泡沫驱前预注低矿化度水提高油湿砂岩原油采收率

为提高泡沫驱原油采收率,通过室内岩心驱替实验研究了预注低矿化度水再进行泡沫驱的驱油效果以及原油组成及注入水矿化度对该驱替方式驱油性能的影响。研究结果表明,低矿化度水驱能反转岩石润湿性,将油湿岩石改变为水湿岩心。采用矿化度130000 mg/L的模拟地层水水驱至98%后注入2 PV的低矿化度水(矿化度2784 mg/L)再按气/起泡剂溶液体积流量1∶1交替注入氮气和质量分数为0.1%的起泡剂溶液2 PV,泡沫驱最高封堵压力为0.242 MPa,低矿化度水驱后泡沫驱比水驱提高采收率14.20%。低矿化度水驱与泡沫驱能产生协同作用,低矿化度水驱后续泡沫驱过程生成了稳定泡沫,提高了泡沫在多孔介质中的封堵能力,从而大幅度提高原油采收率。随着原油酸性组分含量和注入水矿化度的降低,岩心亲水性会更强且泡沫驱性能更好。图4表3参13     

低渗透砂岩润湿性对水驱和复合驱采收率的影响

在砂岩岩心渗透率小于50×10-3μm2条件下,考察驱替相润湿接触角分别为37,86,126和167°的驱油效果,对应水驱采收率平均值依次为16.18%,15.47%,13.94%和9.02%,复合驱采收率依次为21.12%,17.33%,13.53%和5.26%。结果表明,除强亲油性外,其他润湿性对岩心水驱采收率的影响不显著。复合驱提高采收率幅度随润湿性由亲油到亲水变化逐渐提高,其平均值与润湿接触角呈二阶线性负相关关系,即润湿接触角越小,采收率越高,接触角为37°时提高采收率最大。低渗透孔隙微毛细管对原油的捕集作用是制约驱油效率的关键因素,应用复合驱应重点从降低油水界面张力和改变岩石润湿性2方面考虑克服毛管对原油的捕集束缚。     

低渗透油藏改变驱替方向微观机理研究

为了深入探究大庆油田低渗透油藏改变驱替方向提高水驱采收率的机理,利用人造平板岩心和光刻玻璃模型进行水驱油实验,验证改变驱替方向进一步提高水驱采收率的效果。将水驱后的微观剩余油分为5种类型,重点研究了改变驱替方向后各类剩余油的动用比例和驱替运移机理。应用数值模拟技术对现场反九点井网进行模拟,验证了改变驱替方向在现场实际中的可行性。研究结果表明:对于低渗透岩心,随着渗透率的增加,改变驱替方向采收率提高值逐渐增大,水驱采收率的提高值最高可达8.8个百分点;改变注入方向后,簇状剩余油动用比例最大,平均为34.3%;盲端剩余油动用比例最小,平均为15.2%。该项研究为大庆油田低渗透油藏注水调整措施的制订提供了理论指导与技术支持。     

鄂尔多斯盆地浅层特低渗透油藏氮气驱实验研究

浅层特低渗透油藏衰竭式开发效果较差,注水开发过程中存在注不进的问题,氮气驱技术为提高特低渗透油藏采收率提供了一种有效手段。结合矿场实际,通过对特低渗透岩心氮气驱开发效果的研究,分析了注入参数对水驱后氮气驱开发效果的影响,对比了单纯氮气驱和氮气与水交替注入时水驱驱替压力的变化,优化了特低渗透岩心氮气驱与水驱段塞比例。人造和天然岩心驱替实验结果表明,水驱后氮气驱可提高浅层特低渗透油藏采收率3%~10%,二次水驱时驱替压力增加,含水率较低时进行氮气驱效果较好;水驱后氮气驱采出程度与气体注入量变化存在阶梯性上升趋势,改变了以往采收率与气驱注入量单调性上升的认识,对于不同油田的注入要求可以选择气体注入量局域性最优值;相对于单纯氮气驱,氮气与水交替注入采收率有所增加,注入压力可明显提高,气水交替注入6轮次时压力最大增加约1.5 MPa,气水段塞优化最佳比例为2∶1。     

