Experimental investigation on using CO_(2)/H_(2)O emulsion with high water cut in enhanced oil recovery

CO_(2) emulsions used for EOR have received a lot of interest because of its good performance on CO_(2)mobility reduction.However,most of them have been focusing on the high quality CO_(2) emulsion(high CO_(2) fraction),while CO_(2) emulsion with high water cut has been rarely researched.In this paper,we carried out a comprehensive experimental study of using high water cut CO_(2)/H_(2)O emulsion for enhancing oil recovery.Firstly,a nonionic surfactant,alkyl glycosides(APG),was selected to stabilize CO_(2)/H_(2)O emulsion,and the corresponding morphology and stability were evaluated with a transparent PVT cell.Subsequently,plugging capacity and apparent viscosity of CO_(2)/H_(2)O emulsion were measured systematically by a sand pack displacement apparatus connected with a 1.95-m long capillary tube.Furthermore,a high water cut(40 vol%) CO_(2)/H_(2)O emulsion was selected for flooding experiments in a long sand pack and a core sample,and the oil recovery,the rate of oil recovery,and the pressure gradients were analyzed.The results indicated that APG had a good performance on emulsifying and stabilizing CO_(2) emulsion.An inversion from H_(2)O/CO_(2) emulsion to CO_(2)/H_(2)O emulsion with the increase in water cut was confirmed.CO_(2)/H_(2)O emulsions with lower water cuts presented higher apparent viscosity,while the optimal plugging capacity of CO_(2)/H_(2)O emulsion occurred at a certain water cut.Eventually,the displacement using CO_(2)/H_(2)O emulsion provided 18.98% and 13.36% additional oil recovery than that using pure CO_(2) in long sand pack and core tests,respectively.This work may provide guidelines for EOR using CO_(2) emulsions with high water cut.

Flow Characteristics of Crude Oil with High Water Fraction during Non-heating Gathering and Transportation

In order to ensure the safety of the non-heating gathering and transportation processes for high water fraction crude oil,the effect of temperature,water fraction,and flow rate on the flow characteristics of crude oil with high water fraction was studied in a flow experimental system of the X Oilfield.Four distinct flow patterns were identified by the photographic and local sampling techniques.Especially,three new flow patterns were found to occur below the pour point of crude oil,including EW/O&W stratified flow with gel deposition,EW/O&W intermittent flow with gel deposition,and water single-phase flow with gel deposition.Moreover,two characteristic temperatures,at which the change rate of pressure drop had changed obviously,were found during the change of pressure drop.The characteristic temperature of the first congestion of gel deposition in the pipeline was determined to be the safe temperature for the non-heating gathering and transportation of high water cut crude oil,while the pressure drop reached the peak at this temperature.An empirical formula for the safe temperature was established for oil-water flow with high water fraction/low fluid production rate.The results can serve as a guide for the safe operation of the non-heating gathering and transportation of crude oil in high water fraction oilfields.

Experimental study on surface-active polymer flooding for enhanced oil recovery: A case study of Daqing placanticline oilfield, NE China

Experiments on surface-active polymer flooding for enhanced oil recovery were carried out by detection analysis and modern physical simulation technique based on reservoirs and fluids in Daqing placanticline oilfield.The experimental results show that the surface-active polymer is different from other common polymers and polymer-surfactant systems in molecular aggregation,viscosity and flow capacity,and it has larger molecular coil size,higher viscosity and viscosifying capacity,and poorer mobility.The surface-active polymer solution has good performance of viscosity-increasing and viscosity retention,and has good performance of viscoelasticity and deformability to exert positive effects of viscosifying and viscoelastic properties.Surface-active polymer can change the chemical property of interface and reduce interfacial tension,making the reservoir rock turn water-wet,also it can emulsify the oil into relatively stable oil-in-water emulsion,and emulsification capacity is an important property to enhance oil washing efficiency under non-ultralow interfacial tension.The surface-active polymer flooding enlarges swept volume in two ways:Microscopically,the surface-active polymer has mobility control effect and can enter oil-bearing pores not swept by water to drive residual oil,and its mobility control effect has more contribution than oil washing capacity in enhancing oil recovery.Macroscopically,it has plugging capacity,and can emulsify and plug the dominant channels in layers with high permeability,forcing the injected fluid to enter the layer with medium or low permeability and low flow resistance,and thus enlarging swept volume.

