Progress of Microbial Enhanced Oil Recovery in Laboratory Investigation

This paper describes a simple, easy process for screening microorganisms, and introduces a laboratory simulation device and process of microbial enhanced oil recovery (MEOR) , which is a necessary research step for trial in oilfields. The MEOR mechanism and the influence of adsorption, diffusion, metabolism, nutrition, porosity, and permeability are analyzed. The research indicates that different microbes have different efficiencies in EOR and that different culture types play different roles in EOR. The effect of syrup is better than that of glucose, and larger porosity is favorable to the reproduction and growth of microbes, thereby improving the oil recovery. Using crude oil as a single carbon source is more appreciable because of the decrease in cost of oil recovery. At the end of this paper, the development of polymerase chain reaction (PCR) for the future is discussed.

Research on the Jilin Oilfield Field Trials of Microbial Enhanced Oil Recovery

This paper describes the experience of Jilin oilfield trials for Microbial Enhanced Oil Recovery (MEOR). A new technique to identify microbes with DNA for MEOR has been established, and useful microbes selected for use in field trials. Behaviors of bacteria activated in the reservoir, oil recovery and water cut, and the viscosity of crude oil produced through huff & puff testing and flooding with molasses-injection tests, have been investigated in situ. CJF-002, which produces biopolysaccharide, is the best among the microbes used for field trials, as it can use molasses as nutrient and produce a small quantity of CO2 and a mass of water-insoluble biopolymer. The metabolic behavior in the reservoir showed that CJF-002 had a good potentiality for MEOR.

Mechanisms of remaining oil formation by water flooding and enhanced oil recovery by reversing water injection in fractured-vuggy reservoirs

To get a deeper understanding on the formation mechanisms and distribution laws of remaining oil during water flooding, and enhanced oil recovery(EOR) mechanisms by reversing water injection after water flooding, 3D visualization models of fractured-vuggy reservoir were constructed based on the elements and configuration of fractures and vugs, and typical fracture-vug structures by using advanced CT scanning and 3D printing technologies. Then, water flooding and reversing water injection experiments were conducted. The formation mechanisms of remaining oil during water flooding include inadequate injection-production well control, gravity difference between oil and water, interference between different flow channels, isolation by low connectivity channel, weak hydrodynamic force at the far end. Under the above effects, 7 kinds of remaining oil may come about, imperfect well-control oil, blind side oil, attic oil at the reservoir top, by-pass residual oil under gravity, by-pass residual oil in secondary channel, isolated oil in low connectivity channel, and remaining oil at far and weakly connected end. Some remaining oil can be recovered by reversing water injection after water flooding, but its EOR is related to the remaining oil type, fracture-cavity structure and reversing injection-production structure. Five of the above seven kinds of remaining oil can be produced by six EOR mechanisms of reversing water injection: gravity displacement, opening new flow channel, rising the outflow point, hydrodynamic force enhancement, vertically equilibrium displacement, and synergistic effect of hydrodynamic force and gravity.

Mechanisms and experimental research of ion-matched waterflooding to enhance oil recovery in carbonate reservoirs: A case of Cretaceous limestone reservoirs in Halfaya Oilfield, Middle East

Based on systematically summarizing the achievements of previous ion-matched waterflooding researches,the diversity and synergy of oil recovery enhancement mechanisms and the interaction between mechanisms are examined according to two classification standards,and the influence of behaviors of different ions on different mechanisms and oil displacement efficiency are investigated.Ionic strength is proposed to characterize the behavior differences of univalent and divalent ions,the relationships between ionic strength,effective concentration,and mechanisms are established to characterize the ion behavior behind various mechanisms,and evaluate the performance of ion-matched injection water.The mechanisms of enhancing oil recovery by ion-matched waterflooding include:(1)The ion-matched water can reduce the ion strength and match the ion composition of formation water,thereby reducing the difference between the effective concentration of univalent ions and divalent ions on the surface of carbonate rocks,and improving the effective concentration of potential determining ions(especially SO42-).(2)It can improve wettability,oil-water interface properties,pore structure and physical properties of the reservoir,and finally enable the establishment of a new ionic equilibrium conducive to waterflooding while breaking the original equilibrium.In this study,experiments such as relative permeability curve,interfacial tension,and core-flooding were carried out on carbonate core samples from the Cretaceous Mishrif Formation reservoirs in Halfaya Oilfield,Middle East,a method for injection water evaluation was established and the injection water suitable for these reservoirs was selected:6 times diluted seawater.Compared with ordinary seawater,oil displacement efficiency can be increased by more than 4.60%and compared with the optimum dilution of formation water,oil displacement efficiency can be increased by 3.14%.

