Mathematical model for prediction of oil recovery of core-flood tests in process of viscoelastic polymer flooding

In this study a new mathematical model was developed that considers thermal effects, dispersion, effective concentration, elastic behavior of viscoelastic polymers, polymer retention, permeability reduction of aqueous phase, salt effects, inaccessible pore volume, and equivalent shear rate in porous media to predict oil recovery of core-flood experiments in process of viscoelastic polymer flooding as a tertiary stage of enhanced oil recovery. The model was found highly reliable when compared to material balance and experimental data. Displacement performance of core-flood tests could be predicted by presented model, therefore, experimental costs will be decreased significantly.     

非均相复合驱油体系设计与性能评价

为进一步提高聚驱后油藏采收率,针对聚驱后油藏非均质性强、剩余油普遍分布的特点,提出了非均相复合驱油体系。非均相复合驱油体系包括黏弹性颗粒驱油剂（PPG）、表面活性剂和聚合物。通过研究黏弹性颗粒驱油剂的溶胀能力、黏弹性、滤过能力和在岩心中运移性能,及其与表面活性剂、聚合物之间相互作用,得到了适合于胜利高温高盐油藏和聚合物驱后油藏的非均相复合驱油体系1000 mg/L PPG＋1000 mg/L聚合物＋0.3％胜利石油磺酸盐＋0.1％非离子表面活性剂1709。结果表明,PPG可遇水溶胀,耐盐性能好,在油藏中具有封堵和运移性能,较单一聚合物能够更好地提高波及体积。在含水98％条件下注入0.3倍孔隙体积的非均相复合驱油体系,聚合物驱后提高采收率13.6%(OOIP)。该体系可应用于高温高盐油藏或聚合物驱后油藏大幅度提高采收率。     

Use of Oil-in-water Pickering Emulsion Stabilized by Nanoparticles in Combination With Polymer Flood for Enhanced Oil Recovery

Efficient flooding agents are required to produce additional oil from mature reservoir. In this work, oil-in-water Pickering emulsion systems stabilized using nanoparticles, surfactant, and polymer have been developed and tested for enhanced oil recovery with and without a conventional polymer flood. Stability of nanoparticles in the dispersion of surfactant-polymer solution was tested using zeta-potential before use. Several flooding experiments have been conducted using Berea core samples at 13.6 MPa and temperatures of 313 and 353 K. It has been observed that a combination of 0.5 PV polymer flood with 0.5 PV Pickering emulsion was efficient and have resulted in 1–6% additional oil recovery as compared to 0.5 PV Pickering emulsion flooding alone. The injection of polymer flood have shown to enhance the pressure drop in the core sample after emulsion flooding and considered as an important factor for an additional recovery of oil. The effect of temperature on the viscosity of flooding agents in relation to pressure drop and oil recovery have also been investigated. Viscosity and pressure drop of emulsion flood systems have shown to marginally decrease with increase in temperature. Studies on nanoparticle retention using SEM have shown that nanoparticles were retained in the core sample during emulsion flooding which may be detrimental for permeability of core sample. It is observed that Pickering emulsion flood with polymer flood would be effective for the enhanced oil recovery suitable for matured reservoirs.     

黏弹效应改善聚驱效果的数值模拟研究

根据前人实验研究成果，建立黏弹效应本构方程；以临界德博拉数法和临界黏弹流速法作为发生黏弹效应门限的判断方法，建立考虑黏弹效应的数学模型，提出了相应数值计算方法，用编制的软件，结合大庆油田聚合物驱实际，以对比计算方法研究了黏弹效应对聚合物驱油效果的影响。结果表明：聚合物驱油过程中的黏弹现象常发生于注入井与生产井的近井区域，能够起到提高采收率，降低含水率，抑制高渗层水淹的良好驱油效果。对比黏弹模型与原模型的分层吸水，产油，产油量变化，认为利用黏弹效应开发中，低渗层，可使之成为增产主力；生产井附近的黏弹效应可使中，高渗层产油能力反弹，能够提高驱油效果。图1表3参7（黎洪摘）。     

新型聚合物驱油数学模型

建立了能模拟多种分子量聚合物溶液混合驱油和聚合物黏弹性作用驱油机理的数学模型,该模型从弹性效应和黏性效应两个方面描述了聚合物驱油机理。弹性驱油作用的数学描述是:弹性能降低残余油饱和度,使油相相对渗透率提高;黏性驱油作用的数学描述是:聚合物能增加水相黏度,改善油水流度比及扩大驱替液的宏观波及体积。在多种分子量聚合物溶液混合驱油机理数学模型中,每一种分子量聚合物在油藏中流动满足各自独立的物质传输规律,在驱油机理上表现为多种分子量聚合物溶液浓度之和的总浓度总体驱油过程,驱油机理数学模型中的参数表示为各种分子量聚合物相应参数浓度加权平均的形式。所建立的模型能够模拟聚合物驱油提高微观驱油效率和流度控制驱油机理以及所发生的对流、弥散、扩散、吸附等物化现象。实际应用结果表明,该模型具有较强的实用性,可用于聚合物驱油的机理研究、矿场方案优选和开发效果预测。     

