CO2 EOR及其在油藏中的储存

CO2 EOR已在石油行业应用了40多年.近几年,出于对温室效应的考虑,CO2注入油藏作为一种碳埋存方式引起广泛关注.结合EOR进行CO2储存的潜力巨大,且可达到永久封存的目的.目前,CO2EOR已经不存在较大的技术问题,大部分项目利用低廉的天然CO2,经济回报较高.但将人类排放源(如发电厂)中的CO2捕集起来并用于EOR和储存,将会受到经济上的限制.本文阐述了CO2 EOR原理、油藏储存潜力、油田筛选及经济分析,并对北海一个油田进行了实例分析.     

EOR项目中的CO2供应

可用各种方法来获得用于CO2提高石油采收率(EOR)项目的二氧化碳，CO2即可来自工业生产，也可来自产出气。     

CO2不纯度对EOR注气工艺的影响

从技术和经济(如果适当控制操作费用)的角度来看，CO2驱是有前途的EOR方法。注这种温室气体也对环境有益。来自电厂的烟道气是现成的CO2源，但是从这种CO2源中提取用于EOR的CO2将增加项目费用。而且，为了减少纯CO2用量和购买气体费用，通常需要回注采出CO2并且尽可能不提纯。因此，为了设计有成本效益的EOR CO2驱工艺必须了解流体相态中CO2不纯度和混相特性的作用。     

CO2不纯度对EOR注气工艺的影响

从技术和经济（如果适当控制操作费用）的角度来看，CO2驱是有前途的EOR方法。注这种温室气体也对环境有益。来自电厂的烟道气是现成的CO2源，但是从这种CO2源中提取用于EOR的CO2将增加项目费用。而且，为了减少纯CO2用量和购买气体费用，通常需要回注采出CO2并且尽可能不提纯。因此，为了设计有成本效益的EOR CO2驱工艺必须了解流体相态中CO2不纯度和混相特性的作用。     

EOR项目的经济评价：衰竭油田中的CO2埋存

本文发表了在巴西一个成熟小油藏进行CO2EOR的可行性研究。本项研究考虑了两个重要且互补的因素：（1）改善EOR——用CO2驱替一次采油和二次水驱后留在地下的残余油，并成功地在成熟油藏注入40年，延长油田寿命；（2）把CO2储存在油藏中，从而减少温室气体排放。描述了项目的物理学原理，为了估计带有CO2埋存的综合EOR的主要财务因素（捕集、压缩、运输和储存成本），项目评价是从一现金流量模型导出的，涉及油藏生产剖面、价格和成本、资本支出（CAPEX）、运营支出（OPEX）、碳信用额、折旧时间、财政假设等。为了确定最关键变量，进行了敏感性研究。结果表明，项目的净现值（NPV）大约是320万美元，这对一个小成熟油田来说很重要。此外，它还将在20年时间里储存73万吨CO2，从而减少温室气体排放。正如预计的那样，发现项目可行性对油价、油产量和资本支出很敏感。     

智能井技术在SACROC单元CO2EOR项目中的应用：实例研究

描述了得克萨斯Scurry县SACROC单元CO2 EOR项目中应用智能井的实例研究.2005年初实施了一个5口井的先导性试验项目,以证实智能井井下流动控制阀能够限制或隔离产自采油井高渗透层的CO2和控制从注入井注入的CO2分布,目的是减少CO2在注入井和采油井之间的不必要循环,提高波及效率,增加采油量和提高最终采收率.智能井技术和工艺过程可应用于所有EOR/IOR油田开发规划中,特别是CO2 WAG中.实例中采用的智能井技术可以应用于层状、密封的和复杂的油藏中,特别是可以应用于二次和三次采油工艺中.初步结果显示,在保持经济采油量的同时,大幅度减少了CO2采出量.采用智能井设备还能够在不使用钢丝和电缆的情况下在1口井内对不同层进行选择性测试和实施增产增注措施.     

