纳米流体对储层润湿性反转提高石油采收率研究进展

储层岩石的润湿性对于石油采收率至关重要,近年来纳米流体润湿反转技术在提高石油采收率方面的应用得到了广泛关注,并取得了一系列成果。本文首先介绍了利用纳米流体对储层润湿性反转在提高石油采收率方面的应用,包括提高水驱效率和降压增注,其次归纳了润湿性变化的实验评价方法并分析影响纳米流体润湿反转效果的因素,表明纳米材料性质（类型、尺寸、浓度）和地层环境（温度、矿化度）均有不同程度的影响。然后阐述了纳米流体改变储层润湿性的机制,认为其包含纳米流体润湿铺展和纳米颗粒岩石壁面吸附的双重机制。最后指出运用此技术存在的问题和难点,并对以后的研究方向进行了展望。     

树枝状介孔纳米材料形貌调控机制及驱油性能

首先,以硅酸四乙酯（TEOS）和尿素为原料、十六烷基三甲基溴化铵（CTAB）为模板剂,通过双连续相微乳液法制备了树枝状介孔纳米材料（DMSNs）,然后将丙烯酰胺与2-丙烯酰胺基-2-甲基丙磺酸二元聚合物[P（AM-AMPS）]以质量分数0.05%（以DMSNs分散体系质量计）加入DMSNs分散体系形成DMSNs流体。采用FTIR、XRD、SEM、TEM、N₂吸附-脱附对DMSNs进行了表征,考察了反应时间、TEOS添加量（以对二甲苯体积计,下同）、共溶剂、搅拌速率和反应温度对DMSNs性能的影响,探究了DMSNs米流体的润湿性及驱油性能。在反应时间6 h、TEOS添加量25%、以乙二醇为共溶剂、搅拌速率1000 r/min和反应温度85℃的最佳条件下,制备的DMSNs平均粒径为91 nm,比表面积为1094.75 m²/g,孔隙体积为1.862 cm³/g,平均孔径为6.1 nm;DMSNs表面具有特殊的褶皱形态,呈现“片状/层状”的花状介孔结构。DMSNs含量（以去离子水质量为基准,下同）0.10%的DMSNs流体能使岩石的润湿性从油湿性转变为水湿性,油相（正十六烷）接触角从0°增加到132°,可有效改变岩石润湿性,显著提高三次采收率（39.6%）;DMSNs的制备过程为竞争性成核和生长机制,分为初始成核、纵向生长、二次成核+横向生长3个阶段。     

Surfactant-Induced Wettability Alteration of Oil-Wet Sandstone Surface: Mechanisms and Its Effect on Oil Recovery

Different analytical methods were utilized to investigate the mechanisms for wettability alteration of oil-wet sandstone surfaces induced by different surfactants and the effect of reservoir wettability on oil recovery. The cationic surfactant cetyltrimethylammonium bromide (CTAB) is more effective than the nonionic surfactant octylphenol ethoxylate (TX-100) and the anionic surfactant sodium laureth sulfate (POE(1)) in altering the wettability of oil-wet sandstone surfaces. The cationic surfactant CTAB was able to desorb negatively charged carboxylates of crude oil from the solid surface in an irreversible way by the formation of ion pairs. For the nonionic surfactant TX-100 and the anionic surfactant POE(1), the wettability of oil-wet sandstone surfaces is changed by the adsorption of surfactants on the solid surface. The different surfactants were added into water to vary the core surface wettability, while maintaining a constant interfacial tension. The more water-wet core showed a higher oil recovery by spontaneous imbibition. The neutral wetting micromodel showed the highest oil recovery by waterflooding and the oil-wet model showed the maximum residual oil saturation among all the models.     

Effects of compositional variations on CO2 foam under miscible conditions

Foam can mitigate the associated problems with the gas injection by reducing the mobility of the injected gas. The presence of an immiscible oleic phase can adversely affect the foam stability. Nevertheless, under miscible conditions gas and oil mix in different proportions forming a phase with a varying composition at the proximity of the displacement front. Therefore, it is important to understand how the compositional variations of the front affect the foam behavior. In this study through several core‐flood experiments under miscible condition, three different regimes were identified based on the effects of the mixed‐phase composition on CO₂ foam‐flow behavior: In Regime 1 the apparent viscosity of the in‐situ fluid was the highest and increased with increasing x_CO2. In Regime 2 the apparent viscosity increased with decreasing x_CO2. In Regime 3 the apparent viscosity of the fluid remained relatively low and insensitive to the value of x_CO2. © 2017 American Institute of Chemical Engineers AIChE J, 64: 758–764, 2018     