An effective method to predict oil recovery in high water cut stage

The water flooding characteristic curve method based on the traditional regression equation between the oil and water phase permeability ratio and the water saturation is inappropriate to predict the oil recovery in the high water cut stage. Hence, a new water flooding characteristic curve equation adapted to the high water cut stage is proposed to predict the oil recovery. The water drive phase permeability experiments show that the curve of the oil and water phase permeability ratio vs. the water saturation, in the semi-logarithmic coordinates, has a significantly lower bend after entering the high water cut stage, so the water flooding characteristic curve method based on the traditional regression equation between the oil and water phase permeability ratio and the water saturation is inappropriate to predict the oil recovery in the high water cut stage; therefore, a new water flooding characteristic curve equation based on a better relationship between ln（kro/k,.~） and S~ is urgently desirable to be established to effectively and reliably predict the oil recovery of a water drive reservoir adapted to a high water cut stage. In this paper, by carrying out the water drive phase permeability experiments, a new mathematical model between the oil and water phase permeability ratio and the water saturation is established, with the regression analysis method and an integration of the established model, the water flooding characteristic curve equation adapted to a high water cut stage is obtained. Using the new water flooding characteristic curve to predict the oil recovery of the GD3-block of the SL oilfield and the J09-block of the DG oil field in China, results with high predicted accuracy are obtained.

高含水老油田化学驱综合治理新方法及工程实践路径

针对胜利高含水老油田化学驱在科学、技术、管理、工程四个角度面临的开发矛盾,以渤76块为典型单元,在工程实践中进行具体对策分析,构建了“适、专、快、集”的老油田化学驱综合治理新方法。“适”指在老油田科学开发方式转化上,构建不同油藏类型老油田化学驱最佳介入时机模型,提出了在含水率相对较低的阶段,是适合化学驱的有利时机,高效开发方式需“适”介入。“专”指在老油田开发技术应用上,改变传统聚合物先溶解后注入的开发思路,研制可控相转化聚合物,使聚合物先注入后溶解,解决炮眼剪切降解的难题,提高油水流度控制能力,老油田开发矛盾需“专”治理。“快”指在老油田综合管理模式上,改变传统方式,即矿场提问题、研究院设计方案、化工厂生产驱油剂的“串联”管理模式,提出充分发挥矿场、研究院、生产厂三方优势的“并联”管理模式,形成针对单一油藏的产品工业化工艺包以及产业化落地方案,老油田开发技术实现“快”转化。“集”指在老油田工程应用实践上,打破老油田化学驱地面大规模建站的工程工艺模式,采用集约化撬装配注设备,实现老油田化学驱的集约快速配注,老油田工程工艺实现“集”应用。运用上述方法,在胜利油田渤76块综合含水率上升初期,实施由水驱转为可控相转化聚合物驱,实施后一年即见到明显的降水增油效果,单井日产油水平增加8.6t/d,综合含水率降低3.1%,验证了综合治理模式的可行性,为高含水老油田化学驱高效开发提供了有效路径。

高含水油井关停后剩余油再富集速度研究

高含水断块油藏开发末期构造高部位油井在关井一段时间后,会产生剩余油再富集现象。目前关于剩余油再富集速度的研究中,对剩余油运移过程的影响因素考虑不够全面,影响计算精度。针对该问题,在对运移中剩余油再富集受力分析的基础上建立小油滴状和柱状剩余油再富集速度模型,通过正交试验确立2种剩余油再富集速度的主要敏感因素,并建立了2种剩余油再富集速度及再富集时间图版。研究结果表明:存在驱替压差时,储层渗透率为影响2种剩余油再富集速度的主控因素;当储层渗透率一定,驱替压差的增大和原油黏度的减小有利于2种剩余油再富集速度的增大;同一注采井距位置处的小油滴距离孔隙中滞留柱状剩余油越近,聚集过程中剩余油再富集时间越长,但数值上增加不多。该研究对高含水油藏剩余油再富集潜力区评价具有借鉴意义。