海上油田不同种类聚合物黏弹性能实验研究

随着三次采油技术应用规模的不断扩大,聚合物驱油技术己成为油田开发的必然选择.聚合物驱油方法是在注入水中添加一定浓度聚合物,从而改变注入水的黏弹性能来提高注水波及体积和驱替效率的一种采油方法.可见,聚合物驱油技术本质就是聚合物溶液的黏弹效应,依据油田开发的实际需求,通过室内实验和理论分析,对不同种类驱油用聚合物分子形态及...     

聚合物驱波及系数和驱油效率的计算方法研究

根据室内三维物理模拟聚合物驱油实验含油饱和度的测定结果,深入探讨了非均质砂岩油田聚合物驱油过程中,扩大波及系数和增加驱油效率对提高采出程度贡献率的定量计算方法,并给出了分析解释.结果表明,在3层非均质模型聚合物驱油过程中,聚合物驱提高采收率的贡献主要来源于提高波及系数的贡献,聚合物的黏弹性也具有提高驱油效率的作用.通过计算得出,在有隔层模型中增加驱油效率对提高聚合物驱采出程度的贡献占11.85%,扩大波及体积的贡献占88.15%;聚合物溶液在模型高渗透层内提高驱油效率作用的效果要好于中、低渗透层.     

砾岩油藏水驱与聚合物驱微观渗流机理差异

砾岩油藏特殊的沉积环境导致储层孔隙结构呈现复模态特征,渗流系统以“稀网-非网状”流态为主,水驱与聚合物驱微观渗流机理及两者差异的研究成为油藏提高采收率的难点和关键。克拉玛依油田属于典型的砾岩油藏,选取实际岩心为研究对象,采用CT扫描技术研究了亲水和弱亲油岩石的水驱和聚合物驱微观驱替机理,并且在驱油效率影响因素分析的基础上,建立了2种驱替方式下砾岩油藏的最终采收率计算模型。实验结果表明：砾岩油藏亲水岩石水驱与聚合物驱渗流机理均以沿岩石表面“爬行”驱替为主,而弱亲油岩石则均以沿孔隙中部“突进”驱替为主,由于渗流机理的差异性,亲水岩石水驱后残余油主要在细喉道及孔隙交汇处赋存,聚合物溶液通过更强的剪切拖拽作用把这些残余油切割成许多小油滴,进而随着聚合物溶液顺利通过狭窄的喉道向前运动,以达到提高油藏采收率的目的;弱亲油岩石水驱后残余油主要以油膜形态及细孔道赋存为主,聚合物溶液以更强的剪切应力促使油膜通过桥接连通和形成油丝2种方式从颗粒表面被聚合物驱替带走。由于聚合物溶液与注入水溶液的性质存在本质差别,导致复模态的孔隙结构对聚合物溶液渗流和驱替的影响远小于水驱溶液。因此,针对2种不同润湿性的岩石,储层孔隙结构是水驱油效率的主控因素,物性和含油性的影响较小,而聚合物驱效果则与水驱后残余油饱和度具有较好的相关性,利用建立的模型可以有效地预测2个驱替阶段油藏的采收率。     

基于非均质大模型的特高含水油藏提高采收率方法研究

针对特高含水开发阶段水油比急剧上升、注水量大幅增加和现有技术适应性差等问题,采用非均质物理大模型探索了进一步提高水驱后和聚合物驱后特高含水油藏采收率的方法。研究了聚合物驱-井网调整、自聚集微球-活性剂驱等不同驱替阶段含油饱和度的分布特征,分析了试验过程中注入压力、采收率的变化情况。研究发现,采用井网调整改变流线方向结合聚合物驱扩大波及系数的方法,可使水驱后处于特高含水期油藏的采收率提高26.0%;自主研发的自聚集微球能够运移至油层深部封堵优势渗流通道,迫使后续驱油剂发生液流转向,进入剩余油潜力区,从而提高聚合物驱后特高含水期油藏的驱油效率,自聚集微球-活性剂体系的残余阻力系数是聚合物的1.5~1.6倍,可使聚合物驱后特高含水油藏的采收率提高5%以上。研究结果表明,水驱后特高含水期油藏可采取井网调整结合聚合物驱的方法提高其采收率,而对于高波及系数和高采出程度的聚合物驱后油藏,可采用微球活性剂相结合的深部调堵驱油方法提高其采收率。      