Key theoretical and technical issues and countermeasures for effective development of Gulong shale oil, Daqing Oilfield, NE China

Aiming at the four issues of underground storage state,exploitation mechanism,crude oil flow and efficient recovery,the key theoretical and technical issues and countermeasures for effective development of Gulong shale oil are put forward.Through key exploration and research on fluid occurrence,fluid phase change,exploitation mechanism,oil start-up mechanism,flow regime/pattern,exploitation mode and enhanced oil recovery(EOR)of shale reservoirs with different storage spaces,multi-scale occurrence states of shale oil and phase behavior of fluid in nano confined space were provided,the multi-phase,multi-scale flow mode and production mechanism with hydraulic fracture-shale bedding fracture-matrix infiltration as the core was clarified,and a multi-scale flow mathematical model and recoverable reserves evaluation method were preliminarily established.The feasibility of development mode with early energy replenishment and recovery factor of 3o%was discussed.Based on these,the researches of key theories and technologies for effective development of Gulong shale oil are proposed to focus on:(1)in-situ sampling and non-destructive testing of core and fluid;(2)high-temperature,high-pressure,nano-scale laboratory simulation experiment;(3)fusion of multi-scale multi-flow regime numerical simulation technology and large-scale application software;(4)waterless(CO_(2))fracturing technique and the fracturing technique for increasing the vertical fracture height;(5)early energy replenishment to enhance oil recovery;(6)lifecycle technical and economic evaluation.Moreover,a series of exploitation tests should be performed on site as soon as possible to verify the theoretical understanding,optimize the exploitation mode,form supporting technologies,and provide a generalizable development model,thereby supporting and guiding the effective development and production of Gulong shale oil.

Nanoparticle-reinforced foam system for enhanced oil recovery(EOR):Mechanistic review and perspective

Boosted by economic development and rising living standards,the world's carbon dioxide emissions remain high.Maintaining temperature rises below 1.5℃ by the end of the century requires rapid global carbon capture and storage implementation.The successful application of carbon capture,utilization,and storage(CCUS)technology in oilfields has become the key to getting rid of this predicament.Foam flooding,as an organic combination of gas and chemical flooding,became popular in the 1950s.Notwithstanding the irreplaceable advantages,as a thermodynamically unstable system,foam's stability has long restricted its development in enhanced oil and gas recovery.With special surface/interface effects and small-size effects,nanoparticles can be used as foam stabilizers to enhance foam stability,thereby improving foam seepage and oil displacement effects in porous media.In this paper,the decay kinetics and the stabilization mechanisms of nanoparticle-reinforced foams were systematically reviewed.The effects of nanoparticle characteristics,including particle concentration,surface wettability,particle size,and type,and reservoir environment factors,including oil,temperature,pressure,and salinity on the foam stabilization ability were analyzed in detail.The seepage and flooding mechanisms of nanoparticle-reinforced foams were summarized as:improving the plugging properties of foams,enhancing the interaction between foams and crude oil,and synergistically adjusting the wettability of reservoir rocks.Finally,the challenges in the practical application of nanoparticle-reinforced foams were highlighted,and the development direction was proposed.The development of nanoparticle-reinforced foam can open the way toward adaptive and evolutive EOR technology,taking one further step towards the high-efficiency production of the petroleum industry.