温度和注入压力对二氧化碳驱油效果的影响规律实验

二氧化碳驱油过程中通过二氧化碳在原油中的溶解而改变原油物性,从而提高采收率,但温度和注入压力对二氧化碳驱油效果及驱替过程中原油物性的影响规律有待深入研究。通过岩心驱替实验及原油物性测试实验对其进行了研究,结果表明,在22℃条件下,原油采收率随注入压力的增加变化较小;在60℃条件下,当二氧化碳为气态时,注入压力对原油采收率影响较小,当注入压力升高使二氧化碳处于超临界状态时,原油采收率会大幅度提高,但换油率迅速下降,而当注入压力高于最小混相压力时采收率增幅变缓。见气时注气量对比结果显示,气态二氧化碳驱比超临界或液态二氧化碳驱更容易发生气窜。产出原油物性分析结果表明,二氧化碳驱过程中,随着生产时间的增加,产出原油组分越来越轻,原油密度和粘度也逐渐减小;相同温度下,随着注入压力的升高,产出原油密度和粘度减小。     

碳酸盐岩油藏低矿化度水驱作用机理实验

碳酸盐岩油藏低矿化度水驱应用潜力巨大，为了更好地推广其矿场应用而针对性开展作用机理的实验研究。首先，岩心驱替实验研究注入水矿化度和关键离子组成对采收率的影响；而后，润湿角测定实验分析注入水矿化度和关键离子组成对碳酸盐岩表面润湿性的影响；最终，根据实验结果建立碳酸盐岩油藏低矿化度水驱作用机理。研究发现：低矿化度水驱能有效改变碳酸盐岩表面润湿性进而提高油藏采收率，存在最优矿化度使得碳酸盐岩表面润湿性变化最大、采收率最高；Mg²⁺和SO₄^2-对碳酸盐岩表面润湿性和原油采收率的影响效果不同；随着溶液中Mg²⁺浓度升高，碳酸盐岩表面润湿性变化不断增强、原油采收率不断升高；随着溶液中SO₄^2-浓度增加，碳酸盐岩表面润湿性变化先增强后减弱、原油采收率先增加后稳定。碳酸盐岩油藏低矿化度水驱作用机理在于润湿性的改变：①SO₄^2-吸附在正电性的碳酸盐岩矿物表面，中和表面电荷，促进了Mg²⁺向矿物表面运动；②Mg²⁺与碳酸盐岩矿物表面的Ca²⁺发生取代反应，造成原油组分的解离。     

注入水性质对中东地区碳酸盐岩油藏驱油效果的影响

中东地区碳酸盐岩储层以孔隙介质为主,注水是未来重要的开发方式,而注入水的性质影响了注水提高采收率的效果。利用中东地区M层碳酸盐岩油藏岩心,通过改变注入水矿化度、钙离子和硫酸根离子质量浓度,研究注入水性质对驱油效果的影响。结果表明,随着注入水矿化度的减小,水驱采收率增大;降低矿场注入水中钙离子质量浓度或相对比例、增加矿场注入水中硫酸根离子质量浓度或相对比例,均有利于提高水驱采收率,改善驱油效果。矿场注水过程中可以通过改变注入水矿化度和离子质量浓度提高驱油效果,还须进一步结合现场水源水量及其他限制条件优选注入水源。     

张店油田储层注水影响因素探讨

张店油田在注水开发过程中，出现注水难和注不进去的现象，通过岩心试验评价不同毛管力，不同润湿性，不同温度下模拟注水以及注表面活性剂的岩心驱替试验，并结合张店油田储层有关特征，对影响张店油田注水驱油效果的因素做出分析评价。研究结果表明，毛细管力是影响注水的重要因素之一，随着样品水润湿性程度的增加，注水压力升高，驱油效率减小。注水温度越低高含蜡原油结蜡严重，影响注水。表面活性荆能降低油水界面张力，从而降低注入压力，提高原油采收率。     