聚合物驱宏观渗流机理的三维油藏物理模拟研究

利用高温高压复杂驱动体系三维物理模拟系统研究聚合物驱提高原油采收率的宏观渗流机理。用模型上布置的压差传感器和饱和度测量探针,测量了聚合物驱的开采效果、压力场和饱和度场变化。对于三维物理模型,聚合物在油藏内的吸附、滞留等作用使流动阻力增大、油藏压力上升、液流转向。聚合物从主流线流向两侧的剩余油区,不仅驱替出主流线上的剩余油,而且通过提高波及范围驱替出两侧剩余油区内的剩余油,在油藏内形成一个从主流线向两侧扩展的油墙,提高了宏观波及体积。三维物理模拟研究动态饱和度场和压力场,能够更好地描述聚合物驱提高原油采收率的驱油机理。图8参13     

Influences of fracture orientation on oil recovery by water and polymer flooding processes: An experimental approach

The major objectives of this study are to experimentally investigate the influences of fracture orientation on oil recovery by water and polymer flooding processes. Four flood experiments were conducted at simulated reservoir conditions of temperature and pressure. The fifth experiment was carried out using core sample without fracture as a base run to compare the performance of fractured and unfractured formations under water and/or polymer flooding(s). Viscosity variation of actual crude oil and polymer solutions of different concentrations was measured under different temperatures.The results indicated that waterflooding the unfractured carbonate reservoirs provided higher oil recovery than formations of a single fracture. A carbonate reservoir of a single-horizontal fracture in the direction of oil flow (0° inclination angle) recovered the highest oil recovery while a similar formation of a single-vertical fracture perpendicular to oil flow direction (90° inclination angle) produced the lowest one by waterflooding. The increase of fracture inclination angle decreases oil recovery by waterflooding.For polymer flooding after complete waterflooding, the results showed that all fractured carbonate formations of different inclination angles produced higher oil recovery than unfractured ones. The highest oil recovery by polymer flooding was produced from formation of a single fractured of 30° inclination angle, while the lowest recovery was obtained from formation of 90° inclination angle. In addition, the ultimate recovery of combined water and polymer flooding processes in fractured carbonate reservoirs proved that the best recovery was gained from the horizontally fractured formations.     

无碱二元体系的黏弹性和界面张力对水驱残余油的作用

三元复合驱含碱驱油体系会大幅度降低聚合物溶液的黏弹性,引起地层粘土分散和运移、形成碱垢及导致地层渗透率下降。为此提出利用不加碱可形成超低界面张力的聚合物/甜菜碱表面活性剂二元复合体系驱油。通过流变性实验及微观模型驱油实验,分析了表面活性剂对聚合物表面活性剂二元复合体系黏弹性的影响和聚合物表面活性剂二元复合体系的黏弹性及界面张力对采收率的影响。对聚合物表面活性剂二元复合体系提高水驱后残余油采收率机理的研究表明:在驱替水驱后残余油过程中,聚合物表面活性剂二元复合体系利用了聚合物溶液的黏弹特性和表面活性剂的超低张力界面特性,水驱后残余油以油丝和乳状液形式被携带和运移,随着二元驱油体系的黏弹性的增加和界面张力的降低,水驱后二元驱后的采收率增加,降低界面张力的驱油效果(指达到超低)比提高体系的黏弹性的效果更明显。     

聚驱后井网加密与二元复合驱结合提高采收率实验研究

国内一些油田已陆续进入聚合物驱后续水驱阶段,亟待研发聚驱后进一步提高采收率技术。为此,应用物理模拟方法,研究了聚驱后井网加密和二元复合驱相结合进一步提高采收率方法。实验过程中,利用饱和度监测技术测量物理模型含油饱和度的变化规律。实验结果表明,聚驱后油层仍有大量剩余储量,通过井网加密和二元复合驱结合可进一步提高采收率29.86%。     

聚合物驱后注气稳定重力复合驱数值模拟

聚合物驱后剩余油分布高度零散、顶部油层剩余油难以动用,而聚驱后的主导技术尚无明确方法。在原油受力分析的基础上,提出了油藏顶部注气、底部三元复合驱的思路。针对大庆聚合物驱后区块,进行了不同驱替方式的预测对比研究。结果表明,注气稳定重力复合驱效果最好,提高采收率幅度达到了13.53%。对比不同驱替方式的顶部油层剩余油饱和度,注气稳定重力复合驱能够将顶部低渗透油层有效动用,剩余油大幅减少。分析不同时间点的纵向剩余油饱和度分布,顶部注气后利用纵向压差驱替剩余油向下运移,底部实施三元复合驱利用平面压差驱替剩余油,实现了立体驱替。注气稳定重力复合驱技术为聚驱后提高采收率技术的发展提供了新思路。     