卓有成效的EOR方案的编制

高油价和对未来石油供给的担心使EOR——可显著提高现有油藏采收率的一组技术——重新受到青睐。EOR的大部分试验仍然是在美国，如西得克萨斯二叠盆地的CO2驱和加利福尼亚圣华金河谷的一些热力采油法。在加拿大阿尔伯达盆地，对沥青（原油）的热力开采正在迅速地发展，而热采方案也已在委内瑞拉、印度尼西亚等国家和地区获得成功应用。化学驱和聚合物驱正中国付诸实施。     

智能井在SACROC单元CO2 EOR项目中的应用：实例研究

本文描述了在得克萨斯Scurry县SACROC单元CO2 EOR项目中应用智能井的实例研究。在2005年初实施了一个有5口井的先导性试验项目，目的是证实智能井井下流动控制阀能够限制或隔离产自采油井高渗透层的CO2和控制从注入井注入的CO2分布。目的是减少CO2在注入井和采油井之间的不必要循环，提高波及效率，增加呆油量和提高最终采收率。这一目的是通过采用有成本效益并且适合这一目的的智能井系统达到的。可以把在本文中描述的智能井技术和工艺过程应用于所有EOR／IOR油田开发规划中，特别是可以应用于C02WAG中。可以把在该实例中采用的智能井技术应用于层状、形成封存箱的和复杂的油藏，特别是可以应用于二次和三次采油井网。初步结果显示，在保持经济呆油量的同时，大幅度减少了CO2采出量。采用智能井设备还能够在不使用钢丝和电缆的情况下在一口井内对不同层进行选择性测试和实施增产增注措施。     

量化EOR作业中的温室气体减排

提高石油采收率（EOR）已被认为是埋存二氧化碳（CO2）的有希望的方法。当原本要排放到大气中的CO2用于该项处理时，留在地下的CO2就代表了温室气体（GHG）排放的减少。 随着公司寻求使与EOR有关的减排在市场上交易，精确地量化埋存的CO2量就很重要。减排的购买者需要确保他们所购买的减排是真实的。然而，EOR项目作业过程中CO2和甲烷（CH4）的损失常常不能完全计入减排。由于少量难以捉摸的损失可能被计入，因此确定了设备可能导致的更大损失。本文发表了一种用于量化EOR导致的净温室气体减排的方法，该方法是建立在对作业设施的观察基础上的。文章表明，在量化温室气体减排过程中需要考虑生产设施的运行问题。文章得出结论，EOR作业中的CO2和甲烷的损失可能会很大，除非它们能被充分考虑到，否则任何声称的减排都可能存在问题。     

美国CO2驱油补充项目的潜力分析

由于原油价格持续走高、美国常规原油产量持续下降和对温室气体排放的关注,人们对CO2 EOR技术重新产生了兴趣。该技术面临的挑战在于是否可以获得足够量的CO2,基础设施能否满足要求,以及CO2的成本是不是足够低。对1673个潜在CO2EOR的候选油藏进行了分析。为了确定CO2的可利用性,图示了EOR候选油藏沿线的天然和工业CO2资源。工业CO2运输到生产现场其成本包括收集成本和管线运输费,由此可以确定EOR项目的经济性和开发情况。分析表明,如果通过大规模地收集和购买工业源CO2增加CO2的供应量,并且油价在$45～60／bbl之间,可以实现CO2EOR日增油1．2×10^6bbl和日埋存CO2300×10^6t．     

水驱废弃油藏CO2驱提高采收率技术研究

中原油田经过30多年高速水驱开发,已进入总体递减阶段,但油藏高温、高地层水矿化度特点限制了化学驱的应用。为改善特高含水开发后期油藏开发效果,中原油田在濮城油田沙一下水驱废弃油藏开辟了先导试验区。以CO2驱提高水驱废弃油藏采收率为目的,研究形成的特高含水期油藏剩余油微差异刻画技术、CO2驱驱油机理认识、注采参数优化方法,以及配套防腐、防窜工艺技术,已应用于2个试验井组,采出程度提高了6.5%。预计濮城沙一下整体实施后,原油采收率提高9.9%,年增产原油超过2×104t,为探索水驱废弃油藏及特高含水油藏提高采收率提供了一项新技术。     