基于投影寻踪模型的特高含水油藏剩余油可采潜力评价方法

影响特高含水油藏剩余油可采潜力的因素极其复杂,且各因素的影响程度差异明显,常规方法多以剩余油饱和度或剩余油储量丰度等单一指标评价剩余油潜力,难以有效指导特高含水油藏剩余油挖潜。在充分考虑特高含水油藏剩余油可采潜力影响因素的基础上,综合表征储层非均质性、剩余油可采储量规模、水淹状况以及油水分流能力的差异,构建了特高含水油藏剩余油可采潜力量化评价指标体系,并考虑不同指标对剩余油可采潜力控制程度的差异,将加速遗传算法与投影寻踪模型相结合来确定各评价指标的客观权重,从而构建了剩余油可采潜力指数,形成特高含水油藏剩余油可采潜力量化评价新方法。以渤海Q油田南区主力产层NmIL砂体为例,开展特高含水油藏剩余油可采潜力量化评价,结果表明,新方法可综合表征不同区域位置的储层物性、可采储量丰度和油水分流能力对剩余油可采潜力的影响,实现了主力产层NmIL砂体剩余油可采潜力分布的差异化定量评价,优势可采潜力区域刻画明显,将其作为NmIL砂体下一步井网加密调整潜力区域,以精准指导加密水平井的部署,为特高含水油藏剩余油挖潜提供了一种全新的分析方法与思路。

断块油藏高含水井关井后剩余油再动用运移规律微观模拟

基于微观可视化光刻玻璃模型,从微观角度定性、定量研究了断块油藏高含水井关井后剩余油再动用运移规律,并开展了影响因素分析。结果表明:水驱后关井期间剩余油再动用类型主要为滴状、柱状和簇状。关井期间剩余油会沿模型倾斜方向向高部位运移聚集,有利于后续水驱阶段进一步提高驱油效率。地层倾角的增大、原油黏度的减小有利于剩余油再动用;关井时间的增加有利于剩余油向高部位采出端接近聚集;后续水驱阶段注入速度的增大会增加波及面积。

胜利油田油藏数值模拟技术新进展及发展方向

油藏数值模拟技术是油藏分析的重要手段,是油田开发人员编制开发方案、开展动态跟踪调整、进行提高油藏采收率研究等工作的有力工具。为明确胜利油田油藏数值模拟技术的未来发展方向,回顾了胜利油田60年以来油藏数值模拟应用技术和自主知识产权软件研发的发展历程,着重总结了“十三五”以来适配油田当前地质及开发特征的特高含水期精细油藏描述、低渗透油藏压驱开发、非均相复合驱、稠油油藏多元热复合驱、CO_(2)高压混相驱、页岩油大规模压裂整体开发等多个领域的数值模拟应用技术创新性进展;介绍了涵盖水驱、化学驱、微观、智能模拟等不同方向的多款胜利特色油藏数值模拟软件的研发及应用情况。最后指出在当前胜利油田的开发形势下,油藏数值模拟在精细程度、规模、效率和协作方式等方面面临着更大的挑战,油藏数值模拟需要进一步向一体化、并行化、智能化方向发展,为胜利油田开发提质增效提供技术支撑。

缓交联高强度封堵剂研究进展

综述了目前油田主要应用的封堵剂的发展情况,介绍了含水率较高的油田实施窜流封堵技术,分析了不同类型的深部封堵剂优劣特性及适用情况,总结和展望了未来缓慢交联的封堵剂技术的发展趋势。

特高含水期原油低温集输温度边界确定方法

随着国内油田逐渐进入开采后期,本文提出黏壁温度作为综合含水率70%~90%的高含水低温集油的评价指标已进入推广阶段且效果显著,但在现场降温试验中发现含水率90%以上的特高含水期原油管线实际运行温度与黏壁温度预测结果之间存在一定误差。因此,针对特高含水期原油开展低温集输温度边界条件研究,对完善油田低温集输技术具有重要意义。利用环道实验装置进行了特高含水期原油黏壁凝油冲刷实验,对特高含水期原油油水两相流动特性和油相黏壁特性进行分析,确定了屈服应力是阻碍黏壁凝油在管道内被冲刷剥离最主要的影响因素。编制了特高含水期原油低温集油温度预测软件,利用油田单井集油管线的现场降温试验进行了验证,误差在2℃范围内,满足工程运用需求。

