关键词： NAPL修复   孔隙尺度   助溶剂增溶   粉煤灰   纳米颗粒泡沫  

摘要： 由于原油泄漏及有机溶剂不当处置,目前地下水NAPL(non-aqueous phase liquid,非水相流体)污染问题日益凸显,严重威胁到我国地下水用水安全。因为NAPL自身水溶性小,生物降解性低和界面张力高的原因,常规的修复方式难以高效快速地进行清除修复。选用助溶剂-纳米颗粒泡沫协同修复的方式,先通过泡沫驱替作用对孔隙通道中的NAPL进行驱替清除,而后对驱替之后残余的NAPL通过助溶剂的增溶作用进行溶解清除,有望实现地下水中NAPL污染的高效修复。因此,本文研究孔隙尺度助溶剂的增溶机制和纳米颗粒泡沫的驱替机理,为宏观场地污染物迁移数值模拟提供关键参数,为实际场地污染修复优化方案提供过程信息。论文基于拉曼光谱技术,定量观测静止状态和流动状态下NAPL在助溶剂溶液中的溶解过程,获取NAPL与助溶剂溶液的分子扩散过程与助溶剂冲洗对死端孔隙中NAPL增溶机制和影响规律;使用新型粉煤灰纳米颗粒制备泡沫,观测水驱和泡沫驱对二维孔隙介质中NAPL的修复过程,研究粉煤灰纳米颗粒最佳浓度配比。主要工作和认识如下:(1)建立了定量拉曼观测孔隙空间污染物浓度场的技术方法。采用封汞技术制备了标准样品,获取常压不同温度下PCE(四氯乙烯)-乙醇-水三相组成与拉曼参数之间的定量关系,可以实现不同温度下孔隙空间污染物浓度场的定量观测。(2)使用毛细管模拟一维单孔隙,定量观测了静态条件下PCE与不同浓度乙醇溶液的溶解过程。静态条件下,溶解完全由分子扩散主导,借助定量拉曼光谱,测定了PCE在乙醇溶液以及乙醇在PCE中的溶解度与扩散系数,测试数据显示:随着乙醇浓度的增加,溶解度和扩散系数均会逐渐变大,PCE和乙醇的溶解扩散过程加快。其中乙醇浓度从50%提高到80%时,PCE溶解度提高约14倍,PCE扩散系数提高1.3倍,说明增加乙醇浓度能够明显提高PCE的增溶能力和溶解速率。在溶解后期,70%乙醇溶液中界面附近PCE浓度仍会提高0.02,保持乙醇溶液中PCE存在较大的浓度梯度,使得静止状态下PCE的溶解速率为55%乙醇溶液的两倍,因此在实际使用过程中,对于不流动孔隙,乙醇浓度从55%提高到70%,乙醇用量增加20%可以将溶解速率提高100%,实现低成本高效修复。(3)在实际注入助溶剂溶液进行土壤和含水层冲洗修复过程中,残留在介质死端孔隙中NAPL污染物清除难度很大,如何清除残余NAPL,避免其长期污染,是助溶剂冲洗技术的研究重点。为模拟死端孔隙中的修复过程,利用透明微孔隙模型模拟二维平面孔隙介质,借助拉曼光谱定量观测乙醇溶液冲洗下死端孔隙中污染物浓度场,直观观测PCE的溶解过程。结果发现死端孔隙内部也有对流流动存在,对流流动将界面饱和PCE的乙醇溶液带出死端孔隙,同时新的乙醇溶液补充进去,以此来加快PCE的溶解。(4)定量拉曼光谱技术获取了优势通道冲洗流动条件下,不同乙醇浓度、注入流量和孔喉尺寸对死端孔隙中浓度分布的影响,揭示孔隙尺度NAPL的溶解机理和影响规律:乙醇浓度增加对孔隙内部的对流流动没有明显的影响,而是通过提高PCE溶解度,可以让流动的乙醇溶液携带出更多溶解态的PCE,以此来加快PCE的溶解,乙醇浓度从50%增加到70%,PCE溶解速率能够提高89%,提升幅度大于乙醇用量增加比例;注入流量增大主要通过加快靠近优势通道孔隙中的对流流动过程,来加快PCE的溶解,但是对PCE溶解的影响相对较小,注入流量从1μl/min增加到5μl/min,溶解速率仅提升52%,提升幅度远小于乙醇溶液用量增加比例;孔喉尺寸增大主要通过增强远离优势通道孔隙中的对流来加快PCE的溶解,孔喉从0.3 mm增加到0.4 mm,PCE溶解速率增加约3倍,说明孔喉大小对后期PCE的溶解速率起到决定性作用,是模拟预测修复效果的关键参数。因此在助溶剂冲洗后期,选择高浓度助溶剂溶液按照较低流量的注入方式会更适用于实际修复。(5)在实际场地中,NAPL污染物下渗后会受到地下水的长期冲洗,形成长期固存的残余NAPL污染,因此后期的清除修复工作也是基于残余NAPL污染展开的。为模拟残余NAPL的分布状态,实验使用微孔隙模型模拟孔隙介质中饱和NAPL分布在水流冲洗下的驱替清除过程,结果显示NAPL污染物在侵入地下水后可以被流动的地下水进行部分清除,在水流穿透NAPL区域到达出口前,NAPL可以被水流驱替清除,但是在穿透之后会沿着形成的优势通道流动,很少会进入其他孔隙中进行有效清除,形成长期固存的残余NAPL污染,需要采取必要的修复方法进行清除。(6)粉煤灰作为实现废物资源化的新兴材料,制备的泡沫可以对孔隙介质中的NAPL进行有效驱替清除从而提升修复效益。通过观测不同配比的粉煤灰纳米颗粒泡沫对水驱后的残余NAPL进行驱替清除过程,发现泡沫能有效增大波及率,提高残余NAPL的清除效率;随着纳米颗粒

