Monitoring the Effect of Discontinuous Shales on the Surfactant Flooding Performance in Heavy Oil Reservoirs Using 2D Glass Micromodels

Although most heavy oil reservoirs contain discontinuous shaly structures, there is a lack of fundamental understanding how the shaly structures affect the oil recovery efficiency, especially during surfactant flooding to heavy oils. Here, an experimental study was conducted to examine the effect of discontinuous shales on performance of surfactant flooding by introducing heterogeneities to represent streaks of shale in five-spot glass micromodels. Results show that oil recovery in presence of shale streak is lower than in its absence. Based on the authors’ observations, the presence of flow barriers causes premature breakthrough of injected fluids and also an unstable displacement front. As well, displacement efficiency of surfactant flooding is dependent strongly on the shale distribution configuration. Increasing shale content causes reduction of ultimate oil recovery and also severe fingering during water flooding while it compensates during surfactant flooding considerably. In shaly patterns, in the case of surfactant flooding, the oil recovery after breakthrough increases significantly, while it changes much less for the case of water flooding as well as flooding in homogeneous model. Oil recovery efficiency and breakthrough time improved with increasing surfactant concentration. However, beyond a specific limit of sodium dodecyl sulfate concentration, around 2000 ppm, incremental oil recovery becomes insignificant. Presence of connate water in surfactant flooding scheme can improve the recovery efficiency in shaly patterns. Results of this work can be helpful to investigate the optimal location of injection/production wells during enhanced oil recovery schemes in shaly reservoirs using five-spot micromodels.     

应用CT扫描技术研究低渗透岩心水驱油机理

通过CT扫描技术在线获得不同时刻岩心内流体饱和度的沿程分布信息,探索了低渗透岩心水驱油机理,并讨论了驱替速度(毛管数)、束缚水存在状况和非均质性对微观孔隙介质中流体渗流分布特征及微观驱油机理的影响.实验结果表明,当驱替速度较高时,含水饱和度增量沿程分布呈现对流式的直进形态,此时微观驱油机理以活塞式推进为主;当驱替速度较低时,毛管压力开始起作用,使含水饱和度增量沿程分布范围拓宽,在很小的注入孔隙体积倍数下出口端即会见水,此时微观驱油机理以卡断或爬行为主.另外,与无束缚水时相比,束缚水的存在使得含水饱和度增量沿程分布推进前缘变得更加平缓,这是因为预先存在于小孔隙中的水很容易被注入水补充聚集,在含水饱和度增量沿程分布推进前缘到达前有充足的时间形成稳定的隔断阻塞孔喉,因此束缚水的存在促进了卡断现象的发生.在强非均质性岩心中,含水饱和度增量沿程分布前缘的推进更加分散、均匀,这是因为孔隙介质的微观非均质性使得驱替产生的毛管阻力具有较大差异,使得指进和绕流成为主要的微观驱油机理.     

砾岩油藏复合体系驱油机理研究：以克拉玛依砾岩油藏为例

砾岩油藏由于孔隙结构的特殊性，水驱油效率往往不高，近年来出现的复合体系驱替方法能够有效地提高油藏驱油效率。以克拉玛依砾岩油藏为例，利用微观模拟技术研究了砾岩油藏特殊孔隙结构条件下水驱残余油在复合体系作用下的起动、分散、运移及聚集问题。实验表明，三元复合体系各组分之间的协同效应使得它克服了单相化学剂驱油的缺点，聚合物较好地控制了流度，碱起到牺牲剂的作用，使表活剂能够向更深的地方扩散，既提高了驱油效率又降低了表活剂的用量，从而降低了成本；“油墙”的形成、发展与稳定运动对驱油效率有较大的影响，对“油墙”的形成机理进行了初步探讨；同时，详细分析了不同孔隙结构的驱油机理以及对驱油效率的影响。实验结果表明，三元复合体系能够较大幅度提高原油采收率，是提高砾岩油藏采收率的有效途径之一。图１表２参３（郭海莉摘）     

一种高效廉价驱油体系的室内研究

为研究胜利油田三次采油后期(包括注聚、注胶)提高采收率的接替技术,拓宽三次采油研究领域,开展了高效驱油体系的研制工作。针对胜利油田的油水特点,筛选出多种表面活性剂试样及其复配体系进行油水界面张力测定,成功研制出具有良好驱油性能的复合驱配方。室内物理模拟试验结果显示,这种驱油体系可在水驱基础上提高采收率19％。     