美国碳酸盐岩油藏提高采收率历史与现状

如果不包括中东的资源,相当大一部分（甚至更多）世界油气储量都蕴藏在碳酸盐岩油藏中。碳酸盐岩油藏孔隙度通常低并且可能是裂缝性的。除了原油和混合润湿岩石特性外,以上这两个特性通常导致采收率低。况且,在有效采用加密钻井方案和井波及策略（大部分是堵气和堵水）的情况下,采收率还是达不到OOIP（原始石油地质储量）的40%～50%。自20世纪70年代以来,在碳酸盐岩油藏中实施的EOR（提高原油采收率）油田项目越来越多。通过实施油田项目证明了其提高采收率的技术能力并且估算出了长期作业费用。采收率的提高直接增加了储量,延长了不同油藏的开采期限。本文介绍了在美国碳酸盐岩油藏实施的注CO2、火烧油层、注氮、注烃气、注蒸汽和EOR化学驱的历史与现状。     

用钻特殊井方法提高采收率

尽管三次采油过程的各种提高采收率技术在经济、合理、最大限度的开采石油方面发挥了重要作用,但由于许多技术目前尚处于部分工业运用及实验室研究阶段,加上许多技术本身的局限性和油藏的复杂性,导致其效果并不理想。随着钻井技术的进步,水平井、侧钻水平井、分支井、大位移井等特殊井在提高石油采收率上的贡献日见报道,但是从观念认识上,往往没有把这些钻井方法列入提高石油采收率的技术之列。文中在讨论目前各种提高采收率技术的优点和不足之处的基础上,提出了对现有采收率技术不适用的油藏而言,用特殊井提高采收率比现有各种提高采收率技术优越,并阐述了钻井方法提高采收率技术的优点及其前景。     

Experimental Investigation of Viscous Surfactant Based Enhanced Oil Recovery

Crude terephthalic acid (CTA) as a chemical compound is used for flooding here as an alternative to the traditional hydrolyzed polyacrylamide (HPAM) because of its availability and economical aspects and higher efficiency. Crude oil samples from an Iranian oil field were used during the flooding tests. Sand packed models using two different sizes of sand mainly 50 and 100 meshes were employed in this investigation. A comparison between water flooding and CTA flooding as a secondary oil recovery process revealed that the oil recovery factor was improved by 10% OOIP when CTA after water flooding was used in secondary state. The effect of various injection rates and different concentration of chemical solutions on the recovery factor have been checked. Besides, experimental results improved the surfactant behavior of the CTA solution in water. Experiments showed that oil recovery factor increased by 5% OOIP when SDS solution was used in tertiary state. Experiments were performed in laboratory temperature and pressure around 10 bars.     

CO2驱采油实现温室气体减排研究概述

由于环境保护的需要,减少CO2的排放量成为世界各大石油公司重要的研究课题。采用CO2驱油工艺不仅可以显著提高原油的采收率,还可以减少CO2向大气层的排放量(简称CO2减排),同时可减少90%以上的天然气注入量。现有烟气控制技术可满足收集燃煤电厂CO2的需求。在石油行业,也可利用高含盐采出水沉淀和合成聚合物来实现CO2减排。     

Detection and Reuse of the Produced Chemicals in Chemical Enhanced Oil Recovery Operations