关键词： 页岩   孔隙结构   孔径分布   压汞   液氮吸附   临兴区块  

摘要： 为了揭示鄂尔多斯盆地东缘海陆过渡相页岩微观孔隙结构特征及其主控因素,丰富对该区块海陆过渡相煤系页岩孔隙发育特征与孔隙结构的认识,对临兴地区页岩进行扫描电镜、高压压汞和液氮吸附分析以表征微观孔隙结构特征,同时结合孔隙率、TOC含量、岩石矿物含量、黏土相对含量、有机质成熟度测试结果对页岩孔隙结构发育主控因素进行研究。结果表明:研究区页岩发育粒内孔、粒间孔、溶蚀孔和微裂缝,有机质内部偶见孔隙、可见微裂隙,与矿物伴生时周边发育微裂隙;页岩总孔容介于0.00146~0.01081m L/g,介孔占比81.9%,比表面积介于0.35~3.65 m^(2)/g,孔径分布以单峰型为主,分布范围主要在200 nm以内,主峰孔径在45 nm左右,本溪组、太原组页岩孔隙连通性优于山西组,太原组宏孔占比优于本溪组、山西组;页岩总有机碳含量对页岩孔隙发育的影响复杂,对宏孔发育具有一定的积极作用,脆性矿物含量对总孔、介孔发育有积极作用,黏土矿物含量对总孔和介孔发育起消极作用,其中,脆性矿物和黏土矿物通过影响介孔的发育来控制页岩中孔隙的发育程度。基于页岩孔隙结构多尺度定性–定量表征及其控制因素研究对临兴区块海陆过渡相页岩气资源量评价、甜点优选与开发具有重要指导意义,丰富了对海陆过渡相页岩储层的地质认识。

关键词： Pore-throat size distribution   Yield stress fluids   Pore-network modeling   Laboratory experiments   measurements   Hydraulic properties  