Emerging applications of nanomaterials in chemical enhanced oil recovery:Progress and perspective

In enhanced oil recovery,different chemicalmethods utilization improves hydrocarbon recovery due to their fascinating abilities to alter some critical parameters in porous media,such as mobility control,the interaction between fluid to fluid,and fluid to rock surface.For decades the use of surfactant and polymer flooding has been used as tertiary recovery methods.In the current research,the inclusion of nanomaterials in enhanced oil recovery injection fluids solely or in the presence of other chemicals has got colossal interest.The emphasis of this review is on the applicability of nanofluids in the chemical enhanced oil recovery.The responsiblemechanisms are an increment in the viscosity of injection fluid,decrement in oil viscosity,reduction in interfacial and surface tension,and alteration of wettability in the rock formation.In this review,important parameters are presented,which may affect the desired behavior of nanoparticles,and the drawbacks of nanofluid and polymer flooding and the need for a combination of nanoparticles with the polymer are discussed.Due to the lack of literature in defining the mechanism of nanofluid in a reservoir,this paper covers majorly all the previous work done on the application of nanoparticles in chemical enhanced oil recovery at home conditions.Finally,the problems associatedwith the nano-enhanced oil recovery are outlined,and the research gap is identified,which must be addressed to implement polymeric nanofluids in chemical enhanced oil recovery.

Mechanism investigation of steam flooding heavy oil by comprehensive molecular characterization

Steam flooding is a widely used technique to enhance oil recovery of heavy oil.Thermal viscosity reduction and distillation effect are considered as two main displacement mechanisms in steam flooding process.However,the molecular composition understanding and contribution for oil production are still unclear.In this study,the composition analysis of the heavy oil was investigated in the core scale steam flooding process with the temperature from 120 to 280℃.The crude oil,produced oils and residual oils were characterized comprehensively by gas chromatography and high-resolution mass spectrometry.It is found that steam flooding preferentially extracts aromatics and remains more resins in the residual oil.Viscosity reduction is the dominant mechanism when steam is injected at a low temperature.Large molecular heteroatoms with high carbon number and high double bond equivalent(DBE)are eluted into the produced oil,while compounds with low carbon number and low DBE are remained in the residual oil.As the steam temperature rises,the increased distillation effect results in the extraction of light hydrocarbons from the residual oil to the produced oil.More small heteroatoms with low carbon number and low DBE enter into the produced oil,especially in the none water cut stage.The compositional difference of produced oils is characterized in DBE versus carbon number distribution of the N and O containing compound classes.This work uses a variety of composition analysis methods to clarify the steam flooding mechanism and provides a novel understanding of steam flooding mechanisms with various temperatures and production stages from the molecular perspective.

The mechanism of hydraulic fracturing assisted oil displacement to enhance oil recovery in low and medium permeability reservoirs

Aiming at the technology of hydraulic fracturing assisted oil displacement which combines hydraulic fracturing,seepage and oil displacement,an experimental system of energy storage and flowback in fracturing assisted oil displacement process has been developed and used to simulate the mechanism of percolation,energy storage,oil displacement and flowback of chemical agents in the whole process.The research shows that in hydraulic fracturing assisted oil displacement,the chemical agent could be directly pushed to the deeper area of the low and medium permeability reservoirs,avoiding the viscosity loss and adhesion retention of chemical agents near the pay zone;in addition,this technology could effectively enlarge the swept volume,improve the oil displacement efficiency,replenish formation energy,gather and exploit the scattered residual oil.For the reservoir with higher permeability,this measure takes effect fast,so to lower cost,and the high pressure hydraulic fracturing assisted oil displacement could be adopted directly.For the reservoir with lower permeability which is difficult to absorb water,hydraulic fracturing assisted oil displacement with surfactant should be adopted to reduce flow resistance of the reservoir and improve the water absorption capacity and development effect of the reservoir.The degree of formation energy deficit was the main factor affecting the effective swept range of chemical agents.Moreover,the larger the formation energy deficit was,the further the seepage distance of chemical agents was,accordingly,the larger the effective swept volume was,and the greater the increase of oil recovery was.Formation energy enhancement was the most important contribution to enhanced oil recovery(EOR),which was the key to EOR by the technology of hydraulic fracturing assisted oil displacement.

