Microbial Enhanced Oil Recovery (MEOR)

Abstract

Microbial enhanced oil recovery (MEOR) represents the use of microorganisms to extract the remaining oil from reservoirs. This technique has the potential to be cost-efficient in the extraction of oil remained trapped in capillary pores of the formation rock or in areas not swept by the classical or modern enhanced oil recovery (EOR) methods, such as combustion, steams, miscible displacement, caustic surfactant-polymers flooding, etc. Thus, MEOR was developed as an alternative method for the secondary and tertiary extraction of oil from reservoirs, since after the petroleum crises in 1973, the EOR methods became less profitable. Starting even from the pioneering stage of MEOR (1950s) studies were run on three broad areas, namely, injection, dispersion, and propagation of microorganisms in petroleum reservoirs; selective degradation of oil components to improve flow characteristics; and metabolites production by microorganisms and their effects.     

An Evaluation for Two Bacillus Strains in Improving Oil Recovery in Carbonate Reservoirs

Many successful field cases of microbial enhanced oil recovery (MEOR) method have been reported for sandstone reservoirs. The objective of this study is to investigate the potential of MEOR method in UAE carbonate reservoirs. Two Bacillus strains were incubated at temperatures from 35 to 55°C, and their effects on crude oil properties and recovery were examined. It was discovered the strain could effectively reduce interfacial tension. Bacteria solutions were subsequently injected into a glass Hele-Shaw model to simulate microbial flooding in a fracture. It was observed that both strains grown under 45°C achieved maximum enhanced recovery of over 13%. Core flooding tests were conducted at elevated temperature of 70°C with limestone core. The two strains achieved enhanced oil recovery of more than 4.5%. The observation on core flooding test indicated selective plugging as the dominant recovery mechanism.     

胜利油田微生物采油技术研究与应用进展

胜利油田微生物采油技术历经二十多年的室内研究和现场试验,机理研究取得深入认识,技术体系日趋完善,已进入工业化应用阶段。微生物界面趋向性、嗜烃乳化、界面润湿改性等主导驱油机理认识更加深入,并实现了量化表征,为菌种(群)改造和调控指明了方向;建立系统的油藏菌群结构分子生物学分析、采油功能菌激活调控、三维物理模拟驱油等微生物采油技术体系;现场试验从单井吞吐到微生物驱,从外源微生物到内外源微生物共同作用,近几年通过微生物+其它工艺组合的方式大幅提高了该技术油藏适应性。目前已进入全面先导实验向工业化应用的转化阶段。截至2019年12月胜利油田微生物驱油已实施10个区块,累积增油量为30×10⁴ t。微生物驱技术在沾3普通水驱稠油油藏现场试验取得成功的基础上,又在辛68高温高盐稠油油藏和草13热采低效稠油油藏微生物驱现场试验取得突破。针对不同类型稠油油藏建立了微生物复合气体等复合吞吐工艺,扩大微生物单井吞吐技术应用规模,到2019年12月已实施400余口油井单井吞吐,累积增油量为8×10⁴ t。     

微生物提高原油采收率室内研究进展

介绍了一套简便易行的用于微生物采油菌株筛选的程序和室内微生物驱油模拟实验装置及模拟过程。简要阐明了微生物的采油机理,并对吸附、扩散、细菌代谢、营养、孔隙度、渗透率等因素的影响进行了分析。不同细菌具有不同的驱油效果;培养基类型对原油采收率的影响较大,利用糖蜜培养的细菌其采收率优于采用葡萄糖培养的;油层的孔隙度越大,越有利于细菌的增殖,从而使原油采收率提高。考虑到采油成本,以原油为唯一碳源的研究更有前景。最后简单介绍了聚合酶链式反应并展望了微生物采油技术的前景。     

Bacillus菌株提高碳酸盐油藏采收率的实验研究

微生物驱油技术(MEOR)近年来在世界多个油田取得了成功,大部分的实验室研究和现场应用都是针对砂岩油藏进行的,该技术在碳酸盐油藏中的研究很有限.两株Bacillus细菌在特定的温度下繁殖后,其代谢物被用于油水界面张力测试、玻璃模型驱油实验和碳酸盐岩心采收率实验.结果表明,细菌代谢物可大幅降低界面张力,并有效提高采收率.根据实验现象,微生物在碳酸盐岩石中的驱油机理是对高渗透率裂缝的选择性封堵.     