摘要： Substantial progress has been recently achieved in the development of a clean alternative to mercury intrusion porosimetry (MIP) based on single-phase flow measurements in porous samples using yield stress fluids. However, no study to date has examined the scale of the pore length actually provided by the yield stress fluids porosimetry method (YSM) in consolidated porous media. Indeed, while the results of YSM were compared to those provided by MIP in the past, the relationships between the characterized pore size distribution (PSD) and the actual pore geometry have still not been addressed for this type of porous media. This issue is of special interest to geoscientists involved in seeking relevant information from core characterization operations. With this aim in mind, the objective of the present paper is to evaluate the agreement between the PSDs characterized by YSM, the pore-opening size distributions provided by MIP tests, and the pore-throat and pore-body size distributions obtained from X-ray computed microtomography. For this purpose, a set of artificial and natural porous samples with permeability values extending over two magnitudes were characterized by using both YSM and MIP laboratory tests. Then, the results were matched to the model pore geometries extracted from digital images of the real microstructure. This analysis led to the main conclusion that YSM can be reliably used as an adequate substitute for MIP in the case of the investigated consolidated media, given the general agreement observed between these methods.

关键词： 特高含水期   剩余油   VOF方法   复杂多孔介质   两相流  

摘要： 准确认识多孔介质内水驱剩余油的微观赋存状态对于改善高含水油田水驱开发效果,提高水驱采收率具有重要意义。在对Volume of Fluid(VOF)方法验证的基础上,充分利用其追踪两相界面动态变化、再现微观渗流物理过程的优势,开展特高含水期砂岩油藏物性条件、驱替方式对剩余油微观赋存特征和采收率的影响研究。通过分析典型孔隙结构的微观渗流特征和剩余油受力情况,揭示不同类型微观剩余油的动用机制和规律:水湿条件下驱替速度的增大和驱替方向的改变会使得微观剩余油分布较为分散且采收率得到不同程度的提高;油湿及高黏度比条件下毛管阻力、黏滞力较大,剩余油多以簇状和多孔状聚集分布,采出程度相对较低。

关键词： Flow boiling   Micro-porous structure   Trapped liquid   Liquid bridge   Film flow   Heat transfer enhancement  

摘要： Flow boiling is an important heat dissipation method for cooling high heat flux surfaces in many industrial *** heat transfer can be further enhanced by using porous media surfaces due to their high specific surface ***,although flow boiling in channels is well understood,the phasechange behavior with the additional capillary effect induced by the porous structures is not well understood,and the design of the porous structures is difficult to avoid dryout and over-temperature accidents.A pore-scale lab-on-a-chip method was used here to investigate the flow boiling heat transfer characteristics inside micro-porous *** flow patterns,captured in the two-phase region with a uniform pore-throat size of 30 lm,showed that liquid was trapped in the pore-throat structures as both dispersed liquid bridges and liquid ***,the liquid film was shown to be moving on the wet solid surface by laser-induced fluorescence and particle tracking.A theoretical analysis showed that the capillary pressure difference between adjacent liquid bridges could drive the liquid film flows,which helped maintain the coolant supply in the two-phase *** pore-throat parameters could be designed to enhance the capillary pressure difference with multiple throat sizes of 10–90 lm which would enhance the heat transfer 5%–10%with a 5%–23%pressure drop *** research provides another method for improving the flow boiling heat transfer through the porous structure design besides changing the surface wettability.