生物表面活性剂驱油研究进展

第三次采油技术的发展促进了表面活性剂在油田生产中成熟而稳定的应用。与化学合成表面活性剂相比,生物表面活性剂具有无毒等优势,在近些年呈现出热点研究态势,部分成果业已得到应用。本文从生物表面活性剂的驱油机理、纯化、应用3个方面进行论述,并对其发展趋势进行了展望。在驱油机理方面,主要通过降低油水界面张力、乳化残油以及润湿性反转3种作用,保障开采后期的油藏采收率。在纯化方面,单一方法制备生物表面活性剂技术已经较为成熟,但这些方法均具有一定局限性;采用两种或多种方法联用,既可以降低纯化成本又可以提高产率,成为未来生物表面活性剂纯化技术的发展趋势。在应用方面,主要体现在与化学表面活性剂进行复配后定向注入油藏进行驱油;此外,近年来也开发出利用高效营养剂激活本源微生物,诱导其产生表面活性物质继而富集、驱油的新技术。     

Instability due to wettability alteration in displacements through porous media

Wettability of some petroleum reservoir rocks can be altered by changing the brine composition, e.g., lowering salinity or adding surfactants. Wettability alteration can mobilize stranded oil and enhance oil recovery. Analytical solutions for 1D tertiary low-salinity floods show two saturation shocks one of which is associated with an adverse mobility ratio. The adverse mobility ratio across this shock is not very large, about 1.5-3 in the cases considered. As the viscosity ratio increases, the width of the oil bank decreases and one of the shocks disappears at a high viscosity ratio (>10). The remaining shock at high viscosity ratio is stable. A viscous fingering model is applied to describe the flow instability in relatively homogeneous multi-dimensional porous media. It shows that the viscous fingering is mild and the breakthrough of low-salinity injectant is only 11-31% faster than in the 1D flow. Numerical simulation of these displacements in 2D permeability fields show that the fingering model approximates the average saturation profile if the standard deviation in permeability heterogeneity is low. Fingering behavior depends mostly on permeability standard deviation, but not on correlation length for the spherical variogram model used in this study. Low-salinity floods are expected to be mildly unstable due to the low mobility ratio at adverse saturation shocks.     

乳化/润湿耦合作用稠油流动减阻新思路

稠油节能增输是解决常规原油日渐枯竭、保障原油接替的紧迫需求,然而稠油黏度高、流道黏附性强,使其输送异常困难,是稠油节能增效输送技术瓶颈。根据前期研究本文作者发现,活性水作用下稠油乳化降黏的同时可改变稠油与管内壁界面特性,以及稠油提高采收率——润湿性之润湿反转,提出管输稠油乳化降黏及其流固界面润湿耦合作用流动减阻新思路。本文基于国内外相关研究成果的系统分析,探讨稠油乳化降黏、流固界面润湿及耦合减阻的有效性,剖析活性水作用乳化/润湿耦合减阻存在的主要问题,理论分析稠油在管输过程中实现乳化/润湿耦合减阻的可行性。结果表明,乳化/润湿减阻思路在理论上是可行的,而且在表面活性剂作用下乳化降黏的同时管输流固界面润湿反转更容易实施,然而,乳化/润湿减阻实际应用缺乏充分认识尚需深入研究其相关科学问题;其深入研究有望理解与认识流固界面特性对流动阻力的影响作用,可解决管输稠油流动阻力之难题,将为稠油流动改进提供理论与技术支撑,在稠油管输节能增效方面具有广阔的应用前景。     

壬基酚聚氧丙烯聚氧乙烯醚磺酸盐应用性能

合成了壬基酚聚氧丙烯聚氧乙烯醚磺酸盐（NPESO-3-4）,采用高效液相色谱法检测了目标产物中原料的含量,同时测定了其表面张力、乳化能力、润湿性及模拟驱油率并与壬基酚聚氧乙烯醚磺酸盐的性能（NPESO-0-4）做了比较。结果表明：与NPESO-0-4相比,NPESO-3-4水溶液降低表面张力的能力略低,但降低表面张力的效率较高。二者与胜利孤东原油之间的界面张力均在10-1 mN?m-1数量级,但NPESO-3-4能将油性表面润湿反转为中间润湿,乳化能力和模拟驱油率明显高于NPESO-0-4,说明含氧丙烯链节的阴-非离子表面活性剂在三次采油中有很好的应用价值。     

硅胶与高岭土的润湿性及荧光和驱油研究

利用Ｗａｓｈｂｕｒｎ方程测量固体粉末的润湿性,研究了十二烷基苯磺酸钠（ＳＤＢＳ）水溶液在硅胶及高岭土两种固体粉末表面上的接触角,用荧光猝灭法测定了ＳＤＢＳ在水溶液里的胶束平均聚集数。并由此探讨了十二烷基苯磺酸钠水溶液在固体粉末表面上的润湿性,表面活性剂的临界胶束浓度（ＣＭＣ）与表面含油粉末脱油率的关系。     