Study of a plugging microbial consortium using crude oil as sole carbon source

A microbial consortium named Y4 capable of producing biopolymers was isolated from petroleum-contaminated soil in the Dagang Oilfield, China. It includes four bacterial strains： Y4-1 （Paenibacillus sp.）, Y4-2 （Actinomadura sp.）, Y4-3 （Uncultured bacterium clone） and Y4-4 （Brevibacillus sp.）. The optimal conditions for the growth of the consortium Y4 were as follows： temperature about 46 ℃, pH about 7.0 and salinity about 20.0 g/L. The major metabolites were analyzed with gas chromatographymass spectrometry （GC-MS）. A comparison was made between individual strains and the microbial consortium for biopolymer production in different treatment processes. The experimental results showed that the microbial consortium Y4 could produce more biopolymers than individual strains, and the reason might be attributed to the synergetic action of strains. The biopolymers were observed with optical and electron microscopes and analyzed by paper chromatography. It was found that the biopolymers produced by the microbial consortium Y4 were insoluble in water and were of reticular structure, and it was concluded that the biopolymers were cellulose. Through a series of simulation experiments with sand cores, it was found that the microbial consortium Y4 could reduce the permeability of reservoir beds, and improve the efficiency of water flooding by growing biomass and producing biopolymers. The oil recovery was enhanced by 3.5% on average. The results indicated that the consortium Y4 could be used in microbial enhanced oil recovery and play an important role in bioremediation of oil polluted environments.

Features and imbibition mechanisms of Winsor Ⅰ type surfactant solution in oil-wet porous media

The relationship between NaCl concentration and the phase change behavior of microemulsion of anionic surfactant was characterized by the salinity scan experiments.The wettability of WinsorⅠtype surfactant solution(WⅠsolution)and the effect of NaCL concentration on phase change behavior of WⅠsolution and imbibition in oil-wet porous media were investigated by microfluidic experiments in this study.The WⅠsolution and WinsorⅠtype microemulsion are similar in wetting phase with stronger wettability than other phases.Two main mechanisms of WⅠsolution enhancing imbibitions recovery in oil wet porous media are the wetting phase drive and residual oil solubilization.Under the salinity condition of WinsorⅠtype microemulsion,the NaCl concentration has strong impact on the imbibition mechanism of WⅠsolution,the higher the NaCl concentration,the complex the imbibition process and the higher the imbibition efficiency will be.The NaCl concentration has strong impact on the solubilization ability to oil of the WⅠsolution,the higher the NaCl concentration,the stronger the solubility of the WⅠsolution to residual oil will be.

Relationship between Microbial Community Characteristics and Flooding Efficiency in Microbial Enhanced Oil Recovery

Microbial enhanced oil recovery (MEOR) is the research focus in the field of energy development as an environmentally friendly and low cost technology. MEOR can bes divided into indigenous microbial oil recovery and exogenous microbial oil recovery. The ultimate goal of indigenous microbial flooding is to enhance oil recovery via stimulation of specific indigenous microorganisms by injecting optimal nutrients. For studying the specific rule to activate the indigenous community during the long-term injection period, a series of indigenous displacement flooding experiments were carried out by using the long-core physical simulation test. The experimental results have shown that the movement of nutrients components (i.e., carbon/nitrogen/phosphorus) differed from the consumption of them. Moreover, there was a positive relationship between the nutrients concentration and bacteria concentration once observed in the produced fluid. And the trend of concentration of acetic acid was consistent with that of methanogens. When adding same activators, the impacts of selective activators to stimulate the indigenous microorganisms became worse along with the injection period, which led to less oil recovery efficiency.