Abstract

The alkaline-surfactant-polymer (ASP) floods have been increasingly applied in the oil fields because of their high ultimate oil recovery. However, a major technical challenge is how to reduce the amount and the cost of chemicals used so that ASP floods can become cost-effective as well. On the other hand, field applications show that the chemical concentrations remain relatively high in the produced liquids of ASP floods. Therefore, successful detection and reuse of these produced chemicals can substantially reduce their capital cost and environmental impact. In this article, several experimental methods are developed to detect each chemical and quantify its concentration in the produced liquids. Also re-injection of the produced chemicals is conducted to further enhance oil recovery. First, the respective interactions of alkali, surfactant, and polymer with the oil-brine-sand system are studied. Second, the interfacial tension (IFT) is measured as a function of alkaline concentration by using the axisymmetric drop shape analysis technique for the pendant drop case. In addition, the synergistic effects of alkali and surfactant on reducing the IFT are studied. Third, coreflood tests are performed for alkaline, surfactant, alkaline-surfactant, polymer, and ASP floods to determine their respective tertiary oil recovery. Hence, how each chemical contributes to enhanced oil recovery is better understood. Fourth, the produced chemical concentrations are measured and compared with their injected concentrations to determine the potential of reusing these chemicals in practice. Finally, the follow-up coreflood tests are conducted by re-injecting the produced liquids into a new sand pack or Berea core. The re-injection coreflood test results show that the produced chemicals can be reused to effectively enhance oil recovery.     

Detection and Reuse of the Produced Chemicals in Chemical Enhanced Oil Recovery Operations

The alkaline-surfactant-polymer (ASP) floods have been increasingly applied in the oil fields because of their high ultimate oil recovery. However, a major technical challenge is how to reduce the amount and the cost of chemicals used so that ASP floods can become cost-effective as well. On the other hand, field applications show that the chemical concentrations remain relatively high in the produced liquids of ASP floods. Therefore, successful detection and reuse of these produced chemicals can substantially reduce their capital cost and environmental impact. In this article, several experimental methods are developed to detect each chemical and quantify its concentration in the produced liquids. Also re-injection of the produced chemicals is conducted to further enhance oil recovery. First, the respective interactions of alkali, surfactant, and polymer with the oil-brine-sand system are studied. Second, the interfacial tension (IFT) is measured as a function of alkaline concentration by using the axisymmetric drop shape analysis technique for the pendant drop case. In addition, the synergistic effects of alkali and surfactant on reducing the IFT are studied. Third, coreflood tests are performed for alkaline, surfactant, alkaline-surfactant, polymer, and ASP floods to determine their respective tertiary oil recovery. Hence, how each chemical contributes to enhanced oil recovery is better understood. Fourth, the produced chemical concentrations are measured and compared with their injected concentrations to determine the potential of reusing these chemicals in practice. Finally, the follow-up coreflood tests are conducted by re-injecting the produced liquids into a new sand pack or Berea core. The re-injection coreflood test results show that the produced chemicals can be reused to effectively enhance oil recovery.     

Simulation of Silica Nanoparticle Flooding for Enhancing Oil Recovery

Obtaining accurate relative permeability curves from coreflood experiments is imperative for characterizing a reservoir and estimating its production capability. As the relative permeabilities are not directly measurable, they are inferred from the measured data utilizing some mathematical model of the physical process. This procedure is referred to as inverse modelling. The inverse problem is to obtain estimates of the relative permeability functions using the data measured during displacement experiments. It concerns on the unsteady state relative permeabilities that are obtained from waterflood and suspension of silica nanoparticle flood experiments. For each experiment, recovery and pressure drop data were collected and used in a coreflood simulator. The coreflood simulator used in this study is the Sendra. As the relative permeability is a function of saturation, the authors required the estimates of the entire function. The results show that it is possible to determine one set of relative permeability curves that reconcile several nanosilica flooding experiments simultaneously using the history match method.     

多相泡沫体系调驱提高原油采收率试验研究

通过复配泡沫和聚合物凝胶微球形成多相泡沫体系,并进行了多相泡沫体系在多孔介质中的驱油实验。通过激光粒度分析仪对聚合物凝胶微球的粒径进行测量,其粒径分布均匀,且与地层孔喉匹配。针对多相泡沫的起泡能力和稳定性,采用搅拌法对其各组分的浓度进行优选。微球封堵试验表明,微球能在岩心中不断地封堵和运移,使注入压力和阻力系数增加,后续水驱仍有较高的残余阻力系数。在双管非均质驱油试验中,多相泡沫优先进入高渗管并具有良好的调剖效果,从而改善地层非均质性,使泡沫驱替低渗管,调剖与驱油结合,有效地提高原油采收率。