微生物采油矿场应用研究进展

对国内外微生物采油（MEOR）矿场试验研究进展情况作了综述。分初期到中期（上世纪70世代以前）和中期到现在（70年代以后）,简述了全世界进行的MEOR矿场试验,列表介绍了1979年以后发表的21例MEOR的注入微生物,实验方式（单井吞吐或驱替）及结果,讨论并列表给出了MEOR的矿物应用条件,并与其他EOR方法作了比较,论述并讨论了MEOR矿场试验的一般程序,包括油田调查,注入微生物选择,对油 层的适应性,与油层本源微生物的竞争特性,提高采收率及添加的营养源,对MEOR矿场应用前景作了展望。     

微生物提高采收率技术综述

作为主要产油国之一,中国对提高采收率技术的研究与应用给予极大的关注。微生物驱油是作为焦点之一的一项先进技术。本文简要介绍了微生物驱油发展历史并详细介绍其试验及推广情况以及相关特色。本文提出了微生物驱油机理,微生物可以产生气体、酸、表面活性剂以及聚合物,这些物质能够改善碳氢化合物结构,降低其粘度,并能在压力升高的情况下有效驱油。早期现场试验是利用微生物开采残余油气。微生物及其反应物存在对中国许多油田油气增产具有极大的作用。至于新陈代谢研究一些油田的现场应用表明,准确分析和评价新陈代谢并进一步优选微生物是非常重要的,而且微生物驱油方案应用于超稠油田也取得相对好的结果。     

Effects of hydrocarbon solvents on simultaneous improvement in displacement and sweep efficiencies during CO2-enhanced oil recovery

The addition of hydrocarbon solvent such as liquefied petroleum gas (LPG) to the CO₂ stream leads to miscible conditions in reservoirs at lower pressures by reducing the minimum miscibility pressure (MMP). Under miscible conditions, improved displacement and vertical sweepout occur simultaneously. The influences of LPG concentration and composition on the displacement and sweep efficiencies during CO₂-LPG enhanced oil recovery (EOR) were investigated. Enhanced displacement efficiency was assessed through oil viscosity reduction and oil saturation change. Moreover, the miscible flooding induced by LPG addition, which resulted in increased solvent viscosity and a lower density difference between the injected fluid and reservoir oil, provided a smaller viscous gravity number, and improved the sweep efficiency, alleviating the impact of solvent gravity override. For CO₂-LPG EOR, oil recovery increased up to 52% as compared with that for CO₂ flooding. The amount of incremental oil recovery with 100% butane in the LPG was 16%, as compared with the 100% propane case. Mitigated gravity override enabled CO₂-LPG EOR to enhance sweep efficiency. Results indicated that the compositional modeling of the EOR process with the addition of LPG provided more accurate prediction on the performance of CO₂-LPG EOR.     

Microemulsions in Enhanced Oil Recovery: A Review

Abstract

Microemulsions have recently made advances in enhanced oil recovery processes in which chemicals, especially surfactants, are used to recover the oil from natural oil reservoirs. This technique relies on the knowledge of interfacial properties among oil, water, and solid rock reservoirs in the occasional presence of natural gas under extreme conditions. Surfactant-based chemical systems have been reported in many academic studies and their technological implementation is a potential candidate in enhanced oil recovery (EOR) activities. For instance, it was determined that a mobilized buffer (polymer) with viscosity either equal to or greater than the mobilized oil enhanced the recovery efficiency considerably. However, EOR based on chemicals like alkaline–surfactant–polymer (ASP) is a complex technology requiring a high level of expertise for its industrial implementation. The surfactant–polymer interaction is a rapidly growing research area for efficient oil recovery by improving slug integrity, adsorption, and mobility control. This review article evaluates the injecting fluid system to highlight some recent advances in the use of chemicals in EOR, especially with microemulsions. It further reveals the current status and future outlook for EOR technology in oil fields and describes the opportunities for strategic utilities and load growth in petroleum industry.     

微生物采油需要进一步解决的问题

探讨制约微生物采油技术发展的关键问题，认为制约的主要因素不是油藏条件，而是研究技术本身不够完善。有两个问题值得注意：其一，对油藏中微生物结构认识的局限性。目前鉴定和分析微生物使用传统的微生物培养和显徽技术，只能发现生态环境中很少的一部分微生物，不能得到油藏产出液中有多少种微生物及其含量、所希望的微生物种群在其中是否属优势菌群等关键参数。其二，物理模拟驱油实验的局限性。目前的微生物驱油物理模拟研究基本沿用化学驱物理模拟研究设备和方法，一般使用人造岩心(国外多数使用天然岩心)，不能真实模拟油藏环境而准确反映微生物驱油的真实效果，研究得出的参数也就不能用于现场试验。最后，提出了微生物采油技术需要进一步解决的关键问题及其解决方法．参15     