高含水油田剩余油研究方法、分布特征与发展趋势

为了提高高含水油田剩余油研究与评价效果,基于大量文献调研,梳理了剩余油的概念、影响因素,从剩余油微观分布、宏观分布和饱和度定量分析3个方面总结了剩余油研究方法及其适用条件,概括了水驱油藏、稠油油藏和化学驱油藏的剩余油分布特征,进一步提出了目前剩余油研究的难点和发展趋势。结果表明:剩余油的影响因素主要包括地质构造、沉积微相、储层非均质性和井网密度、井网模式、注采系统的完善程度、生产动态等;剩余油研究方法包括实验分析方法、数值模拟方法和矿场测试方法等,各种方法的研究目的和适用条件不同,测试结果反映不同位置、不同尺度下的剩余油饱和度分布;高含水油田剩余油分布总体呈现高度分散和相对富集的特征,剩余油微观分布呈现连续相和非连续相多种形式;剩余油研究发展趋势包括但不限于以下5方面:超大物理模型的构建、多尺度高分辨率成像系统集成、考虑不同驱替介质及物性时变与非连续相非线性渗流的数值模拟改进方法、多学科多方法矿场测试的综合应用及大数据人工智能的广泛应用。

高含水原油在不同管材中的低温集输特性研究

目前,我国大部分油田已进入高含水期,采出液的流动特性发生变化,使降低集输温度成为可能。然而,关于管道材质对低温集输特性影响的研究相对较少。因此,利用现场实验装置对钢管与玻璃钢管中高含水原油低温集输特性进行了研究。结果表明,管线降低掺水量之后,井口回压上升,实验管道末点的油温缓慢下降;不同掺水量下井口回压上升过程不同,高掺水量下更容易实现低温集输;当掺水量相同时,玻璃钢管的黏壁温度低于钢管的黏壁温度,玻璃钢管低温集输的最低掺水量低于相同情况下钢管的掺水量。对黏壁温度实验数据进行拟合,得到了不同管材的黏壁温度计算模型,计算结果准确度较高,对高含水期油田实际生产中低温集输的可行性判断及其安全运行管理具有指导意义。

高含水原油低温集输研究进展

中国部分油田采出液含水率高达90%以上,造成地面集输系统的大量热能损耗。在国家“双碳”目标下,低温集输工艺将成为油田节能降耗的主要手段。本文总结了原油低温集输管道水力热力计算研究现状,重点阐述了原油组成、水相组成及流动条件对低温黏壁现象的影响。对现阶段应用较为广泛的低温集输黏壁预测模型作了总结和分析,梳理了低温集输边界条件的研究方法与实验装置。通过开展单井和集输干线现场低温输送试验充分验证了低温集输的可行性,为现场开展低温集输工作积累了宝贵的工程案例经验。最后,就低温集输黏壁现象未来的研究方向提出了展望,认为应加强理论预测模型的建立。

Kenics型静态混合器对含水原油均质化效果影响数值模拟

目的针对含水原油在输送过程中水分分布不均匀或大量聚集的现象,将Kenics静态混合器引入到含水原油输送过程中,并对其均质化效果进行分析。方法采用FLUENT软件对管道内流场进行模拟,并用变异系数和液滴平均粒径对均质化效果进行评价,分析了混合单元排列方式、扭角、长径比和数量对均质化效果的影响。结果使用排列方式为异向叉排、扭角为240°、长径比为0.5、数量为10个的Kenics静态混合器不仅能使油水两相分布均匀,还能获得更小的液滴平均粒径,从而实现更好的均质化效果。结论排列方式为异向叉排时均质化效果最好;随着扭角的增大,管线出口的变异系数和液滴平均粒径呈下降趋势;随着长径比的减小和数量的增多,出口的变异系数值趋于相同,但能获得更小的液滴平均粒径。通过均质化处理后,可以使取样样本更加准确地体现储罐原油的含水率,避免造成油品交接纠纷,保证油品外输任务的完成。

物理模拟融合油藏精细刻画法表征特低渗油藏中高含水期剩余油分布

中国低渗透油藏分布广泛,其中大部分区块已进入中高含水期,并且由于剩余油类型及成因不明确导致采出程度普遍较低,因此延长低渗透油藏稳产期是亟需解决的问题。结合井口生产资料和储层水驱前缘波及系数对油藏模型进行历史拟合,建立了特低渗油藏剩余油的精细刻画模型,并综合利用静动态物理模拟实验、生产资料动态分析等方法,明确了特低渗油藏中高含水期剩余油成因及类型,据此提出了针对性的剩余油挖潜策略,最终在姬塬油田耿155区长1特低渗油藏进行了现场应用。研究结果表明,特低渗油藏剩余油主要分为储层平面和垂向非均质性导致的储层非均质型剩余油、局部储层注采不对应导致的注采不完善型剩余油以及储层黏土矿物运移膨胀导致的欠注型剩余油,针对性挖潜后目标井组采出程度提高5.1%~12.4%。经现场应用后,预测原油累计采出量相比原始措施提高15.6%~37.3%,为特低渗油藏中高含水期挖潜提供理论和技术支撑。