2清洁压裂液返排液驱油体系性能评价及矿场应用

为实现清洁压裂液返排液体系的重复利用,针对一类新型纳米复合清洁压裂液体系展开室内研究,评价了返排液作为驱油体系的界面活性、润湿性、乳化性能以及吸附性能.在此基础上,对驱油体系提高低渗透油藏岩心水驱后的采收率进行了研究.结果表明:在驱油体系质量分数为0.08％,温度为60℃的条件下,与脱气原油之间的界面张力即可达到10-3mN/m数量级,可以使稠油黏度降低率达到95％以上,并具有良好的乳化性能;驱油体系能够使亲水岩石表面转变为中性润湿;驱油体系中的表面活性剂在岩心中的最终滞留量为2.8 mg/g,而纳米颗粒的滞留量为8.8mg/g.岩心模拟驱油实验结果说明,驱油体系可以使饱和脱气原油低渗岩心水驱后的采收率平均提高17.26％,取得了良好的驱油效果.矿场试验结果表明,增油效果显著.     

龙虎泡油田活性水驱油室内实验研究

针对大庆外围低渗透油田注水压力高、吸水能力差以及水驱采收率低等问题,选取龙虎泡油田进行活性水驱油室内物理模拟实验研究。表面活性剂筛选实验结果表明,十二烷基苯磺酸钠配制的活性水溶液/原油体系界面张力可达0.2041 mN/m,且与地层水配伍性良好,比水驱采收率提高16.6%。驱油实验结果表明,水驱速度、活性水浓度、活性水注入量、注入时机均对驱油效果产生一定的影响,当水驱速度为1.0 mL/min、活性水浓度为0.3%、活性水注入量为0.3 PV 时驱油效果最佳。现场实验应选取低含水井进行活性水驱油,当含水率较高时,适当提高活性水浓度以保持开发效果。     

Wettability alteration and spontaneous imbibition in oil-wet carbonate formations

Alkaline/surfactant flooding has been widely tested for its ability to improve oil recovery, but little effort has been made toward understanding the controlling mechanisms and variables. This paper investigates the effect of electrolyte concentration, surfactant concentration and water/oil ratio on wettability, phase behavior, and displacement from a narrow gap. Wettability of calcite can be altered to about intermediate-wet to preferentially water-wet with alkaline/surfactant systems. Anionic surfactant adsorption can be significantly reduced in the presence of sodium carbonate.     

聚合物表面活性剂溶液微观驱油特征

为从微观研究聚合物表面活性剂(简称聚表剂)的驱油机理和驱油效果,采用微观刻蚀仿真模型进行微观可视化驱油实验,并与岩心驱替实验驱油效果对比。结果表明,在微观驱油实验中,水驱后微观模型中产生6种类型残余油,而聚表剂驱后对盲端残余油的驱替效果不明显;聚表剂的驱油机理主要是通过其增黏作用、黏弹性作用和乳化作用来扩大波及体积,降低渗流阻力",拉""、拽"残余油,将大油滴乳化分散成小油滴,从而将残余油有效驱出;不同浓度的聚表剂在微观模型和岩心驱替实验中的驱油效果基本相符,聚表剂浓度越大,残余油启动能力越高,驱油效果越好。聚表剂质量浓度为2000 mg/L时的驱油效果最好,采收率增幅为19.69%。图27表1参15     

表面活性剂对超低渗透油藏渗流特征的影响

针对超低渗透岩心,通过宏观驱替实验研究不同界面张力的表面活性剂对单相启动压力、油水两相启动压力、相对渗透率曲线、降压效果及提高采收率效果的影响,分析表面活性剂对超低渗透油藏渗流规律的影响。研究结果表明,随驱替液界面张力的降低,单相启动压力明显降低。油水两相启动压力实验中,在油水两相相同流速比下,随界面张力的降低,油水两相启动压力梯度逐渐降低,含水饱和度逐渐增大。从束缚水饱和度到残余油饱和度,随含水饱和度的增加,油水两相启动压力梯度先缓慢下降,后迅速下降。相渗曲线实验中,随表面活性剂质量分数的增加,油水两相渗流区增大,油相相对渗透率增大,残余油下水相相对渗透率增加,残余油饱和度降低,油气采收率升高,水相(端点以内)渗透率基本没有变化。表面活性剂段塞驱替实验中,岩心一次水驱后,注入表面活性剂可明显降低超低渗透岩心的注入压力、提高岩心采收率,且油水界面张力越低,降压效果越好,提高采收率幅度越大。     

化学驱中动态界面张力行为的研究进展

汇总了近年来强化采油动态界面张力研究进展的报道,阐述了驱油过程中的动态界面张力行为,总结了碱浓度、油相粘度、驱替液粘度对原油/碱体系及原油/碱/聚合物体系动态界面张力的影响和表面活性剂、离子强度对原油/碱/表面活性剂体系及原油/碱/表面活性剂/聚合物体系动态界面张力的影响,并对上述影响因素进行了归纳。     

