使不考虑温度及多相渗流的影响 ,其仍受到结垢量和油层渗透性的双重影响。一般结垢量越大 ,油层渗透性越差 ,结垢对油层的伤害越严重。随油层渗透性变差 ,结垢量不同引起的结垢油层伤害程度的差异减小 ;随结垢量增大 ,渗透性不同 ,油层结垢伤害程度的差异减小。

超临界CO_2-水两相流与CO_2毛细捕获:微观孔隙模型实验与数值模拟研究

CO_2毛细捕获机制是CO_2地质封存中的关键科学问题,然而有关孔隙尺度下(微米极)超临界CO_2毛细捕获的研究较少.采用高压流体-显微镜-微观模型实验装置,开展超临界CO_2条件(8.5 MPa,45?C)下CO_2驱替水(排水)和水驱替CO_2(吸湿)实验,采用高分辨率照相机采集CO_2水两相流运动图像,并借助光学显微镜直接观测孔隙尺度下CO_2毛细捕获特征.同时,采用计算流体动力学方法对实验过程进行三维数值模拟.数值模拟不仅反映了实验过程中两相流驱替锋面的推进过程,还刻画了孔隙尺度下被捕获的CO_2液滴/团簇三维空间形态特征.最后,基于数值模拟给出了CO_2初始饱和度与残余饱和度曲线,即毛细捕获曲线,并对比分析了3种毛细捕获曲线预测模型(即Jurauld模型、Land模型和Spiteri模型)的优劣.分析表明,Jurauld模型的描述能力稍优于Land模型,Spiteri模型的描述能力较弱.由于Land模型只需单个参数,且参数具有明确的物理意义,因此在实际工程中,建议优先采用Land模型.

白豹地区长3储层微观非均质性的实验研究

目的探讨鄂尔多斯盆地白豹地区长3储层的微观非均质性特征。方法通过真实砂岩微观模型实验对储层进行研究。结果白豹地区长3储层为致密型砂岩,真实砂岩微观模型实验直观地显示出长3储层具有很强的微观非均质性。结论砂岩的成岩作用和孔隙结构是影响本区长3储层微观非均质性的主要原因。在低渗透砂岩中,溶蚀作用引起砂岩产生强烈的非均质性,而这些砂岩则形成长3储层的高渗带。

姬塬延安组储层水驱油效率及影响因素

应用真实砂岩微观模型对樊家川、元城油田侏罗系延９、延１０油层两相驱替过程进行了观察、研究。实验结果表明：研究区微观砂岩模型无水期驱油效率低；驱油效率与注入水入口压力成反比，而与渗透率成正比；樊中区驱油效率为三个区块中最高的，延９２为延９油层组三个小层中驱油效率最高的；影响驱油效率的主要因素是驱替压力、渗透率、孔隙结构非均质性和视孔喉体积比。

聚合物/羧基甜菜碱二元复合体系驱替水驱后残余油的机理

实验研究在30℃下进行。实验聚表二元复合体系为1.0 g/L HPAM、2.0 g/L羧基甜菜碱在矿化度3.7 g/L的模拟大庆油田采出水中的溶液,与模拟大庆油(黏度10 mPa.s)间的界面张力为5.8×10-3mN/m,1-1000 s-1范围的表观黏度与1.0 g/L HPAM溶液十分接近。在玻璃刻蚀大庆油藏仿真均质微观模型上,水驱20 PV的采收率为55.795%,注入20 PV二元体系使采收率增加39.724%;在二元复合体系驱替过程中,注入、采出口之间主流区域内的水驱后残余油在二元复合体系作用下发生变形,伸长并形成油丝,主要以油丝的形式被驱出;过渡区和边角区的残余油则主要以W/O乳状液的形式被驱出。W/O乳状液中的乳化水滴通过圈闭、Y型孔道挤压及水滴变形、断裂这3种方式形成并汇集为比较连续的W/O乳状液流,二元复合体系以W/O乳状液的形式由主流区扩展到两侧的过渡区,再进入边角区,启动死油区的残余油,从而扩大了波及体积,提高了驱油效率。图5参11。

双辊连铸薄带凝固组织仿真模拟的微观模型

在研究双辊薄带连铸工艺凝固过程的基础上 ,运用金属凝固的基本原理 ,并用现代计算机仿真技术建立了双辊连铸薄带凝固的形核、枝晶尖端的生长动力学、柱状晶向等轴晶生长的转变 (CET)的解析模型及仿真模型 ,为双辊连铸薄带凝固组织形成的仿真模拟奠定了基础。