丘陵油田水驱后注气混相驱可行性实验

吐哈盆地丘陵油田地层油为轻质油,油藏的非均质性导致水驱采收率较低,目前已进入高含水期。针对油藏水驱后注气混相驱可行性问题,首先利用细管实验测试了一级分离器气与地层油的混相压力,并优选了能实现混相的混相助剂类型（液化石油气、甲苯、乙二醇丁醚、CO2、富化的天然气）及段塞注入量;其次用油田地层岩心组成的长岩心研究了高含水状态下混相助剂段塞驱+一级分离器气驱+后续水驱的驱油效果。细管实验结果表明,目前地层条件下一级分离器气驱替地层油要实现混相驱需要在注入气前方加入混相助剂段塞。长岩心混相驱油实验结果表明,水驱后气驱可以较大幅度地提高原油采收率,在注入气前方加入混相助剂段塞,驱油效果明显提高,随混相助剂段塞注入量的增加采收率增加;但在地层油中溶解能力稍弱的混相助剂（如CO2、富化的天然气）与溶解能 力强的混相助剂（如LPG）的作用规律不同,且并不是注入量越大越好。     

砂岩油藏智能水驱提高采收率作用机理实验

智能水驱是一项低成本、环保、潜力巨大的油田开发新技术。以国外众多学者的研究成果为依据,分析归纳智能水驱提高采收率的作用机理主要包括:类碱驱、微粒迁移、多组分离子交换和储层润湿性转变,并通过物理模拟实验验证智能水驱的提高采收率机理。研究结果表明:用智能水驱进行岩心流动实验时,产出水的pH值明显高于高矿化度水驱,最大pH值能够达到8.23,说明智能水驱能够发挥类似碱驱的作用从而提高采收率;用智能水分别驱替未煅烧和650℃下煅烧过的岩心,最终采收率分别为56.48%和53.45%,因煅烧过的岩心内粘土不再发生迁移,其采收率明显低于未煅烧的,说明智能水驱过程中微粒的迁移能够提高采收率;检测智能水驱产出液中各离子的质量浓度发现,Ca~(2+)的质量浓度先大幅度增加后逐渐降低,Mg~(2+)的质量浓度先小幅度增加再逐渐减小,最终逐渐趋于平稳,说明水驱过程中存在少量Mg~(2+)交换Ca~(2+)以及智能水中的H~+交换粘土表面大量的Ca~(2+)的过程,可见智能水驱过程中多组分离子发生了交换,从而提高了采收率;70 h后在油滴1周围改滴智能水,油滴与岩心的接触角由最初的124°逐渐减小,最终降至67°,润湿性由亲油性变为亲水性,可见智能水驱能够使岩心表面的润湿性发生转变,从而提高采收率。     

低渗透油藏水驱转空气泡沫驱提高采收率物理模拟实验

为进一步提高镇泾油田低渗透油藏原油采收率,利用室内驱油物理模拟技术,开展了水驱转空气泡沫驱提高采收率实验研究,探讨了空气泡沫驱对低渗透油藏水驱开发效果的影响。实验结果表明,在模拟地层条件下,初始水驱阶段的平均采收率为29.06%,水驱转空气泡沫驱后,采收率得到明显提高,增量均在10%以上;再次水驱后,最终采收率平均可达到45.42%。随着空气泡沫注入速度的增加,采收率呈上升趋势,但增幅逐渐减小。注入速度越大,气体突破时间越早,不过实验过程中并未发生明显的因气窜而导致采收率降低的现象;在相同条件下,空气泡沫注入总量为1倍孔隙体积时的采收率比0.6倍孔隙体积时的高5%。研究认为,通过交替注入起泡剂溶液与空气实现空气泡沫驱对于注水开发的低渗透油藏进一步提高原油采收率是可行的。     