Experimental Investigation of Flooding Hydrolyzed–Sulfonated Polymers for EOR Process in a Carbonate Reservoir

The main purposes of this study were to scrutinize experimentally effects of polymer and rock types on the oil recovery using water and polymer flooding processes. Four dynamic flooding experiments were carried out at simulated reservoir condition of temperature and pressure. According to the obtained results, the ultimate oil recovery by water flooding in highly fractured reservoirs was less than reservoirs with the microfractures. The results of polymer flooding showed that in addition the polymer molecular weight, the sulfonation of polymers also affects the oil recovery.     

七东1低渗砾岩油藏聚合物驱配方设计及应用*

为提高砾岩油藏采收率,针对七东1区砾岩低渗储层强非均质性、水驱采出程度低、剩余油饱和度较高等特点,在七东1区实施聚合物驱。通过理论计算、聚合物注入性及流动性分析、天然岩心驱油实验,对聚合物相对分子质量和注入浓度进行了筛选,并在七东1区进行了矿场应用。结果表明,七东1区低渗砾岩储层可注入浓度不高于1000 mg/L、相对分子质量400×10~4以下的聚合物,采收率可提高4%数9%。针对低渗透油藏特点,形成了驱油体系与油藏流体等黏驱替流度控制技术。试验区于2016年1月全面注入相对分子质量为350×10~4、质量浓度为800 mg/L的聚合物溶液。截至2019年2月,聚合物驱阶段产油8.01×10~4t,阶段采出程度14.5%,降水增油效果明显。图6表6参14。     

交联聚合物封堵平面非均质油藏物理模拟

利用平面非均质填砂模型进行了有机交联聚合物封堵的油藏物理模拟实验,对比研究了水驱、聚合物驱和交联聚合物封堵对开采效果的影响.通过布置49个高精度的压差传感器测量交联聚合物封堵过程中油藏压力场的动态变化,用数码相机照相定性地观察了油藏流体变化情况.实验中发现,交联聚合物封堵最终采收率比水驱提高33%,比聚合物驱提高14%.交联聚合物能有效地封堵高渗条区,形成"段塞",改变了油藏内流体流动方向,扩大了波及范围,驱替出低渗区的油,提高了采收率.     

利用体积CT法研究聚合物驱中流体饱和度分布

对CT图像进行了X射线硬化处理、X射线漂移校正、图像矩阵变换及体积CT位置校正,研究出用体积CT对岩心流体饱和度进行测量的技术。利用该技术对聚合物驱过程中油水饱和度分布进行了测量,结果表明,该技术适合于测量聚合物驱过程中油水饱和度分布。尽管试验中使用了均质岩心,在水驱阶段形成了明显的水窜通道,窜流通道上的油饱和度明显低于其他区域,微观波及的不均匀性非常明显。注入聚合物段塞后,有效地富集了水驱之后的剩余油,利用聚合物驱,除了能改善波及体积外,还成功地观察到水驱之后进一步提高洗油效率的现象     

大庆油田聚合物驱油工业化推广应用研究

对大庆油田聚合物驱油工业化推广应用的驱油效果进行分析研究以后，认为聚合物的驱油效果除了与已经研究过的聚合物的分子量、溶液浓度、用量、注入速度和注入方式等工艺技术条件有关外，还与地质条件和含油饱和度等因素有关。目前，大庆油田聚合物驱油已经取得采收率２．０１％的明显效果，预测最终采收率可提高１３．０％左右。     

The Effect of Alkali and Surfactant on Polymer Molecular Structure

Abstract

With the technical development of enhanced oil recovery (EOR), the alkali/surfactant/polymer (ASP) compound flooding technique has been the necessary choice in Daqing oilfield. Compared to average polymer flooding, ASP compound solution decreases the interfacial tension (IFT) between water and crude oil; however, the viscosity and viscoelasticity of ASP solution were performed by surfactant and alkali, both of which could affect the polymer moleculal structure and the oil recovery of ASP flooding. Considering practical requirements in oilfield development, much effort has been focused on the effect of alkali and surfactants on polymer solution by laboratory experiment and theoretical analysis. The results indicate that alkali and surfactants cause the interfacial tension decrease; at the same time, the molecular structure of the polymer is changed and the viscosity and viscoelasticity of polymer solutions are decreased. In addition, alkali neutralizes with negative ion on polymer molecular and causes the polymer molecular chains to curl up, forming a “band” molecular structure. Those actions could make viscoelastic behavior and rheological property of ASP solution weak.