An Experimental Investigation of Foam for Gas Mobility Control in a Low-Temperature Fractured Carbonate Reservoir

Abstract

This work concerns the experimental investigation of surfactant alternating CO₂ injection in carbonate rocks. The core samples provided from a low-temperature fractured light oil reservoir, located in southwest Iran. The experiments were designed to observe the effect of CO₂–foam injection on gas mobility and oil recovery at different surfactant concentrations. The core samples were initially saturated with synthetic/field brine, 5,000 ppm, and then flooded with live oil to reach connate water saturation at reservoir condition, 115°F and 1,700 psia. The commercial surfactant used was sodium lauryl sulfate as an anionic surfactant. The results of this work, along with field-scale simulation and/or economic considerations, could be helpful in making reliable decisions about optimum condition of foam-assisted water-alternating-gas (FAWAG) processes.

Core flooding results demonstrated that macroscopic sweep efficiency increased due to foam generation inside the core. In addition, it led to an increase of between 5 and 12% in the recovery factor in comparison to a water-alternating-gas (WAG) process. Furthermore, the value of the critical micellar concentration for the surfactant–oil system was about 2,000 ppm.

After primary and secondary recovery processes, there is a large amount of trapped oil in the reservoir. Extensive research has been directed toward enhancing the recovery of this oil, but limited success has been achieved. FAWAG injection appears to have more applicability to recover the trapped resources. However, little attention has been paid to experimental investigation of FAWAG processes in low-temperature oil reservoirs.     

改性碱木质素表面活性剂在三次采油中的应用研究

研究了改性碱木质素ML(自制 )作为三次采油表面活性剂和石油磺酸钠复配 ,与原油产生超低界面张力条件并进行了岩心驱替试验。结果表明ML能和石油磺酸钠、碱、聚合物配合将油水界面张力降至超低范围 ,用改性木质素代替 50 %ORS 41表面活性剂 ,复合驱采收率可达到 2 0 %左右 ,略高于纯ORS 41三元复合体系的复合驱采收率 ,使用改性碱木质素可较大幅度地降低驱油成本 ,具有广泛的应用前景     

阴离子双子表面活性剂驱油体系研究

对一种新型双子表面活性剂GA12-4-12的耐盐性和驱油性能进行了研究。该表面活性剂在含NaCl为2.35×105 mg/L、CaCl2为1.5×104 mg/L的地层水溶液中表现出良好的表面活性,其临界胶束浓度为538.6mg/L。GA12-4-12溶液与稀油间的油水界面张力随着无机盐含量的增加而降低并趋于稳定,当NaCl含量为250g/L,能使界面张力降至2.2×10-3 mN/m。在高矿化度模拟地层水条件下,GA12-4-12及其与非离子表面活性剂复合体系SP的油水动态界面张力均能达到超低(10-3 mN/m)。进行模拟驱油实验表明,GA12-4-12与SP复合体系提高水驱采收率分别为6.25%、10.67%。     

长庆油田延安组油层光刻显微孔隙模型水驱油研究

本文介绍一种新型显微孔隙模型制作技术、实验方法及实验结果。模型制作采用光刻技术直接将实际岩心的孔隙结构复制下来,因而比较真实。用这种模型分别进行了油驱水和水驱油实验,观察了残余水和残余油类型及形成机理。模形是亲水的。实验结果证实,油驱水之后形成的残余水饱和度受多种因素控制,储集岩孔隙结构的非均质性是形成残余水的主要因素,水驱油过程中卡断和绕流现象十分普遍,这是形成残余油的主要原因。实验还考虑了实际油层的排驱压力和油田注水压力锑度的关系。     

桩西115区块表面活性剂驱技术研究与应用

胜利油田桩西采油厂桩115区块属于高温中低渗油藏,为进一步改善区块注采矛盾,本文通过考察不同浓度4种甜菜碱表面活性剂溶液与桩115区块原油间的界面张力及其在石英砂表面的吸附规律,开发了以甜菜碱表面活性剂为主剂、以碱木素为牺牲剂的低界面张力驱油体系。该体系在石英砂表面的静态吸附量为0.4 mg/g;无需同碱复配,即可使油水界面张力降至5×10-4mN/m。物理模拟实验表明,在水驱后注入0.3 PV冻胶堵剂+0.3 PV低界面张力驱油体系,原油采收率可提高17%。2008年1月在桩115-5井组采用驱替方案进行了现场试验,截止2010年5月净增原油1632 t。图13参7     