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。     

Simulation of Natural Depletion and Miscible Gas Injection Effects on Asphaltene Stability in Petroleum Reservoir Fluids

Abstract

Natural depletion of petroleum reservoirs as well as gas injection for enhance oil recovery, are unavoidable processes in the oil industry. Foremost, prediction of the problems due to these two processes is very necessary and important. So many field and experimental experiences have shown that heavy organic depositions, especially asphaltene deposition, are principal results during these processes. Results of laboratory simulation of asphaltene deposition during the natural depletion of petroleum reservoirs and also during gas injection and enhanced oil recovery (EOR) processes are reported here. This is achieved through the design of a new experimental setup for the investigation of pressure and composition effects on asphaltene deposition in petroleum fluids at high pressure and high temperature conditions. In this work, asphaltene deposition during decreasing pressure, from pressures greater than reservoir pressure to pressures below the bubble point pressure (natural depletion) and also asphaltene deposition during natural gas injection in reservoir conditions, are studied for three samples—one recombined sample and two bottomhole samples. All of the obtained results from this work conform to theoretical and other experimental works.     

Comparison of in-situ and ex-situ microbial enhanced oil recovery by strain Pseudomonas aeruginosa WJ-1 in laboratory sand-pack columns

Microbial enhanced oil recovery (MEOR) applies biotechnology to improve residual crude oil production from substratum reservoir. MEOR includes in-situ MEOR and ex-situ MEOR. The former utilizes microbial growth and metabolism in the reservoir, and the latter directly injects desired active products produced by microbes on the surface. Taking biosurfactant-producing strain Pseudomonas aeruginosa WJ-1 for research objects, in-situ enhanced oil recovery and ex-situ enhanced oil recovery by biosurfactant-producing strain WJ-1 were comparatively investigated in sand-pack columns.The results showed that P.aeruginosa WJ-1 really proliferated in sand-pack columns, produced 2.66 g/L of biosurfactant, altered wettability, reduced oil-water interfacial tension (IFT) and emulsified crude oil under simulated in-situ process. Results also showed that higher biosurfactant concentration, lower IFT, smaller average diameters of emulsified crude oil were obtained in in-situ enhanced oil recovery experiment than those in ex-situ enhance oil recovery experiment. Similar wettability alteration was observed in both in-situ and ex-situ enhanced oil recovery experiment. The flooding experiments in sand-pack columns revealed that the recovery of in-situ was 7.46%/7.32% OOIP (original oil in place), and the recovery of the ex-situ was 4.64%/4.49% OOIP. Therefore, in-situ approach showed greater potential in enhancing oil recovery in contrast with ex-situ approach. It is recommended that the stimulation of indigenous microorganisms rather than injection of microbial produced active products should be applied when MEOR technologies were employed.     

Simulation of Natural Depletion and Miscible Gas Injection Effects on Asphaltene Stability in Petroleum Reservoir Fluids

Natural depletion of petroleum reservoirs as well as gas injection for enhance oil recovery, are unavoidable processes in the oil industry. Foremost, prediction of the problems due to these two processes is very necessary and important. So many field and experimental experiences have shown that heavy organic depositions, especially asphaltene deposition, are principal results during these processes. Results of laboratory simulation of asphaltene deposition during the natural depletion of petroleum reservoirs and also during gas injection and enhanced oil recovery (EOR) processes are reported here. This is achieved through the design of a new experimental setup for the investigation of pressure and composition effects on asphaltene deposition in petroleum fluids at high pressure and high temperature conditions. In this work, asphaltene deposition during decreasing pressure, from pressures greater than reservoir pressure to pressures below the bubble point pressure (natural depletion) and also asphaltene deposition during natural gas injection in reservoir conditions, are studied for three samples—one recombined sample and two bottomhole samples. All of the obtained results from this work conform to theoretical and other experimental works.     

Modelling of microbial enhanced oil recovery application using anaerobic gas-producing bacteria

Microbial enhanced oil recovery （MEOR） methods apply injection of bacteria to depleted oil reservoirs to produce oil, which had remained unrecovered after the conventional methods of production. The ability ofthermophilic anaerobic bacteria to produce gas as the main mechanism in potential MEOR in high salinities of 70-100 g/L was investigated in this study. Maximum gas production of up to 350 mL per 700 mL of salty solution was produced at a salinity of 90 g/L stably during 2-4 days of experiment. The experimental results were upscaled to the Snorre Oilfield, Norway, and simulated using ECLIPSE software for 27 months. The best scenarios showed that the increase in oil recovery on average was at 21% and 17.8% respectively. This study demonstrated that anaerobic bacteria used in biogas plants could be an attractive candidate for MEOR implementation due to their ability to withstand high temperature and salinity, and produce gas in large volumes.     