Effect of crude oil ageing on low salinity and low salinity surfactant flooding

Injection of brine with lower salinity than the connate brine has proven to give a moderate increase in oil recovery in sandstones. Recent research has shown that this process will significantly benefit from introducing surfactant optimised for low salinity environment.The mechanisms underlying increased recovery by low salinity brine injection are not yet fully understood. However, research to date suggests that they are related to complex crude oil/brine/rock interactions. With this in mind, the present paper investigates primarily how the extent of oil recovery from Berea sandstones subjected to long term exposure of crude oil is influenced by (1) low salinity water injection and (2) combined process low salinity water injection with surfactant flooding.Core displacement tests were conducted on four Berea cores (30 cm), two in a natural state and two that had been subject to extensive crude oil ageing at high temperature. Results obtained from different flooding steps are discussed in terms of oil recovery and effluent properties including turbidity, pH- and ion analysis (Na⁺, Mg²⁺, Ca²⁺). The results effectively illustrate that oil recoveries from the aged cores are higher during both low salinity water injection and low salinity water injection combined with surfactant flooding. An assessment of how tertiary oil recovery in aged and unaged cores varies with surfactant concentration is also presented.Effluent ion analysis from low salinity water floods showed that Mg²⁺ ions were strongly retained in the aged core while Ca²⁺ ions were being produced from both aged and unaged cores. The latter was attributed mainly to calcite dissolution. Results obtained from pressure profiles, effluent ion analysis and turbidity tests suggest higher production and elution of fine particles from the unaged core.     

一次和二次聚合物驱驱替液与原油黏度比优化研究

研究了不同原油黏度原油油藏一次聚合物驱和二次聚合物驱时驱替液与原油黏度比对提高采收率的影响,并对合理黏度比区间进行了优化。研究结果表明:在相同原油黏度条件下,随着黏度比的增大,聚合物驱提高采收率幅度变大,但黏度比大到一定程度后采收率提高幅度的增加不明显;在相同黏度比条件下,二次聚合物驱采收率提高幅度明显低于一次聚合物驱,如果要达到一次聚合物驱时的采收率提高幅度,则需要较高的黏度比;二次聚合物驱时,聚合物注入时机越早越好。绘制了合理黏度比的理论图版,利用该图版可以检验矿场实施单元注入参数的合理性,且为一次聚合物驱及二次聚合物驱的合理注入参数设计提供了依据。     

Performance of low.salinity water flooding for enhanced oil recovery improved by SiO2 nanoparticles

flooding changes the ion composition or brine salinity for improving oil recovery. Recently, the application of nanoparticles with low-salinity water flooding has shown remarkable results in enhanced oil recovery (EOR). Many studies have been performed on the effect of nanofluids on EOR mechanisms. Their results showed that nanofluids can improve oil recovery when used in low-salinity water flooding. In this work, the effects of injection of low-salinity water and low-salinity nanofluid (prepared by adding SiO₂ nanoparticles to low-salinity water) on oil recovery were investigated. At first, the effects of ions were investigated with equal concentrations in low-salinity water flooding. The experimental results showed that the monovalent ions had better performance than the divalent ions because of them having more negative zeta potential and less ionic strength. Also, low-salinity water flooding recovered 6.1% original oil in place (OOIP) more than the high-salinity flooding. Contact angle measurements demonstrated that low-salinity water could reduce the contact angle between oil and water. Then in the second stage, experiments were continued by adding SiO₂ nanoparticles to the K⁺ solution which had the highest oil recovery at the first stage. The experimental results illustrated that the addition of SiO₂ nanoparticles up to 0.05 wt% increased oil recovery by about 4% OOIP more than the low-salinity water flooding.     

离子组成及矿化度对低矿化度水驱采收率的影响

低矿化度水驱提高采收率对注入水和地层水的离子组成有一定的要求。在室内砂岩岩心驱替实验的基础上,采用对比的方法,研究了注入水和地层水的离子组成对低矿化度水驱提高采收率的影响。结果表明：在进行三次采油模式下的低矿化度水驱时,地层水中含有二价阳离子Ca²⁺或Mg²⁺均可提高采收率,且Ca²⁺的效果要好于Mg²⁺;只有注入水的矿化度低于油藏油水系统低矿化度效应启动阈值时,采收率才会提高。分析实验结果确定,地层水中含有二价阳离子Ca²⁺或Mg²⁺,以及注入水的矿化度低于由油藏油水系统决定的矿化度阈值,是实现低矿化度水驱提高采收率的必要条件。     

Pre-prepared Microemulsion Flooding in Enhanced Oil Recovery: A Review

It is evident that one of the important applications of microemulsions is in enhanced oil recovery (EOR) process due to its unique properties such as ultra-low interfacial tension. The injection of microemulsion slug reduces the interfacial tension between the crude oil and reservoir brine, which leads to mobilization of substantial fraction of residual oil. In general microemulsion flooding is classified into two distinct categories, pre-prepared and in situ prepared, depending on its preparation method. The authors present a detailed discussion of microemulsion preparation and summarizes major articles on pre-prepared microemulsion flooding in EOR processes. Their review opens new horizons for the future researches on pre-prepared microemulsion flooding in EOR processes by organizing the literature data and comparing them.     