关键词： Porous materials  

摘要： Researches on the thermo-hydro-mechanical (THM) coupling effect in porous media from the perspective of pore-scale is of great significance for the study of enhanced oil recovery, nuclear storage, and geological sequestration of CO2. In order to study the migration of oil resources in porous media in the deep oil reservoir, we used a combined method to realize the THM process occurring in porous media. The Darcy-Brinkman-Biot method was applied to simulate the THM process and the calculation of thermal stress was achieved by adding the Duhamel-Neumann thermoelastic stress to the model. A water-oil two-phase flow process considering THM coupling effect in porous media was then realized. The model has simulated flow of multiphase fluid in the pore space by solving the Navier-Stokes equations and calculated flow of the fluid in the rock matrix by solving the Darcy equation. The two processes were coupled with a series of momentum exchange equations to obtain the displacement of solid particles, thus realizing the fluid-solid coupling effect. On this basis, a heat transfer model was added to numerical model to consider the influence of temperature field on the two-phase flow process. Temperature field acts on the matrix in the form of thermoelastic stress to realize the THM coupling process. Based on the model, we simulated the flow process of water-oil two-phase fluid in a two-dimensional porous media model. The results have shown that: (1) the direction of thermal stress was opposite to that generated by fluid-structure coupling effect, which made the total stress smaller than that under the fluid-structure coupling effect;(2) the porosity of the model increased with the increase of temperature, however, when the injection temperature difference reached 150 K, the porosity no longer increased significantly;(3) with the increase of temperature, the relative permeability of the water phase increased and the equal-permeability point shifted to the left. © 2021, Chinese J

关键词： 微观结构   等效孔隙网络模型   孔隙尺度   孔喉结构参数   绝对渗透率   各向异性  

摘要： 以羊场湾不粘煤为研究对象,基于micro-CT扫描实验和Avizo处理软件,对煤中孔裂隙、矿物质以及煤基质进行精确提取与分割,并通过三维重构技术,得到了连通孔裂隙模型;在此基础上,进一步建立了具有孔裂隙形态学拓扑结构的等效孔隙网络模型,统计分析了煤中孔喉结构参数,包括孔隙半径、孔隙体积、喉道半径、喉道长度以及配位数;基于孔隙尺度的渗流模拟,实现了孔裂隙空间单相水的可视化渗流过程,并计算了3个方向的绝对渗透率。研究结果表明:羊场湾不粘煤中以片状孔隙群和大尺度互相垂直的裂隙发育为主,平均孔隙半径和喉道半径分别为106、27.79μm,平均配位数为3.45;在单相水渗流过程中,孔裂隙空间内的渗流速度明显高于流入流出端,3个方向的渗透率表现出明显的各向异性,其中y方向的绝对渗透率数值最大,x方向的渗透率最小。

关键词： 多孔介质   渗流   荧光倒置显微镜   孔隙尺度   碳封存  

摘要： 为了更好地从微观尺度揭示流动机理,研制了高温高压多相渗流显微成像实验系统,开发了孔隙尺度的多相流体成像识别技术。以CO_(2)在不同孔隙通道结构微芯片中驱替咸水实验为例,介绍了该实验系统的使用步骤和方法,利用荧光倒置显微镜结合高速相机,捕获了CO_(2)咸水层封存中的两相微观渗流过程。通过后期图像处理可以定量分析饱和度等物性参数,为系统掌握多相流体微观渗流规律提供了必要的基础实验数据,为工程应用提供一定的理论参考。

关键词： 纳米流体驱油   提高采收率   孔隙尺度模拟   流体体积法  

摘要： 基于不同渗透率岩心的三维微观模型,采用流体体积法对纳米流体驱油进行数值模拟;利用实验测得的含SiO_(2)纳米颗粒的悬浮液界面张力、接触角和黏度,针对质量分数为0~1%、具有不同粒径的SiO_(2)纳米颗粒的水基悬浮液,研究了纳米颗粒质量分数和粒径、驱替液流速、原油黏度和岩心渗透率对纳米流体驱油效率的影响。研究表明:采收率随着颗粒质量分数的增加而增加,纳米颗粒质量分数增加到0.5%时,与水驱相比采收率可提高约19%;纳米流体驱油采收率随着纳米颗粒粒径的减小而增加;在毛管数接近临界值的注入模式下使用纳米流体驱油对高黏低渗储集层提高采收率最为有效,且提高采收率幅度随着驱替速度的增加而减小;原油黏度越大,岩石渗透率越小,纳米流体驱油提高采收率的效果越明显。图16表2参37。