Characteristics and mechanisms of supercritical CO_(2) flooding under different factors in low-permeability reservoirs

In recent years,supercritical CO_(2)flooding has become an effective method for developing lowpermeability reservoirs.In supercritical CO_(2)flooding different factors influence the mechanism of its displacement process for oil recovery.Asynchronous injection-production modes can use supercritical CO_(2)to enhance oil recovery but may also worsen the injection capacity.Cores with high permeability have higher oil recovery rates and better injection capacity,however,gas channeling occurs.Supercritical CO_(2)flooding has a higher oil recovery at high pressure levels,which delays the occurrence of gas channeling.Conversely,gas injection has lower displacement efficiency but better injection capacity at the high water cut stage.This study analyzes the displacement characteristics of supercritical CO_(2)flooding with a series of experiments under different injection and production parameters.Experimental results show that the gas breakthrough stage has the fastest oil production and the supercritical CO_(2)injection capacity variation tendency is closely related to the gas-oil ratio.Further experiments show that higher injection rates represent significant ultimate oil recovery and injection index,providing a good reference for developing low-permeability reservoirs.

Laboratory studies of rice bran as a carbon source to stimulate indigenous microorganisms in oil reservoirs

There is a great interest in developing cost-efficient nutrients to stimulate microorganisms in indigenous microbial enhanced oil recovery（IMEOR） processes.In the present study,the potential of rice bran as a carbon source for promoting IMEOR was investigated on a laboratory scale.The co-applications of rice bran,K2HPO4 and urea under optimized bio-stimulation conditions significantly increased the production of gases,acids and emulsifiers.The structure and diversity of microbial community greatly changed during the IMEOR process,in which Clostridium sp.,Acidobacteria sp.,Bacillus sp.,and Pseudomonas sp.were dominant.Pressurization,acidification and emulsification due to microbial activities and interactions markedly improved the IMEOR processes.This study indicated that rice bran is a potential carbon source for IMEOR.

Experimental characterization and mechanism of hydraulic pulsation waves driving microscopic residual oil

To clarify microscopic mechanisms of residual oil displacement by hydraulic pulsation wave,microscopic visualization experiments of hydraulic pulsation wave driving residual oil were carried out by using the microscopic visualization device of pulsating water drive.For the four types of residual oil left in the reservoir after water flooding,i.e.membrane,column,cluster,and blind end residual oils,hydraulic pulsation waves broke the micro-equilibrium of the interface by disturbing the oil-water interface,so that the injected water invaded into and contacted with the remaining oil in small pores and blind holes,and the remaining oil was pushed or stripped to the mainstream channel by deformation superposition effect and then carried out by the injected water.In the displacement,the pulsation frequency mainly affected the cluster and blind end remaining oil,and the hydraulic pulsation wave with a frequency of about 1 Hz had the best effect in improving the recovery.The pulsation amplitude value mainly affected the membrane and column residual oil,and the larger the amplitude value,the more remaining oil the hydraulic pulsation wave would displace.The presence of low intensity continuous flow pressure and holding pressure end pressure promoted the concentration of pulsating energy and greatly improve the recovery of cluster residual oil.The rise in temperature made the hydraulic pulsation wave work better in displacing remaining oil,improving the efficiency of oil flooding.

胶囊聚合物驱提高采收率方法

针对常规聚合物驱剪切易降解、注入困难等难题,提出了胶囊聚合物驱提高采收率方法,采用多尺度渗流实验及模拟技术分析了胶囊聚合物驱渗流机制与驱油机理。研究表明:胶囊聚合物驱具有易注入、抗剪切、地层可控释放、吸附滞留率小的优势,具有很好的远距离运移能力,可实现聚合物驱“油藏深部增黏”;胶囊聚合物增黏程度越高,抑制黏性指进的能力越强,驱替前缘越趋于均匀,驱替波及范围越大。胶囊聚合物的释放性能主要受温度影响,温度越高,胶囊聚合物溶液增黏速度越快,而矿化度对胶囊聚合物溶液增黏速度的影响很小。胶囊聚合物驱适用于传统聚合物驱效果不佳的高含水油藏、井距较大的海上聚合物驱油藏、常规聚合物注入性较差的中低渗透油藏等。实施胶囊聚合物驱应“因地制宜”,根据目标油藏条件设计合理的胶囊粒径、释放时间以达到最优的驱油效果。

微生物提高油藏原油采收率进展

文章从油藏中普遍存在的采油微生物类群及其驱油机制、微生物采油技术的矿场应用、采油微生物的响应等方面对油藏微生物及其提高原油采收率进展进行综述.同时从营养剂在油藏储层中的分布、油藏环境下微生物生长代谢活性、油藏微生物定向调控等方面阐述了微生物采油技术发展的基础问题.