克拉玛依油田Ⅲ类砾岩油藏氮气泡沫驱可行性

克拉玛依油田Ⅲ类砾岩油藏原油黏度较高、层内非均质严重,水驱开发效果较差,目前已有部分区块转注蒸汽开发。对该类区块中较有代表性的二中西区、六中区进行了常温泡沫驱油配方研究和室内一维物理模拟评价实验。结果表明,泡沫驱油体系注入量达到0.3 PV,可以提高采收率20%以上;注入段塞达到0.5 PV时,提高采收率有明显的拐点,推荐矿场试验注入段塞0.6 PV.泡沫驱油技术用在非均质严重的普通稠油油藏,可显著提高采收率。     

An Integrated Investigation of Enhanced Oil Recovery in South Slattery Minnelusa Reservoir,Part 1: Polymer Injection

Abstract

The authors investigated polymer flooding as an enhanced oil recovery (EOR) means in the South Slattery Minnelusa reservoir. The South Slattery field is stepping into the end of secondary waterflood. The priority payzone, Minnelusa A, is characterized by low permeability and high saline brine. As an integrated investigation, the water flooding efficiency was analyzed as the fundamental to EOR research. Then, experiment and simulation methods were adopted to estimate the feasibility of polymer injection and to assess the flooding potential. The predicted recoveries of different injection schemes are presented and the development efficiencies are analyzed.     

The Role of Wettability in Petroleum Recovery

Various findings on core handling effects and crude oil/brine/rock (COBR) interactions have indicated how the wettability of a core sample is altered when retrieved from a reservoir. Moreover, it is revealed that wettability of a core will affect almost all types of physical parameters necessary for reservoir management, such as capillary pressure. However, the most accurate results are obtained when native or restored-state cores are used with native crude oil and brine at reservoir temperature and pressure. Such conditions provide core that have the same wettability as the reservoir. Equally, the wettability of originally water-wet rock can be altered by the adsorption of polar compounds and/or the deposition of organic material that was originally in the crude oil. The degree of alteration is determined by the interaction of the oil constituents, the mineral surface, and the brine chemistry. Factors that influence wettability alteration are considered, and how this in turn affects the capillary pressure, is determined. Due to the capillary pressure dependence on water saturation, the effect of wettability alteration on reserve estimation through the initial water saturation is shown. The implications for oil recovery prediction and reservoir management are discussed. The main objective is to do a critical analysis on how wettability alteration dictates the success or failure of reservoir management irrespective of the technical or operational input, early in the life of a reservoir. It is believed that reserve estimation at the early stage is either optimistic or pessimistic with the consequent effect on oil recovery prediction and reservoir planning. The overall effect would be poor reservoir management at the early life of the reservoir, which effects on the later life of the reservoir is inestimable. This explains why the petroleum business is the riskiest business in the world. This would continue to be so unless a method is devised to measure reservoir parameters in situ, devoid of wettability alteration to any extent.     

无机盐与沥青质的协同作用对油藏润湿性的影响

选用两种原油沥青质样品,对沥青质在岩石孔隙表面吸附所引起的润湿性改变进行了实验研究。测定结果表明,岩样润湿性改变的程度主要与沥青质的来源和岩样所含盐水的组成有关。盐水中无机阳离子的类型对沥青质所引起的油藏岩石润湿性改变有十分重要的作用。在浓度相同的情况下,阳离子价数越高,对润湿性的影响越大。盐水中的无机阴离子对沥青质引起的润湿性改变影响很小。在油气开采过程中,地层水和注入水的离子组成,特别是所含阳离子的类型,是影响油藏岩石润湿状态的一个不可忽视的因素。