质子交换膜燃料电池内含水气体扩散层的冻结特性研究

为了研究含水气体扩散层（GDL）的冻结特性及水分迁移规律,设计并搭建了含水GDL冻结过程的可视化观测系统。制备了不同润湿性的含水GDL,并对含水GDL的冻结过程进行了可视化实验研究,分析了含水GDL冻结过程中的温度变化,以及润湿性和过冷度对于结冰概率的影响。实验结果表明：含水GDL中的某点突然结冰引发整个GDL内水的过冷状态释放,随后在液固相变的体积膨胀作用下,尚未冻结的过冷水被挤压到GDL孔隙外;疏水性GDL会在更高过冷度下产生冻结现象;随着含水GDL温度的降低,内部过冷水的冻结概率不断增加。本研究探索了含水GDL的冻结特性,可为今后解决质子交换膜燃料电池（PEMFC）冷启动过程中GDL低温冻结问题奠定基础。     

The effect of different porous media on moisture loss and oil absorption profiles during frying using glass micromodels

Microstructure plays a key role in oil absorption during frying. The aim of this work was to improve our understanding of the relationship between microstructure and oil absorption, through the use of glass micromodels to obtain evidence of transport phenomena in three porous networks. Micromodels were saturated with water and partially immersed in oil at 190°C. Moisture and oil profiles were imaged to get water and oil saturation maps. Image and fractal analyses were performed to describe the morphology of the evaporation and oil fronts. Results showed that higher porosity facilitated the moisture removal and promoted greater oil absorption during cooling. The fractal dimension showed that microstructures with a relatively high number of fine capillaries were less stable and propitiated fingering during the advance of the evaporation front. In all matrices, the disruption of the surface oil film due to air penetration was a critical factor to stop oil imbibition. © 2015 American Institute of Chemical Engineers AIChE J, 62: 629–638, 2016     

FIVE-SPOT INJECTION/PRODUCTION WELL LOCATION DESIGN BASED ON FRACTURE GEOMETRICAL CHARACTERISTICS IN HEAVY OIL FRACTURED RESERVOIRS DURING MISCIBLE DISPLACEMENT: AN EXPERIMENTAL APPROACH

Mapping fracture characteristics by using seismic acquisition and processing is important not only to identify sweet spots, but also to optimize production, especially for unconventional heavy oil reservoirs. In this experimental work we used five-spot micromodels initially saturated with heavy oil to find the optimum well locations during first-contact miscible displacement. The experiments were performed at a fixed injection rate on fractured micromodels with various patterns. The optimum location for injection/production wells was found in the pattern where fractures make an angle of 45° with the mean flow direction. Moreover, oil recovery was increased with the density, length, level of scattering, and discontinuity of fractures. The analysis of the experimentally measured recovery curve revealed that there are three distinct stages for each displacement. The efficiency of the first stage was found to be dominated by dispersion and diffusion. However, the recovery of the second stage was significantly affected by the fracture orientation. The displacement efficiency of the third stage was controlled by solvent dispersion, which is at maximum for the pattern with higher density, length, scattering, and discontinuity of fractures. Saturation monitoring showed that the fracture geometrical characteristics strongly affected the splitting, spreading, and shielding of the produced fingers and solvent front shape and consequently affected the recovery factor. As a result, five-spot micromodels can be used to investigate the optimum location of injection/production wells during miscible displacements in fractured heavy oil reservoirs.     

Application of microbial enhanced oil recovery technology in water‐based bitumen extraction from weathered oil sands

When using the water‐based extraction processes (WBEPs) to recover bitumen from the weathered oil sands, very low bitumen recovery arisen from the poor liberation of bitumen from sand grains is always obtained. Application of microbial enhanced oil recovery (MEOR) technology in WBEPs to solve the poor processability of the weathered ore was proposed. It was found that processability of the microbial‐treated weathered ore was greatly improved. The improved processability was attributed to the biosurfactants production in the culture solution, alteration of the solids wettability, degradation of the asphaltene component, and the decrease of the bitumen viscosity, which collectively contributed to the bitumen liberation from the surface of sand grains. Although it still has many issues to be solved for an industrial application of the MEOR technology in oil sands separation, it is believed that the findings in this work promote the solution to the poor processability of the weathered ore. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2985–2993, 2014     

SIMULTANEOUS HEAT AND FLUID FLOW IN POROUS MEDIA: CASE STUDY: STEAM INJECTION FOR TERTIARY OIL RECOVERY

Heat transfer and fluid flow in porous media occur simultaneously in thermal enhanced oil recovery and significantly increase the rate of energy transfer. The purpose of this investigation was to take advantage of such contemporary transfers and to study heavy oil recovery efficiency using hot-water flooding, cold-water flooding, and steam injection into porous media. A set of multistage laboratory tests was performed to find the temperature profile during steam injection as a means of tertiary oil recovery. Sand-packed models were utilized to investigate the oil recovery efficiency during cold and hot water injection as well as steam flooding for both secondary and tertiary oil production stages. An oil bank was formed in steam injection during the tertiary oil recovery from a vertical standing sand-packed model, resulting in very high oil recovery efficiency. Steam injection was found to be very effective, compared to cold- and hot-water flooding, for the recovery of heavy oil. Based on the principles of transport phenomena in porous media, a mathematical model was developed to predict the temperature profile during the steam injection process. Satisfactory agreement is achieved between the temperature profile predicted from the model and the experimental results.