Enhanced oil recovery from carbonate reservoirs by spontaneous imbibition of low salinity water

An experimental study was performed to investigate the impact of low salinity water on wettability alteration in carbonate core samples from southern Iranian reservoirs by spontaneous imbibition. In this paper, the effect of temperature, salinity, permeability and connate water were investigated by comparing the produced hydrocarbon curves. Contact angle measurements were taken to confirm the alteration of surface wettability of porous media. Oil recovery was enhanced by increasing the dilution ratio of sea water, and there existed an optimum dilution ratio at which the highest oil recovery was achieved. In addition, temperature had a very significant impact on oil recovery from carbonate rocks. Furthermore, oil recovery from a spontaneous imbibition process was directly proportional to the permeability of the core samples. The presence of connate water saturation inside the porous media facilitated oil production significantly. Also, the oil recovery from porous media was highly dependent on ion repulsion/attraction activity of the rock surface which directly impacts on the wettability conditions. Finally, the highest ion attraction percentage was measured for sodium while there was no significant change in pH for all experiments.     

聚合物驱后石油磺酸盐体系提高采收率室内实验研究

针对孤岛油田中一区Ng4砂层组油藏条件,开展了聚合物驱后以石油磺酸盐为主剂的表面活性剂驱油提高采收率的室内实验研究工作。通过大量的室内实验,研制出以石油磺酸盐为主剂的复配体系,并开展了驱油效率实验。对比了几种低界面张力活性剂驱油体系的驱油效果,筛选出效果最好曲石油磺酸盐驱油配方体系：0．3％SLPS-01C＋0．1％助剂1#。研究了不同转注时机对石油磺酸盐体系提高采收率效果的影响,在注聚合物后含水率最低时,由于聚合物驱的作用,形成“油墙”,可防止表面活性剂窜流,此时转注石油磺酸盐体系效果最好,洗油效果最佳。图4表7参21     

聚能等流度高效驱油新方法研究

对于非均质多油层油藏,现有开采理论和技术难以大幅度挖掘难采及滞留的剩余油,提出了同步聚能等流度调控大幅度提高采收率的新方法和驱油机理.通过等流度设计,实现了非均质层内的分流、聚能、聚流过程,达到大幅度驱油节能、节约注入水、减少注剂、降低投资、高效挖掘难采剩余油及大幅度提高采收率和开采效益的目的.数值模拟研究和对岩心渗透率为0.1～3.0μm²的非均质油层室内实验表明,水驱后聚能等流度驱油均获得较好效果,大幅度减少了注剂量、提高了驱油效率和采收率(60%～80%).现场试验分析表明,该方法能大幅度提高采收率.     

Recovery of residual oil using the alkali/surfactant/polymer process: effect of alkali concentration

An experimental study was conducted to examine the effectiveness of sodium carbonate in alkali, surfactant and polymer combined slugs in recovering waterflood residual oil. The effects of sodium carbonate concentration on the slug viscosity, interfacial tension, and phase behavior were first examined. Core flood experiments were conducted with unfired linear Berea sandstone cores. The incremental oil recovery, oil cut, residual resistance factor, and chemical propagation were measured for each flood.A significant oil bank was formed for all combined slugs having sodium carbonate concentration ≥1 wt%. The incremental oil recovery, oil cut and the injectivity of the combined slugs greatly improved as sodium carbonate concentration was increased. The effect of sodium carbonate concentration on chemical propagation was dramatic for the synthetic surfactant; a slight delay in surfactant breakthrough and a much slower rate of surfactant propagation were observed at high sodium carbonate concentrations.The results obtained in the present study indicate that the residual oil was recovered by two mechanisms: low interfacial tension and wettability reversal. The former mechanism is dominant at sodium carbonate concentrations ≤1 wt%, whereas the latter plays an important role only at high sodium carbonate concentrations.     

弱凝胶在多孔介质中的微观驱替机理

利用室内微观驱替实验装置,采用透明的单层油砂充填模型研究了弱凝胶驱和后续水驱过程中不同时刻各相流体在多孔介质中的分布。微观驱替实验结果表明,弱凝胶沿原先被水占据的大孔道流动,并且可以通过变形被挤入窄小孔喉,在弱凝胶的前沿存在稳定的水胶界面。在后续注水过程中,存在于大孔道的弱凝胶迫使后续注入水改向进入未被注入水波及的小孔隙,驱替的残余油滴聚集并形成油墙。弱凝胶的流体改向作用是提高微观波及效率和采收率的主要因素;弱凝胶的粘弹作用有利于在油藏深部进行深度调剖。