致密油藏驱渗结合采油可行性研究

致密油藏孔喉较小而渗吸作用显著,为提高致密油藏水驱效率,提出驱渗结合采油方法,同时利用驱替与渗吸作用。为验证该方法的可行性与主控因素,在水驱模型的基础上,考虑了渗吸作用,并基于实验数据特征建立了渗吸项模型,建立了驱渗结合采油数值模拟模型。结果表明,渗吸作用有效增加了注入水的波及面积,有效置换出基质中的原油,提升了采油效率;主控地质因素包括基质/裂缝孔隙度、渗透率和渗吸经验参数,主控工程因素包括注水压力、裂缝间距和半长;现场应用表明相较水驱方式,驱渗结合采油的日产油速度提高了约1倍,受效时间约为200 d,提高累产约为340 t,说明驱渗结合采油工艺可有效提高中国致密油藏的采收率,所建模型可用于驱渗结合采油的优化设计。

驱油用纳米材料在提高采收率方面研究进展

随着对石油资源需求不断上升和开采难度不断增加,提高采收率的技术需要不断创新,纳米材料作为一种新型材料,由于具有纳米尺寸和独特晶界结构,导致其具有独特的性质,在提高采收率方面具有很大的潜力。本文系统综述了纳米材料在提高采收率方面的作用机理,包括降低表/界面张力,增加毛细管数;结构分离压力作用,微观展示石油从岩石上剥离;改变润湿性,加强水渗吸作用;增强乳液和泡沫稳定性从而增强体系稳定性;改善流度比增加体积波及效率;抑制沥青沉积,催化沥青分解,防止孔隙堵塞和减少地层伤害;抑制颗粒运移、减少地层伤害等。列举了纳米材料在低渗透油藏、稠油油藏和高含水油藏等条件下提高采收率的矿场案例,指出了纳米材料的油田规模化应用所面临的挑战。

微生物及其代谢物提高低渗透油藏渗吸采收率

自发渗吸是低渗透油藏采油的重要方法,微生物提高渗吸采收率的主要采油机理详细研究报导较少。使用从油藏环境中分离得到的专利菌株波茨坦短芽孢杆菌BS3096和铜绿假单胞菌LZ3-2,通过自发渗吸实验研究了细菌和培养基的选择、微生物的生长条件、细菌的代谢产物生物表面活性剂、菌体影响等因素对微生物提高采收率的影响。研究结果表明,含有脂肽生物表面活性剂的渗吸液可以使油水界面张力从0.8848mN/m降低至0.2055mN/m,接触角由116.4°减小至42.8°,使岩石的润湿性从油湿变为水湿。油水界面张力的降低和岩石润湿性的改变对提高渗吸原油采收率影响显著,BS3096产的脂肽生物表面活性剂渗吸采收率可达60%;铜绿假单胞菌PAO1产的鼠李糖脂渗吸采收率为56.26%;LZ3-2产的糖蛋白类生物乳化剂对原油的具有乳化效果,乳化率为6.96%。渗吸实验中,BS3096菌体在岩心内大量累积,选择性地封堵大孔喉通道,使渗吸液分流至低渗区的小孔隙中将原油驱替出来,可使采收率提高7.5百分点。在相同的实验条件和表面活性剂浓度下,生物表面活性剂和化学表面活性剂自发渗吸作用强弱顺序为生物型>阴离子型>非离子型>阳离子型,脂肽生物表面活性剂的渗吸采收率比化学型表面活性剂高11.8百分点~41.5百分点。本研究为低渗透油藏提供了一种高效经济且环境友好的提高原油采收率的方法,为微生物及其代谢产物在现场的应用提供了理论支持。