微生物采油技术在国内外的研究现状及实例

介绍了微生物提高石油采收率的发展概况，基本原理与方法，探讨了ＭＥＯＲ技术的应用条件，综述了ＭＥＯＲ的矿场应用及效果。根据微生物处理的油层筛选标准，提出了中原油田部分油区可以利用ＭＥＯＲ的技术提高采收率。     

多孔介质微生物提高原油采收率模型

通过分析微生物在多孔介质中的运移规律,建立了能反映微生物驱油过程的三维三相(油、气、水)四组分数学模型,模型中的组分有微生物、营养物、溶解氧以及代谢产物(生物表面活性剂)。模型分析了对流、扩散、微生物生长和死亡、趋化性、营养物消耗、代谢产物生成、各组分吸附和微生物解吸附等特性,并考虑了微生物吸附造成渗透率下降、代谢产物降低原油黏度和油-水界面张力等性质。进一步根据数学模型研制了对应的模拟器,在给定参数条件下,对微生物驱油效果进行了预测,分析了最大比生长速率、微生物吸附常数、趋化性系数以及代谢产物得率对微生物驱油的影响,进一步揭示了微生物提高采收率的作用机理。     

激活内源微生物提高原油采收率技术

微生物采油技术可按微生物来源分为外源微生物采油和内源微生物采油两大类，本文综述了通过注入营养剂和混气水激活油层内本源微生物的采油技术，该项技术的工艺较简单，在俄罗斯已进入较大规模的矿场应用试验。综述的论题包括；绪言；基本原理，矿场试验及相关研究；矿场试验设计；矿场试验跟踪监测；对中国微生物采油技术发展的意义。     

Using biosurfactant producing bacteria isolated from an Iranian oil field for application in microbial enhanced oil recovery

Microbial enhanced oil recovery (MEOR) is a useful technique to improve oil recovery from depleted oil reservoirs beyond primary and secondary recovery operations using bacteria and their metabolites. In the present study, the biosurfactant production potential of Bacillus licheniformis microorganisms that were isolated from oil samples of Zilaei reservoir in the southwest of Iran was explored under extreme conditions. Growth media with different temperatures of 40, 50, 60, and 70°C; salinities of 1, 3, 5, and 7 wt%; and yeast extract concentrations of 0.5, 1, 1.5, and 2 g/L were used to find the optimum growth conditions. The results demonstrated that bacteria grown in a mineral salt solution with temperature of 50°C, salinity of 1 wt% and yeast extract concentration of 1 g/L has the highest growth rate and therefore, these conditions are the optimum conditions for growing the introduced bacterium. This isolate was selected as the higher biosurfactant producer. The obtained biosurfactants by bacteria isolated in a medium with these conditions could reduce the interfacial tension of crude oil/water system from 36.8 to 0.93 mN/m and surface tension of water from 72 to 23.8 mN/m. The results of the core flooding tests showed that the tertiary oil recovery efficiency due to the injection of microorganisms was 13.7% of original oil in place and bacteria could reduce the oil viscosity by 41.242% at optimum conditions. Based on these results, the isolated microorganism is a promising candidate for the development of microbial oil recovery processes.     

石油磺酸盐复合体系在稠油热采领域的应用研究

胜利油田稠油热采主要采用蒸汽吞吐的方式。其中新开发稠油区块注汽压力高、注汽干度低和老区多轮次吞吐后采收率低、油汽比低是影响热采效果的主要因素。油水之间的高界面张力导致蒸汽驱替效率低是多轮次吞吐后开发效果变差的主要原因之一。针对以上问题开展石油磺酸盐复合体系提高稠油开发效果室内研究,对石油磺酸盐复合体系配方进行优化研究,通过高温岩心驱替实验研究磺酸盐复合体系降低注汽压力的能力,研究石 油磺酸盐复合体系提高注入蒸汽驱替效率和岩心采收率的能力,研究不同注入方式对提高采收率的影响,研究结果表明石油磺酸盐体系可有效降低蒸汽注入压力,提高驱替效率和岩心采收率。2004年在胜利油田单家寺油田、孤岛油田、孤东油田现场应用12井次,单井降低注汽压力0．5～2．6MPa,周期采油量增加190～480t,截至2004年底已累计增油4600t。