注CO_(2)改善河南双河油田低渗储层注水能力机理研究

针对双河油田低渗储层注水能力差、注水水质不达标和高凝原油蜡沉积等问题,通过自主设计的水-CO_(2)储层注入能力评价装置,开展流动性实验、CO_(2)驱油实验,结合岩心扫描电镜等测试手段,明确双河低渗储层注水能力差的主要机制,探索CO_(2)改善低渗储层注入能力的主要机理。结果表明,产出水中的悬浮颗粒和油中蜡晶等组分的沉积可导致孔隙堵塞,从而降低储层的注水能力。CO_(2)对产出水中无机悬浮颗粒及岩石碱性矿物、碳酸盐岩矿物有明显溶蚀作用,是显著提高储层注水能力的主要机理。CO_(2)可溶解在岩石表面的原油蜡质组分沉积,有效改善储层注水能力。同时,CO_(2)驱提高采收率效果明显,采收率提高13.01%~21.51%,后续水驱进一步提高5.40%~6.04%。研究表明:注CO_(2)可显著改善双河油田低渗储层注入能力,为CO_(2)增注驱油技术在现场应用提供理论支撑。

同心双锥型高含水油水两相管式旋流分离特性

针对常规切向入口旋流分离器处理高含水采出液效果较差以及分离效率受入口流速影响较大等问题,率先提出中心细锥体和外筒倒锥体的同心双锥型油水两相管式分离构造。综合高含水率、大处理量等因素综合作用,建立油-水两相分离Mixture多相流模型和流场RNG k-ε湍流模型,并采用SIMPLE压力-速度耦合算法对模型进行求解,依据求解结果揭示同心双锥型管式分离腔室内旋流场的动态分布状况,量化分析中心锥角度变化对油水两相管式分离效率的具体影响程度,探究油滴粒径、入口流速等参数对管式旋流分离性能的作用机制。结果表明,随中心锥角度不断增加,同心双锥型管式旋流分离效率呈现先升高再降低的变化趋势,最佳中心锥角度为82°;增大油滴粒径能升高油池聚集性,有利于提升分离性能,当油滴粒径由0.3 mm增至0.6 mm时,分离效率由85.6%提至94.5%;入口流速对分离效率的影响相对较小,当入口流速由5 m·s^(-1)提至11 m·s^(-1),分离效率仅由93.3%升至96.9%,流速相差6 m·s^(-1)时,分离效率仅相差3.5%。

复杂断块油藏高含水期剩余油分布规律研究

对于复杂断块油藏注水开发后期,剩余油分布规律刻画难度大,如何寻找剩余油甜点区成为提高水驱采收率关键。以H区块为例,在分析不同韵律性储层水淹特征基础上,开展剩余油分布特征研究,剩余油主要分布在生产井间、断层附近剩余油富集以及正韵律和渗透率极差小的反韵律厚油层顶部,并对不同类型剩余油制定合理的挖潜对策,包括实施加密井、老井侧钻及厚层顶部部署水平井等,现场部署实施各类井23口,日注水量增加440方,日产油量最高增加170t,采油速度提高0.28%,阶段累增油5.7万t,预计可提高水驱采收率5%,实现水驱控制储量有效动用。

高含水油气混合物井筒结蜡特性研究

为有效治理结蜡问题,必须探究油气田开发周期内井筒结蜡规律,针对不同生产参数下结蜡特点制定相适应的防治措施。建立了高含水油气混合物井筒结蜡模型,分析了不同参数对井筒结蜡的影响。结果表明:随着产液量的增加,初始析蜡井筒里程向后偏移,流体内部蜡沉积量显著减少,但管壁最大结蜡厚度基本不变。随着流体温度的升高,流体内蜡沉积体积分数明显降低,初始析蜡井筒里程向后偏移,当地层流体温度低于75℃时,应注意设置清蜡防蜡措施。随着压力的升高,流体内蜡沉积体积和管壁结蜡厚度变化并不明显。当含水率升高时,流体内蜡沉积体积分数和管壁最大结蜡厚度明显降低,在油田开发后期高含水阶段,井筒结蜡量相对较少,可适当减少部分清蜡措施。